Molecular Epidemiology of Campylobacter coli Strains Isolated from Different Sources in New Zealand between 2005 and 2014

Abstract

Campylobacteriosis is one of the most important foodborne diseases worldwide and a significant health burden in New Zealand. Campylobacter jejuni is the predominant species worldwide, accounting for approximately 90% of human cases, followed by Campylobacter coli Most studies in New Zealand have focused on C. jejuni; hence, the impact of C. coli strains on human health is not well understood. The aim of this study was to genotype C. coli isolates collected in the Manawatu region of New Zealand from clinical cases, fresh poultry meat, ruminant feces, and environmental water sources, between 2005 and 2014, to study their population structure and estimate the contribution of each source to the burden of human disease. Campylobacter isolates were identified by PCR and typed by multilocus sequence typing. C. coli accounted for 2.9% (n = 47/1,601) of Campylobacter isolates from human clinical cases, 9.6% (n = 108/1,123) from poultry, 13.4% (n = 49/364) from ruminants, and 6.4% (n = 11/171) from water. Molecular subtyping revealed 27 different sequence types (STs), of which 18 belonged to clonal complex ST-828. ST-1581 was the most prevalent C. coli sequence type isolated from both human cases (n = 12/47) and poultry (n = 44/110). When classified using cladistics, all sequence types belonged to clade 1 except ST-7774, which belonged to clade 2. ST-854, ST-1590, and ST-4009 were isolated only from human cases and fresh poultry, while ST-3232 was isolated only from human cases and ruminant sources. Modeling indicated ruminants and poultry as the main sources of C. coli human infection.

Importance: We performed a molecular epidemiological study of Campylobacter coli infection in New Zealand, one of few such studies globally. This study analyzed the population genetic structure of the bacterium and included a probabilistic source attribution model covering different animal and water sources. The results are discussed in a global context.

FIG 1

Minimum spanning tree of C. coli STs from 4 different sources. Each node represents an ST; its size is proportional to the frequency of isolation and the colors represent the different source types. The thickness of the connecting lines is proportional to the similarities between STs, with the thickest connector linking single-locus variants. The shaded area represents members of the ST-828 CC.

FIG 2

Molecular phylogenetic analysis by maximum likelihood method. The 27 STs found in this study and 9 STs from clades 2 and 3 from Sheppard et al. (30) were used. Clade 1 is indicated in red, clade 2 in yellow, and clade 3 in green. C. coli STs in the work of Sheppard et al. (30) are indicated with an asterisk. The tree is drawn to scale, with branch lengths measured in the number of substitutions per site. The scale bar represents a genetic distance of 0.01 (i.e., 1% of the nucleotides differ).

FIG 3

Rarefaction curves of the human, poultry, ruminant, and environmental water C. coli STs. The shaded areas represent the 95% CrI. Note that the poultry and ruminant upper boundary of the 95% CrI does not reach the point estimate of the human curve at maximum sample size. The environmental water curve overlaps the human curve.