J Microbiol Methods, 2005 Feb, 60(2), 259 - 68 Specific detection of cytopathogenic Listeria monocytogenes using a two-step method of immunoseparation and cytotoxicity analysis; Gray KM et al.; The development of rapid methods for detection of viable Listeria monocytogenes is crucial to prevent listeriosis and product recalls . While immunomagnetic separation has been used for isolating Listeria spp., lack of specificity and pathogenicity determination render this method unsatisfactory . A two-step method using Protein A agarose beads (Immunobeads) coated with a more specific antibody, monoclonal antibody (MAb)-C11E9 for L . monocytogenes was developed . Immunobeads were allowed to capture Listeria cells from a variety of samples and tested for cytopathogenic action on a murine hybridoma B-lymphocyte, Ped-2E9 cell line by Trypan blue staining, and by an alkaline phosphatase (AP)-based cytotoxicity assay . The two-step method was used to test uninoculated hotdogs, bologna, and raw beef, chicken, and pork samples, following selective enrichment in half-Fraser broth . Pure culture studies proved the assay to be specific for L . monocytogenes, while a similar assay with Dynal(R) Anti-Listeria immunomagnetic beads was positive for L . monocytogenes, L . ivanovii, and L . seeligeri . Detection and confirmation of cytopathogenicity of Listeria cells from food samples after 24-h selective enrichment were completed in 2-4 h . Isolates were further analyzed by the CAMP test for hemolytic activity and RiboPrinter(R) for genomic patterns . Using immunoseparation and cytotoxicity as a two-step rapid method, viable L . monocytogenes could be isolated, detected, and confirmed as cytopathogenic in 28 h or less. J Immunol, 2004 Dec 15, 173(12), 7416 - 25 IFN regulatory factor 3-dependent induction of type I IFNs by intracellular bacteria is mediated by a TLR- and Nod2-independent mechanism; Stockinger S et al.; Like viruses, intracellular bacteria stimulate their host cells to produce type I IFNs (IFN-alpha and IFN-beta) . In our study, we investigated the signals and molecules relevant for the synthesis of and response to IFN by mouse macrophages infected with Listeria monocytogenes . We report that IFN-beta is the critical immediate-early IFN made during infection, because the synthesis of all other type I IFN, expression of a subset of infection-induced genes, and the biological response to type I IFN was lost upon IFN-beta deficiency . The induction of IFN-beta mRNA and the IFN-beta-dependent sensitization of macrophages to bacteria-induced death, in turn, was absolutely dependent upon the presence of the transcription factor IFN regulatory factor 3 (IRF3) . IFN-beta synthesis and signal transduction occurred in macrophages deficient for TLR or their adaptors MyD88, TRIF, or TRAM . Expression of Nod2, a candidate receptor for intracellular bacteria, increased during infection, but the protein was not required for Listeria-induced signal transduction to the Ifn-beta gene . Based on our data, we propose that IRF3 is a convergence point for signals derived from structurally unrelated intracellular pathogens, and that L . monocytogenes stimulates a novel TLR- and Nod2-independent pathway to target IRF3 and the type I IFN genes. Appl Environ Microbiol, 2004 Dec, 70(12), 7555 - 7 Role for compatible solutes glycine betaine and L-carnitine in listerial barotolerance; Smiddy M et al.; Increased listerial barotolerance at elevated osmolarity is attributed, in part, to the presence of accumulated betaine and L-carnitine . The percentage of listerial survival following exposure to 400 MPa for 5 min increased from 0.008 to 0.02% with added L-carnitine (5 mM) and to 0.05% with added betaine (5 mM) . Furthermore, listerial cells incapable of transporting compatible solutes fail to adapt to high pressure at elevated osmolarity. J Morphol . 2004 Nov 29; {Epub ahead of print} Ultrastructural observations of spermatozoa of several tetragnathid spiders with phylogenetic implications (Araneae, Tetragnathidae); Michalik P et al.; The present study reports on the ultrastructure of spermatozoa and spermatogenesis of 12 tetragnathid spiders (10 Tetragnatha species {T . boydi, T . dearmata, T . extensa, T . montana, T . nigrita, T . obtusa, T . pinicola, T . reimoseri, T . shoshone, T . striata}; Pachygnatha listeri and Metellina segmentata) . All species develop typical cleistospermia with a coiled nucleus in the center and a coiled axoneme in the periphery of the cell . Remarkable differences in the sperm ultrastructure of the investigated species comprise the shape of the main sperm cell components (nucleus, acrosomal complex, implantation fossa, and centriolar complex) . Within the observed Tetragnatha species, three types of sperms were characterized: T . montana-type, T . boydi-type, and T . striata-type . The highly derivative T . montana-type is characterized by the following remarkable features: an extremely elongated nucleus, shaped like a corkscrew and twisted around the axoneme (before coiling); a deep implantation fossa; a corkscrew-shaped acrosomal vacuole; after the coiling process, the nucleus is coiled five to six times in the center of the spermatozoon and the axoneme is coiled five to six times peripheral to the nucleus . The T . boydi-type hardly differs from the T . montana-type, but is remarkable due to the triangular-shaped nucleus (in cross section) . The T . striata-type differs especially by a peculiar acrosomal vacuole with a long, slightly curved process and a short appendix, as well as a nucleus that describes only three loose coils around the axoneme (before coiling) . The spermatozoa of Pachygnatha listeri and especially Metellina segmentata differ strikingly from the described Tetragnatha-types and are similar to more primitive araneomorph spermatozoa, such as Hypochilus pococki . The described Tetragnatha-types completely correspond with Okuma's (1988a,b, J Fac Agr Kyushu U 32:165-181, 32:183-213) classification of Tetragnatha species . Furthermore, our results suggest an early derivative systematic position of Pachygnatha within Tetragnathinae and the position of Metellina within the Tetragnathidae . (c) 2004 Wiley-Liss, Inc. Vet Res Commun, 2004 Oct, 28(7), 569 - 79 Humoral and delayed-type hypersensitive responses against listeria monocytogenes phosphatidylinositol-specific phospholipase C in experimentally infected buffaloes; Chaudhari SP et al.; The kinetics of antibody production against phosphatidylinositol-specific phospholipase C (PI-PLC) and the isolation pattern of Listeria monocytogenes from bacteriological samples were studied following oral infection of buffalo calves with 3 x 10(9) cells each of pathogenic L . monocytogenes . Antibodies to PI-PLC appeared by 4-8 days post infection (PI), with a peak between days 7 and 16 PI, when tested by indirect plate-ELISA . Subsequently, antibody titres in all the animals declined and became undetectable on days 26-35 PI onwards until the study concluded on day 211 PI . Dot-ELISA could detect the antibodies to PI-PLC 1-2 days earlier and at higher titres as compared to plate-ELISA . L . monocytogenes could be recovered from faeces, nasal swabs and haemocultures from days 2 to 33, days 2 to 21 and days 11 to 17 PI, respectively . Antibodies to PI-PLC were detected during the course of active infection but their titres declined sharply once animals became culturally negative . Sonicated antigen elicited the highest delayed-type hypersensitivity response, followed by PI-PLC and listeriolysin O. Vet Res Commun, 2004 Oct, 28(7), 561 - 7 Listeria monocytogenes in products of animal origin in Turkey; Akpolat NO et al.; A study was carried out on 430 samples of different foodstuffs (soft cheese, raw chicken, minced beef, sausage, fish) and 400 carcase samples (sheep, young and adult cattle) for screening of Listeria monocytogenes . It was found that only one of the samples contained L . monocytogenes at > 10(3) cfu/ml in the initial examination, but another 42 samples contained L . monocytogenes following an enrichment process . L . monocytogenes was isolated most frequently from raw chicken samples (18%), but was not isolated from sausage samples . Forty-three isolates were defined as serotypes by using Bacto-Listeria-O-antisera Type 1 (Difco 2300-50-2) and Type 4 (Difco 2301-50-1) except that Type poly was not used . For these reasons, all isolates were classified as type 1 or type 4 and the other was termed untypeable . Twenty-one samples were type 1, 17 were untypeable, and 5 were both serotype 4 and untypeable. PLoS Biol . 2004 Dec;2(12):e412 . Epub 2004 Nov 30. In silico reconstitution of Listeria propulsion exhibits nano-saltation; Alberts JB et al.; To understand how the actin-polymerization-mediated movements in cells emerge from myriad individual protein-protein interactions, we developed a computational model of Listeria monocytogenes propulsion that explicitly simulates a large number of monomer-scale biochemical and mechanical interactions . The literature on actin networks and L . monocytogenes motility provides the foundation for a realistic mathematical/computer simulation, because most of the key rate constants governing actin network dynamics have been measured . We use a cluster of 80 Linux processors and our own suite of simulation and analysis software to characterize salient features of bacterial motion . Our "in silico reconstitution" produces qualitatively realistic bacterial motion with regard to speed and persistence of motion and actin tail morphology . The model also produces smaller scale emergent behavior; we demonstrate how the observed nano-saltatory motion of L . monocytogenes,in which runs punctuate pauses, can emerge from a cooperative binding and breaking of attachments between actin filaments and the bacterium . We describe our modeling methodology in detail, as it is likely to be useful for understanding any subcellular system in which the dynamics of many simple interactions lead to complex emergent behavior, e.g., lamellipodia and filopodia extension, cellular organization, and cytokinesis. Infect Immun, 2004 Dec, 72(12), 7374 - 8 Listeria monocytogenes sigmaB contributes to invasion of human intestinal epithelial cells; Kim H et al.; The role of sigma(B) in Listeria monocytogenes infection of human intestinal epithelial cells was investigated . Invasion defects associated with loss of sigma(B) paralleled those of a DeltainlA strain independently of the sigma(B)-dependent P2(prfA) promoter . Concomitantly, amounts of inlA transcript and InlA protein were significantly decreased in the DeltasigB strain. Infect Immun, 2004 Dec, 72(12), 7005 - 11 Immunostimulating properties of intragastrically administered Acetobacter-derived soluble branched (1,4)-beta-D-glucans decrease murine susceptibility to Listeria monocytogenes; Li W et al.; We previously found that AC-1, an extracellular polysaccharide, produced by Acetobacter xylinum and composed of (1,4)-beta-D-glucan with branches of glucosyl residues, showed a strong activity to induce production of interleukin-12 (IL-12) p40 and tumor necrosis factor alpha by macrophages in vitro via Toll-like receptor 4 (TLR-4) signaling . In the present study, we examined the effect of oral administration of AC-1 on protective immunity against Listeria monocytogenes . Mice were given AC-1 or phosphate-buffered saline (PBS) intragastrically 2 days before, on the day of, and 2 days after an intraperitoneal inoculation of L . monocytogenes . The survival rate of AC-1-treated mice was significantly improved and bacterial growth in AC-1-treated mice was severely retarded compared to those of PBS-treated mice after infection with L . monocytogenes . IL-12 p40 levels in serum and magnitudes of CD4+ Th1 and CD8+ Tc1 responses against Listeria antigen were significantly higher in AC-1-treated mice than in PBS-treated mice . The effect of AC-1 on antilisterial activity was diminished in C3H/HeJ mice carrying mutated TLR-4 . Thus, AC-1, a potent IL-12 inducer through TLR-4, enhanced protective immunity against L . monocytogenes via augmentation of Th1 responses . These results suggest that infectious processes driven by intracellular microorganisms could be prevented to develop by the (1,4)-beta-D-glucan. J Immunol, 2004 Dec 1, 173(11), 6694 - 702 Shortening the infectious period does not alter expansion of CD8 T cells but diminishes their capacity to differentiate into memory cells; Williams MA et al.; Following a primary immune response, a portion of effector T cells gives rise to long-lived memory cells . Although primary expansion and differentiation of effector CD8 T cells is dictated by a brief exposure to Ag, it is unclear whether full memory differentiation is also programmed within the same short window . By carefully modulating the kinetics of Listeria monocytogenes infection, we analyzed the requirements for the programming of effector and memory T cell development in vivo . We find that although limiting the infectious period to the first 24-48 h does not impact the size of the primary CD8 response, the ensuing memory population is significantly diminished . This effect is particularly pronounced in the development of tissue-homing memory cells and is inversely proportional to the initial infectious dose . In contrast to CD8 responses, the differentiation of primary CD4 responses was highly dependent on the continued presence of the infection . Shortening the duration of the infection greatly reduced the development of CD4 effector responses in the spleen and prevented their trafficking to peripheral sites of infection . We propose that the stimulus received by CD8 T cells during the early stages of infection largely contribute to the differentiation of CD8 effector cells, whereas continued or distinct signals received at later stages influence their ability to differentiate into memory cells. J Food Prot, 2004 Nov, 67(11), 2544 - 9 Efficacy of acidic electrolyzed water ice for pathogen control on lettuce; Koseki S et al.; Acidic electrolyzed water (AcEW) was used as frozen AcEW (AcEW-ice) for inactivation of Listeria monocytogenes and Escherichia coli O157:H7 on lettuce . AcEW-ice was prepared from AcEW with 20, 50, 100, and 200 ppm of available chlorine by freezing at -40 degrees C and generated 30, 70, 150, and 240 ppm of chlorine gas (Cl2), respectively . The AcEW-ice was placed into styrene-foam containers with lettuce samples at 20 degrees C for 24 h . Although AcEW-ice generating 30 ppm Cl2 had no effect on L . monocytogenes cell counts, AcEW-ice generating 70 to 240 ppm of Cl2 significantly (P < 0.05) reduced L . monocytogenes by ca . 