Development of a ceuE-based multiplex polymerase chain reaction (PCR) assay for direct detection and differentiation of Campylobacter jejuni and Campylobacter coli in Thailand

Isolation, Molecular Detection, and Risk Factors of Campylobacter Infection From Companion Dogs

Background: Campylobacter is an organism that is usually associated with diarrhea in pet animals and humans, as well as other domestic, wild, and laboratory animals. Objective: The aim of the present survey was the isolation, molecular detection, and risk factors of Campylobacter infection from companion dogs referred to the Veterinary Hospital of Ahvaz district, the South-West of Iran. Materials and Methods: Rectal swabs were examined by culture and polymerase chain reaction (PCR) methods from 122 companion dogs (52 diarrheic and 70 clinically healthy). Several risk factors were reviewed, including age, gender, breed, nutrition status, and lifestyle. Results: The results showed that only five samples (4.1%) were positive for Campylobacter spp. in the culture method. Campylobacter spp. was detected in 18 out of 122 dogs by the PCR, yielding an overall prevalence of 14.8%. The most prevalent species of Campylobacter among the referred dogs were C. coli (38.89%) and C. jejuni (33.33%). A lower prevalence was found for C. upsaliensis (11.11%) and C. lari (5.55%). Concurrent infections were observed in two cases of C. upsaliensis + C. lari (5.55%) and C. coli + C. lari (5.55%). No significant difference was noted between healthy (11.43%) and diarrheic (19.23%) dogs (P>0.05). Eventually, age, gender, breed, nutrition status, and lifestyle had no significant effect on Campylobacter infection (P>0.05). Conclusion: Although the prevalence of Campylobacter was moderate in the dog population of Ahvaz district, these bacteria can constitute a public health hazard because of the frequent presence of Campylobacter species in the feces.

Detection of Adulterants and Contaminants in Liquid Foods-A Review

Milk and fruit juices have paramount importance in human diet. Increasing demand of these liquid foods has made them vulnerable to economic adulteration during processing and in supply chain. Adulterants are difficult to detect by consumers and thus necessitating the requirement of rapid, accurate and sensitive detection. The potential adulterants in milk and fruit juices and their limits set by different regulatory bodies have been briefly described in this review. Potential advantages and limitations of various techniques such as physicochemical methods, chromatography, immunoassays, molecular, electrical, spectroscopy with chemometrics, electronic nose, and biosensors have been described. Spectroscopy in combination with chemometrics has shown potential for rapid, precise, and sensitive detection of potential adulterants in these liquid foods.

Detection of virulence, antibiotic resistance and toxin (VAT) genes in Campylobacter species using newly developed multiplex PCR assays

Campylobacter species are one of the leading causes of bacterial gastroenteritis in humans worldwide. This twofold study was sought to: i) develop and optimize four single-tube multiplex PCR (mPCR) assays for the detection of six virulence (ciaB, dnaJ, flaA, flaB, pldA and racR), three toxin (cdtA, cdtB and cdtC) and one antibiotic resistance tet(O) genes in thermophilic Campylobacter spp. and ii) apply and evaluate the developed mPCR assays by testing 470 previously identified C. jejuni, C. coli and C. lari isolates from agricultural water. In each mPCR assay, a combination of two or three sets of primer pairs for virulence, antibiotic resistance and toxin (VAT) genes was used and optimized. Assay 1 was developed for the detection of dnaJ, racR and cdtC genes with expected amplification sizes of 720, 584 and 182bp. Assay 2 generated PCR amplicons for tet(O) and cdtA genes of 559 and 370bp. Assay 3 amplified cdtB ciaB, and pldA genes with PCR amplicon sizes of 620, 527 and 385bp. Assay 4 was optimized for flaA and flaB genes that generated PCR amplicons of 855 and 260bp. The primer pairs and optimized PCR protocols did not show interference and/or cross-amplification with each other and generated the expected size of amplification products for each target VAT gene for the C. jejuni ATCC 33291 reference strain. Overall, all ten target VAT genes were detected at a variable frequency in tested isolates of thermophilic Campylobacter spp. where cdtC, flaB, ciaB, cdtB, cdtA and pldA were commonly detected compared to the flaA, racR, dnaJ and tet(O) genes which were detected with less frequency. The developed mPCR assays are simple, rapid, reliable and sensitive tools for simultaneously assessing potential pathogenicity and antibiotic resistance profiling in thermophilic Campylobacter spp. The mPCR assays will be useful in diagnostic and analytical settings for routine screening of VAT characteristics of Campylobacter spp. as well as being applicable in epidemiological studies by providing information that could be related to the risk of human infection.

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.

