A rat central venous catheter (CVC) infection model was used to assess the importance of the proteinacious autolysin (AtlE) and the polysaccharide intercellular adhesin (PIA) in the pathogenesis of ...Staphylococcus epidermidis CVC-associated infection. Wild-type (wt) S. epidermidis O-47 was significantly more likely to cause a CVC infection than was either of the isogenic mutant strains (AtlE-negative O-47mut1 or PIA-negative O-47mut2). Bacteria were retrieved from the explanted catheters of 87.5% of rats inoculated with S. epidermidis O-47, compared with 25% of rats challenged with either S. epidermidis O-47mut1 or O-47mut2 (P=.007). Peripheral bacteremia was documented in 75% of rats challenged with S. epidermidis O-47, compared with 12.5% and 25% challenged with O-47mut1 and O-47mut2, respectively (P=.009). Metastatic disease was more common in rats inoculated with wt S. epidermidis compared with AtlE- or PIA-deficient mutants. These results confirm the importance of initial adherence, associated with AtlE, and biofilm production, mediated by PIA, in the pathogenesis of S. epidermidis experimental CVC infection
Microbial virulence is a complex and often multifactorial phenotype, intricately linked to a pathogen's evolutionary trajectory. Toxicity, the ability to destroy host cell membranes, and adhesion, ...the ability to adhere to human tissues, are the major virulence factors of many bacterial pathogens, including Staphylococcus aureus. Here, we assayed the toxicity and adhesiveness of 90 MRSA (methicillin resistant S. aureus) isolates and found that while there was remarkably little variation in adhesion, toxicity varied by over an order of magnitude between isolates, suggesting different evolutionary selection pressures acting on these two traits. We performed a genome-wide association study (GWAS) and identified a large number of loci, as well as a putative network of epistatically interacting loci, that significantly associated with toxicity. Despite this apparent complexity in toxicity regulation, a predictive model based on a set of significant single nucleotide polymorphisms (SNPs) and insertion and deletions events (indels) showed a high degree of accuracy in predicting an isolate's toxicity solely from the genetic signature at these sites. Our results thus highlight the potential of using sequence data to determine clinically relevant parameters and have further implications for understanding the microbial virulence of this opportunistic pathogen.
The saeRS two-component regulatory system regulates transcription of multiple virulence factors in Staphylococcus aureus. In the present study, we demonstrated that the saePQRS region in ...Staphylococcus epidermidis is transcriptionally regulated in a temporal manner and is arranged in a manner similar to that previously described for S. aureus. Studies using a mouse foreign body infection model demonstrated that the virulence of strain 1457 and the virulence of a mutant, strain 1457 saeR, were statistically equivalent. However, histological analyses suggested that the polymorphonuclear neutrophil response at 2 days postinfection was significantly greater in 1457-infected mice than in 1457 saeR-infected mice, demonstrating that SaeR influences the early, acute phases of infection. Microarray analysis demonstrated that a saeR mutation affected the transcription of 65 genes (37 genes were upregulated and 28 genes were downregulated); in particular, 8 genes that facilitate growth under anaerobic conditions were downregulated in 1457 saeR. Analysis of growth under anaerobic conditions demonstrated that 1457 saeR had a decreased growth rate compared to 1457. Further metabolic experiments demonstrated that 1457 saeR had a reduced capacity to utilize nitrate as a terminal electron acceptor and exhibited increased production of lactic acid in comparison to 1457. These data suggest that in S. epidermidis SaeR functions to regulate the transition between aerobic growth and anaerobic growth. In addition, when grown anaerobically, 1457 saeR appeared to compensate for the redox imbalance created by the lack of electron transport-mediated oxidation of NADH to NAD⁺ by increasing lactate dehydrogenase activity and the subsequent oxidation of NADH.
Summary
Comparison of live Baltic cod larvae lengths and early‐juveniles with corresponding lengths after preservation in 95% ethyl alcohol for periods of one to 3 years resulted in an average ...shrinkage of 0.70 mm for the entire size range of 4–40 mm standard length cod. Although the relative shrinkage depended on fish size and varied from 2 to 20% of the fresh length, the absolute shrinkage values were not size dependent and did not change during the observed preservation period. Thus a general additive correction value of +0.7 mm can be used to calculate live lengths from measured standard lengths of alcohol‐preserved material.
