Antimicrobial resistance profiles, virulence genes, and genetic diversity of thermophilic Campylobacter species isolated from a layer chicken farm in Korea.

Abstract

ABSTRACT Background: Thermophilic Campylobacter species are among the major etiologies of bacterial enteritis globally. This study aimed at assessing the antimicrobial resistance (AMR) profiles, virulence genes, and genetic diversity of thermophilic Campylobacter species isolated from a layer poultry farm in South Korea. One hundred fifty-three chicken feces were collected from two layer poultry farms in Gangneung, South Korea. The Campylobacter species were isolated by cultural techniques, while PCR and sequencing were used for species confirmation. Antimicrobial susceptibility testing for six antimicrobials [ciprofloxacin (CIP), nalidixic acid (NAL), sitafloxacin (SIT), erythromycin (ERY), tetracycline (TET), and gentamicin (GEN)] was carried out by broth microdilution. Three AMR and nine virulence genes were screened by PCR. Genotyping was performed by flaA-restriction fragment length polymorphism (RFLP) and multilocus sequence typing (MLST). Of the 153 samples, Campylobacter spp. were detected in 55 (35.9%), with Campylobacter jejuni and Campylobacter coli being 49 (89.1%) and six (10.9%), respectively. High-level resistance was observed for CIP (100%), NAL (100%), and TET (C. jejuni, 93.9%; C. coli: 83.3%). No resistance was observed for SIT. The missense mutation (C257T) in gyrA gene was confirmed by sequencing, while the tet(O) gene was similar to known sequences in GenBank. The rate of multidrug-resistant (MDR) strains was 8.2%, and they all belonged to C. jejuni. All Campylobacter isolates possessed five virulence genes (cdtB, cstII, flaA, cadF, and dnaJ), but none possessed ggt, while the rates for other genes (csrA, ciaB, and pldA) ranged between 33.3 and 95.9%. The flaA-RFLP yielded 26 flaA types (C. jejuni: 21 and C. coli: five), while the MLST showed 10 sequence types (STs) for C. jejuni and three STs for C. coli, with CC-607 (STs 3611) and CC-460 (ST-460) being predominant. Among the 10 STs of C. jejuni, three were newly assigned. The findings of this study highlight the increased resistance to quinolones and TET, the virulence potential, and the diverse genotypes among Campylobacter strains isolated from the layer poultry farm. Results: Out of 153 fecal samples, the detection rate of Campylobacter spp. was 35.9% (55), with C. jejuni and C. coli being 89.1% (49) and 10.9% (six), respectively. None of the 20 fecal samples from the second farm was positive for Campylobacter. Conclusion: This study highlights the role of layers as a reservoir of Campylobacter spp., harboring various AMR and virulence genes. The genotyping highlighted that C. jejuni isolates were more diverse than C. coli as analyzed by MLST. The MLST revealed that CC-607 (ST-3611) and CC-460 (ST-460) were the predominant ones, while three STs were newly assigned. ERY, GEN, and SIT need to be appropriately used to prevent or delay the increasing resistance in Campylobacter species. The isolates of this study may present a potential hazard to public health based on their AMR profiles, virulence genes, and genotyping data. Keywords: Campylobacter, quinolones, antimicrobial resistance, flaA RFLP, multilocus sequence typing, poultry, Korea