1.5 log CFU/g . E . coli O157:H7 cell counts were reduced by 1.0 log CFU/g with AcEW-ice generating 30 ppm of Cl2 . AcEW-ice generating 70 and 150 ppm of Cl2 reduced E . coli O157:H7 by 2.0 log CFU/g . Further significant reduction of E . coli O157:H7 (2.5 log CFU/g) was demonstrated by treatment with AcEW-ice generating 240 ppm of Cl2 . However, treatment with AcEW-ice generating 240 ppm of Cl2 resulted in a physiological disorder resembling leaf burn . AcEW-ice that generated less than 150 ppm of Cl2 had no effect on the surface color of the lettuce . AcEW-ice, regardless of the concentration of the emission of Cl2, had no effect on the ascorbic acid content in the lettuce . The weight ratio of lettuce to AcEW-ice required was determined to be over 1:10 . The bactericidal effect of AcEW-ice appeared within the first 2 h . The use of AcEW-ice provides simultaneously for low temperature storage and inactivation of bacteria. J Food Prot, 2004 Nov, 67(11), 2500 - 14 Longitudinal studies on Listeria in smoked fish plants: impact of intervention strategies on contamination patterns; Lappi VR et al.; Four ready-to-eat smoked fish plants were monitored for 2 years to study Listeria contamination patterns and the impact of plant-specific Listeria control strategies, including employee training and targeted sanitation procedures, on Listeria contamination patterns . Samples from the processing plant environment and from raw and finished product were collected monthly and tested for Listeria spp . and Listeria monocytogenes . Before implementation of intervention strategies, 19.2% of raw product samples (n = 276), 8.7% of finished product samples (n = 275), and 26.1% of environmental samples (n = 617) tested positive for Listeria spp . During and after implementation of Listeria control strategies, 19.0% of raw product samples (n = 242), 7.0% of finished product samples (n = 244), and 19.5% of environmental samples (n = 527) were positive for Listeria spp . In one of the four fish plants (plant 4), no environmental samples were positive for L . monocytogenes, and this plant was thus excluded from statistical analyses . Based on data pooled from plants 1, 2, and 3, environmental Listeria spp . prevalence was significantly lower (P < 0.05) for nonfood contact surfaces and the finished product area and for the overall core environmental samples after implementation of control strategies . Listeria prevalence for floor drains was similar before and after implementation of controls (49.6 and 54.2%, respectively) . Regression analysis revealed a significant positive relationship (P < 0.05) between L . monocytogenes prevalence in the environment and in finished products before implementation of control strategies; however, this relationship was absolved by implementation of Listeria control strategies . Molecular subtyping (EcoRI ribotyping) revealed that specific L . monocytogenes ribotypes persisted in three processing plants over time . These persistent ribotypes were responsible for all six finished product contamination events detected in plant 1 . Ribotype data also indicated that incoming raw material is only rarely a direct source of finished product contamination . While these data indicate that plant-specific Listeria control strategies can reduce cross-contamination and prevalence of Listeria spp . and L . monocytogenes in the plant environment, elimination of persistent L . monocytogenes strains remains a considerable challenge. J Food Prot, 2004 Nov, 67(11), 2496 - 9 Dairy farm reservoir of Listeria monocytogenes sporadic and epidemic strains; Borucki MK et al.; Identifying the reservoirs of a pathogen is vital for control of sporadic disease and epidemics . Listeria monocytogenes is a zoonotic foodborne pathogen that is responsible for 28% of food-related deaths in the United States annually, as well as a major cause of massive product recalls worldwide . To examine the role of the dairy farm as a potential source or reservoir for L . monocytogenes subtypes shown to cause human listeriosis, we compared the pulsed-field gel electrophoresis (PFGE) restriction enzyme digestion profiles of L . monocytogenes dairy farm-associated strains (milk, environmental, and bovine) to human sporadic and epidemic disease strains . Twenty-three percent of human sporadic strains had PFGE patterns identical to that of farm isolate(s) . Additionally, three farm environmental strains and one human sporadic strain had a PFGE pattern identical to a strain of L . monocytogenes responsible for the 1985 California epidemic . These data indicate that this epidemic strain continues to cause sporadic human illness and has a potential dairy farm as a reservoir. J Food Prot, 2004 Nov, 67(11), 2488 - 95 Strain-specific differences in the attachment of Listeria monocytogenes to alfalfa sprouts; Gorski L et al.; Contamination of fresh produce with Listeria monocytogenes has resulted in outbreaks of systemic listeriosis and febrile gastroenteritis . Recalls of alfalfa sprouts have occurred due to contamination with L . monocytogenes . Alfalfa sprouts were used as a preharvest model to study the interaction with this human pathogen . Seventeen strains were assessed for their capacity to colonize alfalfa sprouts, and strain-specific differences (not related to source, serotype, or lineage) were revealed when the sprout irrigation water was changed daily . Two of the strains colonized and attached to the sprouts very well, reaching levels of more than 5 log CFU per sprout . The remaining strains varied in their final levels on sprouts between less than 1 to 4.7 log CFU per sprout . All of the L . monocytogenes strains grew to equivalent levels on the sprouts when the irrigation water was not changed, suggesting the differences observed with regular changing of the water resulted from differences in attachment . Further analysis of the best colonizing strains indicated that only between 0.3 and 1 log CFU per sprout could be removed by additional washing of the sprout, and the presence of normal sprout bacteria did not compete with the L . monocytogenes strains on the sprouts . The poorest colonizing strain was able to grow in the irrigation water during the experiment but could not attach to the sprouts . Microscopic examination of the sprouts with L . monocytogenes expressing the green fluorescent protein indicated that L . monocytogenes was associated with the root hairs of the sprouting alfalfa, with few to no cells visible elsewhere on the sprout. J Food Prot, 2004 Nov, 67(11), 2480 - 7 Prevalence and typing of Listeria monocytogenes in ready-to-eat food products on the Belgian market; Van Coillie E et al.; Listeria monocytogenes is a major concern to producers of ready-to-eat foods because of the high mortality rate associated with listeriosis and the widespread nature of the organism . To investigate the prevalence of this pathogen in different ready-to-eat food products on the Belgian market, a variety of 252 ready-to-eat food products, mainly fish and meat products, were analyzed . Overall, L . monocytogenes was detected in 23.4% of the samples . The highest prevalence of L . monocytogenes was found in prepared minced meat (42.1%) and smoked halibut (33.3%) . Contamination levels were in most cases low (<10 CFU/g); however, levels higher than 100 CFU/g were detected in some samples of smoked salmon, smoked halibut, and prepared minced meat . A high prevalence of Listeria innocua (15.8%) and Listeria welshimeri (36.8%) was detected in prepared minced meat . L . monocytogenes strains isolated from different contaminated products were subjected to repetitive element sequence-based PCR (REP-PCR) typing to determine possible associations with product type, producer, or market . REP-PCR patterns were analyzed using BioNumerics software, and seven different groups with at least 90% similarity were identified . The cluster analysis indicates that cross-contamination occurred at the producer and retail level . Serotype identification of the strains by PCR revealed that most belonged to the 1/2a(3a) serotype group. J Food Prot, 2004 Nov, 67(11), 2472 - 9 Effect of prepackage and postpackage pasteurization on postprocess elimination of Listeria monocytogenes on deli turkey products; Muriana P et al.; Surface pasteurization for inactivation of Listeria monocytogenes was evaluated for radiant heat prepackage pasteurization, submersed water postpackage pasteurization, and combinations of the two techniques on various types of ready-to-eat deli turkey products obtained from at least four different manufacturers . Products were inoculated either by in-package liquid inoculum or surface sponge-contact with approximately 10(9) CFU of L . monocytogenes . Additional testing of radiant heat pasteurization was performed with low-level inoculation of product undersides with approximately 100 CFU of L . monocytogenes followed by enrichment recovery after pasteurization . Prepackage pasteurization provided 2.0 to 2.8 log reductions when processed for 60 s and 2.8 to 3.8 log reductions when processed for 75 s . An improved radiant oven provided 3.53 (60 s) and 4.76 (75 s) log reductions of L . monocytogenes . No positive samples were detected after enrichment when 40 samples of deli turkey (4 to 4.5 kg) undersides were inoculated at low levels and processed for 75 s . Submersed water postpackage pasteurization provided 1.95 to 3.0 log reductions when processed for 2, 3, 4, or 5 min, and combinations of the two processes gave 3.0 to 4.0 log inactivation of L . monocytogenes using either 60 + 60 s or 60 + 90 s for the prepackage and postpackage pasteurization processes, respectively . These processes, either individually or in combination, can provide postprocess elimination of bacteria for the manufacture of safe ready-to-eat deli meats. J Food Prot, 2004 Nov, 67(11), 2465 - 71 Control of growth and survival of Listeria monocytogenes on smoked salmon by combined potassium lactate and sodium diacetate and freezing stress during refrigeration and frozen storage; Yoon KS et al.; In this study, we evaluated the antimicrobial effects of different levels of a potassium lactate (PL) plus sodium diacetate (SDA) mixture against the growth and survival of Listeria monocytogenes Scott A inoculated onto smoked salmon stored at 4, 10, and -20 degrees C . The effect of freezing stress on the growth kinetics of L . monocytogenes Scott A on smoked salmon at 4 and 10 degrees C was also investigated . The use of PL+SDA at all tested levels (1.5, 3.3, and 5% of a 60% commercial solution of PURASAL P Opti.Form 4) completely inhibited the growth of L . monocytogenes Scott A on smoked salmon stored at 4 degrees C during 32 days of storage . It also delayed the growth of L . monocytogenes Scott A on smoked salmon stored at 10 degrees C for up to 11 days, but a listeriostatic effect was observed only with 5% PURASAL P Opti.Form 4 at 10 degrees C after 11 days . Addition of PL+SDA at all tested levels decreased the surviving populations of L monocytogenes Scott A on smoked salmon during 10 months of frozen storage at -20 degrees C . Freezing stress significantly (P < 0.001) extended the lag time and delayed the growth of L . monocytogenes Scott A at both 4 and 10 degrees C . However, the effect of freezing stress was more significant at 4 degrees C than at 10 degrees C, indicating the importance of temperature control of smoked salmon during the retail storage period. J Food Prot, 2004 Nov, 67(11), 2450 - 5 Decontamination of strawberries using batch and continuous chlorine dioxide gas treatments; Han Y et al.; Efficacy of chlorine dioxide (ClO2) gas in reducing Escherichia coli O157:H7 and Listeria monocytogenes on strawberries was determined using batch and continuous flow ClO2 gas treatment systems . Effects of continuous ClO2 gas treatment on total aerobic plate count, color, and residual ClO2 and chlorite on strawberries were also evaluated . Strawberries were spot inoculated with 7 to 8 log CFU per strawberry of each pathogen (E . coli O157:H7 and L . monocytogenes), stored for 1 day at 4 degrees C, and treated at 22 degrees C and 90 to 95% relative humidity with 0.2 to 4.0 mg/liter ClO2 gas for 15 or 30 min using a batch treatment system or with 0.6, 1.8, and 3.0 mg/liter for 10 min using a continuous treatment system . Surviving microbial populations were determined using a membrane-transfer plating recovery method . Increased ClO2 gas concentrations resulted in increased log reductions of each pathogen for both the batch and continuous systems . A batch treatment of strawberries with 4 mg/liter ClO2 for 30 min and continuous treatment with 3 mg/liter ClO2 for 10 min achieved greater than a 5-log reduction for both E . coli O157:H7 and L . monocytogenes . After continuous exposure