title: Comparative analysis of multidrug-resistant, non-multidrug-resistant, and archaic methicillin-resistant Staphylococcus aureus isolates from Central Sydney, Australia.
abstract: In this study, the phenotypic and genotypic characteristics of 50 methicillin-resistant Staphylococcus aureus (MRSA) isolates (43 contemporary and 7 archaic strains from the mid-1960s) from four Sydney hospitals in the central Sydney area were compared. Phenotypic analysis based on antibiotic profiles and phage typing patterns categorized the MRSA isolates into three major groups: multidrug resistant (mMRSA), non-multidrug resistant (nmMRSA), and archaic. The nmMRSA isolates could be further subdivided into nmMRSA group 1, which was phage typeable and similar to the archaic group; nmMRSA group 2, which was non-phage typeable and only resistant to ciprofloxacin; and nmMRSA group 3, which was also nontypeable and generally resistant to other antibiotics. The characterization of all five phenotypic groups was then extended by genetic analysis. Restriction fragment length polymorphism (RFLP) analysis showed the 50 isolates could be sorted into 20 group-specific pulsotypes. mecI gene deletions and mutations at various percentages among the five MRSA groups were detected by sequencing. Several mec promoter mutations were also found. The overall findings indicated that nmMRSA strains may have independently acquired mec DNA and are more likely to be newly emergent strains than nmMRSA variants.
authors.affiliation: Department of Infectious Diseases and Immunology, University of Sydney, Australia.
authors.forename: Jason
authors.initials: J
authors.lastname: Watson
authors.forename: Rod
authors.initials: R
authors.lastname: Givney
authors.forename: Mary
authors.initials: M
authors.lastname: Beard-Pegler
authors.forename: Barbara
authors.initials: B
authors.lastname: Rose
authors.forename: John
authors.initials: J
authors.lastname: Merlino
authors.forename: Alison
authors.initials: A
authors.lastname: Vickery
authors.forename: Tom
authors.initials: T
authors.lastname: Gottlieb
authors.forename: Ross
authors.initials: R
authors.lastname: Bradbury
authors.forename: Colin
authors.initials: C
authors.lastname: Harbour
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001315:Australia; D018432:Drug Resistance, Multiple; D005838:Genotype; D006801:Humans; D016106:Methicillin Resistance; D008826:Microbial Sensitivity Tests; D010641:Phenotype; D013211:Staphylococcus aureus / Q000145:classification / Q000187:drug effects* / Q000235:genetics
chemical_list: D000900:Anti-Bacterial Agents