Identification of Campylobacter jejuni isolates from cloacal and carcass swabs of chickens in Thailand by a 5' nuclease fluorogenic polymerase chain reaction assay

A modified molecular beacons-based multiplex real-time PCR assay for simultaneous detection of eight foodborne pathogens in a single reaction and its application

Foodborne disease outbreaks are often caused by one of the major pathogens. Early identification of the causal pathogen is crucial for disease control and prevention. We describe a real-time polymerase chain reaction (rtPCR) assay that can identify, in a single reaction, up to eight common foodborne bacterial pathogens, including Salmonella enterica subsp. enterica, Listeria monocytogenes, Escherichia coli O157, Vibrio parahaemolyticus, V. vulnificus, Campylobacter jejuni, Enterobacter sakazakii, and Shigella spp. This multiplex rtPCR assay takes advantage of modified molecular beacons and the multicolor combinational probe coding strategy to discriminate each pathogen and the homo-tag assisted non-dimer (HAND) system to prevent dimer formation. The detection limits of the assay ranged from 1.3×10(3) colony-forming units (CFU)/g stool (L. monocytogenes) to 1.6×10(4) CFU/g stool (Shigella spp.). The target genes were 100% specific as assessed on 986 reference strains covering 41 species since no cross-reactions were observed. The assay was applied to the detection of foodborne pathogens in 11,167 clinical samples and the results were compared with culture methods for further validation. The sensitivity and specificity of the rtPCR were 100% and 99%, respectively. When performed in a 96-well rtPCR system, more than 90 samples could be analyzed within 3 h. Given the high accuracy, sensitivity, specificity, and short turn-around time, the established assay could be used for the rapid and reliable identification of the causative pathogens responsible for a certain foodborne disease outbreak and rapid screening of these major foodborne pathogens in laboratory-based surveillance of outpatient clinical samples or even food samples.

Prevalence of Campylobacter spp. in poultry and poultry products for sale on the Bulgarian retail market

The aim of this study was to investigate the presence of Campylobacter spp. in poultry and poultry products available for the consumers at retail markets in Bulgaria. Samples (n = 210) of poultry carcasses and poultry products for sale at the retail market in Bulgaria were analysed for the presence of Campylobacter spp., of these 35 frozen whole carcasses, 135 chilled poultry cuts (45 wing cuts, 45 thigh cuts and 45 fillet) and 40 thermally treated (ready-to-eat) poultry products. The results obtained showed that 35.2% of the frozen poultry carcasses for sale in the markets were Campylobacter contaminated. In the chilled poultry cuts Campylobacter was isolated at the highest percentage in wing- and thigh cuts, 91.1% and 88.9%, respectively. The fillet samples were contaminated by Campylobacter in 48.9% of cases. In the chilled poultry products as well as in the frozen carcasses C. jejuni (74.8%/70.3%) was the most commonly isolated Campylobacter species, with the remainder being C. coli (25.2%/29.7%). Campylobacter spp. were not detected in the thermally treated poultry products.

A seven-year survey of Campylobacter contamination in meat at different production stages in Belgium

The presence of Campylobacter was assessed in different samples of poultry, pork and beef meat and carcasses from slaughterhouses, production plants and retail level. An introductory study from 1997 to 1999, had the purpose of establishing the optimum dilution to detect changes in prevalence and allowed a semi-quantitative estimation of poultry and pork contamination. Following this, between 2000 and 2003, 4254 samples were taken in order to study the trends. The poultry matrixes represented the greatest number and the most highly contaminated samples, with 30.9% (in 0.01 g) positive samples, 18.7% (in 1 g), 46.9% (in 25 g) and 19.6% (in 0.01 g) for broiler carcasses, broiler fillets, prepared chicken and layer carcasses, respectively. Broiler carcasses and fillets sampled at retail level were significantly less contaminated than samples from production plants. Pork, beef and veal samples were rarely contaminated and, where contamination existed, it was at a low prevalence (maximum 5.0%). The high and unvarying prevalence of Campylobacter in poultry necessitates the implementation of intervention measures at the primary production level, in addition to methods of minimizing cross-contamination at the processing level. A survey plan in line with the present study could be used in the future to monitor the effects of the planned measures and performance objectives and to follow the evolution of Campylobacter contamination at all stages of the food chain, in accordance with European legislation.

