Real-time PCR detection of Campylobacter spp.: A comparison to classic culturing and enrichment

Clinical and microbiological findings of recurrent Campylobacter spp. gastroenteritis in a tertiary care hospital

INTRODUCTION

Campylobacter spp. is the leading cause of bacterial enteritis in industrialized countries, but the literature about its recurrence is scarce. The objective of this study is to analyze a case series of recurrent campylobacteriosis in adult and pediatric patients.

METHODS

During a two-year period, the demographic, clinical and microbiological data were collected retrospectively from patients who met the clinical criteria of recurrent Campylobacter spp. gastroenteritis. Enteropathogens were identified by a multiplex-PCR gastrointestinal pathogens panel. When Campylobacter spp. was detected, the stool sample was cultured in specific medium and tested for antibiotic susceptibility.

RESULTS

Twenty-four (2.03%) out of 1180 patients with Campylobacter spp. positive-PCR met the inclusion criteria. Thirteen patients suffered from underlying diseases, and 11 had no known risk factors but they were all pediatric patients. From the 24 patients were documented 70 episodes. One patient had two episodes of bacteremia. Coinfection/co-detection with other enteropathogens was found in 10 patients being Giardia intestinalis the most frequent. Twelve (22.6%) out of 53 isolates were resistant to macrolides. One patient had two isolates of multi-drug resistant C. coli, only susceptible to gentamicin.

CONCLUSION

The results suggest the presence of underlying diseases in most adult patients with recurrent Campylobacter spp. infections, particularly primary immunodeficiency. Most of the pediatric patients with recurrent campylobacteriosis lack of known risk factors. Concomitant detection with other enteropathogens was common. The resistance to macrolides was much higher as compared with previous reported rates.

Development of diagnostic tests for pathogen identification and detection of antimicrobial resistance on WHO global priority pathogens using modular real-time nucleic acid amplification test

BACKGROUND

Concerns regarding antimicrobial resistance (AMR) have resulted in the World Health Organization (WHO) designating so-called global priority pathogens (GPPs). However, little discussion has focused on the diagnosis of GPPs. To enable the simultaneous identification of pathogens and AMR, we developed a modular real-time nucleic acid amplification test (MRT-NAAT).

METHODS

Sequence-specific primers for each modular unit for MRT-NAAT pathogen identification and AMR sets were designed. The composition of the reaction mixture and the real-time PCR program were unified irrespective of primer type so to give MRT-NAAT modularity. Standard strains and clinical isolates were used to evaluate the performance of MRT-NAAT by real-time PCR and melting curve analysis. Probit analysis for the MRT-NAAT pathogen identification set was used to assess the limit of detection (LoD).

RESULTS

The MRT-NAAT pathogen identification set was made up of 15 modular units 109-199 bp in product size and with a T_ms of 75.5-87.5 °C. The LoD was < 15.548 fg/μL, and nine modular units successfully detected the target pathogens. The MRT-NAAT AMR set included 24 modular units 65-785 bp in product size with a T_ms of 75.5-87.5 °C; it showed high performance for detecting GPP target genes and variants.

CONCLUSIONS

MRT-NAAT enables pathogen identification and AMR gene detection and is time-effective. By unifying the reaction settings of each modular unit, the modularity where combinations of primers can be used according to need could be achieved. This would greatly help in reflecting the researcher's need and the AMR status of a certain region while successfully detecting pathogens and AMR genes.

Association between asymptomatic infections and linear growth in 18-24-month-old Malawian children

Inadequate diet and frequent symptomatic infections are considered major causes of growth stunting in low-income countries, but interventions targeting these risk factors have achieved limited success. Asymptomatic infections can restrict growth, but little is known about their role in global stunting prevalence. We investigated factors related to length-for-age Z-score (LAZ) at 24 months by constructing an interconnected network of various infections, biomarkers of inflammation (as assessed by alpha-1-acid glycoprotein [AGP]), and growth (insulin-like growth factor 1 [IGF-1] and collagen X biomarker [CXM]) at 18 months, as well as other children, maternal, and household level factors. Among 604 children, there was a continuous decline in mean LAZ and increased mean length deficit from birth to 24 months. At 18 months of age, the percentage of asymptomatic children who carried each pathogen was: 84.5% enterovirus, 15.5% parechovirus, 7.7% norovirus, 4.6% rhinovirus, 0.6% rotavirus, 69.6% Campylobacter, 53.8% Giardia lamblia, 11.9% malaria parasites, 10.2% Shigella, and 2.7% Cryptosporidium. The mean plasma IGF-1 concentration was 12.5 ng/ml and 68% of the children had systemic inflammation (plasma AGP concentration >1 g/L). Shigella infection was associated with lower LAZ at 24 months through both direct and indirect pathways, whereas enterovirus, norovirus, Campylobacter, Cryptosporidium, and malaria infections were associated with lower LAZ at 24 months indirectly, predominantly through increased systemic inflammation and reduced plasma IGF-1 and CXM concentration at 18 months.

Prevalence and Characterization of Campylobacter Species from Chickens Sold at Informal Chicken Markets in Gauteng, South Africa

