Quantification of Campylobacter spp. in chicken carcass rinse by real-time PCR

Role of Maternal Antibodies in the Protection of Broiler Chicks against Campylobacter Colonization in the First Weeks of Life

Thermophilic Campylobacter species are the most common cause of bacterium-mediated diarrheal disease in humans globally. Poultry is considered the most important reservoir of human campylobacteriosis, but so far, no effective countermeasures are in place to prevent the bacterium from colonizing broiler flocks. This study investigated maternal antibodies' potential to offer protection against Campylobacter in broiler chicks via a field trial and an immunization trial. In the field trial, breeder flocks with high and low anti-Campylobacter antibody levels in the yolk were selected based on serological screening. Offspring were subsequently monitored for maternal antibodies and Campylobacter prevalence during early life. Although maternal antibodies declined rapidly in the serum of broilers, offspring from flocks with lower anti-Campylobacter antibody levels seemed to be more susceptible to colonization. In the immunization trial, breeders from a seropositive breeder flock were vaccinated with an experimental bacterin or subunit vaccine. Immunization increased antibody levels in the yolk and consequently in the offspring. Elevated maternal antibody levels were significantly associated with reduced Campylobacter susceptibility in broilers at 2 weeks old but not at 1 and 3 weeks old. Overall, the protective effect of maternal immunity should be cautiously considered in the context of Campylobacter control in broilers. Immunization of breeders may enhance resistance but is not a comprehensive solution.

Novel rpsK / rpsD primer-probe assay improves detection of Campylobacter jejuni and Campylobacter coli in human stool

Campylobacter causes bacterial enteritis, dysentery, and growth faltering in children in low- and middle-income countries (LMICs). Campylobacter spp. are fastidious organisms, and their detection often relies on culture independent diagnostic technologies, especially in LMICs. Campylobacter jejuni and Campylobacter coli are most often the infectious agents and in high income settings together account for 95% of Campylobacter infections. Several other Campylobacter species have been detected in LMIC children at an increased prevalence relative to high income settings. After doing extensive whole genome sequencing of isolates of C. jejuni and C. coli in Peru, we observed heterogeneity in the binding sites for the main species-specific PCR assay (cadF) and designed an alternative rpsKD-based qPCR assay to detect both C. jejuni and C. coli. The rpsKD-based qPCR assay identified 23% more C.jejuni/ C.coli samples than the cadF assay among 47 Campylobacter genus positive cadF negative samples verified to have C. jejuni and or C. coli with shotgun metagenomics. This assay can be expected to be useful in diagnostic studies of enteric infectious diseases and be useful in revising the attribution estimates of Campylobacter in LMICs.

Reducing Campylobacter colonization in broilers by active immunization of naive broiler breeders using a bacterin and subunit vaccine

Campylobacter is the main cause of human gastroenteritis worldwide, with 50 to 80% of the cases related to consumption of poultry products. Maternal antibodies (MAB) from commercial breeder flocks may protect their progeny against infection during the first few weeks of life. We here studied the prevalence of Campylobacter antibody titers in broiler breeder flocks and to which extent immunization of broiler breeders increases maternal anti-Campylobacter titers in their progeny and protects the offspring against Campylobacter colonization. Two vaccines were used: a bacterin mix of 13 Campylobacter strains and a subunit vaccine comprising 6 immunodominant Campylobacter antigens. All sampled on-farm breeder flocks were positive for anti-Campylobacter antibodies, yet in some breeder flocks only very low titers were detected. Vaccination of SPF broiler breeder flocks with both subunit and bacterin vaccines resulted in a prolonged presence of anti-Campylobacter antibodies in the serum and intestinal mucus of chicks. These bacterin- or subunit vaccine-induced MAB conferred protection against Campylobacter colonization in chicks until 7 and 21 d of age, respectively, but only at a low challenge dose (102.5 cfu). The concentration of MAB in the mucus is probably too low to sufficiently capture Campylobacter when higher challenge doses are used. In conclusion, vaccinating broiler breeders protects their offspring against Campylobacter colonization under low pathogen exposure conditions.

