Influence of enrichment and isolation media on the detection of Campylobacter spp. in naturally contaminated chicken samples

Culture-Based Standard Methods for the Isolation of Campylobacter spp. in Food and Water

Campylobacter spp. is a major source of global gastrointestinal infections. Their enteric infections are linked to the consumption of undercooked poultry products, contaminated milk and water, and the handling of wild animals and birds. The detection of Campylobacter spp. in water and food samples mainly depends on culture-based techniques. Public Health England (PHE), the U.S. Food and Drug Administration (FDA), and the International Standard Organization (ISO) have standardized Campylobacter spp. isolation and enumeration procedures for food and water samples, which involve the usage of selective agar media and enrichment broth. Different types of selective plating and enrichment media have been prepared for Campylobacter spp. detection and assessment during regular food surveillance and food poisoning. To date, culture media remains the standard option for microbiological food analysis and has been approved by the U.S. Environmental Protection Agency (US EPA), Food and Agriculture Organization (FAO), and World Health Organization (WHO). This review discusses the standard microbiological protocols for Campylobacter spp. isolation and enumeration in food and water and evaluates detection media (pre-enrichment, selective enrichment, and selective plating) for their rational applications. Moreover, it also elaborates on the advantages and disadvantages of recent chromogenic culture media in Campylobacter spp.-oriented food surveillance. This review also highlights the challenges of culture-based techniques, future developments, and alternative methods for Campylobacter spp. detection in food and water samples.

Comparative Analysis of Quantitative Methods for Campylobacter spp. Quantification: ISO 10272-2:2017, Tempo® and Real-Time PCR in Refrigerated and Frozen Turkey Cuts

New technologies for more effective microbiological assays are being adopted by the food industry to intervene more rapidly in its production chain. The aim of this study was to evaluate the alternative methods of TEMPO® CAM and real-time PCR (rtPCR) Biotecon® in comparison with the ISO 10272-2:2017 reference method for Campylobacter spp. quantification in turkey meat, aiming to validate a quick and easily replicable method in these meat matrices. A total of 416 samples were analyzed over a one-year period. The TEMPO® methodology showed inadequate performance with a significant difference (p < 0.05) compared with the reference methodology; therefore, its use was not recommended for turkey meat matrices. However, the performance of the rtPCR Biotecon® methodology showed adequate performance with no significant difference (p > 0.05), and its use was recommended in turkey meat matrices. The study was limited to exclusive research in turkey meat matrices, and expansion of the research into other matrices is recommended to verify whether the behavior of alternative methodologies is similar. The findings of this study illustrate the necessity for a thorough and comprehensive evaluation during the implementation of alternative methodologies that may potentially supplant conventional approaches.

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.

A culture-based assessment of the microbiota of conventional and free-range chicken meat from Irish processing facilities

Chicken meat is the most popularly consumed meat worldwide, with free-range and ethically produced meat a growing market among consumers. However, poultry is frequently contaminated with spoilage microbes and zoonotic pathogens which impact the shelf-life and safety of the raw product, constituting a health risk to consumers. The free-range broiler microbiota is subject to various influences during rearing such as direct exposure to the external environment and wildlife which are not experienced during conventional rearing practices. Using culture-based microbiology approaches, this study aimed to determine whether there is a detectable difference in the microbiota from conventional and free-range broilers from selected Irish processing plants. This was done through analysis of the microbiological status of bone-in chicken thighs over the duration of the meat shelf-life. It was found that the shelf-life of these products was 10 days from arrival in the laboratory, with no statistically significant difference (P > 0.05) evident between free-range and conventionally raised chicken meat. A significant difference, however, was established in the presence of pathogenesis-associated genera in different meat processors. These results reinforce past findings which indicate that the processing environment and storage during shelf-life are key determinants of the microflora of chicken products reaching the consumer.

