PULSED-FIELD GEL-ELECTROPHORESIS AS A REPLACEMENT FOR BACTERIOPHAGE-TYPING OF STAPHYLOCOCCUS-AUREUS

Bacteriophage typing (BT) (World Health Organization method) has been used at the Centers far Disease Control and Prevention for over 30 yea rs to type isolates of Staphylococcus aureus. Since studies have shown that BT patterns have poor reproducibility and because BT fails to ty pe a high percentage (15 to 20%) of isolates, the Centers for Disease Control and Prevention has converted from using BT to using pulsed-fie ld gel electrophoresis (PFGE) for strain typing S. aureus, We compared the results of BT with results of PFGE for typing 300 isolates of S. aureus, including strains from several well-characterized outbreaks. N inety-six isolates were BT group I, 19 were group II, 82 were group II I, 7 were group V, and 96 were nontypeable. PFGE identified subgroups within each phage group and thus was more discriminating than BT, whic h identified no subgroups. PFGE was able to type all isolates and dist inguish related from unrelated strains of S. aureus. Our modified, sta ndardized PFGE methodology should enable typing laboratories to obtain rapid, reliable results in 3 to 4 days when starting with an isolated colony on agar media.