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Two hundred forty-one strains of Salmonella typhii isolated in Lima, Peru, from October 1981 through February 1983 were tested for susceptibility to antimicrobial agents. Seventy-two strains (29.9%) were resistant to chloramphenicol and other antibiotics, including ampicillin, sulfonamides, and trimethoprim. The minimal inhibitory concentrations of 17 antimicrobial agents were determined for all of these chloramphenicol-resistant strains. Sch 25393, new beta-lactams, new quinolones, and the formulation clavulanic acid-amoxicillin were effective against all the strains. Four different resistance patterns distributed among eight phage types were observed. The 72 resistant S. typhi could transfer the resistance marker into Escherichia coli C1, and all the plasmids belonged to the incompatibility group H1.

The distribution of the aphA6 gene, encoding a 3'-aminoglycoside phosphotransferase type VI, was studied by dot blot hybridization with 115 amikacin-resistant Acinetobacter strains from various geographical areas. Nucleotide sequences related to aphA6 were found in 109 strains belonging to seven species. As inferred from results of Southern hybridization, dissemination of amikacin resistance in Acinetobacter spp. is due to a gene rather than a strain or plasmid epidemic.

Species, biotypes, and phage types were determined for 120 Acinetobacter strains from clinical or environmental sources or from culture collections. These characteristics were compared with cell envelope protein profiles obtained by sodium dodecyl sulfate-polyacrylamide gel electrophoresis hi previous studies. A considerable heterogeneity of species and types was observed by use of the various methods, in particular among strains from different sources. Acinetobacter baumannii was the most commonly found species in isolates from clinical sources, followed by Acinetobacter species 3. Nine biotypes were observed among A. baumannii strains. Further differentiation within most species and biotypes was achieved by protein profile typing and, to some extent, phage typing. Of 120 strains, 49 (41%) were not typeable by phages. Consistent results for the various classification methods were obtained for strains from common sources. Biotyping seemed an appropriate method for the screening of strains, whereas protein profile and phage typing could serve as additional methods to establish the identity or nonidentity of strains. Results of this study suggest that the combination of the typing methods is useful in epidemiological studies.

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