In vitro survival at low ph and acid adaptation response of Campylobacter jejuni and Campylobacter coli

The survival of Campylobacter jejuni and Campylobacter coli at pH 7.0, 6.0, 5.0 and 4.0 for up to 24 h, and the induction of an acid adaptation response in 12 C. jejuni and 10 C. coli strains in early exponential or late stationary phases in tryptic soy broth (TSB) and Brucella broth were investigated. C. coli strains were more sensitive than C. jejuni in media adjusted to pH 5.0 or 4.0 with hydrochloric acid. Five log 10 cfu/mL of C. coli were inhibited at 12 h in pH 5.0, but only 2.5 log 10 cfu/mL of C. jejuni cells were inhibited under the same conditions. No viable cells were detected at 4 h in pH 4.0 from an inoculum of 6 log 10 cfu/mL of C. coli. Late stationary phase cells of C. jejuni exposed to pH 5.0 for 4 h in TSB exhibited a significant (P ≤ 0.05) acid tolerance response when compared to nonexposed cells. Late stationary phase cells of C. coli exposed to pH 5.0 for 3 h in TSB and late stationary and early exponential phase cells exposed to pH 5.0 for 3 h in Brucella broth showed a significant (P ≤ 0.05) acid tolerance response when compared to nonexposed cells. The acid tolerance responses observed for C. jejuni and C. coli conferred adapted cells no more than 1 logic cfu/mL survival advantage over nonadapted cells. Brucella broth appeared to be more protective than TSB for the survival of C. jejuni and C. coli at pH 4.0.