Campylobacter diversity in chicken meat

Abstract T2

**Presenter: Agata Dziegiel (Quadram Institute Bioscience)

Authors: Agata Dziegiel (1), Samuel Bloomfield (1), Raphalle Palau (1), John Wain (1,2), Nicol Janecko (1), Alison E Mather (1,2)

• 1 Quadram Institute Bioscience, Norwich, UK
• 2 University of East Anglia, Norwich, UK

Campylobacter jejuni and Campylobacter coli are the leading bacterial causes of gastroenteritis worldwide. Chicken meat is recognised as the main reservoir of infection, which can cause serious complications. Most current culture methods are tailored to C. jejuni and C. coli isolation, and the true diversity of Campylobacter on chicken is likely underestimated. Genomic analysis of multiple Campylobacter isolates from individual samples can further facilitate insight into the diversity of Campylobacter within and between samples as well as between differing culture approaches. In this study, aspects of traditional culture methods were manipulated (temperature, direct plating/enrichment, enrichment broth type and agar type) and compared to determine Campylobacter prevalence and diversity in 15 chicken meat samples from supermarkets in Norwich, Norfolk, UK. Bolton broth enrichment with alternative selective supplements (CAT broth) yielded the highest number of presumptive isolates (n=115) compared to traditional Bolton broth enrichment (n=31) and direct plating on mCCDA (n=16) and mCCDA without selective supplement (n=5). Incubation at 37C yielded a similar number of isolates (n=84) to incubation at 42C (n=83). The median number of presumptive isolates recovered per sample was 8, with a range of 0-45. From 15 chicken meat samples, 12 were positive for Campylobacter spp. by at least one method. Initial findings from whole genome sequencing of 12 isolates recovered from a single sample identified two distinct major chicken-associated sequence types (ST-257 and ST-5136). Within each ST, the sub-populations were genetically similar; there was a median of 16 pairwise non-recombinogenic SNPs between the seven ST-257 isolates and a median of 18.5 pairwise non-recombinogenic SNPs between the five ST-5136 isolates. Of these twelve isolates, six originated from CAT broth enrichment at 37C followed by selective plating on unsupplemented mCCDA, two from CAT broth enrichment at 42C followed by selective plating on mCCDA, and four from CAT broth enrichment at 42C followed by secondary plating on unsupplemented mCCDA. Both STs were recovered through each of the methods. Ongoing work involves sequencing of all isolates recovered to date, which will allow further insight into diversity of Campylobacter isolates recovered using different culture methods. These pilot study findings may have implications on Campylobacter infection surveillance, source attribution and future outbreak investigations.

Presenting in Speaking session 3 - Epidemiology and public health