Detection of methicillin-resistant staphylococci by using the polymerase chain reaction.

A polymerase chain reaction (PCR)-based test was developed for the detection of mecA in staphylococci. To facilitate this process, a rapid cell lysis procedure was established for the release of DNA from staphylococcal strains. Primers based on the DNA sequence of the mecA gene from Staphylococcus aureus were used in PCRs to screen for the presence of this gene in a total of 98 staphylococcal isolates. Fifty-one isolates were mecA positive (17 S. aureus strains and 34 coagulase-negative staphylococci including S. epidermidis, S. haemolyticus, and S. simulans). Results obtained with PCRs were generally consistent with those of standard microbiological assays. PCRs designed to detect the femA gene (factor essential for methicillin resistance) revealed the presence of the gene in all S. aureus strains examined regardless of the susceptibility profiles of the strains to methicillin. In contrast, femA could not be detected in coagulase-negative staphylococci by PCR with the same primers. Low-stringency hybridization suggested the presence of a gene structurally related to femA in S. epidermidis and other coagulase-negative staphylococci examined.