Campylobacter in food animals and humans in northern Thailand

Cross-sectional, longitudinal, and case-control studies were conducted to describe the epidemiology of Campylobacter in chickens, swine, dairy cows, farm workers, nonfarm residents, and children with diarrhea. Samples were collected in Chiang Mai and Lamphung provinces of northern Thailand from 2000 through 2003. A total of 2,360 samples were processed. Results from the cross-sectional study indicated that the prevalences of Campylobacter in chickens at the farm, slaughterhouse, and market were 64, 38, and 47%, respectively. In swine, the prevalences at the farm, slaughterhouse, and market were 73, 69, and 23%, respectively. Campylobacter prevalence was 14% in dairy cows and 5% in raw milk. The prevalence of Campylobacter on farms was lower in environmental samples than in samples collected from live animals. No Campylobacter isolates were obtained from healthy nonfarm residents, but isolates were obtained from 5 and 18% of farm workers and children with diarrhea, respectively. The prevalence of Campylobacter in pigs in the longitudinal study was 61% at the farm, 46% at the slaughterhouse, and 33% at the market. The majority of Campylobacter isolates from chickens (52%), swine (98%), and farm workers (66%) were Campylobacter coli, whereas the majority of isolates from dairy cows (63%) and children with diarrhea (62%) were Campylobacter jejuni. Most Campylobacter isolates from diarrheal children had single-strand conformation polymorphism profiles similar to those of isolates from chickens. None of the risk factors for infection in children with diarrhea were significantly associated with the isolation of Campylobacter.

Real-time nucleic acid-based detection methods for pathogenic bacteria in food

Quality assurance in the food industry in recent years has involved the acceptance and implementation of a variety of nucleic acid-based methods for rapid and sensitive detection of food-associated pathogenic bacteria. Techniques such as polymerase chain reaction have greatly expedited the process of pathogen detection and have in some cases replaced traditional methods for bacterial enumeration in food. Conventional PCR, albeit sensitive and specific under optimized conditions, obligates the user to employ agarose gel electrophoresis as the means for endpoint analysis following sample processing. For the last few years, a variety of real-time PCR chemistries and detection instruments have appeared on the market, and many of these lend themselves to applications in food microbiology. These approaches afford a user the ability to amplify DNA or RNA, as well as detect and confirm target sequence identity in a closed-tube format with the use of a variety of fluorophores, labeled probes, or both, without the need to run gels. Such real-time chemistries also offer greater sensitivity than traditional gel visualization and can be semiquantitative and multiplexed depending on the specific experimental objectives. This review emphasizes the current systems available for real-time PCR-based pathogen detection, the basic mechanisms and requirements for each, and the prospects for development over the next few years in the food industry.

Application of real-time PCR for quantitative detection of Campylobacter jejuni in poultry, milk and environmental water

Campylobacter jejuni is a leading human food-borne pathogen. The rapid and sensitive detection of C. jejuni is necessary for the maintenance of a safe food/water supply. In this article, we present a real-time polymerase chain reaction (PCR) assay for quantitative detection of C. jejuni in naturally contaminated poultry, milk and environmental samples without an enrichment step. The whole assay can be completed in 60 min with a detection limit of approximately 1 CFU. The standard curve correlation coefficient for the threshold cycle versus the copy number of initial C. jejuni cells was 0.988. To test the PCR system, a set of 300 frozen chicken meat samples, 300 milk samples and 300 water samples were screened for the presence of C. jejuni. 30.6% (92/300) of chicken meat samples, 27.3% (82/300) of milk samples, and 13.6% (41/300) of water samples tested positive for C. jejuni. This result indicated that the real-time PCR assay provides a specific, sensitive and rapid method for quantitative detection of C. jejuni. Moreover, it is concluded that retail chicken meat, raw milk and environmental water are commonly contaminated with C. jejuni and could serve as a potential risk for consumers in eastern China, especially if proper hygienic and cooking conditions are not maintained.

Determination of ciprofloxacin and nalidixic acid resistance in Campylobacter jejuni with a fluorogenic polymerase chain reaction assay

A fluorogenic polymerase chain reaction assay for the gyrA gene was used to determine the frequency of a Thr-86 mutation in Campylobacter jejuni isolates from food animals and humans in northern Thailand and to investigate the correlation between this mutation and bacterial resistance to fluoroquinolones. Eighty-four isolates of C. jejuni were used: 65 from healthy chickens on farms, 16 from chickens at the slaughterhouse, 1 from chicken meat at the market, and 1 from a healthy farm worker. The microbroth dilution technique was used for in vitro susceptibility testing. MIC breakpoints established by the National Antimicrobial Resistance Monitoring System were used to categorize the resistance of C. jejuni to ciprofloxacin and nalidixic acid. Sixty of the 84 C. jejuni isolates tested carried the Thr-86 mutation in the gyrA gene. All isolates with ciprofloxacin MICs of > or = 2 mg/liter carried the mutation, and no isolates with nalidixic acid MICs of < or = 16 mg/liter carried the Thr-86-to-Ile mutation. There was a very strong association between ciprofloxacin resistance and the presence of the mutation (kappa = 0.971, P < 0.01). The association between the presence of the Thr-86-to-Ile mutation and nalidixic acid resistance was weaker (kappa 0.859: P < or = 0.01).