Examination of Campylobacter jejuni putative adhesins leads to the identification of a new protein, designated FlpA, required for chicken colonization

Galactomannan and Vicilin from Fenugreek Seeds (Trigonella foenum-graecum) Impair Early Pathogen-Host Interaction of Campylobacter jejuni with Intestinal Cells via JlpA

Campylobacter jejuni is the leading cause of severe enteritis worldwide. Identification of natural products against C. jejuni that inhibit early-stage host-pathogen interactions is a promising strategy, particularly by blocking bacterial adhesion to and invasion into the host cells. This should help to reduce the bacterial load in vector animals. From the seeds of Trigonella foenum-graecum, an aqueous extract (fenugreek high molecular fraction) of high-molecular compounds (polysaccharides, proteins) was obtained. The polysaccharide was characterized as galactomannan (1,4-mannose backbone, substituted at O-6 with single galactose residues and galactose oligosaccharide chains). The protein part consisted of 50 kDa vicilin as the main compound. The fenugreek high molecular fraction did not influence proliferation of C. jejuni and viability of Caco-2 cells (1 - 1000 µg/mL). The fenugreek high molecular fraction reduced bacterial adhesion to Caco-2 significantly (500 - 1000 µg/mL), which was due to an interaction with the bacterial adhesin JlpA, preventing the interaction of this outer membrane protein to its ligand HSP90α (IC50 = 23.4 µg/mL). Bacterial invasion was reduced significantly. Both polysaccharides as well as vicilin contribute to the observed antiadhesive effect. As vicilin-like proteins are widely found in plants from the Fabaceae family, a vicilin-enriched protein preparation from Pisum sativum was investigated for antiadhesive activity. These findings suggest that fenugreek seeds or vicilin-rich plant extracts could be used to develop novel strategies to control C. jejuni infections in food-producing animals, ultimately helping to decrease the prevalence of campylobacteriosis in humans.

Pathogenicity and virulence of Campylobacter jejuni: What do we really know?

Campylobacter jejuni is the leading cause of bacterial gastroenteritis and is a major public health concern worldwide. Despite its importance, our understanding of how C. jejuni causes diarrhoea and interacts with its hosts is limited due to the absence of appropriate infection models and established virulence factors found in other enteric pathogens. Additionally, despite its genetic diversity, non-pathogenic C. jejuni strains are unknown. Regardless of these limitations, significant progress has been made in understanding how C. jejuni uses a complex array of factors which aid the bacterium to survive and respond to host defences. This review provides an update on fitness and virulence determinants of this important pathogen and questions our knowledge on these determinants that are often based on inferred genomics knowledge and surrogate infection models.

Campylobacter californiensis sp. nov., isolated from cattle and feral swine

Nine Campylobacter strains were isolated from cattle and feral swine faeces: three were recovered during a 2007 Campylobacter-associated outbreak linked to a dairy, and the other six were isolated during a 2009-2010 survey of farms and ranches in Central California. The species identification of these strains could not be determined by 16S rRNA gene sequencing but were most similar to Campylobacter concisus and Campylobacter mucosalis. Additional atpA typing indicated that the nine strains composed a discrete novel clade related to C. concisus and C. mucosalis. A polyphasic study was undertaken here to clarify their taxonomic position. Phylogenetic analyses were performed based on 16S rRNA gene sequences and the concatenated sequences of 330 core genes. The core gene analysis placed the nine strains into a clade well separated from the other Campylobacter taxa, indicating that these strains represent a novel Campylobacter species. Pairwise digital DNA-DNA hybridization and average nucleotide identity values between these strains and other campylobacters are lower than 16 and 73%, respectively, further supporting their placement into a novel taxon. Standard phenotypic testing was performed. All strains are microaerobic or anaerobic, motile, Gram-negative, slightly-curved rods that are oxidase positive but catalase negative. Strains can be distinguished from the other catalase-negative Campylobacter species using phenotypic markers such as motility, oxidase activity, cephalothin resistance, hippuricase activity, growth at 30 °C, and α-haemolysis. The data presented here show that these strains represent a novel species within Campylobacter, for which the name Campylobacter californiensis sp. nov. (type strain RM6914T=LMG 32304T=CCUG 75329T) is proposed.

Activation of the l-fucose utilization cluster in Campylobacter jejuni induces proteomic changes and enhances Caco-2 cell invasion and fibronectin binding

Most Campylobacter jejuni isolates carry the fucose utilization cluster (Cj0480c-Cj0489) that supports the metabolism of l-fucose and d-arabinose. In this study we quantified l-fucose and d-arabinose metabolism and metabolite production, and the impact on Caco-2 cell interaction and binding to fibronectin, using C. jejuni NCTC11168 and the closely related human isolate C. jejuni strain 286. When cultured with l-fucose and d-arabinose, both isolates showed increased survival and production of acetate, pyruvate and succinate, and the respective signature metabolites lactate and glycolic acid, in line with an overall upregulation of l-fucose cluster proteins. In vitro Caco-2 cell studies and fibronectin-binding experiments showed a trend towards higher invasion and a significantly higher fibronectin binding efficacy of C. jejuni NCTC11168 cells grown with l-fucose and d-arabinose, while no significant differences were found with C. jejuni 286. Both fibronectin binding proteins, CadF and FlpA, were detected in the two isolates, but were not significantly differentially expressed in l-fucose or d-arabinose grown cells. Comparative proteomics analysis linked the C. jejuni NCTC11168 phenotypes uniquely to the more than 135-fold upregulated protein Cj0608, putative TolC-like component MacC, which, together with the detected Cj0606 and Cj0607 proteins, forms the tripartite secretion system MacABC with putative functions in antibiotic resistance, cell envelope stress response and virulence in Gram negative pathogenic bacteria. Further studies are required to elucidate the role of the MacABC system in C. jejuni cell surface structure modulation and virulence.

Genes involved in the adhesion and invasion of Arcobacter butzleri

Arcobacter butzleri is a foodborne pathogen that mainly causes enteritis in humans, but the number of cases of bacteraemia has increased in recent years. However, there is still limited knowledge on the pathogenic mechanisms of this bacterium. To investigate how A. butzleri causes disease, single knockout mutants were constructed in the cadF, ABU_RS00335, ciaB, and flaAB genes, which might be involved in adhesion and invasion properties. These mutants and the isogenic wild-type (WT) were then tested for their ability to adhere and invade human Caco-2 and HT29-MTX cells. The adhesion and invasion of A. butzleri RM4018 strain was also visualized by a Leica CTR 6500 confocal microscope. The adhesion and invasion abilities of mutants lacking the invasion antigen CiaB or a functional flagellum were lower than those of the WTs. However, the extent of the decrease varied depending on the strain and/or cell line. Mutants lacking the fibronectin (FN)-binding protein CadF consistently exhibited reduced abilities, while the inactivation of the other studied FN-binding protein, ABU_RS00335, led to a reduction in only one of the two strains tested. Therefore, the ciaB and flaAB genes appear to be important for A. butzleri adhesion and invasion properties, while cadF appears to be indispensable.

