Enhanced laboratory surveillance study of Campylobacter species in England

Introduction. Campylobacteriosis is the leading cause of gastroenteritis worldwide, and Campylobacter species are the most frequently reported zoonotic, bacterial foodborne pathogens in England.Gap statement. Currently, less than 2.0% of Campylobacter isolates in England undergo strain identification and typing, resulting in limited insight into their molecular epidemiology.Aim. To assess the feasibility of using high-throughput whole-genome sequencing (WGS) to generate data for microbiological and epidemiological analysis by the implementation of a 3-month enhanced laboratory surveillance for Campylobacter spp. in England, and to make recommendations for improving the current Campylobacter surveillance strategies.Methodology. All diagnostic laboratories in England were encouraged to refer isolates of Campylobacter spp. for WGS over a 3-month period (7 June-31 August 2021).Results. Over 6,000 Campylobacter species isolates were characterized, of which 87.5% were successfully identified as Campylobacter jejuni and 8.1% as Campylobacter coli. Just over half of the isolates were referred from patients who were male (53%), and C. coli isolates tended to be from older patients than C. jejuni, with median ages of 55 and 44 years, respectively. The most common multi-locus sequencing type clonal complex identified was ST-21, and within this, the sequencing type ST6175 was the most frequently identified, of which 96.8% were predicted to carry antimicrobial resistance determinants, inferring reduced susceptibility to both ciprofloxacin and tetracycline. The four largest C. jejuni 5-single nucleotide polymorphism (SNP) clusters, associated with the larger clonal complexes and sequence type groups (ST6175, ST48, ST6175 and ST5136), accounted for 23.8% (n=1,150/4,838) of SNP typable isolates. Conversely, 28.4% and 39.5% of isolates C. jejuni and C. coli, respectively, appeared to be sporadic, with each isolate assigned a unique SNP address at the 5-SNP level.Conclusion. WGS enabled identification of genetically related clusters of Campylobacter isolates in almost real time and shows potential for monitoring of inferred antimicrobial resistance. However, unlocking its full potential requires referral of sufficient and representative isolates for sequencing with parallel epidemiological data collection.