An Integrated Paper Microfluidic Device Based on Isothermal Amplification for Simple Sample-to-Answer Detection of Campylobacter jejuni

Campylobacter jejuni is recognized as the most common species in the genus Campylobacter that causes foodborne diseases. The main reservoirs harboring C. jejuni are poultry products, which are associated with most illnesses, creating a demand for effective detection methods to achieve point-of-need diagnostics. We developed an easy-to-use, hybrid paper/polymer-based microfluidic device that integrates paper-based DNA extraction, isothermal nucleic acid amplification, and lateral flow detection. Overall, the recombinase polymerase amplification (RPA) reaction was completed in 20 min and demonstrated 100% specificity to C. jejuni, including 2 reference strains and 6 wild strains isolated from the agroecosystem, 9 other Campylobacter subspecies strains, and 11 non-Campylobacter strains. The limit of detection (LOD) was 46 CFU/mL with DNA extracted on the cellulose paper. The sensitivity was reduced to 460 CFU/mL on the integrated hybrid paper/polymer-based microfluidic device. This device could detect C. jejuni spiked at concentrations ranging from 101 to 102 CFU/g in chicken meat after an enrichment of 5 to 10 h. For C. jejuni levels of >102 CFU/g, it managed to confirm positive results immediately, without bacterial enrichment. RPA reagents and primers remained stable on the paper platform at 22°C for 12 h. After lyophilization and storage on paper, the RPA reaction showed consistent sensitivity for 3 days, and the LOD was reduced to 103 CFU/mL when storage was extended to 25 days. The use of this hybrid paper/polymer-based microfluidic device enabled detection of Campylobacter in foods with high specificity and sensitivity, demonstrating its potential as a reliable point-of-need diagnostic platform for on-site conditions due to its low cost, portability, and simplicity. IMPORTANCE The global health and economic burden of Campylobacter prompts the development of novel detection techniques that can be implemented in resource-limited and on-site settings. This study described point-of-need identification of C. jejuni using a hybrid paper/polymer-based microfluidic device that is easy to operate. This device had high specificity and sensitivity toward C. jejuni and significantly reduced the total analysis time compared to conventional culture-based methods. Nucleic acid extraction was simplified from intensive pipetting to a paper dipstick, making it more convenient for use in the field as a promising tool for future routine surveillance and outbreak investigation.

Polyethersulfone-Based Microfluidic Device Integrated with DNA Extraction on Paper and Recombinase Polymerase Amplification for the Detection of Salmonella enterica

Rising consumption, large-scale production, and widespread distribution have been accompanied by an increase in the number of Salmonella infections reported to implicate contaminated food products. We developed a portable origami microfluidic device that enabled rapid detection of S. enterica from sample preparation to end-point detection, including nucleic acid extraction on paper dipstick without pipetting, nucleic acid amplification using isothermal recombinase polymerase amplification (RPA), and lateral flow assay for results readout. We also explored the feasibility of the polyethersulfone (PES) membrane as a new reaction matrix against the widely used chromatography paper to optimize nucleic acid amplification. Nucleic acid amplification was achieved within 20 min and demonstrated 100% specificity to S. enterica. The limit of detection of this PES-based microfluidic device was 260 CFU/mL and equivalent to RPA reaction in tube. A chromatography paper-based microfluidic device was found 1-log less in sensitivity for Salmonella detection compared to the use of PES. This PES-based microfluidic device could detect S. enterica in lettuce, chicken breast, and milk at concentrations of 6 CFU/g, 9 CFU/g, and 58 CFU/mL, respectively, after 6 h enrichment. PES has shown high compatibility to isothermal nucleic acid amplification and great potential to be implemented as an integrated sample-to-answer microfluidic device for the detection of pathogens in various food commodities.

Simultaneous Detection of Salmonella spp. and Quantification of Campylobacter spp. in a Real-Time Duplex PCR: Myth or Reality?

In Europe, there is a process hygiene criterion for Salmonella and Campylobacter on broiler carcasses after chilling. The criterion gives indicative contamination values above which corrective actions are required by food business operators. The reference methods for verifying compliance with the criterion for Salmonella and Campylobacter are international standards EN ISO 6579-1 (2017) and EN ISO 10272-2 (2017), respectively. These methods are time-consuming and expensive for food business operators. Therefore, it would be advantageous to simultaneously detect Salmonella spp. and quantify Campylobacter in the same analysis, using the same sample after the pre-enrichment step for Salmonella recovery. A duplex PCR for Salmonella detection and Campylobacter spp. enumeration was developed. Considering the method as a whole, the LOD and LOQ for Campylobacter enumeration were slightly over the limit of 3 log CFU/g set by the process hygiene criterion. A comparison of the duplex PCR method developed with the ISO method on artificially contaminated bacterial suspensions and on naturally contaminated samples demonstrated a good correlation of the results for Campylobacter enumeration when the duplex PCR was performed on samples taken before or after the pre-enrichment step, but revealed a slight bias with a large standard deviation resulting in widely spaced limits of agreement.

