Distribution of R Factors among Shigella Strains Isolated in Japan (II)

抄録

Shigella strains isolated in Japan from 1968 through 1970 were surveyed for drug resistance and distribution of R factors. Of the 2688 strains, 93.4% were resistant to either one or various combinations of four drugs, tetracycline (TC), chloramphenicol (CM), streptomycin (SM) and sulfanilamide (SA). Among these resistant strains, 74.2, 10.7, 1.48, and 13.6% were quadruply, triply, doubly, and singly resistant, respectively. Fifty-eight per cent of these resistant strains were found to carry R factors when judged by transferability of the resistance. The isolation frequencies of R (TC. CM. SM. SA), R (CM. SM. SA), R (SM. SA), and R (TC. SM. SA) factors were 73.2, 13.0, 11.5, and 1.3%, respectively. The strains resistant to drugs other than the aforementioned four were very few; 4.3, 3.4, and 0.7% being resistant to ampicillin (APC), nalidixic acid (NA), and kanamycin (KM), respectively. Among 117 APC-resistant strains, 97.4% could transfer their APC resistance together with other resistance markers. Seventeen out of 18 KM-resistant strains could transfer KM resistance by mixed culture. But none of the NA-resistant strains could transfer their NA resistance. The authors could demonstrate strains carrying two different R factors in a cell and one of them was consistently an R (SM. SA) factor. These results were very similar to those obtained in surveys of strains isolated from 1965 through 1967.