The main objectives of the proposed research project are: (a) The epidemiological analysis of emerging antibiotic resistance patterns in hospital infections, and (b) The development of experimental models which could contribute to the understanding of the appearance of multiple resistance. Resistance patterns of enteric bacteria will be monitored in several hospitals in New York City, with special emphasis on transferable and nontransferable gentamicin resistance. R factors will be characterized by enzymatic analysis and compatibility patterns. Multiple antibiotic resistance in Staphylococcus will be analyzed with mannitol positive S. epidermidis strains and S. aureus strains of group III. In S. epidermidis genetic markers of plasmids determining mannitol fermentation will be analyzed, followed by attempts of genetic transfer by transduction or transformation. With S. aureus strains of group III it will be attempted to characterize, genetically and biochemically, minocycline and oxacillin resistance. BIBLIOGRAPHIC REFERENCES: E. Noriega, R. E. Leibowitz, A. S. Richmond, E. Rubinstein, S. Schaefler, M. Simberkoff and J. J. Rahal, Jr. Nosocomial Infection Caused by Gentamicin-Resistant Streptomycin-Sensitive Klebsiella. J. Infect. Dis. Vol. 131, S45-S50, 1975.