Characterisation of Aerotolerant Forms of a Robust Chicken Colonizing Campylobacter coli

Abstract

Campylobacter contaminated poultry meat is a major source of human foodborne illness. Campylobacter coli strain OR12 is a robust colonizer of chickens that was previously shown to outcompete and displace other Campylobacter strains from the chicken’s gastrointestinal tract. This strain is capable of aerobic growth on blood agar. Serial aerobic passage increased this aerotolerance as assessed by quantitative assays for growth and survival on solid media. Aerotolerance was also associated with increased peroxide stress resistance. Aerobic passage did not alter cellular morphology or motility or hinder the microaerobic growth rate. Colonization of broiler chickens by aerotolerant C. coli OR12 was significantly lower than the wild-type strain at 3 days after challenge but not by 7 days, suggesting adaptation had occurred. Bacteria recovered from chickens had retained their aerotolerance, indicating this trait is stable. Whole genome sequencing enabled comparison with the wild-type sequence. Twenty-three point mutations were present, none of which were in genes known to affect oxidative stress resistance. Insertions or deletions caused frame shifts in several genes including, phosphoglycerate kinase and the b subunit of pyruvate carboxylase that suggest modification of central and carbohydrate metabolism in response to aerobic growth. Other genes affected include those encoding putative carbonic anhydrase, motility accessory factor, filamentous haemagglutinin, and aminoacyl dipeptidase proteins. Aerotolerance has the potential to affect environmental success and survival. Increased environmental survival outside of the host intestinal tract may allow opportunities for transmission between hosts. Resistance to oxidative stress may equate to increased virulence by virtue of reduced susceptibility to oxidative free radicals produced by host immune responses. Finally, resistance to ambient atmospheric oxygen may allow increased survival on chicken skin, and therefore constitutes an increased risk to public health.

Whole genome sequencing reveals extended natural transformation in Campylobacter impacting diagnostics and the pathogens adaptive potential

“…Survival in harsh environments might be a result of various factors and also dependent on the specific genomic background. In aerotolerant C. coli point mutations were detected in other genes, not obviously implicated in oxidative stress response 48 . Thus, it remains elusive, how Campylobacter species modulate their gene pool in order to adapt to changing environments.…”

Point Deletion or Insertion in CmeR-Box, A2075G Substitution in 23S rRNA, and Presence of erm(B) Are Key Factors of Erythromycin Resistance in Campylobacter jejuni and Campylobacter coli Isolated From Central China

“…Substitutions at 2113 site were found in our isolates. Based on previous reports and the sequenced reference strains, including C. jejuni NCTC 11168 and C. coli OR12 (Parkhill et al, 2000;Perez-Boto et al, 2010;O'Kane and Connerton, 2017), the dominant nucleotide at 2113 site is "C" in C. jejuni and "T" in C. coli, which were defined as wild type in both species in this study. Correlation analysis showed that this substitution was not correlated with erythromycin resistance (p > 0.05).…”

Campylobacter coli From Retail Liver and Meat Products Is More Aerotolerant Than Campylobacter jejuni

“…Campylobacter is an important foodborne pathogen that is transmitted from contaminated food products and water (Newell et al, 2017). Despite being microaerophilic and fastidious organism, many previous reports have reported the isolation of aerotolerant Campylobacter strains that could survive and grow in aerobic conditions (Rodrigues et al, 2015; Oh et al, 2017; O'Kane and Connerton, 2017). In our study, 46.7% (78/167) of tested Campylobacter strains were aerotolerant.…”

“…The availability of complete genome sequences for C. coli and C. jejuni from both retail meat and liver products (Marasini and Fakhr, 2016a,b,c, 2017a,b,c) has facilitated comparative genomic analyses. Furthermore, genomic differences in C. coli and C. jejuni strains (Fouts et al, 2005) might help to explain differences in aerotolerance (O'Kane and Connerton, 2017).…”