DNA TYPING AND CONTROL OF METHICILLIN-RESISTANT STAPHYLOCOCCUS-AUREUSAT 2 AFFILIATED HOSPITALS

OBJECTIVE: To describe control of endemic and outbreak-related methici llin-resistant Straphylacoccus aureus (MRSA) at two affiliated hospita ls. DESIGN: Prospective surveillance of patients with MRSA. Disposable gloves were used by all staff having direct contact with the affected patient or his immediate environment and patient isolates were typed by pulsed-field gel electrophoresis (PFGE) of genomic DNA. Surveillanc e and PFGE typing were used concurrently to identify possible nosocomi al outbreaks, confirm or refute cross-infection, and support a need fo r additional outbreak control interventions. SETTING: A university hos pital (Hospital A) and a university-affiliated public hospital (Hospit al B). PARTICIPANTS: Patients with MRSA colonization or infection over an 18-month interval (June 1993-November 1994). INTERVENTION: Proper handwashing and gloving practices were reemphasized with staff followi ng confirmation of outbreaks. RESULTS: Hospital A had 60 community-acq uired and 48 nosocomial cases of MRSA. Two small outbreaks (affecting a total of seven patients) and two pseudo-outbreaks were identified. H ospital B had 36 community-acquired and 22 nosocomial cases of MRSA. O nly one outbreak affecting five patients occurred. All outbreaks ended shortly after staff meetings that emphasized ongoing and extremely ca reful handwashing and gloving when caring for identified patients. The majority of nosocomial cases at both hospitals were not related epide miologically or had isolates with unique PFGE types. Pseudo-outbreaks were confirmed by demonstrating that isolates from epidemiologically r elated cases (by time and clinical service or hospital unit) had diffe rent PFGE types. Hospital A cases had 39 different PFGE types, and Hos pital B cases had 31 different PFGE types. CONCLUSION: MRSA in hospita ls, including out-breaks identified by prospective surveillance and co nfirmed by PFGE typing, can be controlled by minimal special precautio ns and interventions. This is possible despite the continuous admissio n of patients with MRSA from the community. PFGE typing is useful to c onfirm outbreaks and pseudo-outbreaks, demonstrate differences among e pidemiologically unrelated isolates, and substantiate the efficacy of MRSA control programs within hospitals.