Previous studies have demonstrated that Staphylococcus epidermidis isolates colonizing the skin of healthy humans do not typically encode icaADBC, the genes responsible for the production of ...polysaccharide intercellular adhesin or biofilms. It was therefore hypothesized that the presence of icaADBC was deleterious to the successful colonization of human skin by S. epidermidis. Using a human skin competition model, it was determined that the strong biofilm-producing S. epidermidis strain 1457 was outcompeted at 1, 3, and 10 days by an isogenic icaADBC mutant (1457 ica::dhfr), suggesting a fitness cost for carriage of icaADBC.
The relevance of considering environmental variability for understanding and predicting biological responses to environmental changes has resulted in a recent surge in variability‐focused ecological ...research. However, integration of findings that emerge across studies and identification of remaining knowledge gaps in aquatic ecosystems remain critical. Here, we address these aspects by: (1) summarizing relevant terms of variability research including the components (characteristics) of variability and key interactions when considering multiple environmental factors; (2) identifying conceptual frameworks for understanding the consequences of environmental variability in single and multifactorial scenarios; (3) highlighting challenges for bridging theoretical and experimental studies involving transitioning from simple to more complex scenarios; (4) proposing improved approaches to overcome current mismatches between theoretical predictions and experimental observations; and (5) providing a guide for designing integrated experiments across multiple scales, degrees of control, and complexity in light of their specific strengths and limitations.
Background. Experience with intravenous and aerosolized forms of colistin for the treatment of ventilator-associated pneumonia (VAP) in patients without cystic fibrosis is limited. We aimed to assess ...the safety and efficacy of colistin for the treatment of VAP. Methods. We searched MEDLINE and Cochrane Database of Systematic Reviews for studies comparing colistin vs other antibiotics for treatment of VAP in patients without cystic fibrosis. QUOROM guidelines were followed, the I 2 method was used for heterogeneity, and a random-effects model for odds ratio (OR) estimates. Results. Six controlled studies met the inclusion criteria. Clinical response did not differ significantly between colistin and control groups (OR, 1.14; 95% confidence interval CI, .74-1.77; P = .56; I 2 = 0%). The efficacy of colistin was independent of study design (prospective OR, 0.89 95% CI, .48-1.66; P = .71; I 2 = 0%; retrospective OR, 1.45 95% CI, .79-2.68; P = .23; I 2 = 0%); randomized trials OR, 0.86 95% CI, .43-1.74; P = .68; I 2 = 0%). There was no indication of a significant change in clinical response after controlling for concomitant antibiotic treatment (intercept, 0.121; slope, 0.0315; P = .95). Treatment with colistin vs controls did not affect hospital mortality (OR, 0.92; 95% CI, .50-1.67; P = .78; I 2 = 34.59%) or nephrotoxicity (OR, 1.14; 95% CI, .59-2.20; P = .69; I 2 = 0%). Fourteen single-arm studies have been analyzed, and the results were in concordance with the findings of the controlled studies. Conclusions. Our results suggest that colistin may be as safe and as efficacious as standard antibiotics for the treatment of VAP.
Comparison of live Baltic cod larvae lengths and early-juveniles with corresponding lengths after preservation in 95% ethyl alcohol for periods of one to 3years resulted in an average shrinkage of ...0.70mm for the entire size range of 4-40mm standard length cod. Although the relative shrinkage depended on fish size and varied from 2 to 20% of the fresh length, the absolute shrinkage values were not size dependent and did not change during the observed preservation period. Thus a general additive correction value of +0.7mm can be used to calculate live lengths from measured standard lengths of alcohol-preserved material.
We determined the prevalence of Shiga toxin-producing Escherichia coli (STEC) in diarrheal stool samples from Nebraska by three methods: cefixime-tellurite sorbitol MacConkey (CT- SMAC) culture, ...enterohemorrhagic E. coli (EHEC) enzyme immunoassay, and stx1,2 polymerase chain reaction (PCR). Fourteen (4.2%) of 335 specimens were positive by at least one method (CT-SMAC culture 6 of 14, EHEC enzyme immunoassay 13 of 14, stx1,2 PCR 14 of 14). Six contained serogroup O157, while non-O157 were as prevalent as O157 serogroups.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, ODKLJ, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
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