Enrichment and Direct Plating for Detection of Campylobacter in Chicken Liver Rinse and Exudate

ABSTRACT

Foodborne campylobacteriosis has been traced to undercooked chicken liver dishes; thus, it is important to use the best available culture methods when testing for the presence of Campylobacter. We compared two Campylobacter enrichment broths-Bolton formulation and Neogen formulation-in combination with three selective plating media-Campy-Cefex, Campy-Line and RF Campylobacter agars-for detection of Campylobacter from fresh retail chicken livers. In each of three experiments, nine replicate tubs of chicken livers were sampled by drawing exudate and a pooled rinse of five whole liver lobes. Results are reported as number positive and compared by Fisher's exact test. In experiment 1, no combination of enrichment and plating media significantly outperformed another for detection of Campylobacter (P > 0.05); all tubs were found to include Campylobacter in both exudate and liver rinse. In experiment 2, serial dilutions of samples were plated before and after enrichment. Exudate was found to be significantly more likely than rinse to support detection of Campylobacter by direct plating (P < 0.05); most exudate samples included at least 10 CFU Campylobacter per mL. Enrichment improved detection from rinse, but not exudate; all enrichment and plating combinations resulted ≥1,000 CFU/mL from most enriched samples. In experiment 3, samples were diluted before enrichment to determine effect of enrichment on ever lower numbers of Campylobacter. Enrichment did not improve recovery of Campylobacter from exudate or undiluted rinse (P > 0.05). However, when rinse samples were diluted to lower Campylobacter numbers, enrichment improved detection (P < 0.05). Overall, all media combinations tested were equivalent for detection of Campylobacter from chicken livers; sensitivity for detection seemed to be increased by using liver exudate compared with a pooled rinse of liver lobes.

HIGHLIGHTS

Virulence Profiling, Multidrug Resistance and Molecular Mechanisms of Campylobacter Strains from Chicken Carcasses in Tunisia

Antibiotic resistance in foodborne pathogens is an emergent global health concern. The objectives of this study were to assess antimicrobial resistance (AMR) in Campylobacter isolates from chicken carcasses and to investigate the AMR molecular mechanisms as well as the presence of virulence determinants. The study was performed on 257 samples collected from abattoirs and retail shops in northeastern Tunisia. Forty-eight Campylobacter isolates were recovered and identified as C. jejuni (n = 33) and C. coli (n = 15). Antibiotic resistance was tested against eight antibiotics and high resistance rates were observed against tetracycline (100%), erythromycin (97.9%), ciprofloxacin (73%), nalidixic acid (85.4%), ampicillin (83.3%), amoxicillin/clavulanic acid (22.9%), chloramphenicol (75%), and gentamicin (27.1%). All isolates were multidrug-resistant, and 22 resistance patterns were found. All isolates were screened for AMR genes (tet(O), tet(A), tet(B), tet(L), cmeB, ermB, bla_OXA-61, and aphA-3), and for point mutations in gyrA (C257T substitution) and 23SrRNA (A2075G/A2074C) genes. All screened AMR genes, as well as the C257T and the A2075G mutations, were detected. The virulence genotypes were also determined, and all isolates carried the motility (flaA) and invasion (cadF) genes. Most of them also harbored the cdtA, cdtB, and cdtC genes, encoding the Campylobacter toxin. The screening of the cgtB and the wlaN genes, involved in Guillain-Barré Syndrome expression, revealed the presence of the cgtB in 21.2% of C. jejuni strains, whereas none of them carried the wlaN gene. Our findings highlight the emergence of Campylobacter strains simultaneously harboring several virulence and AMR determinants, which emphasizes the risk of transmission of MDR strains to humans via the food chain. Hence, controlling the dissemination of foodborne pathogens “from the farm to the fork” as well as restricting the use of antimicrobials in husbandry are mandatory to prevent the risk for consumers and to mitigate the dissemination of MDR pathogens.

Campylobacteriosis, Shigellosis and Salmonellosis in Hospitalized Children with Acute Inflammatory Diarrhea in Georgia

This is the first study on campylobacteriosis carried out in Georgia. It targeted 382 hospitalized children with acute inflammatory diarrhea. The study was conducted between July 2020 to July 2021 based on the main infection clinic of the capital city. Culture-based bacteriological methods were followed by phenotypic and Real-time PCR tests for bacterial confirmation and identification. The data revealed recent epidemiologic prevalences of the three main causative bacteria in the target population. Shigella sonnei with 19.1% (95% CI: 15.2%−23.4%) was the most frequently detected pathogen followed by Campylobacter spp. with 12.3% (95% CI: 9.2%−16.0%) and Salmonella spp. with 4.9% (95% CI: 3.0%−7.6%). However, in 63.6% of the samples, the causative agent remained unknown. Species differentiation of Campylobacter spp. revealed 81% Campylobacter jejuni and 19% Campylobacter coli. An epidemiological pyramid with estimated magnification factors may give more insights into the burden of campylobacteriosis among the studied population, resulting in a putative annual incidence of 6 per 1000 children in Tbilisi. Children with campylobacteriosis were younger (median age 40 months (interquartile range (IQR) 22−95)) than with shigellosis (median age 92 months (interquartile range (IQR) 52−140)). However, no statistically significant difference was found with the age range of patients with campylobacteriosis and salmonellosis as well as with salmonellosis and shigellosis. In conclusion, Campylobacter spp. may be suspected to be the second most frequent bacterial causative agent of acute inflammatory diarrhea in hospitalized children and the primary cause in the 0–3 age group in Georgia. In addition, Campylobacter CROMagar showed better selectivity in comparison to mCCDA selective agar of stool samples in our study.