Campylobacter devanensis sp. nov., Campylobacter porcelli sp. nov., and Campylobacter vicugnae sp. nov., three novel Campylobacter lanienae-like species recovered from swine, small ruminants, and camelids

In a previous study characterizing Campylobacter strains deficient in selenium metabolism, 50 strains were found to be similar to, but distinct from, the selenonegative species Campylobacter lanienae. Initial characterization based on multilocus sequence typing and the phylogeny of a set of 20 core genes determined that these strains form three putative taxa within the selenonegative cluster. A polyphasic study was undertaken here to further clarify their taxonomic position within the genus. The 50 selenonegative strains underwent phylogenetic analyses based on the sequences of the 16S rRNA gene and an expanded set of 330 core genes. Standard phenotypic testing was also performed. All strains were microaerobic and anaerobic, Gram-negative, spiral or curved cells with some displaying coccoid morphologies. Strains were motile, oxidase, catalase, and alkaline phosphatase positive, urease negative, and reduced nitrate. Strains within each clade had unique phenotypic profiles that distinguished them from other members of the genus. Core genome phylogeny clearly placed the 50 strains into three clades. Pairwise average nucleotide identity and digital DNA-DNA hybridization values were all below the recommended cut-offs for species delineation with respect to C. lanienae and other related Campylobacter species. The data presented here clearly show that these strains represent three novel species within the genus, for which the names Campylobacter devanensis sp. nov. (type strain RM3662T=LMG 33097T=NCTC 15074T), Campylobacter porcelli sp. nov. (type strain RM6137T=LMG 33098T=CCUG 77054T=NCTC 15075T) and Campylobacter vicugnae sp. nov. (type strain RM12175T=LMG 33099T=CCUG 77055T=NCTC 15076T) are proposed.

Identification and functional characterization of putative ligand binding domain(s) of JlpA protein of Campylobacter jejuni

Among the major Surface Exposed Colonization Proteins (SECPs) of Campylobacter jejuni (C. jejuni), Jejuni lipoprotein A (JlpA) plays a crucial role in host cell adhesion specifically by binding to the N-terminal domain of the human heat shock protein 90α (Hsp90α-NTD). Although the JlpA binding to Hsp90α activates NF-κB and p38 MAP kinase pathways, the underlying mechanism of JlpA association with the cellular receptor remains unclear. To this end, we predicted two potential receptor binding sites within the C-terminal domain of JlpA: one spanning from amino acid residues Q332-A354 and the other from S258-T295; however, the latter exhibited weaker binding. To assess the functional attributes of these predicted sequences, we generated two JlpA mutants (JlpAΔ1: S258-T295; JlpAΔ2: Q332-A354) and assessed the Hsp90α-binding affinity-kinetics by in vitro and ex vivo experiments. Our findings confirmed that the residues Q332-A354 are of greater importance in host cell adhesion with a measurable impact on cellular responses. Further, thermal denaturation by circular dichroism (CD) confirmed that the reduced binding affinity of the JlpAΔ2 to Hsp90α is not associated with protein folding or stability. Together, this study provides a possible framework for determining the molecular function of designing rational inhibitors efficiently targeting JlpA.

High molecular/low acetylated chitosans reduce adhesion of Campylobacter jejuni to host cells by blocking JlpA

Infections caused by Campylobacter spp. are a major cause of severe enteritis worldwide. Multifactorial prevention strategies are necessary to reduce the prevalence of Campylobacter. In particular, antiadhesive strategies with specific inhibitors of early host-pathogen interaction are promising approaches to reduce the bacterial load. An in vitro flow cytometric adhesion assay was established to study the influence of carbohydrates on the adhesion of C. jejuni to Caco-2 cells. Chitosans with a high degree of polymerization and low degree of acetylation were identified as potent antiadhesive compounds, exerting significant reduction of C. jejuni adhesion to Caco-2 cells at non-toxic concentrations. Antiadhesive and also anti-invasive effects were verified by confocal laser scanning microscopy. For target identification, C. jejuni adhesins FlpA and JlpA were expressed in Escherichia coli ArcticExpress, and the influence of chitosan on binding to fibronectin and HSP90α, respectively, was investigated. While no effects on FlpA binding were found, a strong inhibition of JlpA-HSP90α binding was observed. To simulate real-life conditions, chicken meat was inoculated with C. jejuni, treated with antiadhesive chitosan, and the bacterial load was quantified. A strong reduction of C. jejuni load was observed. Atomic force microscopy revealed morphological changes of C. jejuni after 2 h of chitosan treatment, indicating disturbance of the cell wall and sacculi formation by electrostatic interaction of positively charged chitosan with the negatively charged cell surface. In conclusion, our data indicate promising antiadhesive and anti-invasive potential of high molecular weight, strongly de-acetylated chitosans for reducing C. jejuni load in livestock and food production. KEY POINTS: • Antiadhesive effects of chitosan with high DP/low DA against C. jejuni to host cells • Specific targeting of JlpA/Hsp90α interaction by chitosan • Meat treatment with chitosan reduces C. jejuni load.

Pathogenicity assessment of Arcobacter butzleri isolated from Canadian agricultural surface water

BACKGROUND

Water is considered a source for the transmission of Arcobacter species to both humans and animals. This study was conducted to assess the prevalence, distribution, and pathogenicity of A. butzleri strains, which can potentially pose health risks to humans and animals. Cultures were isolated from surface waters of a mixed-use but predominately agricultural watershed in eastern Ontario, Canada. The detection of antimicrobial resistance (AMR) and virulence-associated genes (VAGs), as well as enterobacterial repetitive intergenic consensus-polymerase chain reaction (ERIC-PCR) assays were performed on 913 A. butzleri strains isolated from 11 agricultural sampling sites.

RESULTS

All strains were resistant to one or more antimicrobial agents, with a high rate of resistance to clindamycin (99%) and chloramphenicol (77%), followed by azithromycin (48%) and nalidixic acid (49%). However, isolates showed a significantly (p < 0.05) high rate of susceptibility to tetracycline (1%), gentamycin (2%), ciprofloxacin (4%), and erythromycin (5%). Of the eight VAGs tested, ciaB, mviN, tlyA, and pldA were detected at high frequency (> 85%) compared to irgA (25%), hecB (19%), hecA (15%), and cj1349 (12%) genes. Co-occurrence analysis showed A. butzleri strains resistant to clindamycin, chloramphenicol, nalidixic acid, and azithromycin were positive for ciaB, tlyA, mviN and pldA VAGs. ERIC-PCR fingerprint analysis revealed high genetic similarity among strains isolated from three sites, and the genotypes were significantly associated with AMR and VAGs results, which highlight their potential environmental ubiquity and potential as pathogenic.

CONCLUSIONS

The study results show that agricultural activities likely contribute to the contamination of A. butzleri in surface water. The findings underscore the importance of farm management practices in controlling the potential spread of A. butzleri and its associated health risks to humans and animals through contaminated water.