Two-Round Treatment With Propidium Monoazide Completely Inhibits the Detection of Dead Campylobacter spp. Cells by Quantitative PCR

Campylobacter spp. are known as important foodborne gastroenteric pathogens worldwide. Campylobacter spp. can exist in a viable but non-culturable (VBNC) state under unsuitable environmental conditions, which is undetectable by conventional culture methods. Quantitative polymerase chain reaction (qPCR) can be used to detect VBNC Campylobacter spp.; however, both viable and dead bacteria are detected during qPCR and are indistinguishable. Propidium monoazide (PMA), which can only enter dead bacterial cells through a damaged cell wall/cell membrane, binds to DNA and inhibits qPCR. PMA treatment has been performed along with qPCR (PMA-qPCR) to detect viable bacteria. However, the efficacy of detection inhibition differed among studies, and PMA can potentially enter living cells after changes in cell membrane permeability. In this study, we optimized the PMA treatment method by conducting it before qPCR. Two-round PMA treatment completely inhibited the qPCR signals from dead cells, whereas single-round PMA treatment failed to facilitate this. An optimized PMA-qPCR method was developed using commercial chicken meat, and VBNC Campylobacter spp., which are undetectable using conventional culture-based methods, were successfully detected. In conclusion, this study presents a novel, efficient PMA treatment method for the detection of viable Campylobacter spp., including VBNC Campylobacter spp., in chicken meat. We believe that this method will aid the reliable risk assessment of commercial chicken meat.

Enrichment Free qPCR for Rapid Identification and Quantification of Campylobacter jejuni, C. coli, C. lari, and C. upsaliensis in Chicken Meat Samples by a New Couple of Primers

Campylobacter is the main cause of bacterial foodborne disease and poultry meat is the principal source of human infections. Rapid methods for Campylobacter detection are urgently needed to decrease high bacterial prevalence in poultry products. In this study, we developed new primers, CampyPFw and CampyPRv, that target the 16S-23S rRNA genes of Campylobacter jejuni, C. coli, C. lari and C. upsaliensis. The primers were tested on positive and negative reference strains in pure cultures and in inoculated poultry meat samples before their application in real-time PCR (qPCR) protocol for analyzing chicken meat samples. In parallel, the samples were tested by using the ISO 10272-1:2006 method. The qPCR protocol based on CampyPFw and CampyPRv showed good sensitivity, with the limit of detection of 4.6 × 10² cells/mL in chicken samples without enrichment steps.

Associations among Household Animal Ownership, Infrastructure, and Hygiene Characteristics with Source Attribution of Household Fecal Contamination in Peri-Urban Communities of Iquitos, Peru

Using previously validated microbial source tracking markers, we detected and quantified fecal contamination from avian species and avian exposure, dogs, and humans on household cooking tables and floors. The association among contamination, infrastructure, and socioeconomic covariates was assessed using simple and multiple ordinal logistic regressions. The presence of Campylobacter spp. in surface samples was linked to avian markers. Using molecular methods, animal feces were detected in 75.0% and human feces in 20.2% of 104 households. Floors were more contaminated than tables as detected by the avian marker Av4143, dog marker Bactcan, and human marker Bachum. Wood tables were consistently more contaminated than non-wood surfaces, specifically with the mitochondrial avian markers ND5 and CytB, fecal marker Av4143, and canine marker Bactcan. Final multivariable models with socioeconomic and infrastructure characteristics included as covariates indicate that detection of avian feces and avian exposure was associated with the presence of chickens, maternal age, and length of tenancy, whereas detection of human markers was associated with unimproved water source. Detection of Campylobacter in surface samples was associated with the avian fecal marker Av4143. We highlight the critical need to detect and measure the burden of animal fecal waste when evaluating household water, hygiene, and sanitation interventions, and the possibility of decreasing risk of exposure through the modification of surfaces to permit more effective household disinfection practices. Animals may be a more important source of household fecal contamination than humans in many low-resource settings, although interventions have historically focused almost exclusively on managing human waste.

