Influence of measurement and control of microaerobic gaseous atmospheres in methods for Campylobacter growth studies

A Comprehensive Review for the Surveillance of Human Pathogenic Microorganisms in Shellfish

Bivalve molluscan shellfish have been consumed for centuries. Being filter feeders, they may bioaccumulate some microorganisms present in coastal water, either naturally or through the discharge of human or animal sewage. Despite regulations set up to avoid microbiological contamination in shellfish, human outbreaks still occur. After providing an overview showing their implication in disease, this review aims to highlight the diversity of the bacteria or enteric viruses detected in shellfish species, including emerging pathogens. After a critical discussion of the available methods and their limitations, we address the interest of technological developments using genomics to anticipate the emergence of pathogens. In the coming years, further research needs to be performed and methods need to be developed in order to design the future of surveillance and to help risk assessment studies, with the ultimate objective of protecting consumers and enhancing the microbial safety of bivalve molluscan shellfish as a healthy food.

Metaphenotypes associated with recurrent genomic lineages of Campylobacter jejuni responsible for human infections in Luxembourg

Campylobacter jejuni is a leading cause of foodborne illnesses worldwide. Although considered fragile, this microaerophilic bacterium is able to survive in various challenging environments, which subsequently constitutes multiple sources of transmission for human infection. To test the assumption of acquiring specific features for adaptation and survival, we established a workflow of phenotypic tests related to the survival and the persistence of recurrent and sporadic strains. A representative collection of 83 strains isolated over 13 years from human, mammal, poultry, and environmental sources in Luxembourg, representing different spreading patterns (endemic, epidemic, and sporadic), was screened for survival to oxidative stresses, for acclimating to aerobic conditions (AC), and for persistence on abiotic surfaces. Using the cgMLST Oxford typing scheme for WGS data, the collection was classified into genomic lineages corresponding to host-generalist strains (lineages A and D, CC ST-21), host-specific strains (lineage B, CC ST-257 and lineage C, CC ST-464) and sporadic strains. We established that when a strain survives concentrations beyond 0.25 mM superoxide stress, it is six times more likely to survive hyperoxide stress and that a highly adherent strain is 14 times more likely to develop a biofilm. Surprisingly, more than half of the strains could acclimate to AC but this capacity does not explain the difference between recurrent genomic lineages and sporadic strains and the survival to oxidative stresses, while recurrent strains have a significantly higher adhesion/biofilm formation capacity than sporadic ones. From this work, the genomic lineages with more stable genomes could be characterized by a specific combination of phenotypes, called metaphenotypes. From the functional genomic analyses, the presence of a potentially functional T6SS in the strains of lineage D might explain the propensity of these strains to be strong biofilm producers. Our findings support the hypothesis that phenotypical abilities contribute to the spatio-temporal adaptation and survival of stable genomic lineages. It suggests a selection of better-adapted and persistent strains in challenging stress environments, which could explain the prevalence of these lineages in human infections.

Current methodologies and future direction of Campylobacter isolation and detection from food matrices, clinical samples, and the agricultural environment

Campylobacter spp. are the leading cause of bacterial foodborne infections in both developed and developing countries. The food commodities primarily attributed to campylobacteriosis include raw milk, poultry, seafood, and fresh produce. Furthermore, insects, animal/bird fecal material, and agricultural water have been shown to be the sources of Campylobacter contamination in these commodities. Both established and emerging species of Campylobacter have been recovered from food and environmental sources. Therefore, optimal detection and isolation of Campylobacter spp., including the emerging species, is critical for improved surveillance, prevention, and traceback of Campylobacter outbreaks. This review focuses on the existing variability in Campylobacter enrichment and isolation procedures used by researchers and regulatory agencies worldwide, for various matrices. Additionally, the challenges associated with developing and validating new culture, molecular, and immunological methods for rapid and sensitive Campylobacter detection are discussed.

