Source and route of methicillin-resistant Staphylococcus epidermidis transmitted to the surgical wound during cardio-thoracic surgery. Possibility ofpreventing wound contamination by use of special scrub suits

The objective of this study was to trace the source and route of transmissi on of methicillin-resistant Staphylococcus epidermidis (MRSE) in the surgic al wound during cardio-thoracic surgery, and to investigate the possibility of reducing wound contamination by wearing special scrub suits. In total 6 5 elective operations for coronary artery bypass grafting (CABG) with or wi thout concomitant valve replacement were investigated. All staff present in the operating room wore conventional scrub suits during 33 operations and special scrub suits during 32 operations. Samples were taken from the hands of the scrubbed team after surgical scrub but before putting on sterile go wns and gloves, and front patients' skin (incisional area of sternum and ve in harvesting area of legs) after preoperative skin preparation with chlorh exidine gluconate. Air samples were taken during operations. Samples were a lso taken from the wound just before closure. Total counts of bacteria on s ternal skin and from the wound (cfu/cm(2)) were calculated as well as total counts of bacteria in the air (cfu/m(3)). Strains of MRSE recovered from t he different sampling sites were compared by pulsed field gel electrophores is (PFGE). It was found that wearing special scrub suits did not reduce the number of air-samples where MRSE was found compared with conventional scru b suits. The risk factor most strongly associated with MRSE in the wound at the end of the operation was preoperative carriage of MRSE on sternal skin ; RR 2.42 [95%, CI 1.43-4.10], P=0.021. By use of PFGE, it was possible to identify the probable source for four MRSE isolates recovered from the woun d. In three cases the source was the patients own skin. Finding MRSE in air -samples, or on the hands of the scrubbed team, were not risk factors for t he recovery of MRSE in the wound at the end of operation. In conclusion, wi th a total bacterial air count around 20cfu/m(3) and a low proportion of MR SE, the reduction of total air counts by use of tightly woven special scrub suits did not reduce air counts of MRSE or wound contamination with MRSE. The patients' sternal skin was the main source for wound contamination with MRSE.