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 log10 cfu/mL of C. coli were inhibited at 12 h in pH 5.0, but only 2.5 log10 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 log10 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 log10 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. PRACTICAL APPLICATIONS This research can help us understand the extent of Campylobacter reduction on meat surfaces by decontamination strategies based on low pH. If the 3 Corresponding author. TEL: 334-844-2608; FAX: 334-844-2641; EMAIL: [email protected] Journal of Food Safety 27 (2007) 326–343. All Rights Reserved. © 2007, The Author(s) Journal compilation © 2007, Blackwell Publishing 326 protection by acid adaptation response is minimal, the surface pH of poultry meat could be decreased temporarily to significantly reduce the contamination with Campylobacter. The reduction effect of lemon-based marinades on artificially inoculated and naturally occurring Campylobacter could be quantified and used to develop low-pH marinades for the reduction of Campylobacter spp. Studies could also focus on the development of new processing and preservation techniques that could reduce Campylobacter spp. in highly contaminated food products. In addition, research on the human health implications of Campylobacter cells that survive other sublethal stressors, such as lowor high-temperature shock or starvation, could elucidate if any crossprotection effect is expressed by Campylobacter spp.