In vitro Assessment of Temperature and pH Dependent Growth Patterns of Campylobacter jejuni and coli

Introduction: Campylobacter spp. are among the main bacterial causes of acute gastroenteritis worldwide. Despite their fragile nature, they survive in the environment and food chain, likely overcoming several stressful challenges. However, little is known about their response to adverse conditions. Purpose: The aim of this study was to investigate the survival of Campylobacter jejuni and coli at various temperatures (32, 37, 42, and 47 °C) and pH ranges (5, 7, and 9) in laboratory media. Methods: ATCC strains of Campylobacter jejuni (BAA-1062) and coli (43481) were cultured separately in tryptic soy broth (TSB). In order to adapt bacteria to a mild stress, broth cultures were further inoculated in TSB at pH 6 and 8. After 24 h, the pH 6 culture was inoculated in TSB at pH 5, while the pH 8 culture in TSB at pH 9. Aliquots of these broths were incubated at 32, 37, 42 and 47 °C. A pH 7 culture was used as control and samples were taken at 0, 2, 4, and 24 h, spread plated onto Campy Cefex agar, and incubated for 48 h at 42 °C. Results: Extreme thermal and pH conditions (i.e. 32 and 47 °C, pH 5 and 9) resulted in variable behavior of Campylobacter spp. Although Campylobacter jejuni and coli populations at pH 5 and 9 were significantly (p<0.05) lower than those at pH 7, the survival populations were approximately 6 log10 CFU/ ml. Temperature (37 and 42 °C) did not affect (p>0.05) the growth patterns of Campylobacter spp. and no interactions between strain, pH, incubation temperature, and sampling time were detected. Significance: Results suggest that Campylobacter jejuni and coli do not respond well to multiple stresses, but have the ability to adapt to low and high pH. Therefore they can resist typical sanitation practices and persist in the environment leading to human illnesses.