Antimicrobial Resistance Profiles, Virulence Genes, and Genetic Diversity of Thermophilic Campylobacter Species Isolated From a Layer Poultry Farm in Korea

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.

Typing of Campylobacter jejuni isolated from poultry on the basis of flaA-RFLP by various restriction enzymes

RFLP analysis of the flagellin (flaA) gene was compared using three different restriction endonucleases i.e DdeI, HinfI and DpnII to determine the genetic diversity among 43 Campylobacter jejuni isolates of poultry origin from the same geographical area. flaA gene was amplified in all the isolates and RFLP analysis showed variations. Dde-based RFLP was found most efficient in discriminating C. jejuni isolates by generating 15 different Dde-RFLP patterns with discriminatory index (D.I) of 0.9258 whereas DpnII produced seven Dpn-RFLP patterns (D.I .= 0.8427). While HinfI enzyme produced only six Hinf-RFLP patterns (D.I .= 0.6977). The discrimination of Dpn-RFLP was comparable to discrimination given by Dde-RFLP analysis, which is generally used to study flaA gene RFLP.