Persistent contamination ofSalmonella,Campylobacter,Escherichia coli, andStaphylococcus aureusat a broiler farm in New Zealand

Intensive poultry production due to public demand raises the risk of contamination, creating potential foodborne hazards to consumers. The prevalence and microbial load of the pathogens Campylobacter, Salmonella, Staphylococcus aureus, and Escherichia coli was determined by standard methods at the farm level. After disinfection, swab samples collected from wall crevices, drinkers, and vents were heavily contaminated, as accumulated organic matter and dust likely protected the pathogens from the disinfectants used. The annex floor also showed high microbial concentrations, suggesting the introduction of pathogens from external environments, highlighting the importance of erecting hygiene barriers at the entrance of the main shed. Therefore, pathogen control measures and proper application of disinfectants are recommended as intervention strategies. Additionally, quantitative polymerase chain reaction (qPCR) was evaluated as a quantification tool. qPCR showed limitations with samples containing low microbial counts because of the low detection limit of the method. Thus, bacterial pre-enrichment of test samples may be necessary to improve the detection of pathogens by qPCR.

Research Note: Lyophilization of hyperimmune egg yolk: effect on antibody titer and protection of broilers against Campylobacter colonization

Oral administration of antibodies is a promising strategy against various infectious diseases. Previously, it was demonstrated that passive immunization by providing hyperimmune egg yolk through the feed reduces Campylobacter jejuni colonization in broilers. Campylobacteriosis is the most commonly reported bacterial foodborne zoonosis worldwide, and poultry products are the number one origin of these bacteria for human infection. To date, no effective control measures exist to limit Campylobacter colonization in the chicken's intestinal tract. Here, the effect of lyophilization of hyperimmune egg yolk on protection of broilers against C. jejuni was investigated. During an in vivo trial, broiler chickens were prophylactically given feed with lyophilized hyperimmune or non-immunized egg yolk powder starting from day 1 after hatch. At day 11, broilers were inoculated with C. jejuni according to a seeder model. Five days later, all broilers were euthanized and cecal content was examined for C. jejuni colonization. No decrease in C. jejuni colonization was found. The freeze-drying resulted in a 16-fold decrease of the antibody titer in the yolk powder compared to the fresh yolks, presumably caused by structural changes in the antibodies. In conclusion, applying freeze-dried hyperimmune egg yolk failed to protect broilers against C. jejuni colonization, possibly because lyophilization affected the antibodies' functionality.

In ovo vaccination of broilers against Campylobacter jejuni using a bacterin and subunit vaccine

Campylobacter jejuni and Campylobacter coli originating from poultry meat have been the most important causes of foodborne bacterial gastroenteritis in the European Union since 2005. In-feed application of maternal antibodies from vaccinated hens was shown to confer protection of broilers against Campylobacter infection. Here, it was investigated if these vaccines can be used to protect broilers against Campylobacter infection after in ovo vaccination. Embryos were immunized in ovo at day 18 with a bacterin or a subunit vaccine and at 19 D post hatch, these birds were inoculated with C. jejuni according to a seeder model. Quantification of C. jejuni in the broilers cecal content showed that the in ovo vaccinated birds were not protected against C. jejuni infection. Quantification of blood anti-Campylobacter antibody titers did not show any induction of Campylobacter-specific serological response in the vaccinated birds, which may explain the lack of protection in the vaccinated chicks.

An easy-to-perform, culture-free Campylobacter point-of-management assay for processing plant applications

Aims

Current culture‐based methods for detection and determination of Campylobacter levels on processed chickens takes at least 2 days. Here we sought to develop a new complete, low‐cost and rapid (approximately 2·5 h) detection system requiring minimal operator input.

Methods and Results

We observed a strong correlation between culture‐based cell counts and our ability to detect either Campylobacter jejuni or Campylobacter coli by loop‐mediated isothermal amplification from the same samples. This knowledge was used to develop a rapid and simple five‐step assay to quantify Campylobacter, which was subsequently assessed for its specificity, reproducibility and accuracy in quantifying Campylobacter levels from processed chickens. The assay was found to be highly specific for C. jejuni and C. coli and was capable of distinguishing between samples that are either within or exceeding the industry set target of 6000 Campylobacter colony forming units (CFU) per carcass (equivalent to 12 CFU per ml of chicken rinse) with >90% accuracy relative to culture‐based methods.

Conclusions

Our method can reliably quantify Campylobacter counts of processed chickens with an accuracy comparable to culture‐based assays but provides results within hours as opposed to days.

Significance and Impact of the Study

The research presented here will help improve food safety by providing fast Campylobacter detection that will enable the implementation of real‐time risk management strategies in poultry processing plants to rapidly test processed chickens and identify effective intervention strategies. This technology is a powerful tool that can be easily adapted for other organisms and thus could be highly beneficial for a broad range of industries.

