Species identification of erythromycin-resistant Campylobacter isolates and optimization of a duplex PCR for rapid detection

Epidemiology of antimicrobial resistant Campylobacter spp. isolated from retail meats in Canada

Campylobacter is an important zoonotic pathogen found in livestock and can cause illness in humans following consumption of raw and undercooked meat products. The objectives of this study were to determine the prevalence of Campylobacter spp. in retail meat (poultry, turkey, pork and beef) purchased in Alberta, Canada and to assess antimicrobial resistance and genetic relatedness of recovered Campylobacter strains with previously isolated strains from clinical and environmental sources. A Comparative Genomic Fingerprinting (CGF) method was used for assessing genetic relatedness of isolates. A total of 606 samples comprising 204, 110, 145 and 147 samples of retail chicken, turkey, ground beef and pork, respectively, were obtained. Campylobacter was isolated from 23.5% (48/204) of chicken samples and 14.2% (8/110) of turkey samples. Pork and beef samples were negative for Campylobacter. Campylobacter jejuni was the most common (94.6%) spp. found followed by C. coli (5.4%). Resistance to tetracycline was found in 48.1% of isolates, followed by resistance to ciprofloxacin (5.5%), nalidixic acid (5.5%), azithromycin (1.78%), and erythromycin (1.78%). All isolates were susceptible to clindamycin, florfenicol, gentamicin and telithromycin. Tetracycline resistance was attributable to the presence of the tetO gene. CGF analysis showed that Campylobacter isolated from poultry meat in this study were genetically related to clinical isolates recovered from human infections and to those isolated from animals and the environment.

Molecular epidemiology, virulence determinants and antimicrobial resistance of Campylobacter spreading in retail chicken meat in Central China

Background

Campylobacter species are the major food-borne pathogens which could cause bacterial gastroenteritis in humans. Contaminated chicken products have been recognized as the primary vehicles of Campylobacter transmission to human beings. In this study, the prevalence of Campylobacter in retail chicken meat in Central China was investigated, and the isolates were further characterized using molecular approaches and tested for antibiotic resistance.

Results

A total of 302 chicken samples purchased from April 2014 to April 2015 were tested. The level of Campylobacter contamination was enumerated by most probable number-PCR (MPN-PCR). The Campylobacter positive rate was 17.2% (52/302), with bacterial count varying from 3.6 to 360 MPN/g in positive samples. A total of 52 Campylobacter strains, including 40 Campylobacter jejuni and 12 Campylobacter coli, were isolated from the positive samples. To examine the genetic diversity of the isolates, multilocus sequence typing (MLST) technology was applied, which identified 23 sequence types (STs) belonging to seven clonal complexes (CCs) and unassigned. Among them, the dominant CCs of C. jejuni included CC-353 and CC-464, and the dominant CCs of C. coli were CC-828 and CC-1150. Antibiotic resistance analysis showed that all of the isolates were resistant to norfloxacin and ciprofloxacin. 23 virulence-associated genes were tested in the isolates, which showed that the number of virulence-associated genes detected in the C. jejuni isolates ranged from 16 to 21, while in most of the C. coli isolates ranged from 12 to 16. Virulence-associated genes, flaA, flgB, flgE2, fliM, fliY and cadF were detected in all isolates. VirB11, however, was not detected in any of the isolates.

Conclusions

To the best of our knowledge, this is the first report on the contamination level and molecular biological features of Campylobacter strains in retail chicken meat in Central China, which showed high genetic diversity and remarkable antibiotic resistance. This study provided scientific data for the risk assessment and evaluation of Campylobacter contamination in retail chicken products.

Electronic supplementary material

The online version of this article (doi:10.1186/s13099-016-0132-2) contains supplementary material, which is available to authorized users.

Detection and quantification of Campylobacter jejuni and Campylobacter coli using real-time multiplex PCR

AIMS

We describe a real-time quantitative multiplex polymerase chain reaction (qmPCR) assay to identify and discriminate between isolates of Campylobacter jejuni and Campylobacter coli.

METHODS AND RESULTS

Two novel sets of primers and hydrolysis probes were designed to amplify the unique DNA sequences within the hipO, ccoN and cadF genes that are specific to Camp. jejuni and Camp. coli. Using the designed optimized qmPCR assay conditions, the amplification efficiency is in range from 108 to 116%. These qmPCR assays are highly specific for Camp. jejuni and Camp. coli, as seen through testing of 40 Campylobacter strains and 17 non-Campylobacter strains. In chicken juice and tap water models spiked with known quantities of Camp. jejuni, qmPCR detected 10(2) -10(3) CFU ml(-1) within 4 h.

CONCLUSIONS

The qmPCR assays developed in this study provide reliable and simultaneous detection and quantification of Camp. jejuni and Camp. coli, with good amplification reaction parameters.

SIGNIFICANCE AND IMPACT OF THE STUDY

Following further validation, the qmPCR assay reported here has the potential to be applied to various sample types as an alternative and rapid methodology.