Molecular structures mediating adhesion of Campylobacter jejuni to abiotic and biotic surfaces

Microaerophilic, Gram-negative Campylobacter jejuni is the causative agent of campylobacteriosis, the most common bacterial gastrointestinal infection worldwide. Adhesion is the crucial first step in both infection or interaction with the host and biofilm formation, and is a critical factor for bacterial persistence. Here we describe the proteins and other surface structures that promote adhesion to various surfaces, including abiotic surfaces, microorganisms, and animal and human hosts. In addition, we provide insight into the distribution of adhesion proteins among strains from different ecological niches and highlight unexplored proteins involved in C. jejuni adhesion. Protein-protein, protein-glycan, and glycan-glycan interactions are involved in C. jejuni adhesion, with different factors contributing to adhesion to varying degrees under different circumstances. As adhesion is essential for survival and persistence, it represents an interesting target for C. jejuni control. Knowledge of the adhesion process is incomplete, as different molecular and functional aspects have been studied for different structures involved in adhesion. Therefore, it is important to strive for an integration of different approaches to obtain a clearer picture of the adhesion process on different surfaces and to consider the involvement of proteins, glycoconjugates, and polysaccharides and their cooperation.

Campylobacter jejuni: targeting host cells, adhesion, invasion, and survival

Campylobacter jejuni, causing strong enteritis, is an unusual bacterium with numerous peculiarities. Chemotactically controlled motility in viscous milieu allows targeted navigation to intestinal mucus and colonization. By phase variation, quorum sensing, extensive O-and N-glycosylation and use of the flagellum as type-3-secretion system C. jejuni adapts effectively to environmental conditions. C. jejuni utilizes proteases to open cell-cell junctions and subsequently transmigrates paracellularly. Fibronectin at the basolateral side of polarized epithelial cells serves as binding site for adhesins CadF and FlpA, leading to intracellular signaling, which again triggers membrane ruffling and reduced host cell migration by focal adhesion. Cell contacts of C. jejuni results in its secretion of invasion antigens, which induce membrane ruffling by paxillin-independent pathway. In addition to fibronectin-binding proteins, other adhesins with other target structures and lectins and their corresponding sugar structures are involved in host-pathogen interaction. Invasion into the intestinal epithelial cell depends on host cell structures. Fibronectin, clathrin, and dynein influence cytoskeletal restructuring, endocytosis, and vesicular transport, through different mechanisms. C. jejuni can persist over a 72-h period in the cell. Campylobacter-containing vacuoles, avoid fusion with lysosomes and enter the perinuclear space via dynein, inducing signaling pathways. Secretion of cytolethal distending toxin directs the cell into programmed cell death, including the pyroptotic release of proinflammatory substances from the destroyed cell compartments. The immune system reacts with an inflammatory cascade by participation of numerous immune cells. The development of autoantibodies, directed not only against lipooligosaccharides, but also against endogenous gangliosides, triggers autoimmune diseases. Lesions of the epithelium result in loss of electrolytes, water, and blood, leading to diarrhea, which flushes out mucus containing C. jejuni. Together with the response of the immune system, this limits infection time. Based on the structural interactions between host cell and bacterium, the numerous virulence mechanisms, signaling, and effects that characterize the infection process of C. jejuni, a wide variety of targets for attenuation of the pathogen can be characterized. The review summarizes strategies of C. jejuni for host-pathogen interaction and should stimulate innovative research towards improved definition of targets for future drug development. KEY POINTS: • Bacterial adhesion of Campylobacter to host cells and invasion into host cells are strictly coordinated processes, which can serve as targets to prevent infection. • Reaction and signalling of host cell depend on the cell type. • Campylobacter virulence factors can be used as targets for development of antivirulence drug compounds.

Antimicrobial Resistance and Pathogenicity of Aliarcobacter butzleri Isolated from Poultry Meat

Aliarcobacter butzleri (A. butzleri) is an emergent zoonotic food-related pathogen that can be transmitted through the consumption of poultry meat. Data regarding the pathogenicity and resistance of A. butzleri are still scarce, and the presence of virulent MDR strains of this zoonotic pathogen in poultry meat is an issue of particular concern to public health. This study aimed to characterize the pathogenicity and antimicrobial resistance profiles of A. butzleri strains isolated from poultry meat sold at retail markets in São Paulo, Brazil. The minimum inhibitory concentrations of 27 strains were determined using the broth microdilution method. The results showed that 77.7% of the isolates were resistant to clindamycin, 62.9% to florfenicol, 59.2% to nalidixic acid, 11.1% to azithromycin, 7.4% to ciprofloxacin and telithromycin, and 3.7% to erythromycin and tetracycline, although all were susceptible to gentamicin. Moreover, 55.5% of the virulent isolates were also multidrug-resistant (MDR). Three strains were selected for pathogenicity tests in vitro and in vivo. The tested strains expressed weak/moderate biofilm production and showed a diffuse adhesion pattern (3 h) in HeLa cells and toxicity in Vero cells (24 h). Experimental inoculation in 11-week-old chicks induced a transitory inflammatory enteritis. Intestinal hemorrhage and destruction of the intestinal crypts were observed in the rabbit ileal loop test. Considering the fact that Brazil is a major exporter of poultry meat, the data from this study point to the need of improvement of the diagnostic tools, as well as of the adoption of surveillance guidelines and more specific control strategies to ensure food safety, reducing the presence of pathogenic MDR strains in broilers.

How It All Begins: Bacterial Factors Mediating the Colonization of Invertebrate Hosts by Beneficial Symbionts

Beneficial associations with bacteria are widespread across animals, spanning a range of symbiont localizations, transmission routes, and functions. While some of these associations have evolved into obligate relationships with permanent symbiont localization within the host, the majority require colonization of every host generation from the environment or via maternal provisions. Across the broad diversity of host species and tissue types that beneficial bacteria can colonize, there are some highly specialized strategies for establishment yet also some common patterns in the molecular basis of colonization. This review focuses on the mechanisms underlying the early stage of beneficial bacterium-invertebrate associations, from initial contact to the establishment of the symbionts in a specific location of the host's body. We first reflect on general selective pressures that can drive the transition from a free-living to a host-associated lifestyle in bacteria. We then cover bacterial molecular factors for colonization in symbioses from both model and nonmodel invertebrate systems where these have been studied, including terrestrial and aquatic host taxa. Finally, we discuss how interactions between multiple colonizing bacteria and priority effects can influence colonization. Taking the bacterial perspective, we emphasize the importance of developing new experimentally tractable systems to derive general insights into the ecological factors and molecular adaptations underlying the origin and establishment of beneficial symbioses in animals.

Case of necrotic enteritis associated with campylobacteriosis and coccidiosis in an adult Indian peacock (Pavo cristatus)

Background

To date, Campylobacter jejuni has not been found to be pathogenic to peafowl. The available publications show that out of a total of 44 samples tested from peafowl, this bacterium was isolated only in two cases. Eimeria pavonina infestations in the peafowl have been described, but no fatal cases have been reported yet.

