Genomic Characterization of Fluoroquinolone-Resistant Thermophilic <i>Campylobacter</i> Strains Isolated from Layer Chicken Feces in Gangneung, South Korea by Whole-Genome Sequencing

• Main Authors: Noel Gahamanyi, Dae-Geun Song, Kye-Yoon Yoon, Leonard E. G. Mboera, Mecky I. Matee, Dieudonné Mutangana, Erick V. G. Komba, Cheol-Ho Pan, Raghavendra G. Amachawadi
• Format: Article
• Language: English
• Published: MDPI AG 2021-07-01
• Series: Genes
• Subjects: <i>Campylobacter</i>; layer chicken; fluoroquinolone-resistant; phylogenetic analysis; whole-genome sequencing; Korea
• Online Access: https://www.mdpi.com/2073-4425/12/8/1131

Thermophilic <i>Campylobacter</i> species of poultry origin have been associated with up to 80% of human campylobacteriosis cases. Layer chickens have received less attention as possible reservoirs of <i>Campylobacter</i> species. Initially, the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of two archived <i>Campylobacter</i> isolates (<i>Campylobacter jejuni</i> strain 200605 and <i>Campylobacter coli</i> strain 200606) from layer chickens to five antimicrobials (ciprofloxacin, nalidixic acid, erythromycin, tetracycline, and gentamicin) were determined using broth microdilution while the presence of selected antimicrobial resistance genes was performed by polymerase chain reaction (PCR) using specific primers. Whole-genome sequencing (WGS) was performed by the Illumina HiSeq X platform. The analysis involved antimicrobial resistance genes, virulome, multilocus sequence typing (MLST), and phylogeny. Both isolates were phenotypically resistant to ciprofloxacin (MIC: 32 vs. 32 µg/mL), nalidixic acid (MIC: 128 vs. 64 µg/mL), and tetracycline (MIC: 64 vs. 64 µg/mL), but sensitive to erythromycin (MIC: 1 vs. 2 µg/mL) and gentamicin (MIC: 0.25 vs. 1 µg/mL) for <i>C. jejuni</i> strain 200605 and <i>C. coli</i> strain 200606, respectively. WGS confirmed C257T mutation in the <i>gyr</i>A gene and the presence of <i>cme</i>ABC complex conferring resistance to FQs in both strains. Both strains also exhibited <i>tet</i>(O) genes associated with tetracycline resistance. Various virulence genes associated with motility, chemotaxis, and capsule formation were found in both isolates. However, the analysis of virulence genes showed that <i>C. jejuni</i> strain 200605 is more virulent than <i>C. coli</i> strain 200606. The MLST showed that <i>C. jejuni</i> strain 200605 belongs to sequence type ST-5229 while <i>C. coli</i> strain 200606 belongs to ST-5935, and both STs are less common. The phylogenetic analysis clustered <i>C. jejuni</i> strain 200605 along with other strains reported in Korea (CP028933 from chicken and CP014344 from human) while <i>C. coli</i> strain 200606 formed a separate cluster with <i>C. coli</i> (CP007181) from turkey. The WGS confirmed FQ-resistance in both strains and showed potential virulence of both strains. Further studies are recommended to understand the reasons behind the regional distribution (Korea, China, and Vietnam) of such rare STs.