ABSTRACT

This study determined the prevalence, characteristics, and risk factors of Campylobacter species contamination of chicken carcasses sold at informal poultry outlets in Gauteng province, South Africa. Within six townships, 151 chicken carcasses were collected from 47 outlets. Carcass swab, cloacal swab, and carcass drip samples were collected from each chicken, along with a matched questionnaire on risk factors regarding Campylobacter contamination. Sample-inoculated Bolton broth (BB) was cultured to isolate Campylobacter species by bacteriological methods. Subsequent confirmation and characterization of Campylobacter were conducted using polymerase chain reaction (PCR). Isolated Campylobacter strains were evaluated for the presence of six virulence genes (ciaB, dnaj, pldA, racR, flaA, and flaB), three toxin genes (cdtA, cdtB, and cdtC), and one antimicrobial resistance gene (tetO). The overall prevalence of Campylobacter was 23.4% (106 of 453), with sample type-specific prevalence being 17.2% (26 of 151), 25.8% (39 of 151), and 27.2% (41 of 151) for the carcass swabs, cloacal swabs, and carcass drip, respectively, following bacteriological isolation and confirmation by PCR. The overall prevalence of Campylobacter species was 93.5% by PCR, which varied significantly (P = 0.000) by sample: 99.2, 98.4, and 82.8% for carcass swabs, cloacal swabs, and carcass drip, respectively, by using PCR to detect Campylobacter in BB. Important risk factors for carcass contamination by Campylobacter included the slaughter of culled breeders and spent chickens, the use of stagnant water, and poor sanitation. Virulence and toxin gene frequencies were higher in C. jejuni-positive (82.5%) than in C. coli-positive (71.4%) BB cultures, but tetracycline resistance gene (tetO) frequency was higher in C. coli (75.9%) than in C. jejuni (48.10%). The observed high frequencies in C. jejuni recovered from street-vended chickens may pose food safety and therapeutic concerns to consumers.

HIGHLIGHTS

Bacterial concentration and Campylobacter spp. quantification differ when fresh or ultra-frozen samples are analysed over time using molecular biology and culture-based methods

The study aimed to delineate the robustness of the culture-based and molecular biology methods to assess the total bacterial concentration and Campylobacter jejuni (C. jejuni) quantification in caecal content, analysed as fresh or after being stored immediately at ultra-low (-80°C) temperature at different time points (for 3, 7, 14, 28 and 62 days post collection). The caecal content was collected from birds that were artificially colonised with C. jejuni (in-vivo), and quantification was performed using both colony-forming unit (CFU) and qPCR. The results showed that storage time affected the output of culture-based analyses but mostly did not alter concentration retrieved via qPCR. After an initial ~4.5 log₁₀ reduction in CFU observed from fresh (day 0) to frozen samples, bacterial concentration retrieved with culture-based methods seemed to be constant in samples frozen for 3 to 62 days, indicating a possible threshold for C. jejuni loss of viability due to effect of storage temperature. Ranking order analyses, revealed that the molecular biology technique was able to attribute somewhat the same relative C. jejuni concentrations to the samples analysed via qPCR. However, day 0 measurements from culture-based methods were associated with the absence of or negatively weak correlations with the rest of the time points, but ranking order was maintained from day 3 onwards. On the other hand, ranking order correlations were less constant when measuring total bacterial concentration through qPCR. The study suggests that if biological samples can’t be analysed as fresh (immediately after collection) and have to be stored prior to analysis, then storage at -80°C samples be recommended to avoid the temporal-dependent effects on C. jejuni concentrations. In addition, irrespective of the method of analysis, an initial loss of CFU must be factored in when interpreting the results obtained from frozen samples.

A Cutoff Determination of Real-Time Loop-Mediated Isothermal Amplification (LAMP) for End-Point Detection of Campylobacter jejuni in Chicken Meat

Campylobacter jejuni is one of the leading causes of foodborne illness worldwide. C. jejuni is commonly found in poultry. It is the most frequent cause of contamination and thus resulting in not only public health concerns but also economic impacts. To test for this bacterial contamination in food processing plants, this study attempted to employ a simple and rapid detection assay called loop-mediated isothermal amplification (LAMP). The best cutoff value for the positive determination of C. jejuni calculated using real-time LAMP quantification cycle (Cq) was derived from the receiver operating characteristic (ROC) curve modeling. The model showed an area under curve (AUC) of 0.936 (95% Wald CI: 0.903–0.970). Based on Youden’s J statistic, the optimal cutoff value which had the highest sensitivity and specificity from the model was calculated as 18.07. The LAMP assay had 96.9% sensitivity, 95.8% specificity, and 93.9 and 97.9% positive and negative predictive values, respectively, compared to a standard culture approach for C. jejuni identification. Among all non-C. jejuni strains, the LAMP assay gave each of 12.5% false-positive results to C. coli and E. coli (1 out of 8 samples). The assay can detect C. jejuni at the lowest concentration of 103 CFU/mL. Our results suggest a preliminary indicator for the application of end-point LAMP assays, such as turbidity and UV fluorescence tests, to detect C. jejuni in field operations. The LAMP assay is an alternative screening test for C. jejuni contamination in food samples. The method provides a rapid detection, which requires only 9 min with a cutoff value of Cq. We performed the extraction of DNA from pure cultures and the detection of C. jejuni using the LAMP assay within 3 h. However, we were not able to reduce the time for the process of enrichment involved in our study. Therefore, we suggest that alternative enrichment media and rapid DNA extraction methods should be considered for further study. Compared to other traditional methods, our proposed assay requires less equipment and time, which is applicable at any processing steps in the food production chain.

Impact of the gut microecology on Campylobacter presence revealed by comparisons of the gut microbiota from chickens raised on litter or in individual cages

Background

Poultry is the major reservoir of Campylobacter that contributes to human campylobacteriosis and threatens food safety. Litter contact has been linked to Campylobacter colonization, but the gut microecological impact underlying this link remains not fully clear. Here, we sought to investigate the impact of the gut microecology on the presence of Campylobacter by examining the microbiota in the duodenum, jejunum, ileum, ceca, and feces from chickens raised on commercial litter and in individual cages at 0–57 days of age.

Results

Through litter contact, the presence of Campylobacter was found to benefit from microecological competition among Lactobacillus, Helicobacter, and genera that are halotolerant and aerobic or facultatively anaerobic in the upper intestine, such as Corynebacterium and Brachybacterium. The presence was also promoted by the increased abundance in obligate anaerobic fermentation microbes, especially members of the orders Clostridiales and Bacteroidales. The longitudinal analysis supported the vertical or pseudo-vertical transmission but suggested that colonization might occur immensely at 7–28 days of age. We observed a host genetic effect on the gut microecology, which might lead to increased heterogeneity of the microecological impact on Campylobacter colonization.