Case presentation

The four-year-old peacock was presented with chronic diarrhea, emaciation and weakness. Post mortem examination revealed enlarged and pale kidneys, small intestinal mucosal necrosis and thickening of intestinal wall, and pericardial effusion. The histopathological examination revealed necrotic enteritis with marked mononuclear cells infiltration associated with the presence of coccidia, additionally there was histological evidence of septicemia in liver and kidneys. Bacteria identification was based on light microscopy of the small intestine sample, culture, and biochemical tests. Further identification was based on PCR. Antimicrobial susceptibility profile was created by determination of minimal inhibitory concentration (MIC) values for 6 antimicrobial agents from 5 different classes. PCR assays were performed to detect virulence factors genes responsible for motility, cytolethal distending toxin production, adhesion and internalization. Bacteriology of the small intestine sample showed abundant growth almost exclusively of Campylobacter jejuni, resistant to ciprofloxacin, gentamycin and ampicillin. Bacteria was sensitive to Amoxicillin + clavulanic acid, tetracycline, and erythromycin. All tested virulence factors genes have been detected. The parasitological examination was performed by microscopic examination of fresh faeces and intestinal content, and revealed the moderate number of Eimeria pavonina, Histomonas meleagridis, single Capillaria spp. eggs as well Heterakis spp. like parasites.

Conclusion

The above case shows that a virulent isolate of Campylobacter jejuni in combination with a parasitic invasion may cause chronic enteritis in peafowl, which most likely led to extreme exhaustion of the host organism and death.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12917-022-03260-1.

Genomic and Phenotypic Characteristics in Geographically Separated Clinical Campylobacter jejuni ST353CC Isolates

Campylobacter jejuni fecal isolates of eight international travelers, 5 of which had traveled to Ecuador and 3 to Bangladesh, were characterized, and the possible relationship between bacterial traits and clinical symptoms was further analyzed. All eight isolates belonged to the same Multi-Locus Sequence Type clonal complex (ST353CC). The three isolates from Bangladesh were all of the same sequence type (ST-9438), and when compared to isolates of various other sequence types, they had a larger quantity of unique genetic content, higher expression levels of some putative virulence genes involved in adhesion and invasion (flpA, ciaB and iamA), and showed higher adhesion levels to human HT-29 colon cancer cells in an in vitro infection model. However, in contrast to the seemingly higher pathogenic potential of these bacterial isolates, travelers infected with the ST-9438 isolates had no or only very mild symptoms, whereas the other individuals, whose bacterial isolates seemed to have less pathogenic potential, generally reported severe symptoms. When studying the 16S rRNA gene-based fecal microbiota in samples collected prior to travel, there was an individual variation in the relative abundance of the three major bacterial phyla Actinobacteria, Bacteroidetes and Firmicutes, but there were no associations between composition and diversity of microbiota and development of severe symptoms from the infection. It remains to be confirmed by larger studies whether an individual's characteristics such as gut microbiota, might be related to the severity of symptoms in Campylobacter infections.

Genomic Characterisation of Campylobacter jejuni Isolates Recovered During Commercial Broiler Production

Background:Campylobacter is commonly transmitted to humans from chickens. Campylobacter jejuni is the species most frequently associated with human illness, and the most prevalent species recovered from poultry.

Objective: The objective of this study was to analyse a sub-population of C. jejuni from two broiler flocks on the farm and at slaughter using whole-genome sequencing to gain insights into the changes in the Campylobacter population during broiler production, including changes in virulence and antimicrobial resistance profiles.

Methods: In this study, ten composite faecal samples (n=10), obtained by pooling ten fresh faecal samples (n=10), were collected in the broiler house on two farms on days 14, 21, 28, and 34 (n=80) and ten composite (n=10) caecal samples were collected at the time of slaughter for each flock (n=20). These were tested for C. jejuni using the ISO 10272-2:2016 method. Seven isolates were randomly selected from each of the nine Campylobacter-positive sampling points (n=63) and were subjected to antimicrobial susceptibility tests. Their genomes were sequenced and the data obtained was used to characterise the population structure, virulence, antimicrobial resistance determinants and inter-strain variation.

Results: The Farm 1 isolates had three MLST types (ST257-257, ST814-661 and ST48-48) while those on Farm 2 were ST6209-464 and ST9401. Interestingly, only the MLST types positive for most of the virulence genes tested in this study persisted throughout the production cycle, and the detection of antimicrobial resistance determinants (gyrA T86I and tetO) increased after thinning and at slaughter, with the detection of new strains.

Conclusion: The persistence of the most virulent strains detected in this study throughout the production cycle has important implications for the risk to consumers and requires further investigation. The detection of new strains within the population corresponding with the time of thinning and transportation reflects previous reports and provides further evidence that these activities pose a risk of introducing new Campylobacter strains to broiler batches.

Virulence factors of foodborne pathogen Campylobacterjejuni

Campylobacter jejuni is a highly frequent cause of gastrointestinal foodborne disease in humans throughout the world. Disease outcomes vary from mild to severe diarrhea, and in rare cases the Guillain-Barré syndrome or reactive arthritis can develop as a post-infection complication. Transmission to humans usually occurs via the consumption of a range of foods, especially those associated with the consumption of raw or undercooked poultry meat, unpasteurized milk, and water-based environmental sources. When associated to food or water ingestion, the C. jejuni enters the human host intestine via the oral route and colonizes the distal ileum and colon. When it adheres and colonizes the intestinal cell surfaces, the C. jejuni is expected to express several putative virulence factors, which cause damage to the intestine either directly, by cell invasion and/or production of toxin(s), or indirectly, by triggering inflammatory responses. This review article highlights various C. jejuni characteristics - such as motility and chemotaxis - that contribute to the biological fitness of the pathogen, as well as factors involved in human host cell adhesion and invasion, and their potential role in the development of the disease. We have analyzed and critically discussed nearly 180 scientific articles covering the latest improvements in the field.

Campylobacter jejuni genotypes are associated with post-infection irritable bowel syndrome in humans

Campylobacter enterocolitis may lead to post-infection irritable bowel syndrome (PI-IBS) and while some C. jejuni strains are more likely than others to cause human disease, genomic and virulence characteristics promoting PI-IBS development remain uncharacterized. We combined pangenome-wide association studies and phenotypic assays to compare C. jejuni isolates from patients who developed PI-IBS with those who did not. We show that variation in bacterial stress response (Cj0145_phoX), adhesion protein (Cj0628_CapA), and core biosynthetic pathway genes (biotin: Cj0308_bioD; purine: Cj0514_purQ; isoprenoid: Cj0894c_ispH) were associated with PI-IBS development. In vitro assays demonstrated greater adhesion, invasion, IL-8 and TNFα secretion on colonocytes with PI-IBS compared to PI-no-IBS strains. A risk-score for PI-IBS development was generated using 22 genomic markers, four of which were from Cj1631c, a putative heme oxidase gene linked to virulence. Our finding that specific Campylobacter genotypes confer greater in vitro virulence and increased risk of PI-IBS has potential to improve understanding of the complex host-pathogen interactions underlying this condition.

