Campylobacter jejuni Genotypes and Antibiotic Resistance, July and August 2022, Finland

The seasonal peak for campylobacteriosis is during July and August in Finland. A large portion of cases are known to be travel related, but due to limited reporting, true domestic cases are difficult to distinguish. With a questionnaire, 185 domestic cases of C. jejuni campylobacteriosis were identified and corresponding isolates collected for whole genome sequencing (WGS), to characterize the distribution and prevalence of genotypes and antimicrobial resistance markers. Additionally, patient isolates were compared to animal and food isolates from national surveillance. Resistance markers were compared to phenotypic antimicrobial sensitivity testing results to assess functionality of WGS for resistance prediction. The most common multilocus sequence types (MLST) were ST-45 (27%), ST-677 (20%), and ST-230 (7.5%). Nearly half (39%) of the patient isolates clustered with at least one other strain, forming 26 clusters. In general, phenotypic antimicrobial resistance was rare. Erythromycin resistance was practically non-existent, while almost 15% of patient strains were ciprofloxacin resistant. This was notably lower than the proportion of resistant strains reported yearly for all cases in Finland, which included travel-associated cases. Patient strain sequence types that exhibited the most phenotypic ciprofloxacin resistance included ST-50 and ST-230. The most common sequence type, ST-45, was largely susceptible. Resistance was also more prevalent in fur animal and imported meat strains, compared to domestic broiler strains. Strains from confirmed domestic cases and especially those associated with Finnish broiler were largely susceptible to the tested antimicrobials suggesting the majority of resistant strains originate from imported meats or are travel-associated.