Conclusions

The findings advance the understanding of the gut microecological impact on Campylobacter presence in the chicken gut under conditions of litter contact and suggest that manipulations of the gut microecology, as well as the microbes identified in the Campylobacter association networks, might be important for the development of intervention strategies.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12866-021-02353-5.

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.

Simultaneous detection of Marburg virus and Ebola virus with TaqMan-based multiplex real-time PCR method

Background

Marburg virus (MARV) and Ebola virus (EBOV) are acute infections with high case fatality rates. It is of great significance for epidemic monitoring and prevention and control of infectious diseases by the development of a rapid, specific, and sensitive quantitative PCR method to detect two pathogens simultaneously.

Methods

Primers and TaqMan probes were designed according to highly conserved sequences of these viruses. Sensitivity, specificity, linear range, limit of detection, and the effects of hemolysis and lipid on real‐time qPCR were evaluated.

Results

The linearity of the curve allowed quantification of nucleic acid concentrations in range from 10³ to 10⁹ copies/ml per reaction (MARV and EBOV). The limit of detection of EBOV was 40 copies/ml, and MARV was 100 copies/ml. It has no cross‐reaction with other pathogens such as hepatitis b virus (HBV), hepatitis c virus (HCV), human papillomavirus (HPV), Epstein‐Barr virus (EBV), herpes simplex virus (HSV), cytomegalovirus (CMV), and human immunodeficiency virus (HIV). Repeatability analysis of the two viruses showed that their coefficient of variation (CV) was less than 5.0%. The above results indicated that fluorescence quantitative PCR could detect EBOV and MARV sensitively and specifically.

Conclusions

The TaqMan probe‐based multiplex fluorescence quantitative PCR assays could detect EBOV and MARV sensitively specifically and simultaneously.

Preventing Chagas disease: A new RT-qPCR method for rapid and specific quantification of viable Trypanosoma cruzi for food safety

Without standardized methods for rapidly detecting in food matrices viable T. cruzi, foodborne outbreaks remain neglected. In this work, a reverse-transcriptase real-time PCR (RT-qPCR) mRNA-based technique was developed for the rapid and specific detection and quantification of viable Trypanosoma cruzi in açai fruits and juice. The method uses specific primer targeting region on the cyt b gene. The maximum recovery rate of T. cruzi from inoculated açai juice was 82.50%. The limit of detection and quantification in açai juice was 10 parasites/mL for RT-qPCR (mRNA-based) and qPCR (DNA-based). The RT-qPCR efficiency was estimated at 97.27% with an R² of 0.994. The RT-qPCR was shown to be able to discriminate between viable and nonviable cells. This method provides a useful tool for rapid assessment of low concentrations of viable T. cruzi in naturally contaminated food samples, and can be applied industrially as a quality and security method.

Infections and systemic inflammation are associated with lower plasma concentration of insulin-like growth factor I among Malawian children

BACKGROUND

Insulin-like growth factor I (IGF-I) is the most important hormonal promoter of linear growth in infants and young children.

OBJECTIVES

The objectives of this study were to compare plasma IGF-I concentration in a low- compared with a high-income country and characterize biological pathways leading to reduced IGF-I concentration in children in a low-income setting.

METHODS

We analyzed plasma IGF-I concentration from 716 Malawian and 80 Finnish children at 6-36 mo of age. In the Malawian children, we studied the association between IGF-I concentration and their environmental exposures; nutritional status; systemic and intestinal inflammation; malaria parasitemia and viral, bacterial, and parasitic enteric infections; as well as growth at 18 mo of age. We then conducted a pathway analysis to identify direct and indirect associations between these predictors and IGF-I concentration.

RESULTS

The mean IGF-I concentrations were similar in Malawi and Finland among 6-mo-old infants. At age 18 mo, the mean ± SD concentration was almost double among the Finns compared with the Malawians [24.2 ± 11.3 compared with 12.5 ± 7.7 ng/mL, age- and sex-adjusted difference in mean (95% CI): 11.8 (9.9, 13.7) ng/mL; P < 0.01]. Among 18-mo-old Malawians, plasma IGF-I concentration was inversely associated with systemic inflammation, malaria parasitemia, and intestinal Shigella, Campylobacter, and enterovirus infection and positively associated with the children's weight-for-length z score (WLZ), female sex, maternal height, mother's education, and dry season. Seasonally, mean plasma IGF-I concentration was highest in June and July and lowest in December and January, coinciding with changes in children's length gain and preceded by ∼2 mo by the changes in their WLZ.

CONCLUSIONS

The mean plasma IGF-I concentrations are similar in Malawi and Finland among 6-mo-old infants. Thereafter, mean concentrations rise markedly in Finland but not in Malawi. Systemic inflammation and clinically nonapparent infections are strongly associated with lower plasma IGF-I concentrations in Malawi through direct and indirect pathways.

Rapid and Accurate Campylobacter jejuni Detection With CRISPR-Cas12b Based on Newly Identified Campylobacter jejuni-Specific and -Conserved Genomic Signatures

Campylobacter jejuni is among the most prevalent foodborne zoonotic pathogens leading to diarrheal diseases. In this study, we developed a CRISPR-Cas12b-based system to rapidly and accurately detect C. jejuni contamination. Identification of C. jejuni-specific and -conserved genomic signatures is a fundamental step in development of the detection system. By comparing C. jejuni genome sequences with those of the closely related Campylobacter coli, followed by comprehensive online BLAST searches, a 20-bp C. jejuni-conserved (identical in 1024 out of 1037 analyzed C. jejuni genome sequences) and -specific (no identical sequence detected in non-C. jejuni strains) sequence was identified and the system was then assembled. In further experiments, strong green fluorescence was observed only when C. jejuni DNA was present in the system, highlighting the specificity of this system. The assay, with a sample-to-answer time of ∼40 min, positively detected chicken samples that were contaminated with a dose of approximately 10 CFU C. jejuni per gram of chicken, which was >10 times more sensitive than the traditional Campylobacter isolation method, suggesting that this method shows promise for onsite C. jejuni detection. This study provides an example of bioinformatics-guided CRISPR-Cas12b-based detection system development for rapid and accurate onsite pathogen detection.