Development of a Trivalent Construct Omp18/AhpC/FlgH Multi Epitope Peptide Vaccine Against Campylobacter jejuni

Campylobacter jejuni (C. jejuni) is one of the major pathogens contributing to the enteritis in humans. Infection can lead to numerous complications, including but not limited to Guillain-Barre syndrome, reactive arthritis, and Reiter’s syndrome. Over the past two decades, joint efforts have been made toward developing a proper strategy of limiting the transmission of C. jejuni to humans. Nevertheless, except for biosecurity measures, no available vaccine has been developed so far. Judging from the research findings, Omp18, AhpC outer membrane protein, and FlgH flagellin subunits of C. jejuni could be adopted as surface protein antigens of C. jejuni for screening dominant epitope thanks to their strong antigenicity, expression of varying strains, and conservative sequence. In this study, bioinformatics technology was adopted to analyze the T-B antigenic epitopes of Omp18, AhpC, and FlgH in C. jejuni strain NCTC11168. Both ELISA and Western Blot methods were adopted to screen the dominant T-B combined epitope. GGS (GGCGGTAGC) sequence was adopted to connect the dominant T-B combined epitope peptides and to construct the prokaryotic expression system of tandem repeats of antigenic epitope peptides. The mouse infection model was adopted to assess the immunoprotective effect imposed by the trivalent T-B combined with antigen epitope peptide based on Omp18/AhpC/FlgH. In this study, a tandem epitope AhpC-2/Omp18-1/FlgH-1 was developed, which was composed of three epitopes and could effectively enhance the stability and antigenicity of the epitope while preserving its structure. The immunization of BALB/c mice with a tandem epitope could induce protective immunity accompanied by the generation of IgG2a antibody response through the in vitro synthesis of IFN-γ cytokines. Judging from the results of immune protection experiments, the colonization of C. jejuni declined to a significant extent, and it was expected that AhpC-2/Omp18-1/FlgH-1 could be adopted as a candidate antigen for genetic engineering vaccine of C. jejuni MAP.

Next-Generation Antimicrobial Resistance Surveillance System Based on the Internet-of-Things and Microfluidic Technique

Antimicrobial resistance (AMR) of foodborne pathogens is a global crisis in public health and economic growth. A real-time surveillance system is key to track the emergence of AMR bacteria and provides a comprehensive AMR trend from farm to fork. However, current AMR surveillance systems, which integrate results from multiple laboratories using the conventional broth microdilution method, are labor-intensive and time-consuming. To address these challenges, we present the internet of things (IoT), including colorimetric-based microfluidic sensors, a custom-built portable incubator, and machine learning algorithms, to monitor AMR trends in real time. As a top priority microbe that poses risks to human health, Campylobacter was selected as a bacterial model to demonstrate and validate the IoT-assisted AMR surveillance. Image classification with convolution neural network ResNet50 on the colorimetric sensors achieved an accuracy of 99.5% in classifying bacterial growth/inhibition patterns. The IoT was used to carry out a small-scale survey study, identifying eight Campylobacter isolates out of 35 chicken samples. A 96% agreement on Campylobacter AMR profiles was achieved between the results from the IoT and the conventional broth microdilution method. The data collected from the intelligent sensors were transmitted from local computers to a cloud server, facilitating real-time data collection and integration. A web browser was developed to demonstrate the spatial and temporal AMR trends to end-users. This rapid, cost-effective, and portable approach is able to monitor, assess, and mitigate the burden of bacterial AMR in the agri-food chain.

