Antimicrobial resistance patterns and molecular resistance markers of Campylobacter jejuni isolates from human diarrheal cases

Authors: ELHADIDY, MOHAMED - Zewail City Of Science And Technology; ALI, MOHAMED - Zewail City Of Science And Technology; EL-SHIBINY, AYMAN - Zewail City Of Science And Technology; Miller, William - Bill; ELKHATIB, WALID - Badr University; BOTTELDOORN, NADINE - Scientific Institute Of Public Health; DIERICK, KATELIJNE - Scientific Institute Of Public Health

Submitted to: Frontiers in Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/9/2020
Publication Date: 1/17/2020
Citation: Elhadidy, M., Ali, M.M., El-Shibiny, A., Miller, W.G., Elkhatib, W.F., Botteldoorn, N., Dierick, K. 2020. Antimicrobial resistance patterns and molecular resistance markers of Campylobacter jejuni isolates from human diarrheal cases. PLoS One. 15(1):e0227833. https://doi.org/10.1371/journal.pone.0227833.
DOI: https://doi.org/10.1371/journal.pone.0227833

Interpretive Summary: The food-borne pathogen Campylobacter is a natural contaminant of most birds and livestock, with poultry meat the major vehicle for Campylobacter-associated illness in humans. The majority of Campylobacter-caused cases of human gastroenteritis are associated with Campylobacter jejuni. This study characterized 199 C. jejuni strains recovered from human diarrheal samples over a ten-year time period (2006-2015) in Belgium, with all samples screened for antibiotic resistance. Most of the strains demonstrated antibiotic resistance with high rates of resistance towards tetracycline and the quinolone class of antibiotics (ciprofloxacin and nalidixic acid); 9% of the strains demonstrated multi-drug resistance, that is, resistance to three or more classes of antibiotics. However, lower rates of resistance were noted towards erythromycin and streptomycin and none of the isolates characterized demonstrated resistance towards gentamicin. The molecular causes of resistance were investigated in the antibiotic-resistant strains. Most of the quinolone and tetracycline resistant strains possessed mutations or genes previously reported to be associated with resistance towards these antibiotics. However, some resistances could not be associated with previously-reported genes or mutations; thus, their cause remains undetermined.

Technical Abstract: The aim of this study is to characterize the antimicrobial resistance of Campylobacter jejuni recovered from diarrheal patients in Belgium, focusing on the genetic diversity of resistant strains and underlying molecular mechanisms of resistance. Phenotypic screening of 199 clinical C. jejuni isolates was performed by determining the minimum inhibitory concentrations against six commonly-used antibiotics (ciprofloxacin, nalidixic acid, tetracycline, streptomycin, gentamicin, and erythromycin). High rates of resistance were observed against nalidixic acid (56.3%), ciprofloxacin (55.8%) and tetracycline (49.7%); these rates were similar to those obtained from different national reports that estimated antimicrobial resistance in broilers intended for human consumption. Alternatively, lower resistance rates to streptomycin (4.5%) and erythromycin (2%), and absolute sensitivity to gentamicin were observed. C. jejuni isolates resistant to tetracycline or quinolones (ciprofloxacin and/or nalidixic acid) were screened for the presence of the tetO gene and the C257T mutation in the quinolone resistance determining region (QRDR) of the gyrase gene gyrA, respectively. Interestingly, some of the isolates that displayed phenotypic resistance to these antimicrobials lacked the corresponding genetic determinants. Among erythromycin-resistant isolates, a diverse array of potential molecular resistance mechanisms was investigated, including the presence of ermB and mutations in the 23S rRNA gene, the rplD and rplV ribosomal genes, and the regulatory region of the cmeABC operon. Two of the four erythromycin-resistant isolates harboured the A2075G transition mutation in the 23S rRNA gene; one of these isolates exhibited further mutations in rplD, rplV and in the cmeABC regulatory region. The erythromycin resistance gene ermB gene was absent in all isolates. This study expands the current understanding of how different genetic determinants and particular clones shape the epidemiology of antimicrobial resistance in C. jejuni in Belgium. It also reveals many questions in need of further investigation, such as the role of other undetermined molecular mechanisms that may potentially contribute to the antimicrobial resistance of Campylobacter.