A Review of Current and Emerging Approaches for Water Pollution Monitoring

The aquatic ecosystem is continuously threatened by the infiltration and discharge of anthropogenic wastewaters. This issue requires the unending improvement of monitoring systems to become more comprehensive and specific to targeted pollutants. This review intended to elucidate the overall aspects explored by researchers in developing better water pollution monitoring tools in recent years. The discussion is encircled around three main elements that have been extensively used as the basis for the development of monitoring methods, namely the dissolved compounds, bacterial indicator, and nucleic acids. The latest technologies applied in wastewater and surface water mapped from these key players were reviewed and categorized into physicochemical and compound characterizations, biomonitoring, and molecular approaches in taxonomical and functional analyses. Overall, researchers are continuously rallying to enhance the detection of causal source for water pollution through either conventional or mostly advanced approaches focusing on spectrometry, high-throughput sequencing, and flow cytometry technology among others. From this review’s perspective, each pollution evaluation technology has its own advantages and it would be beneficial for several aspects of pollutants assessments to be combined and established as a complementary package for better aquatic environmental management in the long run.

Identification and differentiation of Campylobacter isolated from chicken meat using real-time polymerase chain reaction and high resolution melting analysis of hipO and glyA genes

Background and Aim:

Campylobacter species have been recognized as the most frequently identified bacterial cause of human gastroenteritis. The aims of this study were to identify Campylobacter jejuni and Campylobacter coli species isolated from chicken meat and to analyze the differences in the melting curve patterns of both species.

Materials and Methods:

A total of 105 chicken meat samples collected from slaughterhouses and retailers in six provinces in Indonesia were examined for the isolation and identification of Campylobacter spp. A total of 56 positive isolates of Campylobacter spp. were analyzed using the quantitative real-time polymerase chain reaction and high resolution melting method.

Results:

The prevalence of Campylobacter spp. in chicken meat was found to be 61.9%. Regarding the identification, 23 isolates (41.07%) were C. jejuni, 22 (39.29%) were C. coli, six (10.71%) were a mix between C. jejuni and C. coli, and five isolates (8.93%) were Campylobacter spp. All the C. jejuni and C. coli isolates produced varied melting curve patterns.

Conclusion:

The high prevalence of C. jejuni and C. coli in chicken meat in Indonesia indicates a high risk of the incidence of campylobacteriosis in humans.

Assessing Campylobacter Colonization of Broiler Herds Ante Mortem and Monitoring Campylobacter Contamination Post Mortem by qPCR

Human campylobacteriosis is the most prevalent zoonosis, with chicken meat contributing substantially to the number of cases. Measures to avoid or at least reduce exposure by meat contaminated with Campylobacter (C.) spp. are needed. With regard to the process hygiene criterion introduced in 2018 for Campylobacter spp. on broiler carcasses, we evaluated the performance of a recently developed quantitative real-time PCR (qPCR) for C. jejuni/coli on random caecal samples and chicken meat. With the qPCR on pooled caecal samples not only C. jejuni/coli positive (69.6%) versus negative broiler herds (30.4%) were identified, but herds highly colonized with C. jejuni/coli (39.4%) could also be identified. From the chicken meat samples, 8.0% were positive for C. jejuni/coli by qPCR and 0.7% by enumeration (>10 cfu/g) compared to 58.3% using cultural enrichment. Given the higher sensitivity, the qPCR method could replace the currently used enumeration method to assess the process hygiene criterion for Campylobacter spp. on broiler carcasses. Moreover, with the qPCR, a reliable identification of C. jejuni/coli colonized incoming broiler herds a few days before slaughter is feasible, which provides important information to optimize slaughter processes. Finally, identifying and monitoring herds with high C. jejuni/coli colonization rates could help to individually improve biosecurity measures at farm level, eventually reducing the C. jejuni/coli load on chicken meat.

Association of insularity and body condition to cloacal bacteria prevalence in a small shorebird

Do islands harbour less diverse disease communities than mainland? The island biogeography theory predicts more diverse communities on mainland than on islands due to more niches, more diverse habitats and availability of greater range of hosts. We compared bacteria prevalences of Campylobacter, Chlamydia and Salmonella in cloacal samples of a small shorebird, the Kentish plover (Charadrius alexandrinus) between two island populations of Macaronesia and two mainland locations in the Iberian Peninsula. Bacteria were found in all populations but, contrary to the expectations, prevalences did not differ between islands and mainland. Females had higher prevalences than males for Salmonella and when three bacteria genera were pooled together. Bacteria infection was unrelated to bird’s body condition but females from mainland were heavier than males and birds from mainland were heavier than those from islands. Abiotic variables consistent throughout breeding sites, like high salinity that is known to inhibit bacteria growth, could explain the lack of differences in the bacteria prevalence between areas. We argue about the possible drivers and implications of sex differences in bacteria prevalence in Kentish plovers.

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.

Lenz's Law-Based Virtual Net for Detection of Pathogenic Bacteria from Water

We have developed a method for rapid detection of pathogenic bacteria from water using a virtual net comprising magnetic nanoparticle clusters (MNC). When an external magnetic field was applied to the antibody-functionalized MNC (Ab-MNC) solution in a glass tube (GT), the Ab-MNCs were aligned along the direction of the applied magnetic field to form a wall of MNCs. The injection of a liquid into the GT pushed the MNCs to flow when the drag force exceeded the magnetic force that held the MNCs. In contrast, injection of a liquid into the GT wrapped with a copper tape (Cu-GT) created a magnetic field in the opposite direction of the liquid flow according to Lenz's law, which retained the MNCs inside Cu-GT even at a flow rate 2.5 times higher than the maximum flow rate at which the MNCs were retained inside the GT. As proof of concept, E. coli O157:H7-spiked aqueous solutions were injected into Cu-GT containing Ab-MNCs. The structural flexibility of the Ab-MNC wall allowed the liquid to pass through but induced binding of the bacteria to the Ab-MNC wall, just as the wall acted like a virtual net. The detection limit was 10² CFU/mL of E. coli as measured by an ATP luminometer, and the total assay time was 15 min including 10 min for the isolation and separation steps.