Stephanie Peters, Ben Pascoe, et al. use whole-genome sequencing and phenotypic analysis of clinical strains from patients to identify potential genetic factors involved in irritable bowel syndrome resulting from Campylobacter jejuni infection. Their data suggest that genes involved in the bacterial stress response and biosynthetic pathways may contribute toward irritable bowel syndrome, providing further insight into links between Campylobacter genotypes and risk of disease.

Multi-Omics Approach Reveals the Potential Core Vaccine Targets for the Emerging Foodborne Pathogen Campylobacter jejuni

Campylobacter jejuni is a leading cause of bacterial gastroenteritis in humans around the world. The emergence of bacterial resistance is becoming more serious; therefore, development of new vaccines is considered to be an alternative strategy against drug-resistant pathogen. In this study, we investigated the pangenome of 173 C. jejuni strains and analyzed the phylogenesis and the virulence factor genes. In order to acquire a high-quality pangenome, genomic relatedness was firstly performed with average nucleotide identity (ANI) analyses, and an open pangenome of 8,041 gene families was obtained with the correct taxonomy genomes. Subsequently, the virulence property of the core genome was analyzed and 145 core virulence factor (VF) genes were obtained. Upon functional genomics and immunological analyses, five core VF proteins with high antigenicity were selected as potential core vaccine targets for humans. Furthermore, functional annotations indicated that these proteins are involved in important molecular functions and biological processes, such as adhesion, regulation, and secretion. In addition, transcriptome analysis in human cells and pig intestinal loop proved that these vaccine target genes are important in the virulence of C. jejuni in different hosts. Comprehensive pangenome and relevant animal experiments will facilitate discovering the potential core vaccine targets with improved efficiency in reverse vaccinology. Likewise, this study provided some insights into the genetic polymorphism and phylogeny of C. jejuni and discovered potential vaccine candidates for humans. Prospective development of new vaccines using the targets will be an alternative to the use of antibiotics and prevent the development of multidrug-resistant C. jejuni in humans and even other animals.

Bacteriocinogenic probiotics as an integrated alternative to antibiotics in chicken production - why and how?

The misuse of antibiotics in the livestock industry has played an important role in the spread of resistant superbugs with severe health implications for humans. With the recent ban on the use of antibiotics in poultry and poultry feed in Canada and the USA, poultry farmers will have to rely on the use of alternatives to antibiotics (such as feed acidifiers, antibodies, bacteriophages, antimicrobial peptides, prebiotics, and probiotics) to maintain the same productivity and health of their livestock. Of particular interest are bacteriocinogenic probiotics, that is, bacterial strains capable of producing bacteriocins that confer health benefits on the host. These bacterial strains have multiple promising features, such as the ability to attach to the host mucosa, colonize, proliferate, and produce advantageous products such as bacteriocins and short-chain fatty acids. These not only affect pathogenic colonization but improve poultry phenotype as well. Bacteriocins are antimicrobial peptides with multiple promising features such as being non-harmful for human and animal consumption, non-disruptive to the host microbiota eubiosis, non-cytotoxic, and non-carcinogenic. Therefore, bacteriocinogenic probiotics are at the forefront to be excellent candidates for effective replacements to antibiotics. While evidence of their safety and effectiveness is accumulating in vitro and in vivo in inhibiting pathogens while promoting animal health, their safety and history of use in livestock remains unclear and requires additional investigations. In the present paper, we review the safety assessment regulations and commercialization policies on existing and novel bacteriocinogenic and bacteriocin products intended to be used in poultry feed as an alternative to antibiotics.

Genetic characterisation of a subset of Campylobacter jejuni isolates from clinical and poultry sources in Ireland

Campylobacter spp. is a significant and prevalent public health hazard globally. Campylobacter jejuni is the most frequently recovered species from human cases and poultry are considered the most important reservoir for its transmission to humans. In this study, 30 Campylobacter jejuni isolates were selected from clinical (n = 15) and broiler (n = 15) sources from a larger cohort, based on source, virulence, and antimicrobial resistance profiles. The objective of this study was to further characterise the genomes of these isolates including MLST types, population structure, pan-genome, as well as virulence and antimicrobial resistance determinants. A total of 18 sequence types and 12 clonal complexes were identified. The most common clonal complex was ST-45, which was found in both clinical and broiler samples. We characterised the biological functions that were associated with the core and accessory genomes of the isolates in this study. No significant difference in the prevalence of virulence or antimicrobial resistance determinants was observed between clinical and broiler isolates, although genes associated with severe illness such as neuABC, wlaN and cstIII were only detected in clinical isolates. The ubiquity of virulence factors associated with motility, invasion and cytolethal distending toxin (CDT) synthesis in both clinical and broiler C. jejuni genomes and genetic similarities between groups of broiler and clinical C. jejuni reaffirm that C. jejuni from poultry remains a significant threat to public health.

Campylobacter Virulence Factors and Molecular Host-Pathogen Interactions

Campylobacter jejuni and Campylobacter coli can be frequently isolated from poultry and poultry-derived products, and in combination these two species cause a large portion of human bacterial gastroenteritis cases. While birds are typically colonized by these Campylobacter species without clinical symptoms, in humans they cause (foodborne) infections at high frequencies, estimated to cost billions of dollars worldwide every year. The clinical outcome of Campylobacter infections comprises malaise, diarrhea, abdominal pain and fever. Symptoms may continue for up to two weeks and are generally self-limiting, though occasionally the disease can be more severe or result in post-infection sequelae. The virulence properties of these pathogens have been best-characterized for C. jejuni, and their actions are reviewed here. Various virulence-associated bacterial determinants include the flagellum, numerous flagellar secreted factors, protein adhesins, cytolethal distending toxin (CDT), lipooligosaccharide (LOS), serine protease HtrA and others. These factors are involved in several pathogenicity-linked properties that can be divided into bacterial chemotaxis, motility, attachment, invasion, survival, cellular transmigration and spread to deeper tissue. All of these steps require intimate interactions between bacteria and host cells (including immune cells), enabled by the collection of bacterial and host factors that have already been identified. The assortment of pathogenicity-associated factors now recognized for C. jejuni, their function and the proposed host cell factors that are involved in crucial steps leading to disease are discussed in detail.

Revisiting Campylobacter jejuni Virulence and Fitness Factors: Role in Sensing, Adapting, and Competing

Campylobacter jejuni is the leading cause of bacterial foodborne gastroenteritis world wide and represents a major public health concern. Over the past two decades, significant progress in functional genomics, proteomics, enzymatic-based virulence profiling (EBVP), and the cellular biology of C. jejuni have improved our basic understanding of this important pathogen. We review key advances in our understanding of the multitude of emerging virulence factors that influence the outcome of C. jejuni–mediated infections. We highlight, the spatial and temporal dynamics of factors that promote C. jejuni to sense, adapt and survive in multiple hosts. Finally, we propose cohesive research directions to obtain a comprehensive understanding of C. jejuni virulence mechanisms.