to 3.0 mg/liter ClO2 gas for 10 min followed by 1 week of storage at 4 degrees C, no aerobic microorganisms were detected and the color of the strawberry surface did not change significantly (P > 0.05) . Residues of ClO2 and chlorite on strawberries after the treatment were 0.19 +/- 0.33 mg ClO2 per kg and 1.17 +/- 2.02 mg Cl2 per kg, respectively, whereas after 1 week of storage no ClO2 residues were detected and residual chlorite levels were down to 0.07 +/- 0.12 mg Cl2 per kg . These results suggest that ClO2 gas treatment is an effective decontamination technique for improving the safety of strawberries while extending shelf life. J Food Prot, 2004 Nov, 67(11), 2443 - 9 Fate of Escherichia coli O157:H7 and Listeria monocytogenes in strawberry juice and acidified media at different pH values and temperatures; Han Y et al.; Survival and growth of Escherichia coli O157:H7 and Listeria monocytogenes in strawberry juice and acidified media at different pH levels (pH 3.4 to 6.8) and temperatures were studied . Sterile strawberry juice (pH 3.6) and acidified trypticase soy broth (TSB) media (pH 3.4 to 6.8) were inoculated with approximately 6.7 log CFU/ml E . coli O157:H7 or 7.3 log CFU/ ml L . monocytogenes, incubated for 3 days at 4 and 37 degrees C . Bacterial levels were determined after 2 h, 1 day, and 3 days using surface plating nonselectively on tryptic soy agar and selectively on sorbitol MacConkey agar for E . coli O157:H7 or modified Oxford agar for L . monocytogenes . A spectrophotometer (660 nm) was also used to study growth inhibition of L . monocytogenes in different TSB and strawberry juice media (pH 3.4 to 7.3) . E . coli O157:H7 survived well at pH values of 3.4 to 6.8 at 4 degrees C, but the number of injured cells increased as pH decreased and incubation time increased . At 37 degrees C, E . coli O157:H7 was inactivated at pH of < or = 3.6 but could grow at pH 4.7 . L . monocytogenes was quickly injured at pH of < or = 4.7 within 2 h of storage at 4 degrees C and then was slightly and gradually inactivated as storage time increased . L . monocytogenes survived well at pH 6.8 at 4 degrees C and grew well at 37 degrees C . Growth of L . monocytogenes at 37 degrees C was inhibited in TSB by 1% citric acid and 0.5% malic acids at pH 3.4 or by 50% strawberry juice at pH 4.7 . Bacterial injury and inactivation appeared to be induced by the acids in strawberry juice . The acids, pH value, temperature, and time were important factors for bacterial survival, inactivation, and growth in the media tested. J Food Prot, 2004 Nov, 67(11), 2436 - 42 Effects of recovery, plating, and inoculation methods on quantification of Escherichia coli O157:H7 and Listeria monocytogenes from strawberries; Han Y et al.; Effects of different recovery and inoculation methods on quantification of Escherichia coli O157:H7 and Listeria monocytogenes from strawberries were studied . Strawberries were spot or dip inoculated with 7 to 8 log CFU per strawberry of each pathogen, air dried for 2 h, and stored for 1, 3, and 7 days at 4 degrees C . The inoculated samples were stomached or washed with phosphate-buffered saline (PBS; pH 7.2) or with modified PBS (pH 8.4) . Bacterial levels were determined using a direct selective plating, thin agar layer plating, or membrane-transferring plating (MTP) with tryptic soy agar and sorbital MacConkey agar (E . coli O157:H7) or modified Oxford agar (L . monocytogenes) . Under most test conditions, washing with PBS followed by MTP had significantly higher (P < 0.05) recovery for both bacteria compared with other tested methods . Within a 7-day storage period for spot-inoculated strawberries, a stomaching step resulted in an injury of 0.9 to 1.4 log CFU for E . coli O157: H7 and 1.4 to 1.7 log CFU for L . monocytogenes . When a washing step was used instead, this resulted in an injury of only 0.2 to 0.6 log CFU for E . coli O157:H7 and 0.2 to 0.7 log CFU for L . monocytogenes . Both bacteria could survive on strawberry surfaces, but their recovered levels decreased with the increase of storage time at 4 degrees C for both spot and dip inoculation methods . Dip inoculation generally had a lower recovery than spot inoculation . An ideal protocol to recover and enumerate E . coli O157:H7 and L . monocytogenes from strawberries involved shaking and washing samples with 100 ml of PBS for 15 min at 22 degrees C coupled with a MTP enumeration method. Mol Genet Genomics . 2004 Nov 10; {Epub ahead of print} Listeria monocytogenes infection-dependent transfer of exogenously added DNA to fibroblast COS-1 cells; Stritzker J et al.; The addition of double-stranded circular or linear DNA encoding EGFP (the Enhanced Green Fluorescent Protein) to a Listeria -containing infection medium resulted in up to 8.6% COS-1 cells expressing the reporter protein . The transfer of naked DNA into host cells upon infection by Listeria was found to be dependent on the ability of the bacteria to synthesize internalins and listeriolysin . Since no binding of DNA to the bacterial cells was detected, DNA uptake seems to be the consequence of the simultaneous entry of infection medium, and thus of naked DNA, via the phagosomes induced by the bacterium to facilitate its own entry into the host cells. Lett Appl Microbiol, 2004, 39(6), 528 - 32 Differential inactivation of Listeria monocytogenes by D- and L-lactic acid; Gravesen A et al.; AIMS: To determine inactivation of Listeria monocytogenes by the two lactic acid isomers . METHODS AND RESULTS: The survival of four strains with varying sensitivity to acid was determined following treatment with L- or D-lactic acid at 100 mmol l(-1) (pH 3.7) or HCl at pH 3.37 . There was some, but not complete, similarity in the relative sensitivity of the four strains to the two types of acid . All strains were most sensitive to D-lactic acid, which gave 0.6-2.2 log units greater reduction than L-lactic acid midway in the inactivation curves . Even very low concentrations of the two isomers had an immediate effect on pH(i) which was identical for the two isomers . CONCLUSIONS: The results show that L . monocytogenes is more sensitive to D- than to L-lactic acid; however, this difference is less than the strain variation in L-lactic acid sensitivity . SIGNIFICANCE AND IMPACT OF THE STUDY: This work has implications for the application of lactic acid for food preservation as well as for the understanding of the antibacterial mechanisms of weak organic acids. Lett Appl Microbiol, 2004, 39(6), 483 - 9 Glycopeptide-resistance transferability from vancomycin-resistant enterococci of human and animal source to Listeria spp; de Niederhausern S et al.; AIMS: The glycopeptide-resistance transferability from vancomycin-resistant enterococci (VRE) of clinical and animal origin to different species of Listeria was investigated . METHODS AND RESULTS: Of 36 matings, performed on membrane filter, the glycopeptide resistance was successfully transferred in six attempts, five with donors of animal origin and only one with donors from clinical source . The acquired glycopeptide resistance in Listeria transconjugants was confirmed by the presence of the conjugative plasmid band and by the amplification of the 732-bp fragment of vanA gene in transferred plasmids . CONCLUSIONS: Despite the lower number of bacteria used in this study, the source of enterococci influenced the outcome of mating . Moreover transferred VanA plasmid induced a different expression in Listeria transconjugants, suggesting that gene expression might be influenced by species affiliation of recipients . SIGNIFICANCE AND IMPACT OF THE STUDY: Our data strengthen the opinion that enterococci are an important source of resistance genes for Listeria via the transfer of movable genetic elements . As these strains are commonly found in the same habitats, a horizontal spread of glycopeptide resistance in Listeria spp . could be possible. J Appl Microbiol, 2004, 97(6), 1281 - 8 Relationship between inactivation kinetics of a Listeria monocytogenes suspension by chlorine and its chlorine demand; Virto R et al.; AIMS: Chlorine demand by Listeria monocytogenes cells and inactivation of L . monocytogenes by chlorine (0.6-1.0 mg l(-1)) at different temperatures (4, 20 and 30 degrees C) have been investigated in a batch reactor . METHODS AND RESULTS: Chlorine demand depended on the microbial concentration and was independent on the initial chlorine concentration and temperature . Chlorine decay was modelled by the addition of two first-order decay equations . Inactivation of L . monocytogenes by chlorine depended on the initial microbial concentration, initial chlorine concentration and temperature . A mathematical model based on a biphasic inactivation properly described survival curves of L . monocytogenes and a tertiary model was developed that satisfactorily predicted the inactivation of L . monocytogenes by different concentrations of initial chlorine at different temperatures . CONCLUSIONS: Both available chlorine decay and inactivation of L . monocytogenes by chlorine were biphasic and can be modelled by a two-term exponential model . SIGNIFICANCE AND IMPACT OF THE STUDY: The biphasic nature of survival curves of L . monocytogenes did not reflect the effect of a change of available chlorine concentration during the treatment . The microbial inactivation was caused by successive reactions that occur after the consumption of the chlorine by the bacterial cell components. Int J Food Microbiol, 2004 Dec 15, 97(2), 215 - 9 Factors affecting the antilisterial effects of nisin in milk; Bhatti M et al.; The ability of Listeria monocytogenes to proliferate in milk and the antilisterial activities of nisin are well documented . Although milk fat was reported to reduce the antimicrobial activities of nisin, there is little information on the influence of milk fat on the antilisterial activities of nisin in refrigerated milk, and whether pasteurization and homogenization influence these activities . Fresh, pasteurized, and homogenized milk samples (0.1%, 2.0%, and 3.5% fat) were treated with nisin (0-500 IU/ml) and challenged with 10(4) CFU/ml L . monocytogenes strain Scott A . The organism was most sensitive to nisin in skim milk, showing rapid decline in cell numbers to <10 CFU/ml after 12 days at 5 degrees C following treatment with 250 IU/ml . An initial decline in cell numbers in 2% and whole milk was followed by regrowth of the organism . Loss of the antilisterial effects of nisin was confirmed in homogenized whole milk, whether raw or pasteurized, but not in raw or pasteurized whole milk that was not homogenized . Tween 80, a nonionic emulsifier, partially counteracted the loss of the antilisterial activity of nisin, whereas lecithin, an anionic emulsifier, had no effect . These results demonstrate that the chemical composition and treatment of foods may play an important role in the antilisterial effects of nisin. Scand J Immunol, 2004 Nov, 60(5), 437 - 48 Interferon-gamma mediates neuronal killing of intracellular bacteria; Jin Y et al.; Neurons can be targets for microbes, which could kill the neurons . Just in reverse, we, in this study, report that bacteria can be killed when entering a neuron . Primary cultures of foetal mouse hippocampal neurons and a neuronal cell line derived from mouse hypothalamus were infected by Listeria monocytogenes . Treatment with interferon-gamma (IFN-gamma) did not affect bacterial uptake, but resulted in increased killing of intracellular bacteria, whereas the neuronal cell remained intact . The IFN-gamma-mediated bacterial killing was mapped to the neuronal cytosol, before listerial actin tail formation . Treatment with IFN-gamma induced phosphorylation of the transcription factor STAT-1 in neurons and IFN-gamma-mediated listerial killing was not observed in STAT-1(-/-) neurons or neurons treated with IFN regulatory factor-1 antisense oligonucleotides . IFN-gamma-treated neuronal cells showed increased levels of inducible nitric oxide synthase (iNOS) mRNA, and antisense iNOS oligonucleotides hampered the bacterial killing by neurons upon IFN-gamma treatment . This novel neuronal function - i.e., that of a microbe killer - could play a crucial role in the control of infections in the immuno-privileged nervous system. J Clin Microbiol, 2004 Nov, 42(11), 5270 - 6 Selective discrimination of Listeria monocytogenes epidemic strains by a mixed-genome DNA microarray compared to discrimination by pulsed-field gel electrophoresis, ribotyping, and multilocus sequence typing; Borucki MK et al.; Listeria monocytogenes can cause serious illness in humans, and subsequent epidemiological investigation requires molecular characterization to allow the identification of specific isolates . L . monocytogenes is usually characterized by serotyping and is subtyped by using pulsed-field gel electrophoresis (PFGE) or ribotyping . DNA microarrays provide an alternative means to resolve genetic differences among isolates, and unlike PFGE and ribotyping, microarrays can be used to identify specific genes associated with strains of interest . Twenty strains of L . monocytogenes representing six serovars were used to generate a shotgun library, and subsequently a 629-probe microarray was constructed by using features that included only potentially polymorphic gene probe sequences . Fifty-two strains of L . monocytogenes were genotyped by using the condensed array, including strains associated with five major listeriosis epidemics . Cluster analysis of the microarray data grouped strains according to phylogenetic lineage and serotype . Most epidemiologically linked strains were grouped together, and subtyping resolution was the same as that with PFGE (using AscI and