Molecular detection of Campylobacter jejuni in patients with Crohn's disease in Iran

Background: Crohn's disease is one of the most significant intestinal disorders and is known as inflammatory bowel disease; Campylobacter spp. are one of the leading causes of bacterial gastroenteritis in humans.

Methods: In this study, 60 tissue samples, including 30 cases with Crohn’s disease and 30 cases with no inflammatory bowel disease, were collected. Patients were referred to Taleghani hospital and Behboud clinic between March 2015 and May 2016. Biopsies were used for DNA extraction and assessment of Campylobacter jejuni in patients with Crohn's disease and controls using polymerase chain reaction and quantitative real-time polymerase chain reaction. All positive amplified fragments were sequenced. The gene encoding 16S rRNA, specific to Campylobacter genus, was amplified.

Results: The results were positive for Campylobacter genus in patients with Crohn's disease compared to healthy individuals. The quantitative real-time PCR showed a significantly higher prevalence of Campylobacter jejuni, particularly in hippurate hydrolase in tissue specimens of patients with Crohn's disease compared to control group. The correlation between Campylobacter jejuni and diarrhea symptoms in patients with Crohn's disease and controls was investigated. One positive case of Campylobacter jejuni found in patients without diarrhea was compared with 13 patients with diarrhea.

Conclusion: The present study demonstrated the alarmingly high rate of Campylobacter jejuni prevalence in Crohn's disease patients with diarrhea symptoms. However, further investigation is needed to determine the possible causing factors of this disease.

A sensitive gold-nanorods-based nanobiosensor for specific detection of Campylobacter jejuni and Campylobacter coli

BACKGROUND

Campylobacteriosis is a zoonotic infectious disease that can be mostly undiagnosed or unreported due to fastidious Campylobacter species. The aim of this study was to develop a simple, sensitive, and quick assay for the detection of Campylobacter spp. and taking advantage of the great sensitivity of gold nanorods (GNRs) to trace changes in the local environment and interparticle distance.

METHODS

Characterized GNRs were modified by specific ssDNA probes of cadF gene. First, the biosensor was evaluated using recombinant plasmid (pTG19-T/cadF) and synthetic single-stranded 95 bp gene, followed by a collection of the extracted DNAs of the stool samples. The sensing strategy was compared by culture, PCR, and real-time PCR.

RESULTS AND DISCUSSION

Analysis of 283 specimens showed successful detection of Campylobacter spp. in 44 cases (16%), which was comparable to culture (7%), PCR (15%), and real-time PCR (18%). In comparison with real-time PCR, the sensitivity of the biosensor was reported 88%, while the specificity test for all assays was the same (100%). However, it was not able to detect Campylobacter in 6 positive clinical samples, as compared to real-time PCR. The limit of detection was calculated to be the same for the biosensor and real-time PCR (10² copy number/mL).

CONCLUSIONS

Taking high speed and simplicity of this assay into consideration, the plasmonic nanobiosensor could pave the way in designing a new generation of diagnostic kits for detection of C. jejuni and C. coli species in clinical laboratories.

Real-time recombinase polymerase amplification assay for the rapid and sensitive detection of Campylobacter jejuni in food samples

Campylobacter jejuni (C. jejuni), a foodborne pathogen, is a major contributor to human bacterial gastroenteritis worldwide and detrimental to public health. It is crucial for initiating appropriate outbreak control strategies to rapidly detect C. jejuni. As a novel isothermal gene amplification technique, recombinase polymerase amplification (RPA) has been developed for the molecular detection of diverse pathogens. In this study, we developed a real-time RPA assay so as to achieve the rapid and efficient detection of C. jejuni by targeting the hipO gene. The specificity and senstivity of real-time RPA was validated and the practical applicability of the method for the detection of C. jejuni in artificially contaminated milk and chicken breast samples was proved by comparing their reaction time, sensitivity, and efficacy with those of real-time PCR and culture-based methods. Based on the real-time RPA assay, analysis time was reduced to approximately 13 mins from 60 mins and the results were as reliable as those of the real-time PCR assay. Taken together, in terms of the detection of C. jejuni, the real-time RPA method was simple, rapid, sensitive, and reliable.

Comparison of the Filtration Culture and Multiple Real-Time PCR Examination for Campylobacter spp. From Stool Specimens in Diarrheal Patients

Campylobacter is one of the most common pathogens leading to the bacterial diarrheal illness. In order to set up one effective culture independent assay for the screen of the Campylobacter infection in the diarrheal patients, the quadruple real-time PCR method comparing to the culture based on the enriched filtration method which was recognized as the most effective isolation method was assessed for 190 stool samples from the diarrheal patients collected during the Foodborne Diseases Active Surveillance Network in Beijing. This multiple real-time PCR was designed to identify the Campylobacter genus, C. jejuni, C. coli, and C. lari simultaneously. With the enrichment culture method, 23 (12.1%, 23/190) Campylobacter isolates were obtained (20 C. jejuni and 3 C. coli), however, 31 samples (16.3%, 31/190) were detected positively with the real-time PCR (21 C. jejuni, 8 C. coli, and 2 Campylobacter genus only). With the comparison, the real-time-PCR method is more sensitive than the enrichment filtration method (16.3 vs. 12.1%, p = 0.021). Among the culture-positive samples, 95.7% (22/23) were detected positively by PCR which indicate the specificity of this method was higher. These two methods were consistent well (Kappa = 0.785, p < 0.05). Comparing to the culture methods, the result of the multiple real-time PCR method is sensitive, reliable and rapid. The present study indicated this multiple real-time PCR can be used both for the surveillance network and the preceding screen for bacteria isolation. This is first comparative study between the culture and multiple real-time PCR method for Campylobacter identification in stool specimens from the diarrheal patients.