Campylobacter sp.: Pathogenicity factors and prevention methods-new molecular targets for innovative antivirulence drugs?

Infections caused by bacterial species from the genus Campylobacter are one of the four main causes of strong diarrheal enteritis worldwide. Campylobacteriosis, a typical food-borne disease, can range from mild symptoms to fatal illness. About 550 million people worldwide suffer from campylobacteriosis and lethality is about 33 million p.a. This review summarizes the state of the current knowledge on Campylobacter with focus on its specific virulence factors. Using this knowledge, multifactorial prevention strategies can be implemented to reduce the prevalence of Campylobacter in the food chain. In particular, antiadhesive strategies with specific adhesion inhibitors seem to be a promising concept for reducing Campylobacter bacterial load in poultry production. Antivirulence compounds against bacterial adhesion to and/or invasion into the host cells can open new fields for innovative antibacterial agents. Influencing chemotaxis, biofilm formation, quorum sensing, secretion systems, or toxins by specific inhibitors can help to reduce virulence of the bacterium. In addition, the unusual glycosylation of the bacterium, being a prerequisite for effective phase variation and adaption to different hosts, is yet an unexplored target for combating Campylobacter sp. Plant extracts are widely used remedies in developing countries to combat infections with Campylobacter. Therefore, the present review summarizes the use of natural products against the bacterium in an attempt to stimulate innovative research concepts on the manifold still open questions behind Campylobacter towards improved treatment and sanitation of animal vectors, treatment of infected patients, and new strategies for prevention. KEY POINTS: • Campylobacter sp. is a main cause of strong enteritis worldwide. • Main virulence factors: cytolethal distending toxin, adhesion proteins, invasion machinery. • Strong need for development of antivirulence compounds.

Detection and identification of adhesins involved in adhesion of Campylobacter jejuni to chicken skin

Campylobacter jejuni is the leading cause of bacterial food poisoning worldwide. Chickens are considered to be one of the major reservoirs of Campylobacter infection in humans due to colonization of their intestinal tract. When the chickens are slaughtered and processed, the entire skin of the carcass becomes contaminated with campylobacters. We observed that the number of C. jejuni attached to chicken skin was reduced significantly after treatment of the skin with sodium hydroxide followed by washing with PBS, implying that adhesion factors involved in binding to C. jejuni may exist on skin. Such potential binding-related proteins present in alkaline extracts of the skin surface were detected by a two-dimensional overlay assay and identified by liquid chromatography mass spectrometry (LC-MS). Chicken serum albumin (CSA) was identified as a major protein in these alkaline extracts and confirmed by ELISA to bind specifically to C. jejuni. Moreover, using the same approach, flagellar hook protein E (FlgE) and major outer membrane protein (MOMP) in C. jejuni were identified as bacterial adhesins that bound to the CSA. The ability to bind CSA was also confirmed using recombinant FlgE and MOMP of C. jejuni expressed in Escherichia coli. The present findings suggest that adhesins expressed on C. jejuni cells may bind specifically via proteins present on the skin, as well as by physical attachment.

Refined functional carbohydrates reduce adhesion of Salmonella and Campylobacter to poultry epithelial cells in vitro

The development of interventions to reduce human foodborne pathogens in the gastrointestinal (GI) tract of chickens will be important for improving the microbial food safety of poultry. Saccharomyces-derived prebiotic refined functional carbohydrates (RFC), composed primarily of β-glucans, mannanoligosaccharides (MOS), and D-mannose have been demonstrated to reduce GI colonization of Salmonella and Campylobacter when administered to poultry. Although they are presumed to inhibit adhesion of pathogens to the GI epithelium, this functionality of RFC has not been well characterized. In this study, we investigated the effects of RFC and other prebiotics on the adhesion of Salmonella Typhimurium and Campylobacter jejuni to the LMH chicken epithelial cell line in vitro. The reduction of adherent pathogens was observed to be dose-dependent with C. jejuni being more sensitive than Salmonella to inhibition by RFC. Comparison of the primary constituent carbohydrates of RFC found D-mannose to inhibit both pathogens less effectively than β-glucan and MOS, suggesting that it contributes less to inhibition of pathogen adhesion than the other carbohydrates. Finally, the reduction of adherent pathogens by RFC was compared with that of fructooligosaccharides (FOS), galactooligosaccharides (GOS), and raffinose. All 4 prebiotics inhibited adhesion of both pathogens to chicken epithelial cells. Reduction of adherent Salmonella was greatest with FOS and lowest with GOS, whereas reduction of adherent C. jejuni was greater with RFC and raffinose than with FOS and GOS. These results will inform future research elucidating mechanisms important to adhesion inhibition of pathogens by RFC and other prebiotics.

Designing an efficient multi-epitope vaccine against Campylobacter jejuni using immunoinformatics and reverse vaccinology approach

Campylobacterjejuni causes acute diarrhea as a leading cause of morbidity and mortality in children especially in the developing countries of Asia and Africa. C.jejuni has been identified as a member of the priority pathogens category due to the sudden emergence of multidrug-resistant isolates. Therefore, it is important to develop a protective vaccine against this pathogen. In the present study, the Reverse vaccinology approach was used to identify vaccine targets from the proteome of diarrheagenic C. jejuni strain NCTC11168 for the development of chimeric vaccine candidates against C. jejuni. Pathogen proteins that have adhesin like properties and role in virulence but not present in the human host were selected for the design of a multi-epitope vaccine. MHC class I & II and B-cell epitopes present in the selected vaccine target proteins were screened using different immunoinformatics tools. The commonly predicted epitopes from their corresponding different servers were selected and further shortlisted based on their immunogenicity, antigenicity, and toxicity analysis. Shortlisted peptides were joined by GPGPG linkers to design a multi-epitope vaccine construct. Immune-modulating adjuvant monophosphoryl lipid sequence was added with the vaccine construct's N terminal using EAAAK linkers to enhance the immunogenicity. The designed vaccine construct was evaluated by antigenicity, allergenicity, solubility, and physicochemical analysis using various bioinformatics tools. A three-dimensional model of vaccine construct was modeled by the Phyre2 server and refinement by the GalaxyRefine tool. Constructed model quality was validated by the ProSA-web error-detection tool and the Ramachandran plot. After that vaccine model was docked with TLR-4 protein and complex stability confirmed by molecular dynamics simulation studies. Finally, In-silico cloning of vaccine constructs into a vector was performed to ensuring its effective expression in the microbial system.