Survival and Control of Campylobacter in Poultry Production Environment

Campylobacter species are Gram-negative, motile, and non-spore-forming bacteria with a unique helical shape that changes to filamentous or coccoid as an adaptive response to environmental stresses. The relatively small genome (1.6 Mbp) of Campylobacter with unique cellular and molecular physiology is only understood to a limited extent. The overall strict requirement of this fastidious microorganism to be either isolated or cultivated in the laboratory settings make itself to appear as a weak survivor and/or an easy target to be inactivated in the surrounding environment of poultry farms, such as soil, water source, dust, surfaces and air. The survival of this obligate microaerobic bacterium from poultry farms to slaughterhouses and the final poultry products indicates that Campylobacter has several adaptive responses and/or environmental niches throughout the poultry production chain. Many of these adaptive responses remain puzzles. No single control method is yet known to fully address Campylobacter contamination in the poultry industry and new intervention strategies are required. The aim of this review article is to discuss the transmission, survival, and adaptation of Campylobacter species in the poultry production environments. Some approved and novel control methods against Campylobacter species throughout the poultry production chain will also be discussed.

Membrane Proteocomplexome of Campylobacter jejuni Using 2-D Blue Native/SDS-PAGE Combined to Bioinformatics Analysis

Campylobacter is the leading cause of the human bacterial foodborne infections in the developed countries. The perception cues from biotic or abiotic environments by the bacteria are often related to bacterial surface and membrane proteins that mediate the cellular response for the adaptation of Campylobacter jejuni to the environment. These proteins function rarely as a unique entity, they are often organized in functional complexes. In C. jejuni, these complexes are not fully identified and some of them remain unknown. To identify putative functional multi-subunit entities at the membrane subproteome level of C. jejuni, a holistic non a priori method was addressed using two-dimensional blue native/Sodium dodecyl sulfate (SDS) polyacrylamide gel electrophoresis (PAGE) in strain C. jejuni 81-176. Couples of acrylamide gradient/migration-time, membrane detergent concentration and hand-made strips were optimized to obtain reproducible extraction and separation of intact membrane protein complexes (MPCs). The MPCs were subsequently denatured using SDS-PAGE and each spot from each MPCs was identified by mass spectrometry. Altogether, 21 MPCs could be detected including multi homo-oligomeric and multi hetero-oligomeric complexes distributed in both inner and outer membranes. The function, the conservation and the regulation of the MPCs across C. jejuni strains were inspected by functional and genomic comparison analyses. In this study, relatedness between subunits of two efflux pumps, CmeABC and MacABputC was observed. In addition, a consensus sequence CosR-binding box in promoter regions of MacABputC was present in C. jejuni but not in Campylobacter coli. The MPCs identified in C. jejuni 81-176 membrane are involved in protein folding, molecule trafficking, oxidative phosphorylation, membrane structuration, peptidoglycan biosynthesis, motility and chemotaxis, stress signaling, efflux pumps and virulence.

Efficacy of Lactic Acid and Modified Atmosphere Packaging against Campylobacter jejuni on Chicken during Refrigerated Storage

The present study was conducted to evaluate the combined effect of lactic acid washing and modified atmospheres packaging on the counts of Campylobacter jejuni on chicken legs stored at 4 °C. In experiment 1, inoculated chicken legs were washed with either 1% or 2% lactic acid solution for 5 min or distilled water (control). The treatment with 2% lactic acid reduced C. jejuni counts 1.42 log units after treatment (day 0). In experiment 2, inoculated samples were packaged under different conditions: air, 100%N2, vacuum, 20%CO2/80%N2, or 40%CO2/60%N2. C. jejuni counts were higher in samples packaged under vacuum or atmospheres containing CO2 than in air. In experiment 3, inoculated chicken legs were washed with a 2% lactic acid solution for 5 min or distilled water (control). Samples were packaged under different conditions: air, vacuum, 20%CO2/80%N2, or 40%CO2/60%N2. C. jejuni counts were lower in samples treated with lactic acid than in samples non-treated. However, C. jejuni counts were higher in chicken legs treated with lactic acid and packaged in modified atmospheres than in those treated and packaged in air. Immersion of chicken legs in a solution containing 2% lactic acid can reduce C. jejuni counts on fresh chicken packaged in modified atmosphere.

