Value of molecular epidemiologic analysis in a nosocomial methicillin-resistant Staphylococcus aureus outbreak

Abstract

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 DNA (REAP) was used in the analysis of 45 MRSA isolates. After termination of the outbreak, isolates were retrospectively analyzed in a blind fashion using the newly described technique of arbitrarily primed polymerase chain reaction (AP-PCR). Molecular analyses were compared with epidemiologic and antimicrobial susceptibility data.

Setting: Tertiary care university hospital.

Subjects: Twenty-eight patients and 12 employees infected or colonized with MRSA during a 6-week period.

Results: A clonal relationship demonstrated among isolates from burn unit patients 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 to isolate infected patients and eradicate colonization from patients and staff terminated the outbreak.

Conclusions: Although traditional epidemiologic methods retain their central role in modern hospital infection control, molecular epidemiologic analysis can significantly enhance the ability of infection control officers to analyze and terminate hospital epidemics. The combination of AP-PCR and REAP may prove to be a particularly informative means of tracking the nosocomial spread of microbial strains and their mobile genetic elements.