Susceptibility of O3:K6 and Environmental Strains of Vibrio parahaemolyticus to Acid Inactivation, and Survival Competition between these Strains and Pseudomonas fluorescens and Indigenous Bacteria
YI-SHIN CHEN, MENG-YI CHEN AND HIN-CHUNG WONG*
Department of Microbiology, Soochow University, Taipei City 111, Taiwan (R.O.C.)
(Received: August 13, 2002; Accepted: July 7, 2003)
ABSTRACT
(Received: August 13, 2002; Accepted: July 7, 2003)
Vibrio parahaemolyticus is a common food poisoning pathogen associated with seafood. New O3:K6 strains originating from India in 1996 were the first pandemic strains and spread rapidly throughout many Asian countries. This study examines the characteristics of these new O3:K6 strains with respect to acid susceptibility and survival competition with Pseudomonas fluorescens and indigenous oyster spoilage microflora. Results revealed that the exponential phase cultures of new O3:K6 strains were significantly more tolerant of acid at pH 3.0 than the environmental strains. In these co-culture experiments, survival of the V. parahaemolyticus strains was influenced by the bacterial strains, incubation medium and incubation temperature. All V. parahaemolyticus strains showed similar survival ability when co-cultured with P. fluorescens in 1/10 tryptic soy broth. In the oyster medium, the environmental strain survived better than the new O3:K6 strains at 4 or 25℃. Both of the new O3:K6 strains (1121 and 1137) showed similar survivability in this study. These data offer hints on the survival of the new O3:K6 strains and their ability to spread.
Key words: Vibrio parahaemolyticus, O3:K6, Pseudomonas fluorescens, growth, oyster, acid susceptibility