Analysis of risk factors associated with antibiotic-resistant Escherichia coli

Antimicrobial-resistant bacteria represent a major threat to human and animal health. We compared equine fecal samples (n=264) from 138 horses from hospital and nonhospital (livery stable and riding school) premises in North West England to determine the prevalence of Escherichia coli, Salmonella, and Campylobacter and rates of antimicrobial-resistant E. coli strains. Campylobacter jejuni was detected only in hospitalized horses (1.1%), and no Salmonella was identified. Data analysis of the horses' management and veterinary treatments (Tx) identified risk factors associated with shedding of antimicrobial-resistant E. coli. The hospital was the major source of resistant and multi-drug-resistant (MDR) E. coli. Moreover, shedding of antimicrobial-resistant E. coli was associated significantly with hospitalization for a gastrointestinal problem (odds ratio [OR]:±95% confidence intervals=8.50:1.79-40.32), receipt of oral antimicrobial Tx (OR=3.52:1.11-11.10), multiple antimicrobial Tx in hospital (OR/Tx=1.05:1.01-1.09), or geldings (OR=4.62:1.23-17.46). Interestingly, intravenous antimicrobial Tx was negatively associated with shedding of antimicrobial-resistant E. coli (OR=0.18:0.04-0.76). MDR E. coli was associated with hospitalization, antimicrobial Tx in hospital (OR/Tx=3.65:1.54-8.68), and increased age (OR/year=1.11:1.03-1.19). Thus, equine hospitals in this geographic location appear to be an important source of antimicrobial-resistant and MDR E. coli strains, but unlikely reservoirs of Salmonella or Campylobacter. Thus, it is important to moderate antimicrobial Tx given to hospitalized horses to lessen exposure and fecal shedding of resistant pathogens.

Three-hour molecular detection of Campylobacter, Salmonella, Yersinia, and Shigella species in feces with accuracy as high as that of culture

Campylobacter jejuni and Salmonella, Shigella, and Yersinia species (along with Shiga toxin-producing Escherichia coli) are the most common causes of acute bacterial diarrheal disease in the United States. Current detection techniques are time-consuming, limiting usefulness for patient care. We developed and validated a panel of rapid PCR assays for the detection and identification of C. jejuni, C. coli, Salmonella, and Yersinia species and Shigella and enteroinvasive E. coli in stool samples. A total of 392 archived stool specimens, previously cultured for enteric pathogens, were evaluated by PCR. Overall, 104 stool specimens had been culture positive (C. jejuni/coli [n = 51], Salmonella species [n = 42], Shigella species [n = 6], and Yersinia species [n = 5]). Compared to culture, the overall sensitivity and specificity of PCR detection of these organisms were 92 and 98% (96/104 and 283/288), respectively, from fresh or Cary Blair stool (P = 0.41); 87 and 98% (41/47 and 242/246), respectively, from fresh stool (P = 0.53); and 96 and 98% (55/57 and 41/42), respectively, from Cary Blair stool (P = 0.56). For individual genera, PCR was as sensitive as the culture method, with the exception of Salmonella culture using selenite enrichment for which PCR was less sensitive than culture from fresh, but not Cary Blair (P = 0.03 and 1.00, respectively) stools. This PCR assay panel for the rapid diagnosis of acute infectious bacterial diarrheal pathogens has a sensitivity and specificity equivalent to that of culture for stools in Cary Blair transport medium. Paired with reflexive culture of stools testing positive, this should provide an improvement in care for patients with acute infectious diarrheal disease.

Diagnostic approach to acute diarrheal illness in a military population on training exercises in Thailand, a region of campylobacter hyperendemicity

High rates of Campylobacter fluoroquinolone resistance highlight the need to evaluate diagnostic strategies that can be used to assist with clinical management. Diagnostic tests were evaluated with U.S. soldiers presenting with acute diarrhea during deployment in Thailand. The results of bedside and field laboratory diagnostic tests were compared to stool microbiology findings for 182 enrolled patients. Campylobacter jejuni was isolated from 62% of the cases. Clinical and laboratory findings at the time of presentation were evaluated to determine their impact on the posttest probability, defined as the likelihood of a diagnosis of Campylobacter infection. Clinical findings, the results of tests for inflammation (stool occult blood testing [Hemoccult], fecal leukocytes, fecal lactoferrin, plasma C-reactive protein), and the numbers of Campylobacter-specific antibody-secreting cells in peripheral blood failed to increase the posttest probability above 90% in this setting of Campylobacter hyperendemicity when these findings were present. Positive results by a Campylobacter-specific commercial enzyme immunoassay (EIA) and, less so, a research PCR were strong positive predictors. The negative predictive value for ruling out Campylobacter infection, defined as a posttest probability of less than 10%, was similarly observed with these Campylobacter-specific stool-based tests as well the fecal leukocyte test. Compared to the other tests evaluated, the Campylobacter EIA is a sensitive and specific rapid diagnostic test that may assist with diagnostic evaluation, with consideration of the epidemiological setting, logistics, and cost.