Internal sample process control improves cultivation-independent quantification of thermotolerant Campylobacter

Quantification of Campylobacter is challenging and one major reason is the fact that bacteria lose cultivability due to cold or oxygen stress during storage at retail. Alternative live/dead discriminatory qPCR currently lacks standardization and might overestimate live cells in the presence of dead cells. In this study an internal sample process control (ISPC) was developed. The ISPC consists of a specified number of peroxide-killed C. sputorum cells to be added to each sample in order to monitor (i) the level of reduction of the signal from dead cells and (ii) DNA losses during sample processing. A species-specific fragment of the 16S rRNA gene of C. sputorum was selected as real-time PCR target, based on its similar size and gene copy number compared to the C. jejuni/coli/lari target and confirmed in an exclusivity study. Extension of the amplification oligonucleotides for the target of thermotolerant Campylobacter improved real-time PCR efficiency, rendering the method suitable for quantification according to international standards. Concordant PCR signal variation of both C. jejuni and C. sputorum targets in co-inoculated chicken rinses verified the suitability of the ISPC. This provides a crucial step towards implementation of cultivation-independent quantification for improved food safety of fastidious bacteria.

Evaluation and validation of an alternative method to detect Campylobacter spp. in dairy products

Foods implicated in human campylobacteriosis include raw or undercooked poultry and raw dairy products. Because Campylobacter spp. are the most frequently reported cause of bacterial infection in the European Union and because conventional methods are cumbersome, rapid methods for Campylobacter detection and quantification in food are needed. With this study we sought to validate, according to the standard procedure (UNI EN ISO 16140:2003), an alternative to the reference analytical method (UNI EN ISO 10272-1:2006) for official controls of Campylobacter spp. in raw milk and dairy products. Milk samples collected from 16 milk vending machines located throughout the Genoa metropolitan area were analyzed using two different methods, an enzyme-linked fluorescent assay (ELFA) and a real-time PCR assay, and evaluated in parallel against the reference method. In addition, a total of 460 samples of raw milk collected from milk vending machines were analyzed by ELFA. Results obtained with ELFA showed it was compliant with UNI EN ISO 10272-1:2006 criteria and that the immunoassay had 100% sensitivity, specificity, and accuracy. Regarding samples of milk vending machines, 5.0% (23/460) tested positive at ELFA screening and were subsequently confirmed as C. jejuni. Validation according to UNI EN ISO 16140:2003 of the ELFA method suggests it may be a useful alternative to conventional methods for detecting Campylobacter spp. in official controls.

New colorimetric aptasensor for rapid on-site detection of Campylobacter jejuni and Campylobacter coli in chicken carcass samples

Campylobacter is the most common cause of infectious intestinal disease, with nearly all cases caused by two species: C. jejuni and C. coli. We recently reported a gold nanoparticle-based two-stage aptasensing platform, which was improved in the present study for the rapid and on-site detection of both C. jejuni and C. coli in food samples. Compared to the previous platform, the improved platform yielded a more obvious colour change from red to purple due to the aggregation of gold nanoparticles, and does not require additional time or a pH optimization step for the aptamers to be adsorbed onto the gold nanoparticles. Using a highly specific aptamer that binds to live C. jejuni and C. coli, the improved aptasensor was highly effective for testing pure culture samples. The accuracy of the newly developed platform was comparable (p = 0.688) to that of the gold-standard detection method of tazobactam-supplemented culture, whereas it was superior to the official agar-based detection method (p = 0.016) in a validation study with 50 naturally contaminated chicken carcass samples. This is the first study on a colorimetric sensor that targets both live C. coli and C. jejuni in naturally contaminated samples. In addition, we provide the first evidence that both morphological status and the amount of Campylobacter present play key roles in the effectiveness of colorimetric detection. Thus, suitable selection of an antibody or aptamer with consideration of the morphological status of pathogens in samples is essential for direct detection without enrichment. Our data suggest that the sensor developed in this study can provide an excellent screening method, with a reduction in the detection time from 48 h to 30 min after enrichment, thus saving time, labour, and cost.

The other Campylobacters: Not innocent bystanders in endemic diarrhea and dysentery in children in low-income settings

Background

Campylobacter is one of the main causes of gastroenteritis worldwide. Most of the current knowledge about the epidemiology of this food-borne infection concerns two species, C. coli and C. jejuni. Recent studies conducted in developing countries and using novel diagnostic techniques have generated evidence of the increasing burden and importance of other Campylobacter species, i.e. non-C. coli/jejuni. We performed a nested case-control study to compare the prevalence of C. coli/jejuni and other Campylobacter in children with clinical dysentery and severe diarrhea as well as without diarrhea to better understand the clinical importance of infections with Campylobacter species other than C. coli/jejuni.

