title: Presence of mec genes and overproduction of beta-lactamase in the expression of low-level methicillin resistance among staphylococci.
abstract: Detection of methicillin-resistant staphylococci is critical for the management of infected patients in the hospital. A total of 55 nonreplicated clinical isolates of staphylococci (31 Staphylococcus aureus and 24 coagulase-negative staphylococci; CNS) collected during a one-year period and expressing low-level resistance to methicillin (oxacillin MIC of 2-4 mg/l for S. aureus and 0.5-4 mg/l for CNS) were studied. mec determinants and overproduction of beta-lactamase were investigated and pulsed-field gel electrophoresis (PFGE) was applied as a typing method. Twenty-four S. aureus isolates and 19 CNS carried the mecA gene. The presence of mecR1/mecI and blaR1/blaI genes correlated with the expression of low-level methicillin resistance in CNS. Four mecA-negative isolates (2 S. aureus and 2 CNS) overproduced beta-lactamase. PFGE revealed the presence of 2 major clonal types in mecA-positive S. aureus isolates, and 3 in CNS. Low-level methicillin resistance of staphylococci is correlated with the presence of the mecA gene and overproduction of beta-lactamase.
authors.affiliation: Department of Microbiology, School of Medicine, University of Patras, Patras, Greece.
authors.forename: E
authors.initials: E
authors.lastname: Petinaki
authors.forename: A
authors.initials: A
authors.lastname: Arvaniti
authors.forename: C
authors.initials: C
authors.lastname: Bartzavali
authors.forename: G
authors.initials: G
authors.lastname: Dimitracopoulos
authors.forename: I
authors.initials: I
authors.lastname: Spiliopoulou
mesh_terms: D001426:Bacterial Proteins / Q000096:biosynthesis*; D017931:DNA Primers; D004269:DNA, Bacterial / Q000235:genetics*; D005786:Gene Expression Regulation; D006801:Humans; D016106:Methicillin Resistance / Q000235:genetics*; D016133:Polymerase Chain Reaction; D013203:Staphylococcal Infections / Q000188:drug therapy; D013211:Staphylococcus aureus / Q000187:drug effects* / Q000201:enzymology / Q000235:genetics*; D001618:beta-Lactamases / Q000096:biosynthesis*
chemical_list: D001426:Bacterial Proteins; D017931:DNA Primers; D004269:DNA, Bacterial; C101641:mecR1 protein, Staphylococcus aureus; D001618:beta-Lactamases