Agricultural intensification and the evolution of host specialism in the enteric pathogen Campylobacter jejuni

Modern agriculture has dramatically changed the distribution of animal species on Earth. Changes to host ecology have a major impact on the microbiota, potentially increasing the risk of zoonotic pathogens being transmitted to humans, but the impact of intensive livestock production on host-associated bacteria has rarely been studied. Here, we use large isolate collections and comparative genomics techniques, linked to phenotype studies, to understand the timescale and genomic adaptations associated with the proliferation of the most common food-born bacterial pathogen (Campylobacter jejuni) in the most prolific agricultural mammal (cattle). Our findings reveal the emergence of cattle specialist C. jejuni lineages from a background of host generalist strains that coincided with the dramatic rise in cattle numbers in the 20th century. Cattle adaptation was associated with horizontal gene transfer and significant gene gain and loss. This may be related to differences in host diet, anatomy, and physiology, leading to the proliferation of globally disseminated cattle specialists of major public health importance. This work highlights how genomic plasticity can allow important zoonotic pathogens to exploit altered niches in the face of anthropogenic change and provides information for mitigating some of the risks posed by modern agricultural systems.

Campylobacter jejuni and Campylobacter coli autotransporter genes exhibit lineage-associated distribution and decay

Background

Campylobacter jejuni and Campylobacter coli are major global causes of bacterial gastroenteritis. Whilst several individual colonisation and virulence factors have been identified, our understanding of their role in the transmission, pathogenesis and ecology of Campylobacter has been hampered by the genotypic and phenotypic diversity within C. jejuni and C. coli. Autotransporter proteins are a family of outer membrane or secreted proteins in Gram-negative bacteria such as Campylobacter, which are associated with virulence functions. In this study we have examined the distribution and predicted functionality of the previously described capC and the newly identified, related capD autotransporter gene families in Campylobacter.

Results

Two capC-like autotransporter families, designated capC and capD, were identified by homology searches of genomes of the genus Campylobacter. Each family contained four distinct orthologs of CapC and CapD. The distribution of these autotransporter genes was determined in 5829 C. jejuni and 1347 C. coli genomes. Autotransporter genes were found as intact, complete copies and inactive formats due to premature stop codons and frameshift mutations. Presence of inactive and intact autotransporter genes was associated with C. jejuni and C. coli multi-locus sequence types, but for capC, inactivation was independent from the length of homopolymeric tracts in the region upstream of the capC gene. Inactivation of capC or capD genes appears to represent lineage-specific gene decay of autotransporter genes. Intact capC genes were predominantly associated with the C. jejuni ST-45 and C. coli ST-828 generalist lineages. The capD3 gene was only found in the environmental C. coli Clade 3 lineage. These combined data support a scenario of inter-lineage and interspecies exchange of capC and subsets of capD autotransporters.

Conclusions

In this study we have identified two novel, related autotransporter gene families in the genus Campylobacter, which are not uniformly present and exhibit lineage-specific associations and gene decay. The distribution and decay of the capC and capD genes exemplifies the erosion of species barriers between certain lineages of C. jejuni and C. coli, probably arising through co-habitation. This may have implications for the phenotypic variability of these two pathogens and provide opportunity for new, hybrid genotypes to emerge.

Taking Control: Campylobacter jejuni Binding to Fibronectin Sets the Stage for Cellular Adherence and Invasion

Campylobacter jejuni, a foodborne pathogen, is one of the most common bacterial causes of gastroenteritis in the world. Undercooked poultry, raw (unpasteurized) dairy products, untreated water, and contaminated produce are the most common sources associated with infection. C. jejuni establishes a niche in the gut by adhering to and invading epithelial cells, which results in diarrhea with blood and mucus in the stool. The process of colonization is mediated, in part, by surface-exposed molecules (adhesins) that bind directly to host cell ligands or the extracellular matrix (ECM) surrounding cells. In this review, we introduce the known and putative adhesins of the foodborne pathogen C. jejuni. We then focus our discussion on two C. jejuni Microbial Surface Components Recognizing Adhesive Matrix Molecule(s) (MSCRAMMs), termed CadF and FlpA, which have been demonstrated to contribute to C. jejuni colonization and pathogenesis. In vitro studies have determined that these two surface-exposed proteins bind to the ECM glycoprotein fibronectin (FN). In vivo studies have shown that cadF and flpA mutants exhibit impaired colonization of chickens compared to the wild-type strain. Additional studies have revealed that CadF and FlpA stimulate epithelial cell signaling pathways necessary for cell invasion. Interestingly, CadF and FlpA have distinct FN-binding domains, suggesting that the functions of these proteins are non-redundant. In summary, the binding of FN by C. jejuni CadF and FlpA adhesins has been demonstrated to contribute to adherence, invasion, and cell signaling.

Virulence Traits of Inpatient Campylobacter jejuni Isolates, and a Transcriptomic Approach to Identify Potential Genes Maintaining Intracellular Survival

There are still major gaps in our understanding of the bacterial factors that influence the outcomes of human Campylobacter jejuni infection. The aim of this study was to compare the virulence-associated features of 192 human C. jejuni strains isolated from hospitalized patients with diarrhoea (150/192, 78.1%), bloody diarrhoea (23/192, 11.9%), gastroenteritis (3/192, 1.6%), ulcerative colitis (3/192, 1.5%), and stomach ache (2/192, 1.0%). Traits were analysed with genotypic and phenotypic methods, including PCR and extracellular matrix protein (ECMP) binding, adhesion, and invasion capacities. Results were studied alongside patient symptoms, but no distinct links with them could be determined. Since the capacity of C. jejuni to invade host epithelial cells is one of its most enigmatic attributes, a high throughput transcriptomic analysis was performed in the third hour of internalization with a C. jejuni strain originally isolated from bloody diarrhoea. Characteristic groups of genes were significantly upregulated, outlining a survival strategy of internalized C. jejuni comprising genes related (1) to oxidative stress; (2) to a protective sheath formed by the capsule, LOS, N-, and O- glycosylation systems; (3) to dynamic metabolic activity supported by different translocases and the membrane-integrated component of the flagellar apparatus; and (4) to hitherto unknown genes.

Molecular Dissection of the Campylobacter jejuni CadF and FlpA Virulence Proteins in Binding to Host Cell Fibronectin

Campylobacter jejuni, a zoonotic pathogen that frequently colonizes poultry, possesses two Microbial Surface Components Recognizing Adhesive Matrix Molecule(s) (MSCRAMMs) termed CadF and FlpA that bind to the glycoprotein fibronectin (FN). Previous to this study, it was not known whether the CadF and FlpA proteins were functionally redundant or if both were required to potentiate host cell binding and signaling processes. We addressed these questions by generating a complete repertoire of cadF and flpA mutants and complemented isolates, and performing multiple phenotypic assays. Both CadF and FlpA were found to be necessary for the maximal binding of C. jejuni to FN and to host cells. In addition, both CadF and FlpA are required for the delivery of the C. jejuni Cia effector proteins into the cytosol of host target cells, which in turn activates the MAPK signaling pathway (Erk 1/2) that is required for the C. jejuni invasion of host cells. These data demonstrate the non-redundant and bi-functional nature of these two C. jejuni FN-binding proteins. Taken together, the C. jejuni CadF and FlpA adhesins facilitate the binding of C. jejuni to the host cells, permit delivery of effector proteins into the cytosol of a host target cell, and aid in the rewiring of host cell signaling pathways to alter host cell behavior.