Methodology/Principal findings

Our nested case-control study of 439 stool samples included dysenteric stools, stools collected during severe diarrhea episodes, and asymptomatic stools which were systematically selected to be representative of clinical phenotypes from 9,160 stools collected during a birth cohort study of 201 children followed until two years of age. Other Campylobacter accounted for 76.4% of the 216 Campylobacter detections by qPCR and were more prevalent than C. coli/jejuni across all clinical groups. Other Campylobacter were also more prevalent than C. coli/jejuni across all age groups, with older children bearing a higher burden of other Campylobacter. Biomarkers of intestinal inflammation and injury (methylene blue, fecal occult test, myeloperoxidase or MPO) showed a strong association with dysentery, but mixed results with infection. MPO levels were generally higher among children infected with C. coli/jejuni, but Shigella-infected children suffering from dysentery recorded the highest levels (26,224 ng/mL); the lowest levels (10,625 ng/mL) were among asymptomatic children infected with other Campylobacter. Adjusting for age, sex, and Shigella infection, dysentery was significantly associated with C. coli/jejuni but not with other Campylobacter, whereas severe diarrhea was significantly associated with both C. coli/jejuni and other Campylobacter. Compared to asymptomatic children, children suffering from dysentery had a 14.6 odds of C. coli/jejuni infection (p-value < 0.001, 95% CI 5.5–38.7) but were equally likely to have other Campylobacter infections–odds ratio of 1.3 (0.434, 0.7–2.4). Children suffering from severe diarrhea were more likely than asymptomatic children to test positive for both C. coli/jejuni and other Campylobacter–OR of 2.8 (0.034, 1.1–7.1) and 1.9 (0.018, 1.1–3.1), respectively. Compared to the Campylobacter-free group, the odds of all diarrhea given C. coli/jejuni infection and other Campylobacter infection were 8.8 (<0.001, 3.0–25.7) and 2.4 (0.002, 1.4–4.2), respectively. Eliminating other Campylobacter in this population would eliminate 24.9% of the diarrhea cases, which is almost twice the population attributable fraction of 15.1% due to C. coli/jejuni.

Conclusions/Significance

Eighty-seven percent of the dysentery and 59.5% of the severe diarrhea samples were positive for Campylobacter, Shigella, or both, emphasizing the importance of targeting these pathogens to limit the impact of dysentery and severe diarrhea in children. Notably, the higher prevalence of other Campylobacter compared to C. coli/jejuni, their increasing burden during early childhood, and their association with severe diarrhea highlight the importance of these non-C. coli/jejuni Campylobacter species and suggest a need to clarify their importance in the etiology of clinical disease across different epidemiological contexts.

Campylobacter is a major public health concern in developed and developing countries. C. coli and C. jejuni have long been considered to be the major disease-causing species, and clinical microbiologic approaches target these two species. However, less selective diagnostic approaches have shown the increasing importance of other Campylobacter species (i.e. non-C. coli/jejuni). Our case-control study investigated the association between diarrhea, C. coli/jejuni, and other Campylobacter among 439 stool samples from 201 children in peri-urban communities in Loreto, Peru. Three quarters of the 216 Campylobacter detections were associated with other Campylobacter, whose prevalence increased with age and was greater than that of C. coli/jejuni in all age and clinical groups (dysentery, severe diarrhea, and asymptomatic). Despite their lower prevalence, C. coli/jejuni were more strongly associated with higher levels of myeloperoxidase, clinical dysentery, and the presence of leukocytes and blood in the stool compared to other Campylobacter. Other Campylobacter were equally likely as C. coli/jejuni to be detected in severe diarrhea cases–odds ratio of 1.9 (p-value = 0.018, 95% CI 1.1–3.1) and 2.8 (0.034, 1.1–7.1), respectively. Removing C. coli/jejuni in this population would eliminate 15.1% of diarrhea compared to 24.9% if other Campylobacter were eliminated.

