Persistent Colonization of Ciprofloxacin-Resistant and Extended-Spectrum β-Lactamase (ESBL)-Producing Salmonella enterica Serovar Kentucky ST198 in a Patient with Inflammatory Bowel Disease

Objective: Salmonella enterica serovar Kentucky ST198 has emerged as a global threat to humans. In this study, we aimed to characterize the prolonged carriage of ciprofloxacin-resistant and extended-spectrum β-lactamase (ESBL)-producing S . Kentucky ST198 in a single patient with inflammatory bowel disease (IBD). Methods: Three S . Kentucky strains were collected from a single patient with IBD on 11th January, 23rd January, and 8th February, 2022, respectively. Antimicrobial susceptibility testing, whole-genome sequencing, and phylogenetic analysis with 38 previously described Chinese S . Kentucky ST198 strains from patients and food were performed. Results: All three S . Kentucky isolates belonged to ST198. They carried identical 16 resistance genes, such as bla CTX-M-55 , tet (A), and qnrS1 , and had identical mutations within gyrA (S83F and D87N) and parC (S80I). Therefore, they exhibited identical multidrug-resistant profiles, including the clinically important antibiotics cephalosporins (ceftazidime and cefepime), fluoroquinolones (ciprofloxacin and levofloxacin), and third-generation tetracycline (tigecycline). Our three S . Kentucky strains were classified into the subclade ST198.2– 2, and were genetically identical (2– 6 SNPs) to each other. They exhibited a close genetic similarity (15– 20 SNPs) to the isolate NT-h3189 from a patient and AH19MCS1 from chicken meat in China, indicating a possible epidemiological link between these S . Kentucky ST198 isolates from the patients and chicken meat. Conclusion: Long-term colonization of ciprofloxacin-resistant and ESBL-producing S . Kentucky ST198 in a single patient is a matter of concern. Due to the potential transfer of S . Kentucky ST198 from food sources to humans, ongoing surveillance of this particular clone in animals, animal-derived food products, and humans should be strengthened. Keywords: Salmonella , MDR, Kentucky, persistent colonization