ApaI) and better than that with multilocus sequence typing (using six housekeeping genes) and ribotyping . Additionally, a majority of epidemic strains were grouped together within phylogenetic Division I . This epidemic cluster was clearly distinct from the two other Division I clusters, which encompassed primarily sporadic and environmental strains . Discriminant function analysis allowed identification of 22 probes from the mixed-genome array that distinguish serotypes and subtypes, including several potential markers that were distinct for the epidemic cluster . Many of the subtype-specific genes encode proteins that likely confer survival advantages in the environment and/or host. Microbiology, 2004 Nov, 150(Pt 11), 3843 - 55 sigmaB-dependent gene induction and expression in Listeria monocytogenes during osmotic and acid stress conditions simulating the intestinal environment; Sue D et al.; Listeria monocytogenes must overcome a variety of stress conditions in the host digestive tract to cause foodborne infections . The alternative sigma factor sigma(B), encoded by sigB, is responsible for regulating transcription of several L . monocytogenes virulence and stress-response genes, including genes that contribute to establishment of gastrointestinal infections . A quantitative RT-PCR assay was used to measure mRNA transcript accumulation for the virulence genes inlA and bsh, the stress-response genes opuCA and lmo0669 (encoding a carnitine transporter and an oxidoreductase, respectively) and the housekeeping gene rpoB . Assays were conducted on mid-exponential phase L . monocytogenes cells exposed to conditions reflecting osmotic (0.3 M NaCl) or acid (pH 4.5) conditions typical for the human intestinal lumen . In exponential-phase cells, as well as under osmotic and acid stress, inlA, opuCA and bsh showed significantly lower absolute expression levels in a L . monocytogenes DeltasigB null mutant compared to wild-type . A statistical model that normalized target gene expression relative to rpoB showed that accumulation of inlA, opuCA and bsh transcripts was significantly increased in the wild-type strain within 5 min of acid and osmotic stress exposure; lmo0669 transcript accumulation increased significantly only after acid exposure . It was concluded that sigma(B) is essential for rapid induction of the tested stress-response and virulence genes under conditions typically encountered during gastrointestinal passage . As inlA, bsh and opuCA are critical for gastrointestinal infections in animal models, the data also suggest that sigma(B) contributes to the ability of L . monocytogenes to cause foodborne infections. J Immunol, 2004 Nov 15, 173(10), 5918 - 22 Cutting edge: immunity and IFN-gamma production during Listeria monocytogenes infection in the absence of T-bet; Way SS et al.; The T-box transcription factor T-bet is an important regulator of IFN-gamma production in all cell types and is considered to be essential for the generation of CD4 Th1 T cells . IFN-gamma in turn plays a critical role in immunity to many infectious agents . In this study, we demonstrate that T-bet is not required for host resistance to primary Listeria monocytogenes (LM) infection . In the innate immune phase, control of LM replication, serum IFN-gamma, and numbers of IFN-gamma-producing NK cells were similar in T-bet-deficient and control mice . In the adaptive immune phase, there was no defect in bacterial clearance or in the numbers of LM-specific IFN-gamma-producing CD8 T cells in T-bet-deficient mice and only a modest, although significant, reduction in the numbers of Th1 CD4 T cells and IFN-gamma secretion by CD4 T cells . Thus, host resistance and the generation of IFN-gamma-producing cells in response to LM infection are not substantially compromised in the absence of T-bet. Langmuir, 2004 Nov 9, 20(23), 10283 - 7 Iron and cobalt oxide and metallic nanoparticles prepared from ferritin; Hosein HA et al.; Metallic Fe and Co and Fe- and Co-based oxide nanoparticles were prepared by a novel method utilizing the biologically relevant protein ferritin . In particular, iron and cobalt oxyhydroxide nanoparticles were assembled within horse spleen and Listeria innocua derived ferritin, respectively, in the aqueous phase . Ferritin containing either Fe or Co oxide was transferred and dried on a SiO2 support where the protein shell was removed during exposure to a highly oxidizing environment . It was also shown that the metal oxide particles could be reduced to the respective metal by heating in hydrogen . X-ray photoelectron spectroscopy was used to characterize the composition of the particles and atomic force microscopy was used to characterize the size of the nanoparticles . Depending on the Fe or Co loading and/or type of ferritin used, metallic and oxide nanoparticles could be produced within a range of 20-60 A. Vet Rec, 2004 Oct 9, 155(15), 456 - 9 Listeria monocytogenes in horses in Iceland; Gudmundsdottir KB et al.; Twenty isolates of Listeria monocytogenes associated with five confirmed and four suspected incidents of listeriosis in horses in Iceland were characterised by serotyping, pulsed-field gel electrophoresis and ribotyping . Semiquantitative estimates of the numbers of L monocytogenes were made on faeces from horses with clinical signs of listeriosis and on grass silage fed to them . Large numbers of L monocytogenes were often found in the faeces of horses with severe signs of disease . The 20 isolates could be divided into six genotypes, each incident involving only one genotype . One serovar 1/2a genotype was associated with three confirmed incidents of listeriosis in 1991, 1993 and 1997 . In one incident, the same genotype was isolated from the organs of a horse with listeriosis and from the spoiled grass silage fed to it. Scand J Infect Dis, 2004, 36(10), 709 - 11 Outcome of Listeria monocytogenes prosthetic valve endocarditis: as bad as it looks? Miguel-Yanes JM, Gonzalez-Ramallo VJ, Pastor L. In 1998 we presented 1 successfully treated case of Listeria monocytogenes prosthetic valve endocarditis and made a review of all the cases that had been published to date . We carry out an up-to-date review through Pub-Med of every case of Listeria monocytogenes prosthetic valve endocarditis; mortality rate is calculated and data from several clinical and therapeutical variables are collected; Fisher's exact test is used to identify those variables significantly associated with mortality . Four out of 23 patients died in hospital (17%); among all the variables included, only peripheral embolism (p=0.024), onset on a mechanical prosthesis (p=0.035) and having used only 1 antibiotic instead of a combination of drugs (p=0.026) were independently associated with mortality . Although the overall number of cases is too low to draw definite conclusions (n=23), mortality rate is lower than previously believed . Some variables that have traditionally been associated with a poor prognosis for endocarditides are not for the case of Listeria monocytogenes on valvular prostheses . It seems prudent to treat affected patients with a combination of ampicillin -- or vancomycin, if there is a history of beta-lactam allergy and ampicillin desensitization is not possible -- plus an aminoglycoside. J Food Prot, 2004 Oct, 67(10), 2296 - 301 Control of Listeria monocytogenes with combined antimicrobials on beef franks stored at 4 degrees C; Uhart M et al.; Contamination of ready-to-eat meat products such as beef franks with Listeria monocytogenes has become a major concern for the meat processing industry and an important food safety issue . The objective of this study was to determine the effectiveness of combinations of antimicrobials as aqueous dipping solutions to control L . monocytogenes on vacuum-packaged beef franks stored at 4 degrees C for 3 weeks . Commercial beef franks were dipped for 5 min in three antimicrobial solutions: pediocin (6,000 AU), 3% sodium diacetate and 6% sodium lactate combined, and a combination of the three antimicrobials . Samples were then inoculated with 10(7) CFU/g of either four L . monocytogenes strains individually or a cocktail of the four strains, vacuum packaged, and stored at 4 degrees C for 3 weeks . Sampling was carried out at day 0 and after 2 and 3 weeks of storage . Individual strains, as well as the cocktail, exhibited different responses to the antimicrobial treatments . After 2 and 3 weeks of storage at 4 degrees C, pediocin-treated beef franks showed a less than 1-log reduction for all bacterial strains . Samples treated with the sodium diacetate-sodium lactate combination showed about a 1-log reduction after 2 weeks of storage for all strains and between a 1- and 2-log reduction after 3 weeks of storage, depending on the bacterial strain . When the three antimicrobials were combined, reductions ranged between 1 and 1.5 log units and 1.5 to 2.5 log units after 2 and 3 weeks of storage, respectively, at 4 degrees C . These results indicate that the use of combined antimicrobial solutions for dipping treatments is more effective at inhibiting L . monocytogenes than treatments using antimicrobials such as pediocin separately. J Food Prot, 2004 Oct, 67(10), 2212 - 7 Improved quantitative recovery of Listeria monocytogenes from stainless steel surfaces using a one-ply composite tissue; Vorst KL et al.; Four sampling devices, a sterile environmental sponge (ES), a sterile cotton-tipped swab (CS), a sterile calcium alginate fiber-tipped swab (CAS), and a one-ply composite tissue (CT), were evaluated for quantitative recovery of Listeria monocytogenes from a food-grade stainless steel surface . Sterile 304-grade stainless steel plates (6 by 6 cm) were inoculated with approximately 106 CFU/cm2 L . monocytogenes strain Scott A and dried for 1 h . The ES and CT sampling devices were rehydrated in phosphate buffer solution . After plate swabbing, ES and CT were placed in 40 ml of phosphate buffer solution, stomached for 1 min and hand massaged for 30 s . Each CS and CAS device was rehydrated in 0.1% peptone before swabbing . After swabbing, CS and CAS were vortexed in 0.1% peptone for 1 min . Samples were spiral plated on modified Oxford agar with modified Oxford agar Rodac Contact plates used to recover any remaining cells from the stainless steel surface . Potential inhibition from CT was examined in both phosphate buffer solution and in a modified disc-diffusion assay . Recovery was 2.70, 1.34, and 0.62 log greater using CT compared with ES, CS, and CAS, respectively, with these differences statistically significant (P < 0.001) for ES and CT and for CAS, CS, and CT (P < 0.05) . Rodac plates were typically overgrown following ES, positive after CS and CAS, and negative after CT sampling . CT was noninhibitory in both phosphate buffer solution and the modified disc-diffusion assay . Using scanning electron microscopy, Listeria cells were observed on stainless steel plates sampled with each sampling device except CT . The CT device, which is inexpensive and easy to use, represents a major improvement over other methods in quantifying L . monocytogenes on stainless steel surfaces and is likely applicable to enrichment of environmental samples. J Food Prot, 2004 Oct, 67(10), 2205 - 11 Survival, growth, and thermal resistance of Listeria monocytogenes in products containing peanut and chocolate; Kenney SJ et al.; Outbreaks of listeriosis associated with the consumption of ready-to-eat foods have raised interest in determining growth, survival, and inactivation characteristics of Listeria monocytogenes in a wide range of products . A study was undertaken to determine the thermal tolerance of L . monocytogenes in a peanut-based beverage (3.1% fat), whole-fat (3.5%) milk, wholefat (4.0%) and reduced-fat (1.0%) chocolate milk, a chocolate-peanut spread (39% fat), and peanut butter (53% fat) . The D60 degrees C value (decimal reduction time at 60 degrees C) in peanut beverage (3.2 min) was not significantly different (P > 0.05) than the D60 degrees C value in whole-fat milk (3.3 min) or whole-fat chocolate milk (4.5 min) but significantly lower (P < or = 0.05) than the D60 degrees C value in reduced-fat chocolate milk (5.9 min) . The pathogen was significantly more resistant to heat when enmeshed in chocolate-peanut spread (water activity {aw} of 0.46; D60 degrees C = 37.5 min) and peanut butter (aw of 0.32; D60 degrees C = 26.0 min) than in liquid products . At 10 degrees C, the pathogen grew most rapidly in whole-fat chocolate milk and slowest in peanut beverage . At 22 degrees C, populations increased significantly within 12 and 16 h in whole-fat milk and reduced-fat chocolate milk, respectively, and within 8 h in whole-fat chocolate milk and peanut beverage . Initial populations (3.37 to 4.42 log CFU/g) of L . monocytogenes in chocolate-peanut spread and peanut butter adjusted to an aw of 0.33 and 0.65 declined, but the pathogen was not eliminated during a 24-week period at 20 degrees C . Survival was enhanced at reduced aw . Results indicate that a pasteurization process similar to that used for full-fat milk would be adequate to ensure the destruction of L . monocytogenes in peanut beverage . The pathogen survives for at least 24 weeks in chocolate-peanut spread and peanut butter at an aw range that encompasses that found in these products. J Food Prot, 2004 Oct, 67(10), 2195 - 204 Modeling the growth boundary of Listeria monocytogenes in ready-to-eat cooked meat products as a function of the product salt, moisture, potassium lactate, and sodium diacetate concentrations; Legan JD et al.; A central composite response surface design was used to determine the time to growth of Listeria monocytogenes as a function of four