Challenging the "gold standard" of colony-forming units - Validation of a multiplex real-time PCR for quantification of viable Campylobacter spp. in meat rinses

Campylobacter jejuni is the leading bacterial food-borne pathogen in Europe. Despite the accepted limits of cultural detection of the fastidious bacterium, the "gold standard" in food microbiology is still the determination of colony-forming units (CFU). As an alternative, a live/dead differentiating qPCR has been established, using propidium monoazide (PMA) as DNA-intercalating crosslink agent for inactivating DNA from dead, membrane-compromised cells. The PMA treatment was combined with the addition of an internal sample process control (ISPC), i.e. a known number of dead C. sputorum cells to the samples. The ISPC enables i), monitoring the effective reduction of dead cell signal by the light-activated DNA-intercalating dye PMA, and ii), compensation for potential DNA losses during processing. Here, we optimized the method for routine application and performed a full validation of the method according to ISO 16140-2:2016(E) for the quantification of live thermophilic Campylobacter spp. in meat rinses against the classical enumeration method ISO 10272-2:2017. In order to render the method applicable and cost-effective for practical application, the ISPC was lyophilized to be distributable to routine laboratories. In addition, a triplex qPCR was established to simultaneously quantify thermophilic Campylobacter, the ISPC and an internal amplification control (IAC). Its performance was statistically similar to the two duplex qPCRs up to a contamination level of 4.7 log₁₀Campylobacter per ml of meat rinse. The limit of quantification (LOQ) of the alternative method was around 20 genomic equivalents per PCR reaction, i.e. 2.3 log₁₀ live Campylobacter per ml of sample. The alternative method passed a relative trueness study, confirming the robustness against different meat rinses, and displayed sufficient accuracy within the limits set in ISO 16140-2:2016(E). Finally, the method was validated in an interlaboratory ring trial, confirming that the alternative method was fit for purpose with a tendency of improved repeatability and reproducibility compared to the reference method for CFU determination. Campylobacter served as a model organism, challenging CFU as "gold standard" and could help in guidance to the general acceptance of live/dead differentiating qPCR methods for the detection of food-borne pathogens.

Technical specifications on harmonised monitoring of antimicrobial resistance in zoonotic and indicator bacteria from food-producing animals and food

Proposals to update the harmonised monitoring and reporting of antimicrobial resistance (AMR) from a public health perspective in Salmonella, Campylobacter coli, Campylobacter jejuni, Escherichia coli, Enterococcus faecalis, Enterococcus faecium and methicillin-resistant Staphylococcus aureus (MRSA) from food-producing animals and derived meat in the EU are presented in this report, accounting for recent trends in AMR, data collection needs and new scientific developments. Phenotypic monitoring of AMR in bacterial isolates, using microdilution methods for testing susceptibility and interpreting resistance using epidemiological cut-off values is reinforced, including further characterisation of those isolates of E. coli and Salmonella showing resistance to extended-spectrum cephalosporins and carbapenems, as well as the specific monitoring of ESBL/AmpC/carbapenemase-producing E. coli. Combinations of bacterial species, food-producing animals and meat, as well as antimicrobial panels have been reviewed and adapted, where deemed necessary. Considering differing sample sizes, numerical simulations have been performed to evaluate the related statistical power available for assessing occurrence and temporal trends in resistance, with a predetermined accuracy, to support the choice of harmonised sample size. Randomised sampling procedures, based on a generic proportionate stratified sampling process, have been reviewed and reinforced. Proposals to improve the harmonisation of monitoring of prevalence, genetic diversity and AMR in MRSA are presented. It is suggested to complement routine monitoring with specific cross-sectional surveys on MRSA in pigs and on AMR in bacteria from seafood and the environment. Whole genome sequencing (WGS) of isolates obtained from the specific monitoring of ESBL/AmpC/carbapenemase-producing E. coli is strongly advocated to be implemented, on a voluntary basis, over the validity period of the next legislation, with possible mandatory implementation by the end of the period; the gene sequences encoding for ESBL/AmpC/carbapenemases being reported to EFSA. Harmonised protocols for WGS analysis/interpretation and external quality assurance programmes are planned to be provided by the EU-Reference Laboratory on AMR.

