Population Genetics and Characterization of Campylobacter jejuni Isolates from Western Jackdaws and Game Birds in Finland

Abstract

Poultry are considered a major reservoir and source of human campylobacteriosis, but the roles of environmental reservoirs, including wild birds, have not been assessed in depth. In this study, we isolated and characterized Campylobacter jejuni from western jackdaws (n = 91, 43%), mallard ducks (n = 82, 76%), and pheasants (n = 9, 9%). Most of the western jackdaw and mallard duck C. jejuni isolates represented multilocus sequence typing (MLST) sequence types (STs) that diverged from those previously isolated from human patients and various animal species, whereas all pheasant isolates represented ST-19, a common ST among human patients and other hosts worldwide. Whole-genome MLST revealed that mallard duck ST-2314 and pheasant ST-19 isolates represented bacterial clones that were genetically highly similar to human isolates detected previously. Further analyses revealed that in addition to a divergent ClonalFrame genealogy, certain genomic characteristics of the western jackdaw C. jejuni isolates, e.g., a novel cdtABC gene cluster and the type VI secretion system (T6SS), may affect their host specificity and virulence. Game birds may thus pose a risk for acquiring campylobacteriosis; therefore, hygienic measures during slaughter and meat handling warrant special attention. IMPORTANCE The roles of environmental reservoirs, including wild birds, in the molecular epidemiology of Campylobacter jejuni have not been assessed in depth. Our results showed that game birds may pose a risk for acquiring campylobacteriosis, because they had C. jejuni genomotypes highly similar to human isolates detected previously. Therefore, hygienic measures during slaughter and meat handling warrant special attention. On the contrary, a unique phylogeny was revealed for the western jackdaw isolates, and certain genomic characteristics identified among these isolates are hypothesized to affect their host specificity and virulence. Comparative genomics within sequence types (STs), using whole-genome multilocus sequence typing (wgMLST), and phylogenomics are efficient methods to analyze the genomic relationships of C. jejuni isolates.

Emergence of Genetic Diversity and Multi-Drug Resistant Campylobacter jejuni From Wild Birds in Beijing, China

“…The results suggest that these three genes are conserved amongst different sources. As before, C. jejuni isolates from crows had a truncated gene cluster of about 1400 bp (Sen et al, 2018), C. jejuni isolates from daurian jackdaw also had a truncated gene cluster (Kovanen et al, 2019). However, the most unexpected results were isolates from silver pheasant which also have a truncated gene cluster of about 1400 bp.…”

Core Genome Multilocus Sequence Typing for Food Animal Source Attribution of Human Campylobacter jejuni Infections

“…Many C. jejuni strains exhibit a narrow range of host specificity and this trait can be used to inform source attribution of strains that cause human infections [24,25]. However, strains with close genetic similarity can infect different hosts and established typing methods such as pulsed field gel electrophoresis (PFGE) or seven-gene multilocus sequence typing (MLST) lack the resolution to distinguish between them [10,18,[26][27][28][29]. One proposed solution to this limitation is core genome fingerprinting, a method that expands on the seven loci of C. jejuni MLST to include 40 genomic targets conserved across C. jejuni genomes [29].…”

Whole-Genome Sequencing and Bioinformatic Analysis of Environmental, Agricultural, and Human Campylobacter jejuni Isolates From East Tennessee

“…Using these WGS technologies, groups have begun investigating the genetic relatedness of Campylobacter isolates from various sources (Dearlove et al, 2016;Kovanen et al, 2019), including whole genome MLST (wgMLST) analysis (Cody et al, 2013). For example, wgMLST has been used to examine C. jejuni and C. coli clonal complexes (Sheppard et al, 2012), the presence of Campylobacter antibiotic resistant genotypes (Zhao et al, 2016), and the comparison of isolates recovered in processing plants and on chicken meat (Ma et al, 2014;Guyard-Nicodème et al, 2015).…”