continuous variables: added sodium chloride (0.8 to 3.6%), sodium diacetate (0 to 0.2%), potassium lactate syrup (60% {wt/wt}; 0.25 to 9.25%), and finished-product moisture (45.5 to 83.5%) in ready-to-eat cured meat products . The design was repeated for ready-to-eat uncured meat products giving a fifth categorical variable for cure status . Products were stored at 4 degrees C . The results were modeled using a generalized regression approach . All five main effects, six two-factor interactions, and two quadratic terms were statistically significant . The model was used to show the boundary between growth and no-growth conditions at 4 degrees C using contour plots of time to growth . It was validated using independent challenge studies of cured and uncured products . Generally, the model predicted well, particularly for cured products, where it will be useful for establishing conditions that prevent the growth of L . monocytogenes . For uncured products, there was good agreement overall between predicted and observed times to growth, but the model is less thoroughly validated than for cured products . The model should initially only be used for screening of formulations likely to prevent growth of Listeria monocytogenes in uncured products, with recommendations subject to confirmation by challenge studies. Toxicol Appl Pharmacol, 2004 Nov 1, 200(3), 206 - 18 Suppression in lung defense responses after bacterial infection in rats pretreated with different welding fumes; Antonini JM et al.; Epidemiology suggests that inhalation of welding fumes increases the susceptibility to lung infection . The effects of chemically distinct welding fumes on lung defense responses after bacterial infection were compared . Fume was collected during gas metal arc (GMA) or flux-covered manual metal arc (MMA) welding using two consumable electrodes: stainless steel (SS) or mild steel (MS) . The fumes were separated into water-soluble and -insoluble fractions . The GMA-SS and GMA-MS fumes were found to be relatively insoluble, whereas the MMA-SS was highly water soluble, with the soluble fraction comprised of 87% Cr and 11% Mn . On day 0, male Sprague-Dawley rats were intratracheally instilled with saline (vehicle control) or the different welding fumes (0.1 or 2 mg/rat) . At day 3, the rats were intratracheally inoculated with 5 x 10(3) Listeria monocytogenes . On days 6, 8, and 10, left lungs were removed, homogenized, cultured overnight, and colony-forming units were counted to assess pulmonary bacterial clearance . Bronchoalveolar lavage (BAL) was performed on right lungs to recover phagocytes and BAL fluid to measure the production of nitric oxide (NO) and immunomodulatory cytokines, including tumor necrosis factor-alpha (TNF-alpha), interleukin (IL)-2, IL-6, and IL-10 . In contrast to the GMA-SS, GMA-MS, and saline groups, pretreatment with the highly water soluble MMA-SS fume caused significant body weight loss, extensive lung damage, and a dramatic reduction in pulmonary clearance of L . monocytogenes after infection . NO concentrations in BAL fluid and lung immunostaining of inducible NO synthase were dramatically increased in rats pretreated with MMA-SS before and after infection . MMA-SS treatment caused a significant decrease in IL-2 and significant increases in TNF-alpha, IL-6, and IL-10 after infection . In conclusion, pretreatment with MMA-SS increased production of NO and proinflammatory cytokines (TNF-alpha and IL-6) after infection, which are likely responsible for the elevation in lung inflammation and injury . In addition, MMA-SS treatment reduced IL-2 (involved in T cell proliferation) and enhanced IL-10 (involved in inhibiting macrophage function) after bacterial infection, which might result in a possible suppression in immune response and an increase in susceptibility to infection. Infect Immun, 2004 Nov, 72(11), 6418 - 25 Listeria monocytogenes-based antibiotic resistance gene-free antigen delivery system applicable to other bacterial vectors and DNA vaccines; Verch T et al.; Plasmids represent a powerful tool to rapidly introduce genes into bacteria and help them reach high expression levels . In vaccine development, with live vaccine vectors, this allows greater flexibility and the ability to induce larger antigen amounts through multiple gene copies . However, plasmid retention often requires antibiotic resistance markers, the presence of which has been discouraged in clinical applications by the Food and Drug Administration . Therefore, we developed a Listeria monocytogenes-Escherichia coli shuttle plasmid that is retained by complementation of D-alanine racemase-deficient mutant strains both in vitro and in vivo . Our technology potentially allows the production of antibiotic resistance marker-free DNA vaccines as well as bacterial vaccine vectors devoid of engineered antibiotic resistances . As a proof of concept, we applied the D-alanine racemase complementation system to our Listeria cancer vaccine platform . With a transplantable tumor model, we compared the efficacy of the new Listeria vector to that of an established vector containing a conventional plasmid carrying a tumor-specific antigen . Both vaccine vector systems resulted in long-term regression of established tumors, with no significant difference between them . Thus, the Listeria vaccine vector presented here potentially complies with Food and Drug Administration regulations and could be developed further for clinical use. Res Microbiol, 2004 Nov, 155(9), 741 - 6 Species-specific PCR determination of Listeria seeligeri; Liu D et al.; Listeria seeligeri is a non-pathogenic bacterium coming under the genus Listeria . As this bacterium resembles other Listeria species such as L . monocytogenes and L . ivanovii that are pathogenic to man and animals, it is important that rapid and precise identification techniques be available for L . seeligeri in cases where such determination is desirable . A specific molecular test on the basis of a uniquely present gene region in L . seeligeri will be of particular value under the circumstances . In this report, after comparative screening of genomic DNA from six Listeria species by dot blot hybridization, we isolated one L . seeligeri-specific clone (lse24-315) that contains an insert of 1538 bp . Using primers (lse24-315F and lse24-315R) derived from this clone, we showed that a specific PCR product of 375 bp was generated from genomic DNA of L . seeligeri strains only, but not of other Listeria species or common bacteria . Therefore, the PCR employing primers lse24-315F and lse24-315R provides a rapid, sensitive and specific method for distinguishing L . seeligeri from other Listeria and common bacteria. J Immunol, 2004 Nov 1, 173(9), 5679 - 87 Duration of infection and antigen display have minimal influence on the kinetics of the CD4+ T cell response to Listeria monocytogenes infection; Corbin GA et al.; The T cell response to infection consists of clonal expansion of effector cells, followed by contraction to memory levels . It was previously thought that the duration of infection determines the magnitude and kinetics of the T cell response . However, recent analysis revealed that transition between the expansion and contraction phases of the Ag-specific CD8+ T cell response is not affected by experimental manipulation in the duration of infection or Ag display . We studied whether the duration of infection and Ag display influenced the kinetics of the Ag-specific CD4+ T cell response to Listeria monocytogenes (LM) infection . We found that truncating infection and Ag display with antibiotic treatment as early as 24 h postinfection had minimal impact on the expansion or contraction of CD4+ T cells; however, the magnitudes of the Ag-specific CD4+ and CD8+ T cell responses were differentially affected by the timing of antibiotic treatment . Treatment of LM-infected mice with antibiotics at 24 h postinfection did not prevent generation of detectable CD4+ and CD8+ memory T cells at 28 days after infection, vigorous secondary expansion of these memory T cells, or protection against a subsequent LM challenge . These results demonstrate that events within the first few days of infection stimulate CD4+ and CD8+ T cell responses that are capable of carrying out the full program of expansion and contraction to functional memory, independently of prolonged infection or Ag display. J Immunol, 2004 Nov 1, 173(9), 5652 - 8 Reduced apoptosis and ameliorated listeriosis in TRAIL-null mice; Zheng SJ et al.; Listeriosis is an infectious disease caused by the bacterium Listeria monocytogenes . Although it is well recognized that apoptosis plays a critical role in the pathogenesis of the disease, the molecular mechanisms of cell death in listeriosis remain to be established . We report in this study that mice deficient in TRAIL were partially resistant to primary listeriosis, and blocking TRAIL with a soluble death receptor 5 markedly ameliorated the disease . The numbers of Listeria in the liver and spleen of TRAIL+/+ mice were 10-100 times greater than those in TRAIL-/- mice following primary Listeria infection . This was accompanied by a significant increase in the survival rate of TRAIL-/- mice . Lymphoid and myeloid cell death was significantly inhibited in TRAIL-/- mice, which led to marked enlargement of the spleen . These results establish a critical role for TRAIL in apoptosis during listeriosis. J Immunol, 2004 Nov 1, 173(9), 5644 - 51 Cross-presentation of Listeria-derived CD8 T cell epitopes requires unstable bacterial translation products; Janda J et al.; Presentation of bacteria-derived CD8 T cell epitopes by dendritic cells (DC) requires either their direct infection or that DC acquire and cross-present Ags from other infected cells . We found that cross-presentation of Listeria monocytogenes-derived CD8 T cell epitopes was much stronger than direct Ag presentation by infected murine DC . Cross-presentation of Listeria-derived CD8 T cell epitopes showed unique physiological requirements . It was dependent upon the delivery of unstable bacterial translation products by infected, but still viable, Ag donor cells . Cross-presentation was enhanced both when unstable translation products in infected Ag donor cells were protected from proteasomal degradation and when the production of misfolded bacterial proteins was increased . The requirement of unstable translation products for cross-presentation may represent a novel pathway that functions to focus the CD8 T cell response toward epitopes derived from newly synthesized proteins. Biochem Soc Trans, 2004 Nov, 32(Pt 5), 712 - 4 Lipid rafts clustering and signalling by listeriolysin O; Gekara NO et al.; Listeriolysin O, the major virulent determinant of Listeria monocytogenes, is known for forming pores on cholesterol-rich membranes . In the present study, we reveal its other facet, rafts clustering . By immunofluorescence microscopy, we show that the glycosylphosphatidylinositol-anchored proteins CD14 and CD24, which normally exhibit uniform distribution on J774 cells, undergo clustering upon treatment with LLO . The non-raft marker transferrin receptor is unaffected by such treatment . Rafts clustering might explain the induction of tyrosine phosphorylation observed on LLO-treated cells. J AOAC Int, 2004 Sep-Oct, 87(5), 1123 - 32 Evaluation of VIDAS listeria monocytogenes II (LMO2) immunoassay method for the detection of Listeria monocytogenes in foods: collaborative study; Silberiagel KM et al.; A multilaboratory study was conducted to compare the VIDAS Listeria monocytogenes II (LMO2) immunoassay and the standard cultural methods for the detection of Listeria monocytogenes in foods . Five food types-vanilla ice cream, brie cheese, cooked roast beef, frozen green beans, and frozen tilapia fish-at 3 levels were analyzed by each method . A total of 26 laboratories representing government and industry participated . In this study, 1404 test portions were analyzed of which 1152 were used in the statistical analysis . There were 448 positive by the VIDAS LMO2 assay and 457 positive by the standard culture methods . A chi2 analysis of each of the 5 food types, at the 3 inoculation levels tested, was performed . The resulting chi2 value, 0.36, indicates that overall, there are no statistical differences between the VIDAS LMO2 assay and the standard methods at the 5% level of significance. Proc Natl Acad Sci U S A, 2004 Oct 26, 101(43), 15440 - 5 Epub 2004 Oct 15. A totally synthetic vaccine of generic structure that targets Toll-like receptor 2 on dendritic cells and promotes antibody or cytotoxic T cell responses; Jackson DC et al.; A simple generic peptide-based vaccine structure that targets Toll-like receptor 2-expressing dendritic cells and causes their activation is described . The vaccines are totally synthetic, serve as their own adjuvant, and are composed of (i) a single helper T cell epitope, (ii) a target epitope that is either recognized by CD8+ T cells or B cells, and (iii) a Toll-like receptor 2-targeting lipid moiety, S-{2,3-bis(palmitoyloxy)propyl}cysteine, that is situated between the peptide epitopes to form a branched configuration . The different CD8+ T cell epitopes examined were from (i) influenza virus, (ii) the intracellular bacterium Listeria monocytogenes, and (iii) ovalbumin as a model tumor antigen . Vaccines containing a B cell epitope from gastrin or luteinizing hormone-releasing hormone as a B cell epitope were also examined for their ability to elicit antibody against the parent hormones . Each of the vaccines was capable of inducing either CD8+ T cell or antibody-mediated immune responses . The lipidated vaccines, but not the nonlipidated vaccines, were able