COMPARISON AND APPLICATION OF RIBOSOME SPACER DNA AMPLICON POLYMORPHISMS AND PULSED-FIELD GEL-ELECTROPHORESIS FOR DIFFERENTIATION OF METHICILLIN-RESISTANT STAPHYLOCOCCUS-AUREUS STRAINS

Analysis of sequences in the fragments of the 16S-23S rRNA intergenic spacer region by the ribosome spacer PCR (RS PCR) can differentiate st rains of methicillin-resistant Staphylococcus aureus (MRSA). We compar ed this technique with pulsed-field gel electrophoresis (PFGE) for typ ing MRSA strains and its application during an investigation of an out break. A total of 180 isolates of MRSA collected from various hospital laboratories within the United Kingdom and elsewhere were typed by PF GE and RS-PCR. PFGE identified 17 different types among the 180 strain s examined, and RS-PCR generated 13 different types. PFGE could detect minor genetic variations among the isolates and could identify the va riants which were not discriminated by RS-PCR. Four unique strain type s detected by PFGE were not detected by RS-PCR. When applied to typing the outbreak-related strains from the vascular surgery unit at the Ge neral Infirmary at Leeds, the results of RS-PCR were identical to thos e of PFGE. Our results have shown that RS-PCR is a rapid, inexpensive technique that is highly reproducible and almost as discriminatory as PFGE for typing MRSA isolates and should be useful in the local invest igation of MRSA outbreaks.