Molecular epidemiology of Campylobacter isolates from poultry production units in southern Ireland

Abstract

This study aimed to identify the sources and routes of transmission of Campylobacter in intensively reared poultry farms in the Republic of Ireland. Breeder flocks and their corresponding broilers housed in three growing facilities were screened for the presence of Campylobacter species from November 2006 through September 2007. All breeder flocks tested positive for Campylobacter species (with C. jejuni and C. coli being identified). Similarly, all broiler flocks also tested positive for Campylobacter by the end of the rearing period. Faecal and environmental samples were analyzed at regular intervals throughout the rearing period of each broiler flock. Campylobacter was not detected in the disinfected house, or in one-day old broiler chicks. Campylobacter jejuni was isolated from environmental samples including air, water puddles, adjacent broiler flocks and soil. A representative subset of isolates from each farm was selected for further characterization using flaA-SVR sub-typing and multi-locus sequence typing (MLST) to determine if same-species isolates from different sources were indistinguishable or not. Results obtained suggest that no evidence of vertical transmission existed and that adequate cleaning/disinfection of broiler houses contributed to the prevention of carryover and cross-contamination. Nonetheless, the environment appears to be a potential source of Campylobacter. The population structure of Campylobacter isolates from broiler farms in Southern Ireland was diverse and weakly clonal.

Figure 1. Distribution of flaA-SVR alleles detected according to source, (asterisks signify new flaA-SVR alleles).

Figure 2. Schematic diagram of the flaA-SVR alleles detected on farm 1.

Figure 3. Schematic diagram of the flaA-SVR alleles detected on farm 2.

Figure 4. Schematic diagram of the flaA-SVR alleles detected on farm 3.

Figure 5. Distribution of STs detected according to source (asterisks signify new STs).

Figure 6. Distribution of CCs and STs according to source.

Figure 7. Comparison of flaA-SVR sequences of Campylobacter isolates from breeder and broiler farms and farm environments.

A total of 101 isolates were included. Strain Campylobacter jejuni NCTC11168 was included as a control strain in the pairwise analysis. The arrow indicates the 98% similarity cut-off point. flaA, flaA-SVR allele number; ST, sequence type; CC, clonal complex; Nt, not tested; NA, not assigned; -, not applicable.