Acid adaptation of Vibrio vulnificus and subsequent impact on stress tolerance

Three strains of Vibrio vulnificus were evaluated for their potential to become acid adapted in tryptic soy broth with 2% NaCl acidified using hydrochloric (pH 5.0), citric or acetic acids (pH 5.5). Control and adapted cells were subsequently evaluated for acid tolerance (pH 3.5) in broths acidified with each acid, respectively. Other cross-protective effects: heat tolerance, cold storage survival, and freeze-thaw resistance were evaluated with cells exposed to broths acidified with hydrochloric acid. Acid adaptation was observed with hydrochloric and citric acids (P<0.05) and was dependent on strain, duration of adaptation time, and acid type. The most pronounced acid adaptation response was with hydrochloric acid, regardless of strain (P<0.05). Treatment with chloramphenicol eliminated the acid tolerance response. The three strains were inactivated within 12 min at 47 °C with or without acid adaptation. Acid adaptation increased freeze-thaw resistance and cold storage survival for one strain following 10 h acid adaptation (P<0.05).