We used molecular typing methods to investigate an outbreak of methicillin-resistant Staphylococcus aureus (MRSA) infections in a respiratory care ward in Taiwan. From March to June 2006, the incidence of MRSA infection increased 3.75-fold. The overall carrier rates among the health care workers (HCWs) were 31.3% (total S. aureus), 16.4% (MRSA), and 14.9% (methicillin-sensitive SA, MSSA). Pulsed-field gel electrophoresis (PFGE), multilocus sequence typing (MLST), antibiograms derived from susceptibility testing of MRSA isolates, and multiplex polymerase chain reaction (PCR) provided strong epidemiologic and microbiologic evidence that the outbreak of MRSA infections at our hospital was linked to the same PFGE pulsotype A SCCmec type II, pvl-negative, MLST ST5 strain of MRSA isolated from seven HCWs and five patients. The outbreak was controlled by application of topical fucidin ointment to the anterior nares in all colonized HCWs. Multiplex PCR combined with PFGE and MLST is a feasible method for outbreak investigations in routine clinical laboratories.
