Nosocomial propagation of multiresistant Staphylococcus aureus: an analysis using biotyping and drug sensitivity.

We performed an epidemiologic study of multi-resistant Staphylococcus aureus in our hospital. We combined bacteriologic biotyping and sensitivity to 19 drugs to conduct an environmental investigation. We assumed that complete matching in two or more strains denoted nosocomial propagation. A total of 667 isolates were recovered from a total of 144 patients. In a general surgical ward, 19 (52.8%) out of 36 patients developed an infection. The number of strains for every biotype and the combined susceptibility tended to show negative correlation (r = -0.376) before and after 1990, when an isolation policy was initiated. A similar regression analysis disclosed that between the general surgical ward and other wards the number of strains tended to show a positive association (r = 0.349). Thus, the isolation system employed in the general surgical ward may have arrested the persistence of intraward strains but permitted the interward travel of strains. In conclusion, an analysis of the propagation of multiresistant S. aureus using biotyping and drug sensitivity was found to be an effective method for evaluating the most appropriate measures to counter the endemic spread of this microbe.