The Wild Mouse (Micromys minutus): Reservoir of a Novel Campylobacter jejuni Strain

Campylobacter jejuni is one of the most common zoonotic pathogens worldwide. Although the main sources of human C. jejuni infection are livestock, wildlife can also affect C. jejuni transmission in humans. However, it remains unclear whether wild mice harbor C. jejuni and are involved in the "environment-wildlife-livestock-human" transmission cycle of C. jejuni in humans. Here, we characterized C. jejuni from wild mice and identified genetic traces of wild mouse-derived C. jejuni in other hosts using a traditional approach, along with comparative genomics. We captured 115 wild mice (49 Mus musculus and 66 Micromys minutus) without any clinical symptoms from 22 sesame fields in Korea over 2 years. Among them, M. minutus were typically caught in remote areas of human houses and C. jejuni was solely isolated from M. minutus (42/66, 63.6%). We identified a single clone (MLST ST-8388) in all 42 C. jejuni isolates, which had not been previously reported, and all isolates had the same virulence/survival-factor profile, except for the plasmid-mediated virB11 gene. No isolates exhibited antibiotic resistance, either in phenotypic and genetic terms. Comparative-genomic analysis and MST revealed that C. jejuni derived from M. minutus (strain SCJK2) was not genetically related to those derived from other sources (registered in the NCBI genome database and PubMLST database). Therefore, we hypothesize that C. jejuni from M. minutus is a normal component of the gut flora following adaptation to the gastro-intestinal tract. Furthermore, M. minutus-derived C. jejuni had different ancestral lineages from those derived from other sources, and there was a low chance of C. jejuni transmission from M. minutus to humans/livestock because of their habitat. In conclusion, M. minutus may be a potential reservoir for a novel C. jejuni, which is genetically different from those of other sources, but may not be involved in the transmission of C. jejuni to other hosts, including humans and livestock. This study could form the basis for further studies focused on understanding the transmission cycle of C. jejuni, as well as other zoonotic pathogens originating from wild mice.

Detection of multi-antibiotic resistant Campylobacter coli and Campylobacter jejuni in beef, mutton, chicken and water buffalo meat in Ahvaz, Iran

Campylobacter jejuni and C. coli are the main causes of gastrointestinal diseases in humans even in industrialized countries affecting public health. The aim of the current study was to evaluate the occurrence and antibiotic resistance of C. jejuni and C. coli in chicken meat, beef, mutton and water buffalo meat slaughtered in Ahvaz city, Iran. A total of 380 samples including chicken meat from industrial abattoirs (n = 150), chicken meat from traditional abattoirs (n = 50), fresh packed chicken meat from local markets (n = 30) and beef, mutton and water buffalo meat from industrial abattoirs (50 samples for each meat) in Ahvaz,were collected and tested for the presence of Campylobacter spp. The procedure was one-step enrichment in Preston enrichment broth followed by plating on supplemented blood agar for 24 hr under microaerophilic conditions at 42 ˚C. Suspected colonies were tested by polymerase chain reaction assay and susceptibility of the confirmed isolates to various antibiotics was investigated by the Kirby-Bauer disk diffusion method. Overall, 32 samples (8.40%) were contaminated with Campylobacter spp. Mutton was the most contaminated meat (24%), while fresh packed chicken meat were not contaminated. Among the 32 isolates, 40.60%, 34.40%, 21.90%, and 15.60% were resistant to tetracycline, ciprofloxacin, ampicillin, and streptomycin, respectively. Moreover, a high number of multi-antibiotic resistant Campylobacter spp. was determined. Since foods of animal origin are the most sources of Campylobacter infection, the presence of resistant strains to antibiotics is a potential risk to public health.

