QUANTITATIVE ANTIBIOGRAM AS A TYPING METHOD FOR THE PROSPECTIVE EPIDEMIOLOGIC SURVEILLANCE AND CONTROL OF MRSA - COMPARISON WITH MOLECULAR TYPING

OBJECTIVE: Evaluation of the quantitative antibiogram as an epidemiolo gical tool for the prospective typing of methicillin-resistant Staphyl ococcus aureus (MRSA), and comparison with ribotyping. METHODS: The me thod is based on the multivariate analysis of inhibition zone diameter s of antibiotics in disk diffusion tests. Five antibiotics were used ( erythromycin, clindamycin, cotrimoxazole, gentamicin, and ciprofloxaci n). Ribotyping was performed using seven restriction enzymes (EcoRV, H indIII, KpnI, PstI, EcoRI, SfuI, and BamHI). SETTING: 1,000-bed tertia ry university medical center. RESULTS: During a 1-year period, 31 pati ents were found to be infected or colonized with MRSA. Cluster analysi s of antibiogram data showed nine distinct antibiotypes. Four antibiot ypes were isolated from multiple patients (2, 4, 7, and 13, respective ly). Five additional antibiotypes were isolated from the remaining fiv e patients. When analyzed with respect to the epidemiological data, th e method was found to be equivalent to ribotyping. Among 206 staff mem bers who were screened, six were carriers of MRSA. Both typing methods identified concordant of MRSA types in staff members and in the patie nts under their care. CONCLUSIONS: The quantitative antibiogram was fo und to be equivalent to ribotyping as an epidemiological tool for typi ng of MRSA in our setting. Thus, this simple, rapid, and readily avail able method appears to be suitable for the prospective surveillance an d control of MRSA for hospitals that do not have molecular typing faci lities and in which MRSA isolates are not uniformly resistant or susce ptible to the antibiotics tested.