A MOLECULAR EPIDEMIOLOGIC-STUDY OF METHICILLIN-RESISTANT STAPHYLOCOCCUS-AUREUS INFECTION IN PATIENTS UNDERGOING MIDDLE-EAR SURGERY

The incidence of methicillin-resistant Staphylococcus nut-eus (MRSA) i nfections after middle ear surgery has recently increased at our hospi tal. Most of these infections were thought to be hospital-acquired whe n medical personnel in contact with an MRSA-infected patient may have inadvertently transmitted the pathogen to other patients. To prevent f urther transmission it is essential that such sources of MRSA infectio n and transmission routes be selected out and eradicated. Therefore, i t is necessary to determine whether the strains of MRSA isolated from infected patients are identical to those obtained from medical personn el in order to prove a reciprocal transmission of organisms between me dical personnel and patients. Surveillance bacterial cultures from the anterior nares and hands of medical personnel working in the Departme nt of Otolaryngology, Korea University Guro Hospital, were performed a t two different time points: 6 December 1994 and 17 June 1996. Ribotyp ing with Southern blot technique was used to compare 12 MRSA strains f rom medical carriers with 60 strains identified from the otorrhea of M RSA-infected patients undergoing middle ear surgery. As result, six di fferent MRSA strains were identified (types I, II, III, IV, V and VI) from ribotyping with EcoR1. One distinct subtype, type I strain, was t he most frequently identified strain in both medical carriers and pati ents. Results also showed that 6 MRSA isolates from 10 medical carrier s and 20 from 30 patients contained type I ribotype at first culture. Two medical carriers' isolates and 13 isolates from 30 patients shared the same type I strain at the second surveillance culture, In all, 41 out of 72 MRSA strains (56.9%) shared an identical ribotype pattern. Postoperative MRSA infection rates after treatment of medical carriers and the application of rigorous preventive procedures decreased from 11.9 to 5.7% after first culture and 9.0 to 7.7% following second cult ures. These findings confirm that MRSA transmission can occur between medical personnel and patients and that effective preventive measures can reduce the postoperative infection rate.