Evaluation of different Campylobacter jejuni isolates to colonize the intestinal tract of commercial turkey poults and selective media for enumeration

Consumption of contaminated poultry products is the main source of human campylobacteriosis, for which Campylobacter jejuni is responsible for 90% of human cases. Although chickens are believed to be a main source of human exposure to C. jejuni, turkeys also contribute to cases of human infection. Little is known about the kinetics of C. jejuni intestinal colonization in turkeys, or best selective media for their recovery. Enumeration of C. jejuni from intestinal samples can be challenging because most selective Campylobacter media support the growth of non-Campylobacter organisms. In this study, we sought to compare a) C. jejuni isolates that persistently colonize different compartments of the poult intestinal tract, and b) selective media to enumerate C. jejuni from turkey intestinal samples. Three-week-old poults were orally colonized with C. jejuni isolates NCTC 11168 or NADC 20827 (isolated from a turkey flock). Mock-colonized poults were orally gavaged with uninoculated media. Poults were euthanized at d 3, 7, and 21 post colonization and direct plated on different selective Campylobacter media [Campy Line agar with sulfamethoxazole (CLA-S), CHROMagar Campylobacter (CAC) and Campy Cefex] for enumeration. Isolates NCTC 11168 and NADC 20827 poorly colonized the distal ileum. Both isolates colonized the colon, but the number of NADC 20827 significantly decreased at d 21. Isolates NCTC 11168 and NADC 20827 persistently colonized the cecum for up to 21 days. There was no significant difference in the Campylobacter amount recovered on CLA-S and CAC. Campy Cefex failed to prevent growth of background microbes to enumerate C. jejuni from turkey samples. Two independent PCR assays (multiplex PCR and qPCR) confirmed that colonies grown on CLA-S or CAC were C. jejuni. Data from this study demonstrated that isolates NCTC 11168 and NADC 20827 persistently colonized the cecum, and CLA-S or CAC were successful to enumerate Campylobacter from intestinal samples. These findings will be useful to evaluate the host response by C. jejuni in turkeys, and test pre-harvest strategies to reduce its colonization and promote food safety.

Spotty Liver Disease: A review of an ongoing challenge in commercial free-range egg production

Spotty Liver Disease is an acute infectious disease of layer chickens that was likely first described in the USA and Canada in the 1950s and 1960's. The disease occurs almost exclusively in barn and free-range production systems. Outbreaks usually, but not exclusively occur in young layers (≅25 weeks) at peak of lay. Indicators of SLD include an acute drop in egg production of up to 35%, together with increased mortality of up to 15%. A presumptive diagnosis at post mortem is made with the detection of characteristic small yellow-white necrotic hepatic lesions, together with a fibrinous peri-hepatitis, excess pericardial and peritoneal fluid, and usually enteritis with diarrhoea. Histopathology reveals a multifocal acute hepatocellular necrosis with fibrin and occasional haemorrhage. Control measures trialled include use of antibiotics, improved biosecurity and hygiene, as well as management practices directed at reducing stress in flocks. However, none other than treatment with antibiotics has been consistently effective which suggested a bacterial aetiology. In 2015, a novel fastidious thermophilic, microaerobic campylobacter was isolated from symptomatic SLD flocks in the UK. Subsequently, an Australian group isolated and further characterised a genetically similar bacterium and named it Campylobacter hepaticus. The bacterium can be cultured from the liver and bile of infected birds, although recovery from non-sterile organs such as the caecum and duodenum remains elusive. Consequently, the route of transmission remains unconfirmed, although molecular detection by PCR of C. hepaticus DNA in the gastrointestinal tract and faeces of SLD infected birds is highly suggestive of a faecal-oral route.

Antibody-conjugated ferromagnetic nanoparticles with lateral flow test strip assay for rapid detection of Campylobacter jejuni in poultry samples

The aim of this study was to develop a nanoparticle-based cell capture system combined with a lateral flow test strip (LFT) assay for rapid detection of Campylobacter jejuni from poultry samples. The developed assay was bench-marked against the standard modified Charcoal Cefoperazone Deoxycholate Agar (mCCDA) method according to ISO16140:2003 procedures. The synthesized ferromagnetic nanoparticles (FMNs) were modified with glutaraldehyde, then functionalized with polyclonal antibodies for specific C. jejuni capture and concentration from poultry samples. After lysing captured cells, DNA from C. jejuni was amplified by PCR using the primers designed to target the hipO gene, and the PCR amplicons were detected with the lateral flow test strip assay. Following the ISO16140:2003 guidelines, the relative detection limit, and the inclusivity and exclusivity tests were determined. The results showed that the limit of detection (LOD) of the assay was 10⁰ or 1 cfu/ml with C. jejuni in pure culture and 10¹-10² cfu/ml with target cells spiked in poultry sample. In addition, the inclusivity and exclusivity tests were found to be 100%. Using field chicken samples (n = 60), the assay showed relative accuracy, relative specificity, and relative sensitivity of 96.67%, 100% and 93.33%, respectively. The positive predictive values (PPV) and negative predictive values (NPV), and the kappa index of concordance (k) were calculated as 100% and 93.75%, and 0.93, respectively. The developed assay required approximately 3 h to complete and gave results comparable to those analyzed by the standard culture method, which required 5-7 days. The assay is rapid, easy-to-use, and has potential to be directly applied to C. jejuni detection in various categories of poultry samples.

