Genotypic Characterization and Antimicrobial Susceptibility of Human Campylobacter jejuni Isolates in Southern Spain

Campylobacter jejuni is the main cause of bacterial gastroenteritis and a public health problem worldwide. Little information is available on the genotypic characteristics of human Campylobacter jejuni in Spain. This study is based on an analysis of the resistome, virulome and phylogenetic relationship, antibiogram prediction and antimicrobial susceptibility of 114 human isolates of C. jejuni from a tertiary hospital in southern Spain from October 2020 to June 2023. The isolates were sequenced using Illumina technology, and bioinformatic analysis was subsequently performed. The susceptibility of C. jejuni isolates to ciprofloxacin, tetracycline, and erythromycin was tested. A high resistance rate was obtained for ciprofloxacin (90.6%) and tetracycline (66.7%), and a low resistance rate for erythromycin (0.85%) was detected among the C. jejuni isolates. CC-21 (n=23), ST-572 (n = 13) and ST-6532 (n=13) were the most prevalent clonal complexes (CCs) and sequence types (STs). Concerning the virulome, the cadF, ciaB , and cdtABC genes were detected in all the isolates. A prevalence of 20.1% was obtained for the genes wlaN and cstIII , which are related to the pathogenesis of Guillain-Barré syndrome (GBS). The prevalence of the main antimicrobial resistance markers detected were cmeABC (92.1%), RE-cmeABC (7.9%), the T86I substitution in gyrA (88.9%), blaOXA-61 (72.6%) , tet(O) (65.8%) and ant(6)-Ia (17.1%). High antibiogram prediction rates (>97%) were obtained except for the erythromycin-resistant phenotype. This study contributes significantly to the knowledge of Campylobacter jejuni genomics for the prevention, treatment and control of infections caused by this pathogen, which is relevant to public health. Importance Despite being the pathogen with the greatest number of gastroenteritis cases worldwide, Campylobacter jejuni remains a poorly studied microorganism. The development of whole-genome sequencing (WGS) techniques has led to a better understanding of the genotypic characteristics of this pathogen. These techniques complement the data obtained from the phenotypic analysis of C. jejuni isolates. The zoonotic transmission of C. jejuni through the consumption of contaminated poultry implies approaching the study of this pathogen through the term “One Health.” This is the first study, using WGS, conducted on human isolates of C. jejuni in Spain to date, which allows comparison of the results obtained with similar studies conducted in other countries and with animal and environmental isolates.