Epidemiological stydy of methicillin-resistant Staphylococcus Aureus (MRSA) by pulsed-field gel electrophoresis in burn unit at Siriraj Hospital

Abstract

During 32 weeks consecutive study, it was found that there were 16 out of 30 burn patients (53.33%) who carried MRSA in their nasal cavities, hands, and wounds as well as 8 out of 54 medical personnel (14.81%) were MRSA nasal carriers. MRSA were also isolated from medical equipments which were bed rails, enteral pump, and bath tubs. In the Traumatic ICU, MRSA were isolated from 3 out of 11 patients (27.27%). There was no medical personnel who was MRSA nasal carrier. All MRSA isolates were discriminated into 22 antimicrobial patterns and 5 pulsotypes. The predominant antibiogram type were type 17 and 14. There were only 5 MRSA pulsotypes ; A, B, C, D and E. The most prevalent type in this study was type B. Pulsotype A also consisted of subtype A1, A2 and A3 ; pulsotype B consisted of subtype B1, B2, B3, B4, B5 and B6 ; pulsotype E consisted of subtype E1. There is no correlation between antibiogram and pulsotypes. The results from antimicrobial susceptibility test was indicated that vancomycin was still the effective agent to treat MRSA infection, because all isolates were susceptible to this agent (100%). This study also indicated that the burn unit was still the importan source of MRSA. Eventhough, MRSA with pulsotype B had been shown to be the outbreak strain in the burn unit. The route of transmission was not clearly identified. Carrier among the staff has been shown not to be significant in this study as well as the medical equipment. The spread of the organisms could possibly be transient hand borne, airborne and environment contaminant. The most antimicrobial agents used in the burn unit were beta-lactam antibiotics, which were 1st, 2nd generation of cephalosporin. There were 13 out of 16(81.25%) MRSA-positive patients who received these antimicrobial agents for at least 3 days before MRSA was detected, while only 4 out of 14 (28.57%) MRSA-negative patients received these agents for 3 days or more.