Drug Resistance of Enteric Bacteria IX. Distribution of R Factors in Gram-negative Bacteria from Clinical Sources

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Abstract
Many isolates belonging to the Enterobacteriaceae were collected in 1965 from the inpatients at geographically scattered hospitals in Japan. Among 2,650 Shigella strains examined, 58.4% were found to be drug-resistant; 95.0% of these resistant strains were multiply resistant. Among 434 resistant strains examined, 81% carried R factors that were transferable by cell-to-cell contact. Of 160 isolates of other enteric bacteria, drug-resistant strains included 84.2% of the Escherichia coli , 93.0% of the Klebsiella , and 90.0% of the Proteus cultures. Among these resistant strains, 70.3% of the E. coli , 66.7% of the Klebsiella , and 52.0% of the Proteus were multiply resistant. Of these resistant strains, 84.0% of the E. coli , 88.0% of the Klebsiella , and 50.0% of the Proteus strains carried R factors. These results indicate that R factors are widespread among gram-negative bacteria of clinical significance.