Identification of host-associated alleles by multilocus sequence typing of Campylobacter coli strains from food animals

Abstract

Campylobacter coli is a food-borne pathogen associated increasingly with human gastroenteritis. C. coli has a high prevalence in swine, but is isolated also from cattle and poultry. Multilocus sequence typing (MLST) systems have been developed to differentiate C. coli strains. Although substantial allelic diversity was identified across all seven C. coli MLST loci, no correlations were made in two previous studies between allele or sequence type (ST) and the source of the organism. However, this may be due to either the relatively small number or the low diversity of C. coli strains used to validate both MLST studies. This study describes the typing of 488 C. coli strains from 4 different food animal sources (cattle, chickens, swine and turkeys), collected at different times over a 6 year period from different USA geographical locations. A total of 149 STs were identified. The 185 swine strains were the most diverse, possessing 82 STs. The cattle strains were the most clonal; 52/63 (83 %) strains possessed a single ST (ST-1068). A subpopulation of C. coli strains, collected primarily from turkeys, was identified, containing both C. coli-and Campylobacter jejuni-associated MLST alleles, specifically the C. jejuni allele aspA103. The majority of STs and alleles were host associated, i.e. found primarily in strains from a single food-animal source. Only 12/149 (8 %) STs were found in multiple sources. Additionally, the majority (34/46, 74 %) of major (n>5) alleles were more prevalent in certain hosts (swine, poultry). The presence of host-associated C. coli MLST alleles could lead potentially to more efficient source tracking in this species, especially in the trace-back of both sporadic and outbreak human clinical C. coli strains to animal sources.

The Absence of Intervening Sequences in 23S rRNA Genes of Campylobacter coli Isolates from Turkeys Is a Unique Attribute of a Cluster of Related Strains Which Also Lack Resistance to Erythromycin

“…The absence of IVSs was detected only in strains of certain STs previously designated as cluster II and found primarily for C. coli from turkeys (25). It is noteworthy that each of the two major cluster II IVS-free STs found in this study (ST-1150 and ST-1161) contained alleles that were mostly turkey/poultry associated (25), suggesting that C. coli strains with these STs were adapted to these hosts.…”

“…They had been isolated from cecal or fecal samples from turkeys on various turkey farms in North Carolina during 2001 to 2004 by use of Campylobacter blood-free selective agar with CCDA selective supplement (Oxoid, Basingstoke, Hampshire, England) as described previously (38). Eighty-three of these strains were included in a recent MLST study (25 Antibiotic susceptibility and erythromycin MIC determinations. Antibiotic susceptibility profiles were determined as described previously (22,38).…”

“…ST identification was done using the C. jejuni/C. coli MLST database (http://pubmlst.org/campylobacter/); new sequences were entered into the database and were assigned new allele numbers as described previously (25).…”

“…However, no further data on the prevalence of IVSs in C. jejuni from commercial poultry (broilers and turkeys) are available, and no data have been described for IVSs in C. coli that colonize poultry. In recent studies, we have found that turkeys in eastern North Carolina were frequently colonized by C. coli (22,38), and a subset of such turkey-derived C. coli was characterized by MLST (25).…”

“…MLST appears to be especially promising in the case of C. coli isolated from animal sources. A recent survey of C. coli from turkeys, broilers, cattle, and swine identified several alleles and sequence types (STs) that appeared to be host specific (25).…”