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Methicillin-susceptible S. Aureus (methicillin-susceptible + s._aureu)
Selected AbstractsComparison of methods for the detection of methicillin resistance in Staphylococcus aureus isolates from food productsLETTERS IN APPLIED MICROBIOLOGY, Issue 5 2007M. Corrente Abstract Aims:, To compare several methods for detection of methicillin resistance in Staphylococcus aureus isolates from food. Methods and Results:, Two hundred S. aureus isolates from food of animal origin were screened for methicillin resistance by a PCR assay specific for the mecA gene, an oxacillin agar screen test and a cefoxitin disk diffusion test. Six out of 200 strains (3%) were found to be methicillin-resistant Staphylococcus aureus (MRSA) by PCR. The oxacillin agar screen test detected only one of the MRSA isolates (sensitivity of 16ˇ7%) and mischaracterized three additional strains as MRSA (specificity of 98ˇ45%). None of the MRSA strains was detected by the cefoxitin test (sensitivity of 0%), while 15 methicillin-susceptible S. aureus (MSSA) strains were misclassified as resistant (specificity of 92ˇ3%). Fifteen MSSA strains displayed a ,-lactamase hyperproducer-like phenotype. The six MRSA (mecA-positive) strains resembled the characteristics of heteroresistant strains. Conclusions:, As MRSA of animal origin may display atypical phenotypes, PCR appears to be more reliable for detection of methicillin resistance in animal strains. Significance and Impact of the Study:, The study stresses the need for implementing the methods of screening S. aureus from food of animal origin for methicillin resistance. [source] Staphylococcus aureus as source of catheter-related bloodstream infection evaluated by PFGE and rep-PCR typing in a Brazilian hospital,APMIS, Issue 11 2008GERALDO SADOYAMA Staphylococci are a common cause of catheter-related bloodstream infection (CR-BSI), and epidemiological typing is an important tool for effective infection control. This study evaluated by PFGE and rep-PCR whether Staphylococcus aureus strains isolated from skin and catheter tips were related to specimens isolated from blood. A prospective observational study, carried out in a clinical surgical ward at a Brazilian hospital between September 2000 and November 2002, investigated non-tunneled central venous catheters from 179 patients. S. aureus isolates were mainly obtained from blood (41.4%), while coagulase-negative staphylococci strains were more often isolated from the skin at the catheter insertion site (49.7%) and from the catheter tip (57.5%). Among the 21 strains isolated from 9 patients at 2 or 3 sites simultaneously, 9 were methicillin-resistant S. aureus (MRSA) and 12 were methicillin-susceptible S. aureus (MSSA). Seven patients harbored the same S. aureus strain isolated from the skin, blood and/or catheter tip cultures. MRSA isolates belonged to one PFGE pattern (type A- subtypes A1, A2 and A3), and to two rep-PCR patterns (a and b). MSSA isolates were distinguished in five PFGE (B to F) and in three rep-PCR (c, d and e) patterns. Both PFGE and rep-PCR methods indicated that the skin at the catheter insertion site was the origin of CR-BSI caused by S. aureus. [source] Molecular epidemiology of the nasal colonization by methicillin-susceptible Staphylococcus aureus in Swiss childrenCLINICAL MICROBIOLOGY AND INFECTION, Issue 9 2010C. Mégevand Clin Microbiol Infect 2010; 16: 1414,1420 Abstract Nasal carriage of Staphylococcus aureus contributes to an increased risk of developing an infection with the same bacterial strain. Genetic regulatory elements and toxin-expressing genes are virulence factors associated with the pathogenic potential of S. aureus. We undertook an extensive molecular characterization of methicillin-susceptible S. aureus (MSSA) carried by children. MSSA were recovered from the nostrils of children. The presence of Panton-Valentine leukocidin (PVL), exfoliatins A and B (exfoA and exfoB), and the toxic-shock staphylococcal toxin (TSST-1) and agr group typing were determined by quantitative PCR. A multiple-locus variable-number of tandem repeat analysis (MLVA) assay was also performed for genotyping. Five hundred and seventy-two strains of MSSA were analysed. Overall, 30% were positive for toxin-expressing genes: 29% contained one toxin and 1.6% two toxins. The most commonly detected toxin gene was tst, which was present in 145 (25%) strains. The TSST-1 gene was significantly associated with the agr group 3 (OR 56.8, 95% CI 32.0,100.8). MLVA analysis revealed a large diversity of genetic content and no clonal relationship was demonstrated among the analysed MSSA strains. Multilocus sequence typing confirmed this observation of diversity and identified ST45 as a frequent colonizer. This broad diversity in MSSA carriage strains suggests a limited selection pressure in our geographical area. [source] Is MRSA more virulent than MSSA?CLINICAL MICROBIOLOGY AND INFECTION, Issue 9 2007F. Rozgonyi Abstract Numerous clinical studies have indicated, based on mortality rates, that methicillin-resistant Staphylococcus aureus (MRSA) strains are more virulent than methicillin-susceptible S. aureus (MSSA) strains. In contrast, quantitative laboratory examinations of the presence and magnitude of pathogenic mechanisms and virulence factors in strains of MRSA and MSSA have generated conflicting data. The most important reason for these conflicting results is probably the heterogeneic nature of the resistant population. A comparison of selected and congenic MRSA and MSSA sub-populations of the same strain is required to resolve this issue. [source] Macrolide,lincosamide,streptogramin B resistance phenotypes and genotypes among Staphylococcus aureus clinical isolates in JapanCLINICAL MICROBIOLOGY AND INFECTION, Issue 3 2007T. Otsuka Abstract In total, 269 methicillin-resistant Staphylococcus aureus (MRSA) and 434 methicillin-susceptible S. aureus (MSSA) isolates were investigated to determine their macrolide,lincosamide,streptogramin B (MLSB) resistance phenotypes and genotypes. The constitutive phenotype (61.3% in MRSA, 1.3% in MSSA) and erm(A) gene predominated among the 261 erythromycin-resistant MRSA isolates, while the inducible phenotype (38.7% in MRSA, 94.0% in MSSA) and erm(C) gene were more prevalent among the 150 erythromycin-resistant MSSA isolates. There was a higher incidence of the MLSB inducible phenotype compared with other countries, perhaps because MLSB antibiotics are not recommended as first-line agents against S. aureus in Japan. [source] | ||||||||||