Identification of Atypical Enteropathogenic Escherichia coli O98 from Golden Snub-Nosed Monkeys with Diarrhea in China

Fecal samples (n = 76) were collected from 38 snub-nosed monkeys (Rhinopithecus roxellana) in Shennongjia National Nature Reserve (China) and examined for the presence of enteropathogenic Escherichia coli (EPEC). The 56 samples originated from 30 free-ranging monkeys on the reserve and 20 samples from 8 captive monkeys that were previously rescued and kept at the research center. Eight diarrhea samples were collected from four of the eight captive monkeys (two samples from each monkey), and two EPEC strains (2.6%) (95% confidence interval 0.3–9.2%) were isolated from two fecal samples from two diarrheic monkeys. Both strains belonged to serotype O98 and phylogenetic group D (TspE4C2⁺, ChuA⁺). The virulence gene detection identified these strains as an atypical EPEC (aEPEC) (bfpB^–, stx1^–, and stx2^–) with the subtype eae⁺, escV⁺, and intiminβ⁺. These strains were highly sensitive to all the antibiotics tested. The lethal dose 50% of the two isolates in Kunming mice was 7.40 × 10⁸ CFU/0.2 mL and 2.40 × 10⁸ CFU/0.2 mL, respectively, indicating low virulence. Based on the report that this serotype had been isolated from some other non-human animals and humans with diarrhea, the first identification of aEPEC O98 strains and their drug resistance profile in R. roxellana is of ecological significance for disease control in this endangered species.

A Rapid LAMP-Based Method for Screening Poultry Samples for Campylobacter Without Enrichment

Campylobacter is the most prominent bacterium associated with foodborne disease and the majority of human infection cases are attributed to chicken. Rapid methods capable of determining the Campylobacter status of poultry products in a short time are needed in today's fast-paced food supply chain. In this study, we developed and evaluated an easy to perform, rapid and robust method for direct detection of Campylobacter in poultry carcasses based on loop-mediated isothermal DNA AMPlification (LAMP). The method does not require bacterial culture or DNA purification and generates results in just an hour. A total of 171 swabs from chicken and turkey slaughter houses were analyzed in parallel by both LAMP and conventional culture-based enumeration methods to evaluate the performance of the rapid method. Campylobacter was detected by LAMP in 100% of swabs with an enumeration result of ≥800 cfu/swab, and 98.6% (69 out of 70) of samples reported as negative by enumeration (≤10 cfu/swab) were also negative by LAMP. The method is also suitable for analysis of boot swabs from poultry houses, and therefore it represents a convenient screening tool that can be implemented on farm, at slaughter houses, processing plants or retail, to help with the control of Campylobacter contamination throughout the food supply chain. The inclusion of an internal amplification control prevents any potential false negative results due to DNA amplification inhibitors that might be present in the sample.

Immunomagnetic separation and size-based detection of Escherichia coli O157 at the meniscus of a membrane strip

We developed a facile method for the detection of pathogenic bacteria using gold-coated magnetic nanoparticle clusters (Au@MNCs) and porous nitrocellulose strips. Au@MNCs were synthesized and functionalized with half-fragments of Escherichia coli O157 antibodies. After the nanoparticles were used to capture E. coli O157 in milk and dispersed in a buffer solution, one end of a test strip was dipped into the solution. Due to the size difference between the E. coli–Au@MNC complexes (approximately 1 μm) and free Au@MNCs (approximately 180 nm), only E. coli–Au@MNC complexes accumulated at the meniscus of the test strip and induced a color change. The color intensity of the meniscus was proportional to the E. coli concentration, and the detection limit for E. coli in milk was 10³ CFU mL⁻¹ by the naked eye. The presence of E. coli–Au@MNC complexes at the meniscus was confirmed using a real-time PCR assay. The developed method was highly selective for E. coli when compared with Salmonella typhimurium, Listeria monocytogenes, and Staphylococcus aureus.

E. coli–Au/MNC complexes accumulate at the meniscus of the test strip where the flow velocity reaches a maximum.

Campylobacter hepaticus, the cause of spotty liver disease in chickens, is present throughout the small intestine and caeca of infected birds

Spotty liver disease (SLD) causes significant egg production losses and mortality in chickens and is therefore a disease of concern for some sectors of the poultry industry. Although the first reports of the disease came from the United States in the 1950s it is only recently that the organism that causes the disease was identified, isolated, and characterised as a new bacterial species, Campylobacter hepaticus. The first isolations of C. hepaticus were from the livers and bile of SLD affected birds. Isolates could only be recovered from samples that had a monoculture of C. hepaticus in the tissues, as a selective culturing method has not yet been developed. In non-selective growth conditions the slow growing C. hepaticus is quickly outgrown by many other members of the chicken microbiota. Therefore, it is currently not possible to use a culturing approach to evaluate C. hepaticus carriage in tissues, such as the gastrointestinal tract (GIT), that also carry complex microbial populations. As it is suspected that birds become infected via the faecal-oral route it is important that pathogen carriage in the GIT is investigated. In the present study, a specific and sensitive quantitative real-time PCR assay, based on the glycerol kinase gene of C. hepaticus, was developed. The assay facilitated the detection and quantification of C. hepaticus in tissue samples from clinical cases of SLD. It was shown that in infected birds C. hepaticus colonises the small intestine, increasing in abundance from duodenum to ileum, and is at highest levels within the ceaca. C. hepaticus was also readily detected in cloacal swabs, indicating that thecl-oral infection.

Simultaneous Identification of Campylobacter jejuni, Campylobacter coli, and Campylobacter lari with SmartCycler-Based Multiplex Quantitative Polymerase Chain Reaction

BACKGROUND

Consumption of Campylobacter contaminated food or water is a leading cause of human acute gastroenteritis. Campylobacter jejuni, Campylobacter coli, and Campylobacter lari account for over 95% of total Campylobacter infections. A multiplex quantitative polymerase chain reaction (qPCR) for simultaneous identification of C. jejuni, C. coli, and C. lari was developed for use with the SmartCycler II system.