Molecules Autoinducer 2 and cjA and Their Impact on Gene Expression in

Quorum sensing is a widespread form of cell-to-cell communication, which is based on the production of signaling molecules known as autoinducers (AIs). The first group contains highly species-specific N-acyl homoserine lactones (N-AHLs), generally known as AI-1, which are produced by AHL synthase. The second group, possessing the characteristic structure of a furanone ring, are known as AI-2. The enzyme responsible for their production is S-ribosylhomocysteine lyase (LuxS). In <i>Campylobacter jejuni</i>, AI-2 and LuxS play a role in many important processes, including biofilm formation, stress response, motility, expression of virulence factors, and colonization. However, neither the receptor protein nor the exact structure of the AI-2 molecule have been identified to date. Similarly, little is known about the possible existence of AHL-synthase producing AI-1 and its impact on gene expression. Recently, an analogue of homoserine lactone, called cjA, was isolated from a cell-free supernatant of <i>C. jejuni</i> strain<i></i> 81–176 and from the food isolate c11. The molecule cjA particularly impacted the expression of virulence factors and biofilm formation. This review summarizes the role of AI-2 and cjA in the context of biofilm formation, motility, stress responses, and expression of virulence factors.

Campylobacter jejuni bile exposure influences outer membrane vesicles protein content and bacterial interaction with epithelial cells

Campylobacter jejuni is a prevalent human pathogen and a major cause of bacterial gastroenteritis in the world. In humans, C. jejuni colonizes the intestinal tract and its tolerance to bile is crucial for bacteria to survive and establish infection. C. jejuni produces outer membrane vesicles (OMVs) which have been suggested to be involved in virulence. In this study, the proteome composition of C. jejuni OMVs in response to low concentration of bile was investigated. We showed that exposure of C. jejuni to low concentrations of bile, similar to the concentration in cecum, induced significant changes in the protein profile of OMVs released during growth without affecting the protein profile of the bacteria. This suggests that bile influences a selective packing of the OMVs after bacterial exposure to low bile. A low concentration of bile was found to increase bacterial adhesion to intestinal epithelial cells, likely by an enhanced hydrophobicity of the cell membrane following exposure to bile. The increased bacterial adhesiveness was not associated with increased invasion, instead bile exposure decreased C. jejuni invasion. OMVs released from bacteria upon exposure to low bile showed to increase both adhesion and invasion of non-bile-exposed bacteria into intestinal epithelial cells. These findings suggest that C. jejuni in environments with low concentrations of bile produce OMVs that facilitates colonization of the bacteria, and this could potentially contribute to virulence of C. jejuni in the gut.

A Comparative Evaluation Study of Growth Conditions for Culturing the Isolates of Campylobacter spp

Campylobacter is one of the leading causes of foodborne travelers' diarrhea worldwide. Although a large number cases of campylobacteriosis go undiagnosed or unreported, it is considered as the second most common foodborne illness in the USA affecting over 1.3 million individuals every year. Of various Campylobacter species, C. jejuni, C. coli, and C. lari have been accounted for causing more than 99% of human infections. Thus, there is a need to have efficient isolation method to protect public health on food safety and monitoring the burden of campylobacteriosis. Nevertheless, it is a challenging task as the exposure of environmental stress during isolation process makes Campylobacter species less culturable. Sixteen Campylobacter spp. were used to evaluate the current protocols used in Campylobacter isolation. For optimal recovery, a range of growth media (Bolton, Columbia, Muller Hinton, CVA Campy and mCCDA), incubation temperatures, and additional supplements (including antibiotics) were tested. Blood agars without antibiotics were sufficient for the initial recovery. Afterward, the isolates could grow on agars without any supplements, and in some cases growth was observed in the presence of antibiotics. Incubation at 37 °C was found to be the optimal temperature for the recovery and the growth of most species. Additionally, a food adulteration study was also carried out by artificially contaminating three food matrices that included egg, milk, and infant cereal, with two isolates of C. jejuni and C. coli. Results of this study should provide the insight for culturing and isolation of Campylobacter from food and other sources.