New Approaches on Quantification of Campylobacter jejuni in Poultry Samples: The Use of Digital PCR and Real-time PCR against the ISO Standard Plate Count Method

Campylobacteriosis is the most frequently reported bacterial food-borne illness in the European Union and contaminated broiler meat is considered the most important source of infection in humans. The aim of the present study was to evaluate real-time PCR (qPCR) and digital PCR (dPCR) for quantification of Campylobacter jejuni in 75 broiler neck-skin samples collected from a poultry slaughterhouse, and to compare them with the ISO 10272-2 standard plate count method. For qPCR standard curve, C. jejuni-negative neck-skin samples were spiked with C. jejuni suspension with a known number of bacterial cells. The observed CFU/g values by qPCR correlated greatly with the expected values and qPCR showed good performance with the reliable limit of detection (rLOD) and limit of quantification (LOQ) of three and 31 target copies per reaction, respectively. However, both rLOD (1219 CFU/g) and LOQ (12,523 CFU/g) were beyond the EFSA-proposed critical limit of 500-1,000 CFU/g of neck skin. Although C. jejuni cell counts were ≤1,000 CFU/g in only 7/75 samples by plate counting, they were ≤LOQ in 60/75 and ≤rLOD in 26/75 (≤1,000 CFU/g in 24/75) samples by qPCR. A strong and statistically significant correlation was observed between qPCR and dPCR. Both PCR-based methods correlated significantly with the plate count method; however, the correlation was moderate. Using the Bland-Altman analysis, an average agreement was noted between all three methods, although with a large standard deviation. A significant bias toward overestimation in dPCR was observed, probably due to the relatively high number of false positive calls. The linear dynamic range was comparable in both PCR-based methods; however, qPCR proved to be more suitable for routine use. In the future, the establishment of a reliable molecular quantification of C. jejuni in poultry samples showing a wide range of contamination levels down to the proposed critical limit is needed to enable time- and cost-effective surveillance throughout all stages in the food production chain. As both rLOD and LOQ were beyond this limit, a modification of the procedure is suggested to include less sample dilution prior to DNA extraction to enable PCR-based quantification of C. jejuni at the proposed microbiological criteria.

Comparative analysis and limitations of ethidium monoazide and propidium monoazide treatments for the differentiation of viable and nonviable campylobacter cells

The lack of differentiation between viable and nonviable bacterial cells limits the implementation of PCR-based methods for routine diagnostic approaches. Recently, the combination of a quantitative real-time PCR (qPCR) and ethidium monoazide (EMA) or propidium monoazide (PMA) pretreatment has been described to circumvent this disadvantage. In regard to the suitability of this approach for Campylobacter spp., conflicting results have been reported. Thus, we compared the suitabilities of EMA and PMA in various concentrations for a Campylobacter viability qPCR method. The presence of either intercalating dye, EMA or PMA, leads to concentration-dependent shifts toward higher threshold cycle (CT) values, especially after EMA treatment. However, regression analysis resulted in high correlation coefficient (R(2)) values of 0.99 (EMA) and 0.98 (PMA) between Campylobacter counts determined by qPCR and culture-based enumeration. EMA (10 μg/ml) and PMA (51.10 μg/ml) removed DNA selectively from nonviable cells in mixed samples at viable/nonviable ratios of up to 1:1,000. The optimized EMA protocol was successfully applied to 16 Campylobacter jejuni and Campylobacter coli field isolates from poultry and indicated the applicability for field isolates as well. EMA-qPCR and culture-based enumeration of Campylobacter spiked chicken leg quarters resulted in comparable bacterial cell counts. The correlation coefficient between the two analytical methods was 0.95. Nevertheless, larger amounts of nonviable cells (>10(4)) resulted in an incomplete qPCR signal reduction, representing a serious methodological limitation, but double staining with EMA considerably improved the signal inhibition. Hence, the proposed Campylobacter viability EMA-qPCR provides a promising rapid method for diagnostic applications, but further research is needed to circumvent the limitation.

Phenotypic and genotypic methods for typing Campylobacter jejuni and Campylobacter coli in poultry

Human campylobacteriosis, an infection caused by the bacterium Campylobacter, is a major issue in the United States food system, especially for poultry products. According to the Center for Disease Control, campylobacterosis is estimated to affect over 2.4 million people annually. Campylobacter jejuni and Campylobacter coli are 2 species responsible for the majority of campylobacterosis infections. Phenotypic and genotypic typing methods are often used to discriminate between bacteria at the species and subspecies level and are often used to identify pathogenic organisms, such as C. jejuni and C. coli. This review describes the design as well as advantages and disadvantages for 3 current phenotypic techniques (biotyping, serotyping, and multilocus enzyme electrophoresis) and 6 genotypic techniques (multilocus sequence typing, PCR, pulse-field gel electrophoresis, ribotyping, flagellin typing, and amplified fragment length polymorphisms) for typing pathogenic Campylobacter spp.

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.

