AUTHOR=Awad Amal , Yeh Hung-Yueh , Ramadan Hazem , Rothrock Michael J. 

TITLE=Genotypic characterization, antimicrobial susceptibility and virulence determinants of Campylobacter jejuni and Campylobacter coli isolated from pastured poultry farms

JOURNAL=Frontiers in Microbiology

VOLUME=14

YEAR=2023

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2023.1271551

DOI=10.3389/fmicb.2023.1271551

ISSN=1664-302X

ABSTRACT=<sec id="sec1"><title>Aim</title><p><italic>Campylobacter</italic> is the leading bacterial pathogen that causes foodborne illnesses worldwide. Pasture farming is regarded as an important source of agricultural production for small farming communities. Consumer preference for pasture-raised animal products has increased; however, there is a paucity of information on the microbiological quality of pasture-raised poultry products. The purpose of this study was to explore genetic relatedness of thermophilic <italic>Campylobacter</italic> isolates, to assess antibiotic resistance phenotypically and genotypically, and to screen the presence of virulence determinants of <italic>Campylobacter</italic> isolates from pasture-raised poultry farms from southeastern United States.</p></sec><sec id="sec2"><title>Methods</title><p>Ninety-seven <italic>Campylobacter</italic> isolates previously identified by Q7 BAX<sup>®</sup> System Real-Time PCR were genotyped by multilocus sequence typing (MLST). <italic>Campylobacter</italic> isolates were then evaluated for their phenotypic antimicrobial susceptibility against nine antimicrobial agents using Sensititre plates. Additionally, <italic>Campylobacter</italic> isolates were tested for the presence of antimicrobial resistance-associated elements. Furthermore, <italic>Campylobacter</italic> isolates were screened for the presence of 13 genes encoding putative virulence factors by PCR. These included genes involved in motility (<italic>flaA</italic> and <italic>flhA</italic>), adhesion and colonization (<italic>cadF</italic>, <italic>docC</italic>, <italic>racR</italic>, and <italic>virB11</italic>), toxin production (<italic>cdtA</italic>, <italic>cdtB</italic>, <italic>cdtC</italic>, <italic>wlaN</italic>, and <italic>ceuE</italic>) and invasion (<italic>ciaB</italic> and <italic>iamA</italic>).</p></sec><sec id="sec3"><title>Results</title><p>Among 97 <italic>Campylobacter</italic> isolates, <italic>Campylobacter jejuni</italic> (<italic>n</italic> = 79) and <italic>Campylobacter coli</italic> (<italic>n</italic> = 18) were identified. By MLST, <italic>C. jejuni</italic> isolates were assigned to seven clonal complexes. Among them, ST-353, ST-607 and ST-21 were the most common STs recognized. All <italic>C. coli</italic> (<italic>n</italic> = 18) isolates were included in CC-828. Interestingly, eight STs identified were not belonging any previous identified clonal complex. <italic>Campylobacter</italic> isolates displayed a high resistance rate against tetracycline (81.4%), while a low rate of resistance was observed against macrolides (azithromycin and erythromycin), quinolones and fluoroquinolones (nalidixic acid and ciprofloxacin), aminoglycosides (gentamicin), ketolide (telithromycin), amphenicol (florfenicol) and lincomycin (clindamycin). Thirteen isolates (13.54%) were pan-susceptible to all tested antibiotics, while nine isolates were multi-antimicrobial resistant (MAR; resist to three or more antimicrobial classes). Interestingly, there were no isolates resistant to all antimicrobial classes. Thr86Ile mutation was identified in all quinolones resistant strains. Erythromycin encoding gene (<italic>ermB</italic>) was identified in 75% of erythromycin resistant isolates. The A2075 mutation was detected in one erythromycin resistant strain, while A2074 could not be identified. The <italic>tet</italic>O gene was identified in 93.7% of tetracycline resistant isolates and six tetracycline susceptible isolates. In conclusion, the results of this study revealed that <italic>Campylobacter</italic> isolates from pasture-raised poultry farms showed the ST relatedness to <italic>Campylobacter</italic> isolates commonly associated with humans, indicating pasture-raised broiler flocks, similar to conventionally-reared broiler flocks, as a potential vector for antibiotic-resistant and pathogenic strains of thermophilic <italic>Campylobacter</italic> to humans.</p></sec>