In a study of the Kanagawa phenomenon of Vibrio parahaemolyticus, both Kanagawa-positive and-negative strains were found to produce hemolytic factors that could not be differentiated on Wagatsuma blood agar. The presence of fermentable carbohydrates in media containing high concentrations of NaCl promoted the growth of V. parahaemolyticus and resulted in a marked decrease in medium pH and increased hemolysin production. The Kanagawa hemolysis of test strains differed according to the carbohydrates added. Clearly defined Kanagawa hemolysis was observed in blood agars of high salt content, but the distinction was lost in media containing 3% NaCl. From the results of this study, the Kanagawa hemolysis was interpreted as an expression of quantitative difference in hemolysin production, a conclusion that is clearly demonstrated on special blood agar of high salt content.

A total of 949 strains of Salmonella typhi isolated in Korea from 1968 to 1975 were tested for drug resistance and distribution of R plasmids. Resistance was mostly restricted to streptomycin (SM) and sulfisomidine (SA), singly or in combination, at a low degree. A small number of strains (1.5%) were resistant to four or more drugs: chloramphenicol (CM), tetracycline (TC), SM, SA, ampicillin (AP), and kanamycin (KM). No strain was resistant to nalidixic acid or to a 1:20 mixture of trimethoprim and sulfamethoxazole. Nor was there any strain singly resistant to CM, TC, AP, or KM. Transfer experiments of multiple-drug resistance to Escherichia coli ML1410 showed that all the strains resistant to four or more drugs carried R plasmids, whereas those weakly resistant to three or less drugs did not. The quadruply resistant strains carried one R plasmid determining CM, TC, SM, and SA resistance, and sextuply resistant ones carried two plasmids, one determining CM, TC, SM, and SA resistance and the other determining AP and KM resistance. One strain carrying a plasmid determining AP and KM resistance was also found. The transfer frequency of CM, TC, SM, and SA resistance was much higher than that of AP and KM resistance. The resistance of S. typhi was more efficiently transferred to E. coli at 25°C than at 37°C.

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SUMMARYThe majority (85 %O) of shigella isolated in 1980 and 1981 in Korea were Shigella flexneri, the others were Sh. sonnei (14 %) with only a small number of Sh.dysenteriae. Only 14 of the 459 strains of shigella isolated were susceptible to all 12 drugs tested, and 445 were resistant to three or more drugs. Strains multiply resistant to the six drugs, chloramphenicol (Cm), tetracycline (Tc), streptomycin (Sm), sulfisomidine (Su), ampicillin (Ap) and trimethoprim (Tp) were most frequently encountered, followed by those resistant to Cm, Tc, Sm, Su and Tp. The complete patterns of resistance to drugs except nalidixic acid and rifampin in approximately 73 % of drug-resistant strains were co-transferred to Escherichia coli by conjugation, indicating that the resistance was R plasmid-mediated. Randomly selected R plasmids conferring various patterns of resistance markers were tested for the incompatibility groups, and almost all of them were classified into Inc FIl. Two of three R plasmids conferring resistance to Cm, Tc, Sm and Su were classified into Inc B and one to Inc FIl. Two R types with resistance markers of Cm, Tc, Sm and Ap were not classified with our standard plasmids used.

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