Jpn. J. Infect. Dis., 53, 164-165, 2000

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Short Communication

An Increase in Multi-Drug-Resistant Isolates of Salmonella Typhimurium from Healthy Carriers in Aichi, Japan

Masakado Matsumoto*, Masahiro Suzuki, Reiji Hiramatsu, Mitsugu Yamazaki, Hironori Matsui, Kenji Sakae, Yasumoto Suzuki and Yutaka Miyazaki

Department of Microbiology, Aichi Prefectural Institute of Public Health
7-6 Nagare Tsuji-machi, Kita-ku, Nagoya 462-8576, Aichi, Japan

(Received September 5, 2000. Accepted September 14, 2000)

SUMMARY: To investigate the prevalence of drug-resistant isolates of Salmonella Typhimurium in Aichi, Japan, we performed antimicrobial susceptibility tests for 148 isolates from healthy carriers, and from sporadic and outbreak cases of salmonellosis from 1980 to 1999. We found an increase in drug-resistant isolates from 56% (37/66) in the 1980s to 74% (61/82) in the 1990s due to increasing examples of four-, five-, and six-drug resistances. Of 98 resistant isolates in 1980-1999, 12 were identified as ampicillin (A)-, chloramphenicol (C)-, streptomycin (S)-, sulfonamide (Su)-, and tetracycline (T)-resistant S. Typhimurium (4 in the 1980s, 8 in the 1990s), whose pattern was identical to that of multi-drug-resistant S. Typhimurium definitive phage type 104 (DT104) which has been recently detected in various developed countries. Six-drug-resistance ACSSuTP (piperacillin), in which P was added to the core pattern of the ACSSuT, was also found in four isolates in the 1980s and seven in the 1990s. Another six-drug-resistant pattern, ACSSuTN (nalidixic acid), appeared in five isolates in the 1990s. These multi-drug-resistant isolates were predominately found in healthy carriers (21/28), suggesting that in Aichi the multi- (five- or six-) drug-resistant isolates of S. Typhimurium have existed in healthy carriers as well as in diarrhea patients in 1980 to 1999.

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