Bacillus subtilis PS-216 Antagonistic Activities against Campylobacter jejuni NCTC 11168 Are Modulated by Temperature, Oxygen, and Growth Medium

Abstract

As the incidence of <i>Campylobacter jejuni</i> and campylobacteriosis grows, so does the need for a better understanding and control of this pathogen. We studied the interactions of <i>C. jejuni</i> NCTC 11168 and a potential probiotic, <i>Bacillus subtilis</i> PS-216, in cocultures at different starting ratios and temperatures (20 °C, 37 °C, 42 °C), under different atmospheres (aerobic, microaerobic), and in different growth media (Mueller-Hinton, chicken litter medium, chicken intestinal-content medium). Under microaerobic conditions, <i>B. subtilis</i> effectively inhibited the growth of <i>C. jejuni</i> at 42 °C (log reduction, 4.19), even when <i>C. jejuni</i> counts surpassed <i>B. subtilis</i> by 1000-fold in the starting inoculum. This inhibition was weaker at 37 °C (log reduction, 1.63), while no impact on CFUs was noted at 20 °C, which is a temperature nonpermissive of <i>C. jejuni</i> growth. Under aerobic conditions, <i>B. subtilis</i> supported <i>C. jejuni</i> survival. <i>B. subtilis</i> PS-216 inhibited the growth of <i>C. jejuni</i> in sterile chicken litter (4.07 log reduction) and in sterile intestinal content (2.26 log reduction). In nonsterile intestinal content, <i>B. subtilis</i> PS-216 was able to grow, to a lesser extent, compared to Mueller-Hinton media, still showing potential as a chicken probiotic that could be integrated into the chicken intestinal microbiota. This study showed the strong influence of environmental parameters on the variability of <i>C. jejuni</i> and <i>B. subtilis</i> interactions. Furthermore, <i>B. subtilis</i> PS-216 antagonism was strongest against <i>C. jejuni</i> NCTC 11168 under conditions that might represent conditions in the chicken environment (42 °C, microaerobic atmosphere, chicken litter medium).