Whole genome-based Characterization of Virulence and Antimicrobial Resistance Determinants in Clinical Campylobacter jejuni Isolates from Minnesota, 2018-2021

Campylobacter jejuni is a leading cause of foodborne gastroenteritis globally and is classified by the CDC as a serious public health threat due to increasing resistance to fluoroquinolones and macrolides. This study used whole-genome sequencing to characterize the virulence and antimicrobial resistance profiles of 2,783 clinical C. jejuni isolates collected from Minnesota residents from 2018 through 2021. More than 90% of the isolates had genes related to stress defense (rpoN and htrB), cytolethal distending toxin (cdtA, cdtB, and cdtC), and cell adhesion and invasion (ciaB, cadF, and flaC). A diverse array of antimicrobial resistance genes was detected, with beta-lactam resistance genes having a particularly high prevalence. The gyrA point mutation associated with quinolone resistance was present in 29% of isolates. To evaluate the correlation between genotypic and phenotypic antimicrobial resistance profiles, the antimicrobial susceptibility testing results from a subset of isolates were compared with genotypic resistance profiles. Results showed a strong overall correlation, particularly for tetracycline and quinolones, though 24 discrepancies were detected. In the majority of discrepancies (n=21), genomic antimicrobial resistance markers were absent in isolates that were phenotypically resistant, suggesting possible unknown resistance mechanisms or limitations in current sequencing methods. The remaining three discrepancies occurred in isolates that had the tet(O) resistance gene but were susceptible to tetracycline phenotypically. These findings highlight the value of whole genome sequencing in improving antimicrobial resistance surveillance and understanding virulence factors in C. jejuni, supporting its integration into routine monitoring practices to better manage and understand antimicrobial resistance in foodborne pathogens.