to mediate protection against viral or bacterial infection and mediate prophylactic and therapeutic anticancer activity . The two hormone-based vaccines induced high antibody titers, which in the case of luteinizing hormone-releasing hormone resulted in abrogation of reproductive function . These results highlight the utility of simple, totally synthetic, epitope-based vaccines. Annu Rev Microbiol, 2004, 58, 587 - 610 Molecular determinants of Listeria monocytogenes virulence; Dussurget O et al.; Listeria monocytogenes is the etiological agent of listeriosis, a severe human foodborne infection characterized by gastroenteritis, meningitis, encephalitis, abortions, and perinatal infections . This gram-positive bacterium is a facultative intracellular pathogen that induces its own uptake into nonphagocytic cells and spreads from cell to cell using an actin-based motility process . This review covers both well-established and recent advances in the characterization of L . monocytogenes virulence determinants and their role in the pathophysiology of listeriosis. J Cancer Res Clin Oncol, 2005 Jan, 131(1), 49 - 59 Epub 2005 Jan. Listeria monocytogenes produces a pro-invasive factor that signals via ErbB2/ErbB3 heterodimers; Oliveira MJ et al.; PURPOSE . We have previously demonstrated that conditioned medium from bacteria, some of which were isolated from the colon of cancer patients, stimulate cancer cell invasion in vitro through a 13-mer beta-casein-derived peptide . Since invasion signalling pathways are coordinated by the balance between protein kinases and phosphatases, we investigated the effect of conditioned medium from bacteria on the overall cellular tyrosine phosphorylation . METHODS . The tyrosine phosphorylation level of HCT-8/E11 human colon cancer cells treated with the pro-invasive conditioned medium of Listeria, prepared on top of collagen type I gels (CM(Coll) Listeria/TSB), were analysed by means of immunoprecipitation and Western blot, with specific anti-phosphotyrosine antibodies . RESULTS . We demonstrated that CM(Coll) Listeria/TSB increases the tyrosine phosphorylation level of ErbB2 and ErbB3, members of the epidermal growth factor receptor (EGFR) family, and the association between ErbB3 and the phosphatidylinositol 3-kinase (PI3K) regulatory subunit (p85alpha) . CM(Coll) Listeria/TSB-stimulated ErbB3 tyrosine phosphorylation and cancer cell invasion were independent from EGFR expression and activity but dependent on ErbB2 activity . CONCLUSIONS . The interaction between Listeria and collagen type I produces, next to the 13-mer peptide, at least another pro-invasive factor that signals via ErbB2/ErbB3 heterodimers. Ophthalmologe . 2004 Oct 7; {Epub ahead of print} {Listeria endophthalmitis.}; Berger E et al.; Listeria monocytogenes is a rare cause of endogenous endophthalmitis . During the last 20 years about 30 cases have been published, all of which showed similar clinical features and a profound visual loss mainly owing to delayed diagnosis . This case report is about an otherwise healthy 41-year-old woman whose diagnosis was established 17 days after the onset of symptoms by microbiological cultures . Under sufficient therapy signs of local inflammation disappeared and intraocular pressure decreased . Pars plana vitrectomy was necessary; although post-surgery complications developed, the result was complete recovery of visual acuity. Cancer Immunol Immunother . 2004 Oct 6; {Epub ahead of print} Tumor sensitivity to IFN-gamma is required for successful antigen-specific immunotherapy of a transplantable mouse tumor model for HPV-transformed tumors; Dominiecki ME et al.; Purpose: Many human tumors lose responsiveness to IFN-gamma, providing a possible mechanism for the tumor to avoid immune recognition and destruction . Here we investigate the importance of tumor responsiveness to IFN-gamma in the successful immunotherapy of TC1 tumors that were immortalized with human papillomavirus proteins E6 and E7 . Methods: To investigate the role of IFN-gamma in vivo, we constructed a variant of TC1, TC1.mugR, that is unresponsive to IFN-gamma due to overexpression of a dominant negative IFN-gamma receptor . Results: Using recombinant Listeria monocytogenes that express HPV-16 E7 (Lm-LLO-E7) to stimulate an antitumor response, we demonstrate that sensitivity to IFN-gamma is required for therapeutic efficacy in that Lm-LLO-E7 induces regression of TC1 tumors but not TC1.mugR . In addition, we show that tumor sensitivity to IFN-gamma is not required for inhibition of tumor angiogenesis by Lm-LLO-E7 or for trafficking of CD4(+) and CD8(+) T cells to the tumor . However, it is required for penetration of lymphocytes into the tumor mass in vivo . Conclusions: Our findings identify a role for IFN-gamma in immunity to TC1 tumors and show that loss of tumor responsiveness to IFN-gamma poses a challenge to antigen-based immunotherapy. Cell, 2004 Oct 15, 119(2), 299 - 309 LXR-dependent gene expression is important for macrophage survival and the innate immune response; Joseph SB et al.; The liver X receptors (LXRs) are nuclear receptors with established roles in the regulation of lipid metabolism . We now show that LXR signaling not only regulates macrophage cholesterol metabolism but also impacts antimicrobial responses . Mice lacking LXRs are highly susceptible to infection with the intracellular bacteria Listeria monocytogenes (LM) . Bone marrow transplant studies point to altered macrophage function as the major determinant of susceptibility . LXR-null macrophages undergo accelerated apoptosis when challenged with LM and exhibit defective bacterial clearance in vivo . These defects result, at least in part, from loss of regulation of the antiapoptotic factor SPalpha, a direct target for regulation by LXRalpha . Expression of LXRalpha or SPalpha in macrophages inhibits apoptosis in the setting of LM infection . Our results demonstrate that LXR-dependent gene expression plays an unexpected role in innate immunity and suggest that common nuclear receptor pathways mediate macrophage responses to modified lipoproteins and intracellular pathogens. Cell, 2004 Oct 15, 119(2), 149 - 51 A nuclear strike against Listeria--the evolving life of LXR; Barish GD et al.; LXRs are members of the nuclear receptor superfamily and function as master regulators of cholesterol metabolism . In the macrophage, they control cholesterol efflux and inhibit the transcription factor NF-kappaB-mediated proinflammatory responses . In this issue of Cell, discover surprising, protective functions for LXRalpha in innate immunity. J Agric Food Chem, 2004 Oct 20, 52(21), 6585 - 91 Antimicrobial and physicochemical properties of chitosan-HPMC-based films; Moller H et al.; To prepare composite films from biopolymers with anti-listerial activity and moisture barrier properties, the antimicrobial efficiency of chitosan-hydroxy propyl methyl cellulose (HPMC) films, chitosan-HPMC films associated with lipid, and chitosan-HPMC films chemically modified by cross-linking were evaluated . In addition, the physicochemical properties of composite films were evaluated to determine their potential for food applications . The incorporation of stearic acid into the composite chitosan-HPMC film formulation decreased water sensitivity such as initial solubility in water and water drop angle . Thus, cross-linking of composite chitosan-HPMC, using citric acid as the cross-linking agent, led to a 40% reduction in solubility in water . The water vapor transfer rate of HPMC film, approximately 270 g x m(-2) x day(-1) x atm(-1), was improved by incorporating chitosan and was further reduced 40% by the addition of stearic acid and/or cross-linking . Anti-listerial activity of films was determined on solid medium by a numeration technique . Chitosan-HPMC-based films, with and without stearic acid, inhibited the growth of Listeria monocytogenes completely . On the other hand, a loss of antimicrobial activity after chemical cross-linking modification was observed . FTIR and 13C NMR analyses were then conducted in order to study a potential chemical modification of biopolymers such as a chemical reaction with the amino group of chitosan . To complete the study, the mechanical properties of composite films were determined from tensile strength assays . Pol J Microbiol, 2004, 53(2), 75 - 88 Classes and functions of Listeria monocytogenes surface proteins; Popowska M et al.; Listeria monocytogenes is an opportunistic pathogen that causes infections collectively termed listeriosis, which are related to the ingestion of food contaminated with these gram-positive rods . The pathogenicity of L . monocytogenes is determined by the following virulence factors: listeriolysin O, protein ActA, two phospholipases C, internalins (In1A and In1B), protein CwhA and a metalloprotease . The bacterium is a model organism in studies on the pathogenesis of intracellular parasites . It is able to penetrate, multiply and propagate in various types of eukaryotic cells and is also able to overcome the three main barriers encountered in the host: the intestinal barrier, the blood-brain barrier and the placenta . Based on L . monocytogenes genome sequence analysis 133 surface proteins have been identified . In particular, the large number of proteins covalently bound to murein sets L . monocytogenes apart from other gram-positive bacteria . The ability of this pathogen to multiply in various environments as well as the possibility of its interaction with many kinds of eukaryotic cells is, in fact, made possible by the large number of surface proteins. J Immunol, 2004 Oct 15, 173(8), 5112 - 20 The host resistance locus sst1 controls innate immunity to Listeria monocytogenes infection in immunodeficient mice; Boyartchuk V et al.; Epidemiological, clinical, and experimental approaches have convincingly demonstrated that host resistance to infection with intracellular pathogens is significantly influenced by genetic polymorphisms . Using a mouse model of infection with virulent Mycobacterium tuberculosis (MTB), we have previously identified the sst1 locus as a genetic determinant of host resistance to tuberculosis . In this study we demonstrate that susceptibility to another intracellular pathogen, Listeria monocytogenes, is also influenced by the sst1 locus . The contribution of sst1 to anti-listerial immunity is much greater in immunodeficient scid mice, indicating that this locus controls innate immunity and becomes particularly important when adaptive immunity is significantly depressed . Similar to our previous observations using infection with MTB, the resistant allele of sst1 prevents formation of necrotic infectious lesions in vivo . We have shown that macrophages obtained from sst1-resistant congenic mice possess superior ability to kill L . monocytogenes in vitro . The bactericidal effect of sst1 is dependent on IFN-gamma activation and reactive oxygen radical production by activated macrophages after infection, but is independent of NO production . It is possible that there is a single gene that controls common IFN-dependent macrophage function, which is important in the pathogenesis of infections caused by both MTB and L . monocytogenes . However, host resistance to the two pathogens may be controlled by two different polymorphic genes encoded within the sst1 locus . The polymorphic gene(s) encoded within the sst1 locus that controls macrophage interactions with the two intracellular pathogens remains to be elucidated. Appl Environ Microbiol, 2004 Oct, 70(10), 6299 - 301 Rapid quantitative detection of Listeria monocytogenes in meat products by real-time PCR; Rodriguez-Lazaro D et al.; We describe a quick and simple method for the quantitative detection of Listeria monocytogenes in meat products . This method is based on filtration, Chelex-100-based DNA purification, and real-time PCR . It can detect as few as 100 CFU/g and quantify as few as 1,000 CFU/g, with excellent accuracy compared to that of the plate count method . Therefore, it is a promising alternative for the detection of L . monocytogenes in meat products. Appl Environ Microbiol, 2004 Oct, 70(10), 5833 - 41 Listeria monocytogenes isolates from foods and humans form distinct but overlapping populations; Gray MJ et al.; A total of 502 Listeria monocytogenes isolates from food and 492 from humans were subtyped by EcoRI ribotyping and PCR-restriction fragment length polymorphism analysis of the virulence gene hly . Isolates were further classified into genetic lineages based on subtyping results . Food isolates were obtained through a survey of selected ready-to-eat food products in Maryland and California in 2000 and 2001 . Human isolates comprised 42 isolates from invasive listeriosis cases reported in Maryland and California during 2000 and 2001 as well as an additional 450 isolates from cases that had occurred throughout the United States, predominantly from 1997 to 2001 . Assignment of isolates to lineages and to the majority of L . monocytogenes subtypes was significantly associated with the isolate source (food or human), although most subtypes and lineages included both human and food isolates . Some subtypes were also significantly associated with isolation from specific food types . Tissue culture plaque assay characterization of the 42 human isolates from Maryland and California and of 91 representative food isolates revealed significantly higher average infectivity and cell-to-cell spread for the human isolates, further supporting the hypothesis that food and human isolates form distinct populations . Combined analysis of subtype and cytopathogenicity data showed that strains classified into specific ribotypes previously linked to multiple