MATERIALS AND METHODS

We evaluated and combined previously described primers and probes for Campylobacter detection, designed a new internal amplification control, and optimized the multiplex qPCR for the detection of C. jejuni, C. coli, and C. lari.

RESULTS

This method was 100% specific when tested against a panel of 32 target Campylobacter strains and 31 non-Campylobacter reference strains. Furthermore, there was no cross-reactivity with seven strains from four nontarget Campylobacter species. The amplification efficiency of each target in this multiplex qPCR was over 90%, and each coefficient of linearity was greater than 0.99. With artificially mixed genomic DNA, this method detected as few as two, three, and two genome copies of C. jejuni, C. coli, and C. lari, respectively. This method was also able to detect these three Campylobacter species in artificially contaminated milk with a sensitivity of five spiked cells of each target per reaction.

CONCLUSION

The three Campylobacter targets were simultaneously identified using artificially mixed genomic DNA and spiked raw milk. This SmartCycler-based multiplex qPCR is a rapid, specific, and sensitive method to identify C. jejuni, C. coli, and C. lari.

Campylobacter jejuni Isolation/Enumeration from Environmental Samples

Currently, there is no universally accepted standard media or method for the recovery of Campylobacter species. This is likely due to the ubiquity of the organism in nature, the complex sample matrices from which the organism is often recovered, as well as the fragile/viable-but nonculturable state the organism assumes in response to stress. The use of a sterile filter placed upon a nonselective Brucella Agar Blood Plate (BAB), followed by incubation at 37 °C in a hydrogen-containing atmosphere (Campycheck), is one method to recover stressed and emerging Campylobacter spp. from complex environmental matrices; however, this technique does not currently allow for the enumeration of the recovered organisms. Enumeration is performed using serial dilutions of sample homogenate plated onto modified Campy-Cefex media followed by incubation at either 37 °C or 42 °C in a microaerobic atmosphere.

Sensitivity of Direct Culture, Enrichment and PCR for Detection of Campylobacter jejuni and C. coli in Broiler Flocks at Slaughter

Broiler chicken flocks are a significant source of Campylobacter jejuni and Campylobacter coli that result in the major public health problem of campylobacteriosis. Accurate estimates of the prevalence of both C. coli and C. jejuni in flocks would enhance epidemiological understanding, risk assessment and control options. This study combined results from a panel of 10 detection tests (direct culture, enrichment and PCR) on caecal samples from flocks at slaughter. A parallel interpretation approach was used to determine the presence of Campylobacter spp. and for C. jejuni and C. coli individually. The sample was considered positive if at least one method detected the target and this interpretation was taken to represent a 'proxy gold standard' for detection in the absence of a gold standard reference test. The sensitivity of each individual method to detect Campylobacter spp., C. jejuni and C. coli was then estimated relative to the proxy gold standard. Enrichment in adapted Exeter broth (deficient in polymyxin B) with a resuscitation step was 100% sensitive, whilst direct culture on modified charcoal cefoperazone deoxycholate agar (mCCDA) was highly sensitive (97.9%). Enrichment methods using Preston broth and Bolton broth were significantly less sensitive. Enrichment in Exeter broth promoted the recovery of C. jejuni, whilst enrichment in Bolton broth favoured C. coli. A RT-PCR detection test could identify 80% of flocks that were co-colonised with both species. This study found that 76.3% (n = 127) of flocks were colonised with Campylobacter spp. The majority (95.9%) of Campylobacter-positive flocks were colonised with C. jejuni; however, approximately one-third of positive flocks were simultaneously colonised with both C. jejuni and C. coli. The findings highlight the impact of different detection methodologies on the accuracy of the estimated incidence of both C. jejuni and C. coli entering the abattoir within broiler flocks and the associated public health risks.

Estimating sensitivity and specificity of a PCR for boot socks to detect Campylobacter in broiler primary production using Bayesian latent class analysis

The present study compares three different assays for sample collection and detection of Campylobacter spp. in broiler flocks, based on (i) the collection of faecal samples from intestinal organs (caecum), (ii) individual faecal droppings collected from the bedding and (iii) faecal material collected by socks placed on the outside of a pair of boots (boot socks) and used for walking around in the flock. The two first methods are examined for Campylobacter using a culture method (ISO-10272-2:2006), while the boot socks are tested using PCR. The PCR-assay is a genus specific multiplex PCR with primers targeting 16S rDNA in Campylobacter and primers targeting Yersinia ruckerii. Sixty-seven broiler flocks from Austria and 83 broiler flocks from Denmark were included in this prospective study and 89 of these were found to be positive in at least one method (AT: 49 samples, DK: 40 samples) whereas 61 of these were negative in all assays. In Austria samples for the three assays were collected simultaneously, which facilitates a direct comparison of the diagnostic test performance. In Denmark, however, boot socks and faecal droppings were collected three days before slaughter while caecum samples were collected at slaughter. The results were evaluated in the absence of a gold standard using a Bayesian latent class model. Austrian results showed higher sensitivity for PCR detection in sock samples (0.98; Bayesian credible interval (BCI) [0.93-1]) than for culture of faecal droppings (0.86; BCI [0.76-0.91]) or caecal samples (0.92; BCI [0.85-0.97]). The potential impact of Campylobacter introduction within the final three days before slaughter was observed in Denmark, where four flocks were tested negative three days before slaughter, but were detected positive at the slaughterhouse. Therefore the model results for the PCR sensitivity (0.88; BCI [0.83-0.97]) and cultural ISO-method in faecal samples (0.84; BCI [0.76-0.92]) are lower than for caecal samples (0.93; BCI [0.85-0.98]). In our study, PCR detection on boot sock samples is more sensitive than conventional culture. In view of the advantage of rapid results before slaughter and low costs for sampling, especially in combination with existing Salmonella surveillance systems (just another pair of boot socks needed), this method-matrix combination could be a valuable surveillance tool in the broiler primary production.