Cj0440c Affects Flagella Formation and In Vivo Colonization of Erythromycin-Susceptible and -Resistant Campylobacter jejuni

Campylobacter jejuni is one of the most common foodborne pathogen worldwide. A putative transcriptional regulator, Cj0440c, was up-regulated in the erythromycin-resistant C. jejuni, however, the precise role of Cj0440c is yet to be determined. The aim of this study was to determine the biological functions of Cj0440c. The Cj0440c isogenic mutants were constructed from erythromycin-susceptible C. jejuni NCTC 11168 (S) and -resistant C. jejuni 68-ER (R), designating as SM and RM, respectively. The isogenic Cj0440c mutants (SM and RM) and parental strains (S and R) were subjected to microarray and qRT-PCR analysis to examine the transcriptional profile changes contributed by Cj0440c. The antimicrobial susceptibility, flagellar morphology, in vitro growth and in vivo colonization in chickens were carried out to analyze the biological function of Cj0440c. The results showed that 17 genes were down-regulated in SM compared to S, while 9 genes were down-regulated in RM compared to R. The genes with transcriptional change were mainly involved in flagella biosynthesis and assembly. Using transmission electron microscopy, we found that the filaments were impaired in SM and lost in RM. The chicken colonization experiments showed that Cj0440c mutants (SM and RM) had reduced colonization ability in chickens when compared with corresponding parental strains (S and R). In conclusion, Cj0440c regulates flagella biosynthesis and assembly, and consequently affect the in vivo colonization of erythromycin-susceptible and -resistant C. jejuni.

Lack of Evidence That Selenium-Yeast Improves Chicken Health and Modulates the Caecal Microbiota in the Context of Colonization by Campylobacter jejuni

Faced with ever-increasing demand, the industrial production of food animals is under pressure to increase its production. In order to keep productivity, quality, and safety standards up while reducing the use of antibiotics, farmers are seeking new feed additives. In chicken production, one of these additives is selenium. This element is expected to confer some advantages in terms of animal health and productivity, but its impact on chicken intestinal microbiota as well as on the carriage of foodborne pathogens is unknown. In this study, chickens raised in a level 2 animal facility were fed or not 0.3 ppm of in-feed selenium-yeast until 35 days of age and were inoculated or not with the foodborne pathogen Campylobacter jejuni at the age of 14 days. At the end of the study, body weight, seric IgY, intestinal IgA, seric gluthatione peroxydase activity, the caecal microbiota (analyzed by MiSeq 16S rRNA gene sequencing), and C. jejuni caecal levels were analyzed. The experiment was completely replicated twice, with two independent batches of chickens. This study revealed that, for healthy chickens raised in very good hygienic conditions, selenium-yeast does not influence the bird’s body weight and lowers their seric gluthatione peroxidase activity as well as their intestinal IgA concentrations. Furthermore, selenium-yeast did not modify the caecal microbiota or the colonization of C. jejuni. The results also showed that C. jejuni colonization does not impact any of the measured chicken health parameters and only slightly impacts the caecal microbiota. This study also clearly illustrated the need for true biological replication (independent animal trials) when assessing the microbiota shifts associated with treatments as the chickens microbiotas clearly clustered according to study replicate.

Comparison of Proteomics Profiles of Campylobacter jejuni Strain Bf under Microaerobic and Aerobic Conditions

Campylobacter jejuni accounts for one of the leading causes of foodborne bacterial enteritis in humans. Despite being considered an obligate microaerobic microorganism, C. jejuni is regularly exposed to oxidative stress. However, its adaptive strategies to survive the atmospheric oxygen level during transmission to humans remain unclear. Recently, the clinical C. jejuni strain Bf was singled out for its unexpected ability to grow under ambient atmosphere. Here, we aimed to understand better the biological mechanisms underlying its atypical aerotolerance trait using two-dimensional protein electrophoresis, gene expression, and enzymatic activities. Forty-seven proteins were identified with a significantly different abundance between cultivation under microaerobic and aerobic conditions. The over-expressed proteins in aerobiosis belonged mainly to the oxidative stress response, enzymes of the tricarboxylic acid cycle, iron uptake, and regulation, and amino acid uptake when compared to microaerobic conditions. The higher abundance of proteins related to oxidative stress was correlated to dramatically higher transcript levels of the corresponding encoding genes in aerobic conditions compared to microaerobic conditions. In addition, a higher catalase-equivalent activity in strain Bf was observed. Despite the restricted catabolic capacities of C. jejuni, this study reveals that strain Bf is equipped to withstand oxidative stress. This ability could contribute to emergence and persistence of particular strains of C. jejuni throughout food processing or macrophage attack during human infection.

