|
|
|
|
|
|
Penetration of Meropenem into Pneumonic Human Lung Tissue as Measured by In Vivo Microdialysis. Florian Tomaselli, 2004.Until recently, information on antibiotic pharmacokinetic properties in infected human lung tissue was limited . We therefore studied a microdialysis-based approach for measurement of the penetration of meropenem into the extracellular space fluid of human pneumonic lung parenchyma . The lung penetration of meropenem was determined for seven patients with pneumonia and metapneumonic pleural empyema treated by decortication . Intraoperatively, two microdialysis probes were inserted into pneumonic lung tissue and one was inserted into healthy skeletal muscle for reference values . Serum and microdialysis samples were collected at 20-min intervals for at least 8 h following a single intravenous dose of 1 g of meropenem . The maximum free interstitial concentration (mean and standard deviation) of meropenem in infected lung tissue was 11.4 ± 10.9 mg/liter, and that in serum was 47.3 ± 21.0 mg/liter . The areas under the curve for infected lung tissue (36.2 ± 17.9 mg · h/liter) and serum (95.4 ± 46.6 mg · h/liter) revealed a significant difference . This technique enabled quasi-continuous tissue pharmacokinetic measurements of free, unbound antibiotic in pneumonic lung tissue of patients with pneumonia . The present data corroborate the use of meropenem in the treatment of lung infections caused by extracellular bacteria, demonstrating the excellent distribution profile for meropenem in the interstitial space of human pneumonic lung tissue . Viral Activity in Two Contrasting Lake Ecosystems. Yvan Bettarel, 2004.For aquatic systems, especially freshwaters, there is little data on the long-term (i.e., >6-month period) and depth-related variability of viruses . In this study, we examined virus-induced mortality of heterotrophic bacteria over a 10-month period and throughout the water column in two lakes of the French Massif Central, the oligomesotrophic Lake Pavin and the eutrophic Lake Aydat . Concurrently, we estimated nonviral mortality through heterotrophic nanoflagellate and ciliate bacterivory . Overall, viral infection parameters were much less variable than bacterial production . We found that the frequency of visibly infected cells (FVIC), estimated using transmission electron microscopy, peaked in both lakes at the end of spring (May to June) and in early autumn (September to October) . FVIC values were significantly higher in Lake Pavin (mean [M] = 1.6%) than in Lake Aydat (M = 1.1%), whereas the opposite trend was observed for burst sizes, which averaged 25.7 and 30.2 virus particles bacterium–1, respectively . We detected no significant depth-related differences in FVIC or burst size . We found that in both lakes the removal of bacterial production by flagellate grazing (MPavin = 37.7%, MAydat = 18.5%) was nearly always more than the production removed by viral lysis (MPavin = 16.2%, MAydat = 19%) or ciliate grazing (MPavin = 2.7%, MAydat = 8.8%) . However, at specific times and locations, viral lysis prevailed over protistan grazing, for example, in the anoxic hypolimnion of Lake Aydat . In addition, viral mortality represented a relatively constant mortality source in a bacterial community showing large variations in growth rate and subject to large variations in loss rates from grazers . Finally, although viruses did not represent the main agent of bacterial mortality, our data seem to show that their relative importance was higher in the less productive system . The Escherichia coli metD Locus Encodes an ABC Transporter Which Includes Abc (MetN), YaeE (MetI), and YaeC (MetQ). Christophe Merlin, 2002.We report that the genes abc, yaeC, and yaeE comprise metD, an Escherichia coli locus encoding a DL-methionine uptake system . MetD is an ABC transporter with Abc the ATPase, YaeE the permease, and YaeC the likely substrate binding protein . Expression of these genes is regulated by L-methionine and MetJ, a common repressor of the methionine regulon . We propose to rename abc, yaeE, and yaeC as metN, metI, and metQ, respectively . Genomic Diversification among Archival Strains of Salmonella enterica Serovar Typhimurium LT7. Gui-Rong Liu, 2003.To document genomic changes during long periods of storage, we analyzed Salmonella enterica serovar Typhimurium LT7, a mutator strain that was previously reported to have higher rates of mutations compared to other serovar Typhimurium strains such as LT2 . Upon plating directly from sealed agar stabs that had been stocked at room temperature for up to four decades, many auxotrophic mutants derived from LT7 gave rise to colonies of different sizes . Restreaking from single colonies consistently yielded colonies of diverse sizes even when we repeated single-colony isolation nine times . Colonies from the first plating had diverse genomic changes among and even within individual vials, including translocations, inversions, duplications, and point mutations, which were detected by rare-cutting endonuclease analysis with pulsed-field gel electrophoresis . Interestingly, even though the colony size kept diversifying, all descendents of the same single colonies from the first plating had the same sets of detected genomic changes . We did not detect any colony size or genome structure diversification in serovar Typhimurium LT7 stocked at -70°C or in serovar Typhimurium LT2 stocked either at -70°C or at room temperature . These results suggest that, although colony size diversification occurred during rapid growth, all detected genomic changes took place during the storage at room temperature and were carried over to their descendents without further changes during rapid growth in rich medium . We constructed a genomic cleavage map on the LT7 strain that had been stocked at -70°C and located all of the detected genomic changes on the map . We speculated on the significance of mutators for survival and evolution under environmentally stressed conditions .
|
© 2005
Transgalactic Ltd (manufacturer of Bioscreen C software) |
Privacy Statement | P.O. Box
1393, 00101 Helsinki, Finland,
Last modified: May 25, 2005
| ||||||