Multiplex PCR for direct identification of Campylobacter spp. in human and chicken stools

Differentiation between Campylobacter jejuni and Campylobacter coli is problematic in clinical specimens due to fastidious growth requirements and limited biochemical tests. This study describes a rapid, multiplex PCR protocol for the direct detection and differentiation of C. jejuni and C. coli in stools. An evaluation was carried out of this multiplex protocol based on the detection of cadF (genus specific), and hipO (C. jejuni) and asp (C. coli) genes, using stool from patients with Campylobacter enteritis and chicken. Protocol sensitivity was assessed and specificity determined using a panel of enteric bacteria, and evaluation of 30 diarrhoeic stool specimens culture negative for Campylobacter. Of the 114 specimens (54 human and 60 chicken) evaluated by the protocol, 70 (61.4 %) were identified as C. jejuni, 35 (30.7 %) as C. coli and 9 (7.9 %) as a mixed infection/colonization with both species. All mixed infections were identified as C. jejuni by culture. Among the stool specimens that were culture negative for Campylobacter, two (6.7 %) were C. jejuni positive by multiplex PCR. The protocol sensitivity limit was 0.015-0.016 ng C. jejuni and C. coli DNA mul(-1) in the specimen. There was no cross-reaction with the reference strains assessed. Comparison of hippurate test and multiplex PCR demonstrated 17 isolates with false-positive hippurate enzymic activity and 7 with false-negative activity. This rapid protocol (turnaround time 6 h) is highly sensitive and specific for direct evaluation of stool for these pathogens. It has significant application for routine clinical diagnostic and epidemiological purposes.

Real-time PCR assay for rapid detection and quantification of Campylobacter jejuni on chicken rinses from poultry processing plant

Campylobacter jejuni (C. jejuni) is the leading cause of food-borne gastroenteritis in the United States. Detection of Campylobacter in food samples by conventional culture is cumbersome; therefore, there is a need to develop rapid and cost-effective detection and quantification methods. Eighty-four whole chicken rinses were collected at different stages of processing at three poultry processing plants. After chicken wash collection and DNA extraction, the samples were directly subjected to real-time PCR (rtPCR) without enrichment and also culture. The assay specificity was determined with a range of Campylobacter species, related, and unrelated organisms. Of the 84 samples collected 65 (77%) of the samples were positive by the rtPCR assay and 27 (32%) of the samples tested positive by direct plating to selective agar media. The results were positively concordant for 27 (32%) of the samples. The whole rtPCR assay can be completed within 90min with a detection limit of 1CFU, compared to 5-7 days for enrichment and sub culturing in selective agar. This assay is the first report of rtPCR method capable of detecting and quantifying C. jejuni from chicken rinses without an enrichment step and could be an important, rapid and quantification model for other food-borne pathogens.

The use of multiplex PCR to detect and differentiate food- and beverage-associated microorganisms: a review

Regarding food safety, rapid detection of microbial species is crucial to develop effective preventive and/or adjustment measures. Classical methods for determining the presence of certain species are time-consuming and labor-intensive, hence, molecular methods, which offer speed, sensitivity and specificity, have been developed to address this problem. Multiplex PCR (MPCR) is widely applied in the various fields of microbiology for the rapid differentiation of microbial species without compromising accuracy. This paper describes the method and reports on the state-of-the-art application of this technique to the identification of microorganisms vehiculated with foods and beverages. The identification of both pathogens and probiotics and the species important for food fermentation or deterioration will be discussed. Applications of MPCR in combination with other techniques are also reviewed. Potentials, pitfalls, limitations and future prospects are summarised.

PCR identification of Campylobacter coli and Campylobacter jejuni by partial sequencing of virulence genes

The objective of this study was to utilize a multiplex PCR assay for concurrent detection of Campylobacter spp. and C. coli or C. jejuni, using probes derived from genes cadF and ceuE and an undefined virulence gene. A total of 97 Campylobacter strains, isolated from turkey litter (n=74), chicken livers (n=15) and clinical (n=8) samples, were speciated using the PCR-based assay. PCR amplification of the isolates identified a 400-bp cadF gene, conserved in Campylobacter species, an 894-bp ceuE gene, specific for C. coli, and a 160-bp oxidoreductase gene, specific for C. jejuni. The approximately 35 kDa cadF adhesion proteins allow Campylobacter to bind to the intestinal epithelial cells and the 37 kDa ceuE lipoproteins are involved in siderophore transport. Sequencing of the 160-bp undefined gene yielded a 67% protein identical match with a gene encoding an oxidoreductase subunit in C. jejuni. The specificity of the assay was validated on 36 non-Campylobacter strains (11 Gram-positive and 25 Gram-negative bacteria). The PCR assay identified 59% of turkey and 47% of chicken isolates as C. jejuni, and 41% of turkey and 53% of chicken isolates as C. coli. All human isolates were identified as C. jejuni. The specificity of this assay to detect C. coli or C. jejuni was 97%.

