VALUE OF MOLECULAR EPIDEMIOLOGIC ANALYSIS IN A NOSOCOMIAL METHICILLIN-RESISTANT STAPHYLOCOCCUS-AUREUS OUTBREAK

Objective.-To evaluate two molecular epidemiologic methods used in the analysis of a nosocomial methicillin-resistant Staphylococcus aureus (MRSA) outbreak.Design.-Restriction endonuclease analysis of plasmid D NA (REAP) was used in the analysis of 45 MRSA isolates. After terminat ion of the outbreak, isolates were retrospectively analyzed in a blind fashion using the newly described technique of arbitrarily primed pol ymerase chain reaction (AP-PCR). Molecular analyses were compared with epidemiologic and antimicrobial susceptibility data. Setting.-Tertiar y care university hospital. Subjects.-Twenty-eight patients and 12 emp loyees infected or colonized with MRSA during a 6-week period. Results .-A clonal relationship demonstrated among isolates from bum unit pati ents and staff was clearly distinguishable from MRSA isolates arising from other hospital wards. The combination of REAP and AP-PCR provided complementary information in several instances. Aggressive measures t o isolate infected patients and eradicate colonization from patients a nd staff terminated the outbreak.Conclusions.-Although traditional epi demiologic methods retain their central role in modem hospital infecti on control, molecular epidemiologic analysis can significantly enhance the ability of infection control officers to analyze and terminate ho spital epidemics. The combination of AP-PCR and REAP may prove to be a particularly informative means of tracking the nosocomial spread of m icrobial strains and their mobile genetic elements.