Persistence and Potential Viable but Non-culturable State of Pathogenic Bacteria during Storage of Digestates from Agricultural Biogas Plants

Despite the development of on-farm anaerobic digestion as a process for making profitable use of animal by-products, factors leading to the inactivation of pathogenic bacteria during storage of digestates remain poorly described. Here, a microcosm approach was used to evaluate the persistence of three pathogenic bacteria (Salmonella enterica Derby, Campylobacter coli and Listeria monocytogenes) in digestates from farms, stored for later land spreading. Nine samples, including raw digestates, liquid fractions of digestate and composted digestates, were inoculated with each pathogen and maintained for 40 days at 24°C. Concentrations of pathogens were monitored using culture and qPCR methods. The persistence of L. monocytogenes, detected up to 20 days after inoculation, was higher than that of Salmonella Derby, detected for 7-20 days, and of C. coli (not detected after 7 days). In some digestates, the concentration of the pathogens by qPCR assay was several orders of magnitude higher than the concentration of culturable cells, suggesting a potential loss of culturability and induction of Viable but Non-Culturable (VBNC) state. The potential VBNC state which was generally not observed in the same digestate for the three pathogens, occurred more frequently for C. coli and L. monocytogenes than for Salmonella Derby. Composting a digestate reduced the persistence of seeded L. monocytogenes but promoted the maintenance of Salmonella Derby. The effect of NH[Formula: see text]/NH3 on the culturability of C. coli and Salmonella Derby was also shown. The loss of culturability may be the underlying mechanism for the regrowth of pathogens. We have also demonstrated the importance of using molecular tools to monitor pathogens in environmental samples since culture methods may underestimate cell concentration. Our results underline the importance of considering VBNC cells when evaluating the sanitary effect of an anaerobic digestion process and the persistence of pathogens during the storage of digestates and subsequent land spreading.

Recent Advances in Screening of Anti-Campylobacter Activity in Probiotics for Use in Poultry

Campylobacteriosis is the most common cause of bacterial gastroenteritis worldwide. Campylobacter species involved in this infection usually include the thermotolerant species Campylobacter jejuni. The major reservoir for C. jejuni leading to human infections is commercial broiler chickens. Poultry flocks are frequently colonized by C. jejuni without any apparent symptoms. Risk assessment analyses have identified the handling and consumption of poultry meat as one of the most important sources of human campylobacteriosis, so elimination of Campylobacter in the poultry reservoir is a crucial step in the control of this foodborne infection. To date, the use of probiotics has demonstrated promising results to reduce Campylobacter colonization. This review provides recent insights into methods used for probiotic screening to reduce the prevalence and colonization of Campylobacter at the farm level. Different eukaryotic epithelial cell lines are employed to screen probiotics with an anti-Campylobacter activity and yield useful information about the inhibition mechanism involved. These in vitro virulence models involve only human intestinal or cervical cell lines whereas the use of avian cell lines could be a preliminary step to investigate mechanisms of C. jejuni colonization in poultry in the presence of probiotics. In addition, in vivo trials to evaluate the effect of probiotics on Campylobacter colonization are conducted, taking into account the complexity introduced by the host, the feed, and the microbiota. However, the heterogeneity of the protocols used and the short time duration of the experiments lead to results that are difficult to compare and draw conclusions at the slaughter-age of broilers. Nevertheless, the combined approach using complementary in vitro and in vivo tools (cell cultures and animal experiments) leads to a better characterization of probiotic strains and could be employed to assess reduced Campylobacter spp. colonization in chickens if some parameters are optimized.