A real-time multiplexed PCR assay for rapid detection and differentiation of Campylobacter jejuni and Campylobacter coli

Campylobacter species are the leading agents of bacterial gastroenteritis worldwide. C. jejuni and C. coli together are responsible for more than 95% of all cases of Campylobacter-induced diarrheal disease in the United States. Detection of campylobacteria in clinical samples by conventional culture is problematic and slow due to their complex taxonomy, fastidious growth requirements, and biochemical inertness. The current study describes a rapid, sensitive, and specific real-time polymerase chain reaction (PCR) assay capable of detecting and differentiating C. jejuni (hippuricase gene, hipO) and C. coli (serine hydroxymethyltransferase gene, glyA) in a single reaction, directly from clinical isolates and human feces. The analytical specificity of the assay was demonstrated with a diverse range of Campylobacter species, related organisms, and other diarrhea-inducing bacterial pathogens. The analytical sensitivity of the multiplexed, PCR assay was 10 genome copies for both C. jejuni and C. coli. Following a rapid DNA extraction method (QIAGEN QIAamp DNA stool Mini Kit), the multiplexed PCR identified C. jejuni or C. coli in 100% of fecal samples containing 10(3) colony-forming units (CFU) per gram of feces. This assay represents the first real-time PCR method capable of detecting and differentiating C. jejuni and C. coli in a single reaction.

Campylobacter colonization of sibling turkey flocks reared under different management conditions

Uncertainty exists concerning the key factors contributing to Campylobacter colonization of poultry, especially the possible role of vertical transmission from breeder hens to young birds. A longitudinal study of Campylobacter colonization was performed in two sibling pairs of turkey flocks (four flocks total). Each pair of sibling flocks shared breeder hen populations and was obtained from the same hatchery. One flock of each pair was grown on a commercial farm, and the other was grown in an instructional demonstration unit (Teaching Animal Unit [TAU]). Flocks were located within a 60-mi (96.8-km) radius. The time of placement, feed formulations, stocking density, and general husbandry were the same for both flocks, and each flock was processed at a commercial processing plant following standard feed withdrawal and transport protocols. Both flocks grown on the commercial farms became colonized with Campylobacter between weeks 2 and 3 and remained colonized until processing. Between 80 and 90% of isolates were Campylobacter coli, and the remainder were Campylobacter jejuni. In contrast, neither C. coli nor C. jejuni were isolated from either of the TAU flocks at any time during the production cycle. None of the fla types of Campylobacter from the breeders that provided poults to one of the commercial flocks matched those from the progeny. These results failed to provide evidence for vertical transmission and indicate that this type of transmission either did not occur or was not sufficient to render the TAU turkey flocks Campylobacter positive. Management practices such as proper litter maintenance, controlled traffic between the TAU farm and other turkey flocks, and other less well-defined aspects of turkey production were likely responsible for the absence of Campylobacter in the TAU flocks before harvest.

Microarray-based identification of thermophilic Campylobacter jejuni, C. coli, C. lari, and C. upsaliensis

DNA microarrays are an excellent potential tool for clinical microbiology, since this technology allows relatively rapid identification and characterization of microbial and viral pathogens. In the present study, an oligonucleotide microarray was developed and used for the analysis of thermophilic Campylobacter spp., the primary food-borne pathogen in the United States. We analyzed four Campylobacter species: Campylobacter jejuni, C. coli, C. lari, and C. upsaliensis. Our assay relies on the PCR amplification of specific regions in five target genes (fur, glyA, cdtABC, ceuB-C, and fliY) as a first step, followed by microarray-based analysis of amplified DNAs. Alleles of two genes, fur and glyA, which are found in all tested thermophilic Campylobacter spp., were used for identification and discrimination among four bacterial species, the ceuB-C gene was used for discrimination between C. jejuni and C. coli, and the fliY and cdt genes were used as additional genetic markers specific either for C. upsaliensis and C. lari or for C. jejuni. The array was developed and validated by using 51 previously characterized Campylobacter isolates. All isolates were unambiguously identified on the basis of hybridization patterns with 72 individual species-specific oligoprobes. Microarray identification of C. jejuni and C. coli was confirmed by PCR amplification of other genes used for identification (hipO and ask). Our results demonstrate that oligonucleotide microarrays are suitable for rapid and accurate simultaneous differentiation among C. jejuni, C. coli, C. lari, and C. upsaliensis.