Increasing Drug Resistance in Vibrio cholerae O1 and non-O1 Strains Isolated from Diarrheal Cases in Japan

Drug resistance trends were investigated for 271 Vibrio cholerae O1 (V. c O1) and 401 V. cholerae non-O1 (V. c non-O1) strains isolated from mainly imported diarrheal cases during 1981-2001 in Japan. The results of drug resistance test using 8 drugs (CP, TC, SM, KM, ABPC, ST, NA, and NFLX) showed that 34.7% of the V. c O1 strains and 15.7% of V. c non-O1 strains were multi-drug or mono-drug resistant. The incidence of drug resistant strains has increased since 1991, and it has been remarkable in V. c O1 strains that increased from 1.2% in 1981-1985 to 70.8% in 1996-2001. The drug resistance patterns of the resistant strains classified into 6 types in V. c O1 and 21 types in V. c non-O1. The prevalent patterns recognized were SM (75.5%), CPz·TC·SM·ST (10.6%) and CP·SM·ST (8.5%) in V. c O1, and SM (25.4%) and ABPC (25.4%) in V. c non-O1. Ten V. c O1 strains (3.7%) and 10 V. c non-O1 strains (2.5%) were multi-drug resistant including TC. Among those, 13 strains were isolated from travelers who returned to Japan from Thailand. One V. c O1 strain (0.4%) and 6 V. c non-O1 strains (1.5%) were NA high-resistant and fluoroquinolones low-sensitive. Among those, 4 strains were isolated from travelers who returned to Japan from India.