PSEUDOMONAS-AERUGINOSA SEROTYPE O-12 OUTBREAK STUDIED BY ARBITRARY PRIMER PCR

A total of 16 colonizing and infecting ofloxacin-resistant Pseudomonas aeruginosa strains and two strains isolated from ventilation equipmen t fluids, all with similar colonial morphologies and,vith minor but di stinct susceptibility differences, were suspected of belonging to a si ngle outbreak and were studied by arbitrary primer (AP) PCR. Thirteen nonrelated strains were included to evaluate the discriminatory capaci ty of the technique. AP PCR fingerprinting was compared with serotypin g, phage typing, and antibiotic susceptibility testing. AP PCR was per formed independently with three different primers. The different AP PC R typing systems yielded almost identical patterns for the epidemic st rains and enabled us to differentiate most of the nonrelated strains f rom each other and from the outbreak strains. The combination of AP PC R typing and the phenotyping techniques that we used enabled us to con clude that an outbreak was occurring. In general, the typeability of A P PCR was greater than those of phage typing and serotyping, while the discriminatory powers of the three methods were comparable.