title: The emergence and evolution of methicillin-resistant Staphylococcus aureus.
abstract: Significant advances have been made in recent years in our understanding of how methicillin resistance is acquired by Staphylococcus aureus. Integration of a staphylococcal cassette chromosome mec (SCCmec) element into the chromosome converts drug-sensitive S. aureus into the notorious hospital pathogen methicilin-resistant S. aureus (MRSA), which is resistant to practically all beta-lactam antibiotics. SCCmec is a novel class of mobile genetic element that is composed of the mec gene complex encoding methicillin resistance and the ccr gene complex that encodes recombinases responsible for its mobility. These elements also carry various resistance genes for non-beta-lactam antibiotics. After acquiring an SCCmec element, MRSA undergoes several mutational events and evolves into the most difficult-to-treat pathogen in hospitals, against which all extant antibiotics including vancomycin are ineffective. Recent epidemiological data imply that MRSA has embarked on another evolutionary path as a community pathogen, as at least one novel SCCmec element seems to have been successful in converting S. aureus strains from the normal human flora into MRSA.
authors.affiliation: Department of Bacteriology, Juntendo University, 2-1-1 Hongo Bunkyo-ku, Tokyo 113-8421, Japan. hiram@med.juntendo.ac.jp
authors.forename: K
authors.initials: K
authors.lastname: Hiramatsu
authors.forename: L
authors.initials: L
authors.lastname: Cui
authors.forename: M
authors.initials: M
authors.lastname: Kuroda
authors.forename: T
authors.initials: T
authors.lastname: Ito
mesh_terms: D001426:Bacterial Proteins; D002352:Carrier Proteins / Q000235:genetics; D004251:DNA Transposable Elements; D019143:Evolution, Molecular; D006602:Hexosyltransferases; D006801:Humans; D016106:Methicillin Resistance / Q000235:genetics*; D017720:Molecular Epidemiology; D002267:Muramoylpentapeptide Carboxypeptidase / Q000235:genetics; D016254:Mutagenesis, Insertional; D046915:Penicillin-Binding Proteins; D010458:Peptidyl Transferases; D013203:Staphylococcal Infections / Q000453:epidemiology; D013211:Staphylococcus aureus / Q000187:drug effects* / Q000235:genetics; D020713:Vancomycin Resistance / Q000235:genetics; D001618:beta-Lactamases / Q000235:genetics
chemical_list: D001426:Bacterial Proteins; D002352:Carrier Proteins; D004251:DNA Transposable Elements; D046915:Penicillin-Binding Proteins; D010458:Peptidyl Transferases; D006602:Hexosyltransferases; D002267:Muramoylpentapeptide Carboxypeptidase; D001618:beta-Lactamases; C063912:carbapenemase