Surgical Site Infection by Methicillin-Resistant Staphylococcus aureus after Cardiovascular Operations: An Outbreak and Its Control

We encountered 15 cases of surgical site infection (SSI) by Methicillin-resistant Staphylococcus aureus (MRSA) among 153 patients who underwent a cardiovascular operation in 2000. SSIs consisted of 5 mediastinal infections, 9 surface wound infections and 1 artificial graft infection after an abdominal aortic surgery. All infected cases had been operated on between June and December 2000. Eighty-three cases, which underwent cardiovascular operations during this period, were divided into SSI or no-SSI groups and their clinical data were analyzed. The data included age, gender, preoperative diabetes, urgency, preoperative usage of a device like Swan-Ganz catheter or IABP, preoperative albumin level, preoperative physical state by ASA score, National Nosocominal Infections Surveillance index, duration of operation, usage of a cardiopulmonary bypass, duration of bypass, type of operation, and number of distal anastomoses in CABG operations. Multivariate analysis showed gender (male), diabetes, and emergency operation as independent risk factors for the incidence of SSI by MRSA. One patient, who suffered a mediastinal infection after CABG, had confirmed as demonstrating the colonization of MRSA in sputum preoperatively. Microbiological screening of medical staff showed 2 of the 6 surgical doctors and 3 of the 25 ward nurses exhibited colonization with MRSA. DNA analysis of MRSA, harvested from 5 infected patients, indicated at least 2 strains of MRSA and 1 of the 2 strains was identical to the MRSA that was detected in a doctor. We applied prophylactic measures with reference to the guideline for prevention of surgical site infection announced by CDC in 1999, which included the following: routine work-up of MRSA-colonization, and treatment of all MRSA colonized patients and those undergoing emergency operations with Mupirocin. Preoperative patients were isolated from MRSA-infected or colonized patients. MRSA-colonized surgical personnel were treated with Mupirocin ointment. Cephazoline was administered shortly before and after the operation as a prophylactic antibiotic. Vancomycin was added to Cephazoline in patients with a history of MRSA-colonization or infection. Through hand washing before and after daily contact with patients was emphasised to all medical staff. SSI surveillance conducted by an infection control team was implemented. After the introduction of the prophylactic measurements, one MRSA-SSI was observed among 113 cases who underwent a cardiovasc