ABSTRACT
Methicillin-resistant Staphylococcus aureus (MRSA) is one of the most important causes of hospital infections worldwide. High-level resistance to methicillin is caused by the mecA gene, which encodes an alternative penicillin-binding protein, PBP 2a. To determine the clonal relationships between methicillin-susceptible S. aureus (MSSA) and MRSA, we typed 1,069 S. aureus isolates (493 MSSA isolates and 576 MRSA isolates), collected mainly in North American and European hospitals between the 1960s and the year 2000, using pulsed-field gel electrophoresis and ribotyping. Of 10 widespread S. aureus lineages recognized, 8 had corresponding mecA-positive strains. Multiresistant MRSA strains are found in hospitals worldwide, while unrelated and more susceptible strains represent less than 1% of the MRSA population. This supports the hypothesis that horizontal transfer plays an important role in the dissemination of the mecA gene in the S. aureus population.
Subject(s)
Bacterial Proteins , Carrier Proteins/genetics , Gene Transfer, Horizontal , Hexosyltransferases , Methicillin Resistance/genetics , Muramoylpentapeptide Carboxypeptidase/genetics , Peptidyl Transferases , Staphylococcal Infections/microbiology , Staphylococcus aureus/drug effects , Bacterial Typing Techniques , Electrophoresis, Gel, Pulsed-Field , Humans , Methicillin/pharmacology , Microbial Sensitivity Tests , Penicillin-Binding Proteins , Penicillins/pharmacology , Polymerase Chain Reaction , Ribotyping , Staphylococcus aureus/geneticsABSTRACT
A total of 3,051 methicillin-susceptible Staphylococcus aureus (MSSA) isolates and methicillin-resistant S. aureus (MRSA) isolates in Europe were compared. MRSA isolates constituted 25% of all isolates and were more prevalent in southern Europe. MRSA isolates appeared to be more prevalent in intensive care units than in outpatient departments. Only a small minority of MSSA isolates were multidrug resistant, whereas the majority of MRSA isolates were multidrug resistant.
Subject(s)
Anti-Bacterial Agents/pharmacology , Hospitals, University , Population Surveillance , Staphylococcal Infections/epidemiology , Staphylococcus aureus/drug effects , Drug Resistance, Multiple, Bacterial , Europe/epidemiology , Humans , Methicillin/pharmacology , Methicillin Resistance , Microbial Sensitivity Tests , Staphylococcal Infections/microbiology , Staphylococcus aureus/isolation & purificationABSTRACT
Staphylococcus aureus is thought to have acquired mecA DNA by horizontal transfer. DNA fingerprints made by restriction nucleases that cut certain sequences of DNA are used to compare complete genomes or particular genes between bacteria. We isolated an epidemic mecA(-) meticillin-susceptible S aureus genotype and, subsequently, a rare isogeneic mecA(+) meticillin-resistant S aureus (MRSA) genotype from a neonate who had never been in contact with MRSA. This MRSA contained mecA DNA that was identical to that in a coagulase-negative staphylococcal strain isolated from this patient, but different from other MRSA genotypes. We believe that this MRSA was formed in vivo by horizontal transfer of the mecA DNA between two staphylococcal species.
