Prevalence and characterization of quinolone resistance in Campylobacter spp. isolated in chicken livers from retail stores in Georgia, USA

Authors: Yeh, Hung-Yueh; Cox Jr, Nelson; Hinton Jr, Arthur; Berrang, Mark; Plumblee Lawrence, Jodie; Thompson, Tori

Submitted to: Journal of Food Protection
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/24/2021
Publication Date: 11/24/2021
Citation: Yeh, H., Cox Jr, N.A., Hinton Jr, A., Berrang, M.E., Plumblee Lawrence, J.R., Thompson, T.M. 2021. Prevalence and characterization of quinolone resistance in Campylobacter spp. isolated in chicken livers from retail stores in Georgia, USA. Journal of Food Protection. https://doi.org/10.4315/JFP-21-357.
DOI: https://doi.org/10.4315/JFP-21-357

Interpretive Summary: Campylobacter is responsible for human bacterial foodborne illnesses worldwide and outbreaks have been linked to consumption of under-cooked chicken livers. A total of 250 Campylobacter isolates from chicken livers was used in this study. Accurate, rapid detection and confirmation of Campylobacter species in the poultry products is an integral part of USDA FSIS inspection program. To overcome the problems in traditional culture methods, two PCR assays were compared in identification of Campylobacter species. Results showed that 181 (72%) isolates were identified as Campylobacter jejuni and 69 (28%) isolates were identified as Campylobacter coli by both PCR assays. In addition, antibiotic resistance is an important public health issue and is common in Campylobacter. These liver Campylobacter isolates were assessed the antibiotic resistance spectra. Results showed that a total of 93 (37.2%) isolates were determined to be resistant to at least one antibiotic. Among 88 C. jejuni isolates, 33 isolates (18%) were resistant to ciprofloxacin (CIP) and nalidixic acid (NAL), followed by 25 (14%) isolates resistant to tetracycline (TET) and 18 (10%) isolates resistant to NAL and TET. Two isolates were resistant to four antibiotics tested. One isolate was resistant to five antibiotics tested. For C. coli, two isolates were resistant to TET, and two were resistant to CIP, NAL and TET. Finally, genetic diversity of the quinolone resistance determining regions (QRDR) of the isolates was analyzed. The amino acid sequences of the QRDR regions among the isolates revealed eight point mutations and could be classified into 12 groups. Thirty-eight C. jejuni isolates resistant to CIP and NAL had a point mutation at residue 86 (Thr to Ile substitution). However, six isolates without the substitution at the same position were resistant to CIP and/or NAL. In addition, 10 isolates with a point mutation at residue 86 were susceptible to CIP and NAL. This observation suggests that besides the substitution at 86, other mechanisms may confer resistance to quinolones. Further studies are needed to understand the mechanisms for the quinolone resistance in Campylobacter. Based on our results, the Campylobacter spp. isolated from chicken livers were found to be resistant to the quinolone class and other antibiotics.

Technical Abstract: Campylobacter is the leading bacterial pathogen that causes human foodborne illnesses worldwide and outbreaks have been associated with consumption of under-cooked chicken livers. The objectives of this study were to compare two PCR assays for speciation of 250 Campylobacter isolates, to assess antibiotic resistance of the isolates, and to analyze genetic diversity of the quinolone resistance determining regions (QRDR) of the isolates. Speciation was performed in a double-blind manner, and results showed that 181 (72%) isolates were identified as Campylobacter jejuni and 69 (28%) isolates were identified as Campylobacter coli by both PCR assays. A total of 93 (37.2%) isolates were determined to be resistant to at least one antibiotic. Among 88 C. jejuni isolates, 33 isolates (18%) were resistant to ciprofloxacin (CIP) and nalidixic acid (NAL), followed by 25 (14%) isolates resistant to tetracycline (TET) and 18 (10%) isolates resistant to NAL and TET. Two isolates were resistant to four antibiotics tested. One isolate was resistant to five antibiotics tested. For C. coli, two isolates were resistant to TET, and two were resistant to CIP, NAL and TET. The amino acid sequences of the QRDR regions among the isolates revealed eight point mutations and could be classified into 12 groups. Thirty-eight C. jejuni isolates resistant to CIP and NAL had a point mutation at residue 86 (Thr to Ile substitution). However, six isolates without the substitution at the same position were resistant to CIP and/or NAL. In addition, 10 isolates with a point mutation at residue 86 were susceptible to CIP and NAL. This observation suggests that besides the substitution at 86, other mechanisms may confer resistance to quinolones. Further studies are needed to elucidate the mechanisms for the quinolone resistance in Campylobacter. Based on our results, the Campylobacter spp. isolated from chicken livers were found to be resistant to the quinolone class and other antibiotics.