Value of molecular epidemiologic analysis in a nosocomial methicillin-resistant Staphylococcus aureus outbreak
F. C. Fang, M. McClelland, D. G. Guiney, M. M. Jackson, A. I. Hartstein, V. H. Morthland, C. E. Davis, D. C. McPherson and J. Welsh
Division of Infectious Diseases, University of California-San Diego Medical Center.
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.