human listeriosis outbreaks, as well as those classified into lineage I, are more common among human cases and generate larger plaques than other subtypes, suggesting that these subtypes may represent particularly virulent clonal groups . These data will provide a framework for prediction of the public health risk associated with specific L . monocytogenes subtypes. J Bacteriol, 2004 Oct, 186(20), 6721 - 7 Flagellin from Listeria monocytogenes is glycosylated with beta-O-linked N-acetylglucosamine; Schirm M et al.; Glycan staining of purified flagellin from Listeria monocytogenes serotypes 1/2a, 1/2b, 1/2c, and 4b suggested that the flagellin protein from this organism is glycosylated . Mass spectrometry analysis demonstrated that the flagellin protein of L . monocytogenes is posttranslationally modified with O-linked N-acetylglucosamine (GlcNAc) at up to six sites/monomer . The sites of glycosylation are all located in the central, surface-exposed region of the protein monomer . Immunoblotting with a monoclonal antibody specific for beta-O-linked GlcNAc confirmed that the linkage was in the beta configuration, this residue being a posttranslational modification commonly observed in eukaryote nuclear and cytoplasmic proteins. Parasitol Today, 1988 Dec, 4(12), 340 - 7 Oxidative killing of intracellular parasites mediated by macrophages; Hughes HP; An important function of macrophages is to eliminate invading pathogens, and one of their main weapons involves the generation of lethal oxygen radicals . Yet some parasites and pathogens - notably Leishmania, Toxoplasma, and Listeria and Mycobacterium - make use of macrophages as their primary cellular hosts displaying a capacity to survive the oxidative killing mechanisms of these host cells . It is now clear that more than one pathway is involved in the activation of macrophages to kill intracellular pathogens . Here, Huw Hughes discusses the biochemistry of the oxidative metabolism of macrophages, and the steps taken by parasites to survive within this hostile environment. Nat Rev Immunol, 2004 Oct, 4(10), 812 - 23 Immune responses to Listeria monocytogenes; Pamer EG; Listeria monocytogenes is a Gram-positive bacterium that is often used to study the mammalian immune response to infection because it is easy to culture, is relatively safe to work with and causes a highly predictable infection in laboratory mice . The broad application of this mouse model has resulted in a torrent of studies characterizing the contributions of different cytokines, receptors, adaptors and effector molecules to resistance against infection with Listeria monocytogenes . These studies, which are yielding one of the most comprehensive pictures of the 'battle' between host and microorganism, are reviewed here. J Food Prot, 2004 Sep, 67(9), 1866 - 75 Combining pediocin with postpackaging irradiation for control of Listeria monocytogenes on frankfurters; Chen CM et al.; Frankfurters, in 1-link, 5-link, or 10-link packages, were surface inoculated with a five-strain mixture of Listeria monocytogenes (3.40 or 5.20 log CFU/g) after treatment with 3,000 arbitrary units (AU) or 6,000 AU of pediocin (in ALTA 2341) per link . The frankfurters were vacuum packaged, after which the 1-link and 5-link packages were irradiated at 1.2 or 2.3 kGy and the 10-link packages were irradiated at 1.4 or 3.5 kGy . L . monocytogenes was enumerated following the treatments . Selected treatments were subsequently evaluated during storage at 4, 10, and 25 degrees C for up to 12 weeks . Combination of pediocin with postpackaging irradiation at 1.2 kGy or more was necessary to achieve a 50% reduction of L . monocytogenes on frankfurters in 1-link or 5-link packages . The combination of 6,000 AU of pediocin and irradiation at 2.3 kGy or more was effective in all package sizes for inhibition of the pathogen for 12 weeks at 4 or 10 degrees C . There was a synergistic effect between pediocin and irradiation for inhibition of L . monocytogenes . Storage at 4 degrees C enhanced the antilisterial effects of the treatment combinations, with little or no growth of the pathogen in 1-link or 5-link packages during 12 weeks of storage . In general, these treatments did not affect the sensory quality of frankfurters. J Food Prot, 2004 Sep, 67(9), 1855 - 65 Combining pediocin (ALTA 2341) with postpackaging thermal pasteurization for control of Listeria monocytogenes on frankfurters; Chen CM et al.; Frankfurters packaged in 1-link, 5-link, or 10-link packages were surface-inoculated with a five-strain mixture of Listeria monocytogenes (3.40 or 5.20 log CFU/g) after treatments with 3,000 arbitrary units (AU) or 6,000 AU pediocin (in ALTA 2341) per link . The frankfurters were vacuum packaged, after which the packages were heated in hot water at 71, 81, or 96 degrees C for 30, 60, or 120 s . L . monocytogenes was enumerated following the treatments . Selected treatments were subsequently evaluated during storage at 4, 10, and 25 degrees C for up to 12 weeks . L . monocytogenes was reduced by all treatments, but 81 degrees C or more for at least 60 s in combination with pediocin (Pdn-6000) was necessary to achieve a 50% reduction of initial inoculations . Heat treatments were most effective for 1-link packages and least effective for 10-link packages . Little or no growth of L . monocytogenes occurred on frankfurters for 12 weeks at 4 or 10 degrees C, and for 12 days at 25 degrees C . Generally, the treatments mentioned above did not significantly (P > 0.05) affect the sensory qualities of frankfurters . Therefore, pediocin (in ALTA 2341) in combination with postpackaging thermal treatment offers an effective treatment combination for improved control of L . monocytogenes on frankfurters. J Food Prot, 2004 Sep, 67(9), 1848 - 54 Inactivation of Listeria innocua in nisin-treated salmon (Oncorhynchus keta) and sturgeon (Acipenser transmontanus) caviar heated by radio frequency; Al-Holy M et al.; Recent regulatory concerns about the presence of the pathogen Listeria monocytogenes in ready-to-eat aquatic foods such as caviar has prompted the development of postpackaging pasteurization processes . However, caviar is heat labile, and conventional pasteurization processes affect the texture, color, and flavor of these foods negatively . In this study, chum salmon (Oncorhynchus keta, 2.5% total salt) caviar or ikura and sturgeon (Acipenser transmontanus, 3.5% total salt) caviar were inoculated with three strains of Listeria innocua in stationary phase at a level of more than 10(7) CFU/g . L innocua strains were used because they exhibit an equivalent response to L monocytogenes for many physicochemical processing treatments, including heat treatment . The products were treated by immersion in 500 IU/ml nisin solution and heat processed (an 8-D process without nisin or a 4-D process with 500 IU/ml nisin) in a newly developed radio frequency (RF; 27 MHz) heating method at 60, 63, and 65 degrees C . RF heating along with nisin acted synergistically to inactivate L . innocua cells and total mesophilic microorganisms . In the RF-nisin treatment at 65 degrees C, no surviving L . innocua microbes were recovered in sturgeon caviar or ikura . The come-up times in the RF-heated product were significantly lower compared with the water bath-heated caviar at all treatment temperatures . The visual quality of the caviar products treated by RF with or without nisin was comparable to the untreated control. FEMS Microbiol Lett, 2004 Oct 1, 239(1), 157 - 61 Resistance of Gram-positive bacteria to nisin is not determined by lipid II levels; Kramer NE et al.; Lipid II is essential for nisin-mediated pore formation at nano-molar concentrations . We tested whether nisin resistance could result from different Lipid II levels, by comparing the maximal Lipid II pool in Micrococcus flavus (sensitive) and Listeria monocytogenes (relatively insensitive) and their nisin-resistant variants, with a newly developed method . No correlation was observed between the maximal Lipid II pool and nisin sensitivity, as was further corroborated by using spheroplasts of nisin-resistant and wild-type strains of M . flavus, which were equally sensitive to nisin. FEMS Microbiol Lett, 2004 Oct 1, 239(1), 63 - 70 Influence of environmental conditions on the expression of virulence factors by Listeria monocytogenes and their use in species identification; Lemes-Marques EG et al.; The hemolytic, lecithinase or phosphatidylinositol-specific phospholipase C activities of Listeria monocytogenes can be used to differentiate this pathogenic bacteria from L . innocua, apathogenic, frequently isolated from environmental sources and food . However, the interpretation of these characteristics is problematic because of the variation in the expression of virulence factors by L . monocytogenes, which can be influenced by environmental conditions . We used a cheap, simple plate assay to monitor this expression in strains obtained from various sources and grown under different culture conditions . The results were increasingly significant and were obtained adding activated charcoal and different salts to the culture media, and in some cases changing the culture temperature, all with a rigorous control on the process of media sterilization. Infect Immun, 2004 Oct, 72(10), 5622 - 9 Growth, virulence, and immunogenicity of Listeria monocytogenes aro mutants; Stritzker J et al.; Mutants of Listeria monocytogenes with deletions in genes of the common branch of the biosynthesis pathway leading to aromatic compounds were constructed as possible virulence-attenuated carrier strains for protein antigens or vaccine DNA . aroA, aroB, and in particular aroE mutants showed strongly reduced growth rates in epithelial cells and even in rich culture media . The metabolism of the aro mutants under these conditions was predominantly anaerobic . Aerobic metabolism and a wild-type growth rate were, however, regained upon the addition of vitamin K2, suggesting that the aro mutants are deficient in oxidative respiration due to the lack of menaquinone . Replication of the aro mutants in the host cell's cytosol and cell-to-cell spread were drastically slowed down, and all aro mutants showed high virulence attenuation in mice, i.e., the 50% lethal dose in BALB/c mice was increased at least 10(4)-fold for the aroA, aroB, and aroA/B mutants and >10(5)-fold for the aroE mutant compared to the parent strain . Nevertheless, mice preimmunized with aro mutant bacteria elicited good T-cell response and full protection against a subsequent challenge with the virulent wild-type strain . A total of 5 x 10(6) aroA, aroB, and aroA/B mutant bacteria were sufficient to obtain a protective T-cell response, while 5 x 10(8) aroE or aroA/E mutants were necessary to achieve comparable numbers of antigen-specific T cells . These numbers were well tolerated without causing any signs of disease, indicating that Listeria strains with deletions in genes of the basic branch of the aromatic amino acid pathway could be useful vaccine carriers for inducing T-cell immunity. Eur J Immunol, 2004 Nov, 34(11), 3070 - 81 Expression of selectin ligands on murine effector and IL-10-producing CD4+ T cells from non-infected and infected tissues; Kretschmer U et al.; Endothelial selectins are crucial for the recruitment of leukocytes into sites of inflammation . On T cells, ligands for selectins become induced upon differentiation into the effector/memory stage . Initial in vitro studies suggested a correlation between the Th1 phenotype and ligand expression, but whether this also holds true in vivo remained uncertain . We here analyzed selectin ligands on CD4+ T cells producing IFN-gamma, IL-4 or IL-10, prototypic cytokines of the Th1, Th2 and Tr1 subset, respectively . We analyzed mice infected with influenza virus, the bacterium Listeria, and the parasites Toxoplasma (all Th1 models) or Nippostrongylus (Th2 model) . A link between the Th1 phenotype and ligand expression was not found in vivo . Surprisingly, the potentially regulatory IL-10-producing T cells displayed the highest frequency of ligand-positive cells in general . Within the inflamed tissues, the frequencies of P-selectin-binding cells increased in the dominant subset, either Th1 or Th2 . Up-regulation was also found for E-selectin ligands during influenza, but not Nippostrongylus infection . In conclusion, conditions driving T cell polarization into either Th1 or Th2 in vivo do not affect the expression of selectin ligands, but acquisition of P-selectin binding and hence migration into inflamed tissues is boosted by an inflammatory milieu. J Immunol, 2004 Oct 1, 173(7), 4324 - 30 Intestinal epithelial antigen induces mucosal CD8 T cell tolerance, activation, and inflammatory response; Liu Z et al.; Intestinal autoimmune diseases are thought to be associated with a breakdown in tolerance, leading to mucosal lymphocyte activation perhaps as a result of encounter with bacterium-derived Ag . To study mucosal CD8(+) T cell activation, tolerance, and polarization of autoimmune reactivity to self-Ag, we developed a novel (Fabpl(4x at -132)-OVA) transgenic mouse model expressing a truncated form of OVA in intestinal epithelia of the terminal ileum and colon . We found that OVA-specific CD8(+) T cells were partially tolerant to intestinal epithelium-derived OVA, because oral infection with Listeria monocytogenes-encoding OVA did not elicit an endogenous OVA-specific MHC class I tetramer(+)CD8(+) T cell response and IFN-gamma-, IL-4-, and IL-5-secreting T cells were decreased in the Peyer's patches, mesenteric lymph nodes, and intestinal mucosa of transgenic mice . Adoptive transfer of OVA-specific CD8(+) (OT-I) T cells resulted