Evaluation of potassium clavulanate supplementation of Bolton broth for enrichment and detection of Campylobacter from chicken

Culture-based detection of Campylobacter can be affected by competing flora, temperature, incubation time, and presence of blood. The presence of extended-spectrum β-lactamase (ESBL)-producing Escherichia coli in poultry has become one of the most common factors interfering with the detection of Campylobacter. In the present study, we evaluated potassium clavulanate (ESBL inhibitor) as a supplement in Bolton broth (C-Bolton broth) for enrichment and detection of Campylobacter. First, we determined growth kinetics of Campylobacter in the presence of different concentrations of ESBL E. coli in C-Bolton broth during enrichment. The effects of other factors such as incubation time, incubation temperature, and presence of blood on Campylobacter detection in C-Bolton broth were also investigated. The growth of Campylobacter co-cultured at a low concentration (2 and 4 log10 CFU/mL) of ESBL E. coli was similar to that of Campylobacter alone in C-Bolton broth, and Campylobacter co-cultured at a high concentration (6 and 8 log10 CFU/mL) of ESBL E. coli showed slower growth than the pure Campylobacter culture. The Campylobacter detection limit was 1 log10 CFU/mL when mixed with 2, 4, or 6 log10 CFU/mL of E. coli and 3 log10 CFU/mL when mixed with 8 log10 CFU/mL of E. coli after 48 h enrichment in the broth. Campylobacter detection from chicken feces and litter samples was not affected by incubation time, or presence of blood in the broth. A modified procedure of enrichment in C-Bolton broth at 37°C for 24 h without blood showed a significantly (P ≤ 0.05) higher detection rate and a lower false-negative rate than the ISO 10272-1:2006 method for Campylobacter detection from chicken feces and litter samples. In summary, the present study demonstrates the efficacy of Bolton broth supplemented with potassium clavulanate in the detection of Campylobacter mixed with ESBL E. coli, and an improved procedure to detect Campylobacter from chicken feces and litter samples.

The European Union summary report on antimicrobial resistance in zoonotic and indicator bacteria from humans, animals and food in 2016

The data on antimicrobial resistance in zoonotic and indicator bacteria in 2016, submitted by 28 EU Member States (MSs), were jointly analysed by the EFSA and ECDC. Resistance in bacterial isolates of zoonotic Salmonella and Campylobacter from humans, animals and food, and resistance in indicator Escherichia coli as well as in meticillin-resistant Staphylococcus aureus from animals and food were addressed. 'Microbiological' resistance was assessed using epidemiological cut-off (ECOFF) values; for some countries, qualitative data on isolates from humans were interpreted in a way that corresponds closely to ECOFF-defined 'microbiological' resistance. In Salmonella from humans, the occurrence of resistance to ampicillin, sulfonamides and tetracyclines was high, whereas resistance to third-generation cephalosporins was low. In Salmonella and E. coli isolates from broilers, fattening turkeys and their meat, resistance to ampicillin, (fluoro)quinolones, tetracyclines and sulfonamides was frequently high, whereas resistance to third-generation cephalosporins was rare. The occurrence of ESBL-/AmpC producers was low in Salmonella and E. coli from poultry and in Salmonella from humans. The prevalence of ESBL-/AmpC-producing E. coli, assessed in poultry and its meat for the first time, showed marked variations among MSs. Fourteen presumptive carbapenemase-producing E. coli were detected from broilers and its meat in two MSs. Resistance to colistin was observed at low levels in Salmonella and E. coli from poultry and meat thereof and in Salmonella from humans. In Campylobacter from humans, broilers and broiler meat, resistance to ciprofloxacin and tetracyclines was high to extremely high, whereas resistance to erythromycin was low to moderate. Combined resistance to critically important antimicrobials in isolates from both humans and animals was generally uncommon, but very high to extremely high multidrug resistance levels were observed in certain Salmonella serovars. Specific serovars of Salmonella (notably Kentucky) from both humans and animals exhibited high-level resistance to ciprofloxacin, in addition to findings of ESBL.