Effect of Temperature and pH on the Survival of Campylobacter fetus1

Abstract

Test strains of C. fetus subsp. jejuni and C. fetus subsp. intestinalis failed to survive heating in skimmilk at 60 C for 1 min. A few strains survived heating in skimmilk at 55 C for 1–3 min. D50C values for C. fetus subsp. jejuni and C. fetus subsp. intestinalis in skimmilk ranged from 1.3–4.5 and from 1.0–3.7, respectively. No survivors of C. fetus subsp. jejuni and C. fetus subsp. intestinalis were detected in beef roasts inoculated at levels of 106–107 viable cells per g when the final temperature in the center was 57 and 55 C, respectively. At an internal temperature of 50–53 C, survivors of C. fetus were detected in beef roasts. Storage of skimmilk, beef and ground beef inoculated with C. fetus at −20, 1, 10, 20, 30 or 40 C resulted in decreases in C. fetus count. Survival of C. fetus was best at 1 and 10 C. Rapid increases in C. fetus counts occurred at 37 C in Brucella broth adjusted to pH 6–8. At pH 5, no survivors were detected after 24 h. At pH 9, counts of C. fetus subsp. jejuni decreased rapidly while those of C. fetus subsp. intestinalis increased slightly.