in their preferential expansion in the Peyer's patches and mesenteric lymph nodes and subsequently in the epithelia and lamina propria but failed to cause mucosal inflammation . Thus, CFSE-labeled OT-I cells greatly proliferated in these tissues by 5 days posttransfer . Strikingly, OT-I cell-transferred Fabpl(4x at -132)-OVA transgenic mice underwent a transient weight loss and developed a CD8(+) T cell-mediated acute enterocolitis 5 days after oral L . monocytogenes-encoding OVA infection . These findings indicate that intestinal epithelium-derived "self-Ag" gains access to the mucosal immune system, leading to Ag-specific T cell activation and clonal deletion . However, when Ag is presented in the context of bacterial infection, the associated inflammatory signals drive Ag-specific CD8(+) T cells to mediate intestinal immunopathology. Mil Med, 2004 Aug, 169(8), 600 - 3 A survey of preprocedural antiseptic mouth rinse use in Army dental clinics; Hennessy B et al.; OBJECTIVE: The objective of this project was to evaluate the use of preprocedural mouth rinses in Army dental clinics . MATERIALS AND METHODS: Three hundred six-question surveys were distributed to 10 Army dental organizations throughout the United States and Germany during the period from March 2001 to March 2002 . Two hundred fifty-four surveys were completed and returned . Simple mathematics were used to evaluate answers to the questionnaires . RESULTS: The 254 respondents included military dentists (n = 190), civilian dentists used by the military (n = 27), registered dental hygienists (n = 20), and military-trained dental hygiene technicians (n = 17) . Eighty-four and one-tenth percent of respondents (n = 216) use preprocedural rinses in their practices to prevent possible disease transmission (n = 85) or to decrease chances of postoperative infection (n = 167) . Chlorhexidine gluconate (n = 170) and phenol-based essential oil preparations (n = 84) are the most commonly used products . The perceived greatest benefits of preprocedural rinsing are to decrease oral bacterial load (38%), to decrease incidence of postoperative infection (21%), and to decrease aerosolization of bacteria (8.66%) . CONCLUSIONS: Army dental clinics make extensive use of antimicrobial preprocedural rinses . Chlorhexidine and Listerine (Warner-Lambert Consumer Healthcare, Morris Plains, NJ) are the most commonly used products . Currently available literature appears to support the use of these products in preventing or diminishing the chances of postoperative infection. Proteomics, 2004 Oct, 4(10), 2991 - 3006 The cell wall subproteome of Listeria monocytogenes; Schaumburg J et al.; The surface subproteome of Listeria monocytogenes that includes many proteins already known to be involved in virulence and interaction with host cells has been characterized . A new method for the isolation of a defined surface proteome of low complexity has been established based on serial extraction of proteins by different salts at high concentration, and in all 55 proteins were identified by N-terminal sequencing and mass spectrometry . About 16% of these proteins are of unknown function and three proteins have no orthologue in the nonpathogenic L . innocua and might be involved in virulence mechanisms . Remarkably, a relatively high number of proteins with a function in the cytoplasmic compartment was identified in this surface proteome . These proteins had neither predicted or detectable signal peptides nor could any modification be observed except removal of the N-terminal methionine . Enolase (Lmo2455) is one of these proteins . It was shown to be present in the cell wall of the pathogen by immunoelectron microscopy and, along with heat shock factor DnaK (Lmo1473), elongation factor TU (Lmo2653), and glyceraldehyde-3-phosphate dehydrogenase (Lmo2459), it was found to be able to bind human plasminogen in overlay blots and surface plasmon resonance (SPR) experiments . The KD values of these interactions were determined by SPR measurements . The data indicate a possible role of these proteins as receptors for human plasminogen on the bacterial cell surface . The potential role of this recruitment of a host protease for extracellular invasion mechanisms is discussed. Proteomics, 2004 Oct, 4(10), 3187 - 201 Two-dimensional electrophoresis database of Listeria monocytogenes EGDe proteome and proteomic analysis of mid-log and stationary growth phase cells; Folio P et al.; Listeria monocytogenes is the causative agent of listeriosis, one of the most significant foodborne diseases in industrialized countries . The complete genome of the L . monocytogenes EGDe strain, belonging to the serogroup 1/2a, has been sequenced and is comprised of 2853 open reading frames . The objective of the current study was to construct a two-dimensional (2-D) database of the proteome of this strain . The soluble protein fractions of the microorganism were recovered either in the mid-log or in the stationary phase of growth at 37 degrees C . These fractions were analyzed by 2-D electrophoresis (2-DE), using immobilized pH gradient strips of various pH values (3-10, 3-6, and 5-8) for the first-dimensional separations and 12.5% acrylamide gels for sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) . 201 protein spots corresponding to 126 different proteins were identified by matrix assisted laser desorption/ionization-time of flight-mass spectrometry (MALDI-TOF-MS) . The 2-DE maps presented here provide a first basis for further investigations of protein expression in L . monocytogenes . In this way, the comparison of proteome between cells in the exponential or stationary phase of growth at 37 degrees C allowed us to characterize 161 variations in protein spot intensity, of which 38 were identified . Among the differentially expressed proteins were ribosomal proteins (RpsF, RplJ, and RpmE), proteins involved in cellular metabolism (GlpD, PdhD, Pgm, Lmo1372, Lmo2696, and Lmo2743) or in stress adaptation (GroES and ferritin), a fructose-specific phosphotransferase enzyme IIB (Lmo0399) and different post-translational modified forms of listeriolysin (LLO). J Dairy Sci, 2004 Sep, 87(9), 2803 - 12 Molecular Subtyping and Tracking of Listeria monocytogenes in Latin-Style Fresh-Cheese Processing Plants; Kabuki DY et al.; Latin-style fresh cheeses, which have been linked to at least 2 human listeriosis outbreaks in the United States, are considered to be high-risk foods for Listeria monocytogenes contamination . We evaluated L . monocytogenes contamination patterns in 3 Latin-style fresh-cheese processing plants to gain a better understanding of L . monocytogenes contamination sources in the manufacture of these cheeses . Over a 6-mo period, 246 environmental samples were collected and analyzed for L . monocytogenes using both the Food and Drug Administration (FDA) method and the Biosynth L . monocytogenes detection system (LMDS) . Finished cheese samples from the same plants (n = 111) were also analyzed by the FDA method, which was modified to include L . monocytogenes plating medium (LMPM) and the L . monocytogenes confirmatory plating medium (LMCM) used in the LMDS method . Listeria monocytogenes was detected in 6.3% of cheese and 11.0% of environmental samples . Crates, drains, and floor samples showed the highest contamination rates, with 55.6, 30.0, and 20.6% L . monocytogenes positive samples, respectively . Finished products and food contact surfaces were positive in only one plant . The FDA method showed a higher sensitivity than the LMDS method for detection of L . monocytogenes from environmental samples . The addition of LMPM and LMCM media did not further enhance the performance of the FDA method for L . monocytogenes detection from finished products . Molecular subtyping (PCR-based allelic analysis of the virulence genes actA and hly and automated ribotyping) was used to track contamination patterns . Ribotype DUP-1044A, which had previously been linked to a 1998 multistate human listeriosis outbreak in the United States, was the most commonly identified subtype (20/36 isolates) and was isolated from 2 plants . This ribotype was persistent and widespread in one factory, where it was also responsible for the contamination of finished products . We hypothesize that this ribotype may represent a clonal group with a specific ability to persist in food processing environments . While previous listeriosis outbreaks were linked to Latin-style fresh cheeses made from unpasteurized milk, the presence of this organism in pasteurized cheese products illustrates that persistent environmental contamination also represents an important source of finished product contamination. Inhal Toxicol, 2004 May, 16(5), 311 - 7 Sensitivity to ozone, diesel exhaust particles, and standardized ambient particulate matter in rats with a listeria monocytogenes-induced respiratory infection; Steerenberg P et al.; Ambient particulate matter may increase respiratory allergic skewing of the T-cell-mediated immune response toward a T-helper-2 (Th2) response, with the consequence that the Th1 response develops less well . Successful clearing of a respiratory bacterial infection depends on an adequate Th1 immune response; therefore, the subject would not control the infection as well if exposed to particulate matter . To substantiate this hypothesis, we examined the effect of exposure to diesel exhaust particles (DEP) and urban particulate matter (EHC-93, Ottawa dust) on rats with a Listeria monocytogenes respiratory infection . Since this hypothesis has been confirmed for ozone, we used it as a positive control . Wistar rats were exposed to ozone (2 mg/m3 for 24 h/day for 7 days) and to DEP or to EHC-93 (50 microg/rat intranasally daily for 7 consecutive days) . Twenty-four hours after the last exposure, the rats were infected intratracheally with 1 x 10(6) L . monocytogenes bacteria . The number of L . monocytogenes was determined after 3, 4 and 5 days . Statistically significant increases of the number of L . monocytogenes in rats exposed to ozone were observed in the lungs and spleen at all three times . However, we found no significant differences in the numbers of bacteria that were found in rats exposed to DEP or EHC-93 compared to the saline-treated group at any of the three times . In conclusion, the results of this study do not support the hypothesis that exposure to DEP or EHC-93 reduces subsequent resistance to a respiratory infection in rats . Copyright Taylor & Francis Inc. Syst Appl Microbiol, 2004 Aug, 27(4), 454 - 61 Genetic characterization of Listeria monocytogenes food isolates and pathogenic potential within serovars 1/2a and 1/2b; Cabrita P et al.; A total of 39 Listeria monocytogenes strains isolated from raw milk, smoked meat, chicken carcass and reference strains, belonging to serovars 1/2a, 4a, 1/2b, 3b and 4b, were analysed by RAPD and by polymorphisms of the virulent genes inlAB and iap . Ten isolates, belonging to serovars 1/2a and 1/2b and, collected from raw milk and smoked meat, were further tested for pathogenicity by IP injection into mice . The clustering of the 39 L . monocytogenes strains in 3 groups at 0.45 similarity level, based on molecular typing, was observed . Distribution of serovars in these clusters was in agreement with the proposed three Listeria monocytogenes lineages . Within serovar 1/2b, the 50% lethal dose (LD50) ranged from 8.4 x 10(4) to 1.7 x 10(6) cfu.ml(-1) . One of the serovar 1/2b strains, isolated from smoked meat, exhibited the lowest virulence potential evaluated by LD50 and by mean time to death (MTD) and, from this point of view, was completely different from the other strains . Our results suggest the existence of heterogeneity in virulence levels within serovars 1/2a and 1/2b . However, when comparing the isolates based on genotyping, virulence indicators and food origin, no relation could be assessed. Eur J Immunol, 2004 Oct, 34(10), 2681 - 9 Expression of housekeeping and immunoproteasome subunit genes is differentially regulated in positively and negatively selecting thymic stroma subsets; Nil A et al.; The expression of housekeeping and/or immunoproteasomes in isolated thymic stroma subsets has so far not been analyzed but may have important consequences for self peptide repertoires presented by MHC class I molecules during positive and negative thymic selection . Here we determined the expression of housekeeping and immunoproteasome beta subunits and of PA28 in positively and negatively selecting stroma subsets . Positively selecting cortical thymic epithelial cells (cTEC) expressed only housekeeping but no immunoproteasome beta subunit mRNA and proteins . However, immunoproteasome beta subunits could be induced in cTEC by infection with Listeria monocytogenes or injection of IFN-gamma . In negatively selecting stroma including medullary epithelial cells and dendritic cells, incomplete and low representation of housekeeping beta subunit proteins but high and complete expression of immunoproteasome beta subunit proteins suggests absence of proper housekeeping proteasomes and predominance of immunoproteasomes . Expression of immunoproteasome beta subunits in negatively selecting stroma was independent of IFN-gamma receptor as shown in knockout (KO) mice . Absence of LMP2 altered thymic selection of the MHC class I-restricted transgenic P14 TCR in KO mice . The data suggest that negative selection may primarily involve immunoproteasome peptide repertoires and that peripheral infection may influence peptide repertoires involved in positive selection. J Clin Periodontol, 2004 Oct, 31(10), 878 - 84 Comparative antiplaque and antigingivitis effectiveness of a chlorhexidine and an essential oil mou