Characterization of Swedish Campylobacter coli clade 2 and clade 3 water isolates

Abstract

Campylobacter jejuni and Campylobacter coli are important bacterial enteropathogens. Poultry is the best‐known reservoir for Campylobacter infection but natural bodies of water have also been shown to be important pathways for transmission. Campylobacter can survive in cold water but most of the studies have focused on C. jejuni only. In this paper, we take a closer look at the biology and water survival strategies of C. coli. Eight C. coli isolates cultivated from raw (incoming) surface water at water plants in Sweden were characterized using whole‐genome sequencing and phenotypical assays. Phylogenetic analysis assigned the Swedish water isolates to clades 2 and 3, known to include C. coli of environmental origin. In addition, 53 earlier published sequences of C. coli clade 2 and 3 from environmental waters were included for in silico analyses. Generally, clade 2 isolates had larger genomes, which included a functional tricarballylate utilization locus, while clade 3 isolates contained different genes involved in oxidative stress as well as putative virulence factors. The Swedish water isolates of clade 2 formed large, blurry bacterial colonies on agar, whereas clade 3 colonies were smaller. All Swedish isolates were motile, but clade 3 isolates formed larger motility zones on soft agar, and none of these isolates produced biofilm. Although water survival varied between the analyzed isolates, there were hardly any clade‐specific significant differences. Our results highlight the diversity of C. coli in general, and show differences in metabolic capabilities and ways to handle oxidative stress between clade 2 and 3 water isolates.

Survival of Campylobacter jejuni and Campylobacter coli water isolates in lake and well water

“…In contrast, half of the C. coli isolated were from spring while the rest were from autumn. Hence our present findings may reflect seasonality of C. jejuni in general or a preference for the type of water they were originally isolated from .…”

“…In long term studies, C. jejuni have been shown to be able to survive in culturable form in different types of water for as long as 60 days . In the present study, we analyzed survival over merely eight days as a pilot study in autoclaved tap water could observe a steep decline in C. coli CFUs during the first week of incubation .…”

“…The main bacterial cause of waterborne outbreaks in Sweden is Campylobacter with C. jejuni as the predominant pathogen. We have previously analyzed C. jejuni and C. coli isolates originally cultivated from water with whole genome sequencing and phenotypic analyses , and here we tested the survival of these particular isolates in natural water samples collected in spring and autumn from a local lake and in early summer from a private well. The experiments were performed at 4°C as a low temperature has been suggested to promote survival of Campylobacter in different types of water .…”

“…Seven C. jejuni and eight C. coli isolates originally collected by the National Food Agency in 2000 from raw (incoming) surface water at water works in Sweden (Table ) were included. The C. coli water isolates have previously been identified with phylogenetic analysis to belong to clade 2 (n = 5) and clade 3 (n = 3) . Three of the seven C. jejuni water isolates have been identified as ST‐48, whereas the remaining four belonged to ST‐637, ST‐683, ST‐793, and ST‐8853, respectively .…”

“…Using whole genome sequencing and phenotypical analyses, we recently characterized seven C. jejuni and eight C. coli isolates, originally cultivated from incoming water at water works in Sweden, . In this study, we wanted to investigate the potential of these water isolates to be transmitted to humans and hence tested their ability to survive in untreated water from a Swedish lake and a private well, both used as sources of drinking water.…”