Performance of food safety management systems in poultry meat preparation processing plants in relation to Campylobacter spp. contamination

A diagnostic instrument comprising a combined assessment of core control and assurance activities and a microbial assessment instrument were used to measure the performance of current food safety management systems (FSMSs) of two poultry meat preparation companies. The high risk status of the company's contextual factors, i.e., starting from raw materials (poultry carcasses) with possible high numbers and prevalence of pathogens such as Campylobacter spp., requires advanced core control and assurance activities in the FSMS to guarantee food safety. The level of the core FSMS activities differed between the companies, and this difference was reflected in overall microbial quality (mesophilic aerobic count), presence of hygiene indicators (Enterobacteriaceae, Staphylococcus aureus, and Escherichia coli), and contamination with pathogens such as Salmonella, Listeria monocytogenes, and Campylobacter spp. The food safety output expressed as a microbial safety profile was related to the variability in the prevalence and contamination levels of Campylobacter spp. in poultry meat preparations found in a Belgian nationwide study. Although a poultry meat processing company could have an advanced FSMS in place and a good microbial profile (i.e., lower prevalence of pathogens, lower microbial numbers, and less variability in microbial contamination), these positive factors might not guarantee pathogen-free products. Contamination could be attributed to the inability to apply effective interventions to reduce or eliminate pathogens in the production chain of (raw) poultry meat preparations.

Rapid quantification of viable Campylobacter bacteria on chicken carcasses, using real-time PCR and propidium monoazide treatment, as a tool for quantitative risk assessment

A number of intervention strategies against Campylobacter-contaminated poultry focus on postslaughter reduction of the number of cells, emphasizing the need for rapid and reliable quantitative detection of only viable Campylobacter bacteria. We present a new and rapid quantitative approach to the enumeration of food-borne Campylobacter bacteria that combines real-time quantitative PCR (Q-PCR) with simple propidium monoazide (PMA) sample treatment. In less than 3 h, this method generates a signal from only viable and viable but nonculturable (VBNC) Campylobacter bacteria with an intact membrane. The method's performance was evaluated by assessing the contributions to variability by individual chicken carcass rinse matrices, species of Campylobacter, and differences in efficiency of DNA extraction with differing cell inputs. The method was compared with culture-based enumeration on 50 naturally infected chickens. The cell contents correlated with cycle threshold (C(T)) values (R(2) = 0.993), with a quantification range of 1 x 10(2) to 1 x 10(7) CFU/ml. The correlation between the Campylobacter counts obtained by PMA-PCR and culture on naturally contaminated chickens was high (R(2) = 0.844). The amplification efficiency of the Q-PCR method was not affected by the chicken rinse matrix or by the species of Campylobacter. No Q-PCR signals were obtained from artificially inoculated chicken rinse when PMA sample treatment was applied. In conclusion, this study presents a rapid tool for producing reliable quantitative data on viable Campylobacter bacteria in chicken carcass rinse. The proposed method does not detect DNA from dead Campylobacter bacteria but recognizes the infectious potential of the VBNC state and is thereby able to assess the effect of control strategies and provide trustworthy data for risk assessment.

Development of cpn60-based real-time quantitative PCR assays for the detection of 14 Campylobacter species and application to screening of canine fecal samples

Campylobacter species are important organisms in both human and animal health. The identification of Campylobacter currently requires the growth of organisms from complex samples and biochemical identification. In many cases, the condition of the sample being tested and/or the fastidious nature of many Campylobacter species has limited the detection of campylobacters in a laboratory setting. To address this, we have designed a set of real-time quantitative PCR (qPCR) assays to detect and quantify 14 Campylobacter species, C. coli, C. concisus, C. curvus, C. fetus, C. gracilis, C. helveticus, C. hyointestinalis, C. jejuni, C. lari, C. mucosalis, C. rectus, C. showae, C. sputorum, and C. upsaliensis, directly from DNA extracted from feces. By use of a region of the cpn60 (also known as hsp60 or groEL) gene, which encodes the universally conserved 60-kDa chaperonin, species-specific assays were designed and validated. These assays were then employed to determine the prevalence of Campylobacter species in fecal samples from dogs. Fecal samples were found to contain detectable and quantifiable levels of C. fetus, C. gracilis, C. helveticus, C. jejuni, C. showae, and C. upsaliensis, with the majority of samples containing multiple Campylobacter species. This study represents the first report of C. fetus, C. gracilis, C. mucosalis, and C. showae detection in dogs and implicates dogs as a reservoir for these species. The qPCR assays described offer investigators a new tool to study many Campylobacter species in a culture-independent manner.