Molecular analysis and antimicrobial resistance of Vibrio cholerae O1 in northeastern Thailand.

A total of 84 clinical Vibrio cholerae O1 isolates were collected from Khon Kaen (KK), Udon Thani (UT), Loei (LI), and Nong Khai (NK), northeastern Thailand during cholera outbreaks in 2007 and 2008. The majority of V. cholerae O1 strains carried nearly all the virulence-associated genes (ctxA, zot, and ace) except for four isolates and one isolate from UT and NK, respectively, which carried only tcpA, ompU, hlyA and toxR. None of the V. cholerae O1 strains carried sto. Pulsed field gel-electrophoresis (PFGE) profiling of 16 randomly chosen isolates showed the same PFGE pattern, except for one NK isolate, which was sensitive to all seven antibiotics used in the antimicrobial susceptibility tests. The tests revealed that multi-drug resistance to tetracycline and co-trimoxazole were present in KK strains (92%), followed by LI (75%) and UT (52%) strains. All strains were sensitive to norfloxacin but intermediate resistance to ciprofloxacin was found in a single strain from KK and LI. Differences in antimicrobial resistance among V. cholerae strains with the same PFGE pattern reflect differences in the antimicrobial agents used in each area of northeastern Thailand.