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Secretion and Function of Salmonella SPI-2 Effector SseF Require Its Chaperone, SscB. Shipan Dai, 2004.Salmonella strains utilize a type III secretion system for their successful survival and replications inside host cells . SseF is one of the several effector proteins that are required for conferring this survival ability by altering the trafficking of the Salmonella-containing vacuoles . These effector proteins often require appropriate chaperones to maintain their stabilities inside the bacteria . These chaperones are also known to assist the subsequent secretion and translocation of their substrates . We report here that SscB acts as the chaperone for SseF, an effector for the Salmonella pathogenicity island 2 (SPI-2) . We found that the sscB gene is required for the formation of Salmonella sp.-induced continuous filaments in epithelial cells . Efficient Salmonella replication in macrophages requires SscB function . Intracellular and secretion levels of SseF are greatly reduced in an sscB mutant strain compared to the wild-type strain . A protein stability assay demonstrated that the half-life of SseF is significantly shortened in the absence of SscB . Transcriptional analysis of the sseF gene showed that the effect of SscB on the SseF level is not at the transcriptional level . A coprecipitation experiment indicated that SscB interacts with SseF . In summary, our results indicate that SscB is a chaperone for SPI-2 effector SseF to facilitate its secretion and function inside the host cells . ELVIRA HSV, a Yield Reduction Assay for Rapid Herpes Simplex Virus Susceptibility Testing. R, 2004.A colorimetric yield reduction assay, ELVIRA (enzyme-linked virus inhibitor reporter assay) HSV, was developed to determine the antiviral drug susceptibilities of herpes simplex virus (HSV) . It uses an HSV-inducible reporter cell line . This simple and rapid assay has an objective readout, low inoculum size, and good reproducibility . The results correlate well with those of the plaque reduction assay . Antimicrobial Resistance of Enterococcus Species Isolated from Produce. Lynette M. Johnston, 2004.The purpose of this study was to characterize the antibiotic resistance profiles of Enterococcus species isolated from fresh produce harvested in the southwestern United States . Among the 185 Enterococcus isolates obtained, 97 (52%) were Enterococcus faecium, 38 (21%) were Enterococcus faecalis, and 50 (27%) were other Enterococcus species . Of human clinical importance, E . faecium strains had a much higher prevalence of resistance to ciprofloxacin, tetracycline, and nitrofurantoin than E . faecalis . E . faecalis strains had a low prevalence of resistance to antibiotics used to treat E . faecalis infections of both clinical and of agricultural relevance, excluding its intrinsic resistance patterns . Thirty-four percent of the isolates had multiple-drug-resistance patterns, excluding intrinsic resistance . Data on the prevalence and types of antibiotic resistance in Enterococcus species isolated from fresh produce may be used to describe baseline antibiotic susceptibility profiles associated with Enterococcus spp . isolated from the environment . The data collected may also help elucidate the role of foods in the transmission of antibiotic-resistant strains to human populations . Bacillus subtilis Tolerance of Moderate Concentrations of Rifampin Involves the  B-Dependent General and Multiple Stress Response.Julia Elisabeth Bandow, 2002.Low concentrations of the RNA polymerase inhibitor rifampin added to an exponentially growing culture of Bacillus subtilis led to an instant inhibition of growth . Survival experiments revealed that during the growth arrest the cells became tolerant to the antibiotic and the culture was able to resume growth some time after rifampin treatment . L-[35S]methionine pulse-labeled protein extracts were separated by two-dimensional polyacrylamide gel electrophoresis to investigate the change in the protein synthesis pattern in response to rifampin . The B-dependent general stress proteins were found to be induced after treatment with the antibiotic . Part of the oxidative stress signature was induced as indicated by the catalase KatA and MrgA . The target protein of rifampin, the ß subunit (RpoB) of the DNA-dependent RNA polymerase, and the flagellin protein Hag belonging to the
D regulon were also induced . The rifampin-triggered growth arrest was extended in a sigB mutant in comparison to the wild-type strain, and the higher the concentration, the more pronounced this effect was . Activity of the RsbP energy-signaling phosphatase in the
B signal transduction network was also important for this protection against rifampin, but the RsbU environmental signaling phosphatase was not required . The sigB mutant strain was less capable of growing on rifampin-containing agar plates . When plated from a culture that had already reached stationary phase without previous exposure to the antibiotic during growth, the survival rate of the wild type exceeded that of the sigB mutant by a factor of 100 . We conclude that the general stress response of B . subtilis is induced by rifampin depending on RsbP activity and that loss of SigB function causes increased sensitivity to the antibiotic .
A Pediocin-Producing Lactobacillus plantarum Strain Inhibits Listeria monocytogenes in a Multispecies Cheese Surface Microbial Ripening Consortium. Melanie Loessner, 2003.The growth of Listeria monocytogenes WSLC 1364, originating from a cheese-borne outbreak, was examined in the presence and in the absence of a pediocin AcH-producing Lactobacillus plantarum strain on red smear cheese . Nearly complete inhibition was observed at 102 CFU of L . monocytogenes per ml of salt brine solution, while contamination with Listeria mutants resistant to pediocin resulted in high cell counts of the pathogen on the cheese surface . The inhibition was due to pediocin AcH added together with the L . plantarum culture to the brine solution but not to bacteriocin production in situ on cheese . Pediocin resistance developed in vitro at different but high frequencies in all 12 L . monocytogenes strains investigated, and a resistant mutant remained stable in a microbial surface ripening consortium over a 4-month production process in the absence of selection pressure . In conclusion, the addition of a L . plantarum culture is a potent measure for combating Listeria in a contaminated production line, but because of the potential development of resistance, it should not be used continuously over a long time in a production line .
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