title: Vancomycin susceptibility within methicillin-resistant Staphylococcus aureus lineages.
abstract: Methicillin-resistant Staphylococcus aureus (MRSA) with reduced vancomycin susceptibility vancomycin-intermediate S. aureus (VISA) has been reported from many countries. Whether resistance is evolving regularly in different genetic backgrounds or in a single clone with a genetic predisposition, as early results suggest, is unclear. We have studied 101 MRSA with reduced vancomycin susceptibility from nine countries by multilocus sequence typing (MLST), characterization of SCCmec (staphylococcal chromosomal cassette mec), and agr (accessory gene regulator). We found nine genotypes by MLST, with isolates within all five major hospital MRSA lineages. Most isolates (88/101) belonged to two of the earliest MRSA clones that have global prevalence. Our results show that reduced susceptibility to vancomycin has emerged in many successful epidemic lineages with no clear clonal disposition. Increasing antimicrobial resistance in genetically distinct pandemic clones may lead to MRSA infections that will become increasingly difficult to treat.
authors.affiliation: Southmead Hospital, Bristol, United Kingdom.
authors.forename: Robin A
authors.initials: RA
authors.lastname: Howe
authors.forename: Alastair
authors.initials: A
authors.lastname: Monk
authors.forename: Mandy
authors.initials: M
authors.lastname: Wootton
authors.forename: Timothy R
authors.initials: TR
authors.lastname: Walsh
authors.forename: Mark C
authors.initials: MC
authors.lastname: Enright
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001426:Bacterial Proteins / Q000235:genetics; D015373:Bacterial Typing Techniques; D024881:Drug Resistance, Bacterial / Q000235:genetics; D019143:Evolution, Molecular; D006801:Humans; D016106:Methicillin Resistance; D008826:Microbial Sensitivity Tests; D017422:Sequence Analysis, DNA; D013203:Staphylococcal Infections / Q000382:microbiology; D013211:Staphylococcus aureus / Q000187:drug effects* / Q000235:genetics*; D015534:Trans-Activators / Q000235:genetics; D014640:Vancomycin / Q000494:pharmacology*
chemical_list: C095698:Agr protein, Staphylococcus aureus; D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D015534:Trans-Activators; D014640:Vancomycin