Mucosal delivery of live Lactococcus lactis expressing functionally active JlpA antigen induces potent local immune response and prevent enteric colonization of Campylobacter jejuni in chickens

Successful colonization of the mucosal epithelial cells is the key early step for Campylobacter jejuni (C. jejuni) pathogenesis in humans. A set of Surface Exposed Colonization Proteins (SECPs) are known to take leading role in bacterial adhesion and subsequent host pathogenesis. Among the major SECPs, the constitutively expressed C. jejuni surface lipoprotein Jejuni lipoprotein A (JlpA), interacts with intestinal heat shock protein 90α (Hsp90α) and contributes in disease progression by triggering pro-inflammatory responses via activation of NF-κB and p38 MAP kinase pathways. In addition to its ability to express on the surface, high sequence conservation of JlpA protein among different Campylobacter spp make it a suitable vaccine target against C. jejuni. Given that chickens are the primary source for C. jejuni infection in humans and persistent cecal colonization significantly contribute in pathogen transmission, we explicitly used chickens as a model to test the immune-protective efficacy of JlpA protein. Taking into account that gastro-intestinal tract is the major site for C. jejuni colonization, we chose to use mucosal (intragastric) route as mode for JlpA antigen delivery. To deliver JlpA via mucosal route, we engineered a food grade Lactic acid producing bacteria, Lactococcus lactis (L. lactis) to express functionally active JlpA protein in the surface. Further, we demonstrated its ability to substantially improve the antigen specific local immune responses in the intestine along with significant immune-protection against enteric colonization of C. jejuni in chickens.

Interaction with the host: the role of fibronectin and extracellular matrix proteins in the adhesion of Gram-negative bacteria

The capacity of pathogenic microorganisms to adhere to host cells and avoid clearance by the host immune system is the initial and most decisive step leading to infections. Bacteria have developed different strategies to attach to diverse host surface structures. One important strategy is the adhesion to extracellular matrix (ECM) proteins (e.g., collagen, fibronectin, laminin) that are highly abundant in connective tissue and basement membranes. Gram-negative bacteria express variable outer membrane proteins (adhesins) to attach to the host and to initiate the process of infection. Understanding the underlying molecular mechanisms of bacterial adhesion is a prerequisite for targeting this interaction by “anti-ligands” to prevent colonization or infection of the host. Future development of such “anti-ligands” (specifically interfering with bacteria-host matrix interactions) might result in the development of a new class of anti-infective drugs for the therapy of infections caused by multidrug-resistant Gram-negative bacteria. This review summarizes our current knowledge about the manifold interactions of adhesins expressed by Gram-negative bacteria with ECM proteins and the use of this information for the generation of novel therapeutic antivirulence strategies.

Fibronectin and Its Role in Human Infective Diseases

Fibronectin is a multidomain glycoprotein ubiquitously detected in extracellular fluids and matrices of a variety of animal and human tissues where it functions as a key link between matrices and cells. Fibronectin has also emerged as the target for a large number of microorganisms, particularly bacteria. There are clear indications that the binding of microorganism’ receptors to fibronectin promotes attachment to and infection of host cells. Each bacterium may use different receptors which recognize specific fibronectin domains, mostly the N-terminal domain and the central cell-binding domain. In many cases, fibronectin receptors have actions over and above that of simple adhesion: In fact, adhesion is often the prerequisite for invasion and internalization of microorganisms in the cells of colonized tissues. This review updates the current understanding of fibronectin receptors of several microorganisms with emphasis on their biochemical and structural properties and the role they can play in the onset and progression of host infection diseases. Furthermore, we describe the antigenic profile and discuss the possibility of designing adhesion inhibitors based on the structure of the fibronectin-binding site in the receptor or the receptor-binding site in fibronectin.

Investigating the influence of iron on Campylobacter jejuni transcriptome in response to acid stress

The capacity of C. jejuni to survive acid and capture iron is a requirement for C. jejuni to colonize host and cause infection. Herein, we aimed to characterize the influence of iron on Campylobacter acid response. The capacity of C. jejuni to survive acid stress was greatly enhanced in presence of iron. Moreover, the acid stimulon of C. jejuni under iron-enriched condition was investigated using the microarray approach. A total of 211 genes were differentially expressed in C. jejuni. Differentially expressed genes were included in 21 functional groups that control Campylobacter physiology. C. jejuni induced expression of many genes that were previously shown to be important for Campylobacter acid survival such as flagella biogenesis genes and genes involved in cell envelope biogenesis. The microarray results were validated using RT-qPCR where there was a great similarity in data obtained by both techniques. Finally, comparative analysis with previous studies showed that acid exposure induced expression of many genes in C. jejuni that were not detected in other studies such as genes encoding for the heat shock proteins GroEL and GroES. Current data could help us understand the mechanism of C. jejuni acid survival and consequently overcome infection by this enteric pathogen.

Differences in virulence gene expression between human blood and stool Campylobacter coli clade 1 ST828CC isolates

BACKGROUND

Campylobacter colonise the gastrointestinal tract of warm-blooded animals and are major enteropathogens in humans. C. coli is less common than C. jejuni and accounts for about 10% of the total number of Campylobacter infections although the two species seem to share many virulence determinants. Campylobacter bacteraemia is rare, estimated to occur in less than 1% of the infections, and the exact mechanisms regulating the progression of the infection from the gastrointestinal tract to the blood stream are unclear. Here, we looked at the contribution of C. coli to Campylobacter infections and further compared various virulence traits in C. coli clade 1 blood and stool isolates.

RESULTS

We assessed the numbers of C. jejuni and C. coli among typed isolates in the PubMLST database and found that C. coli accounted for 25.9% of blood isolates, but only 8.9% of the stool isolates. Phylogenetic analysis of 128 C. coli clade 1 whole genome sequences deposited to NCBI revealed no specific clustering of the human blood, stool or animal isolates. Of the six C. coli isolates chosen for phenotypic analyses, stool isolates adhered significantly better to human HT-29 colon cancer cells than the blood isolates, while there was no difference in induced IL-8 levels between the isolates. Furthermore, the stool isolates had two- to fourfold higher RNA expression levels of the flpA, ciaB, iamA and cdt virulence genes than the blood isolates. Finally, we looked at the gene structure of the cdtA, B and C toxin genes and found numerous nucleotide additions and deletions disrupting the open reading frames. In contrast to 58% isolates of animal origin, only 38% and 32% of human blood and stool isolates, respectively, had all three cdt genes intact, a prerequisite to produce functional toxins.

CONCLUSIONS

This study reveals interesting differences between C. coli clade 1 isolates of human and animal origin on one hand, and also between human blood and stool isolates, on the other. The results suggest that C. coli might downregulate and/or inactivate various virulence determinants as the isolates pass from the animal host to the human gastrointestinal tract and enter the human blood stream.

Life at Home and on the Roam: Genomic Adaptions Reflect the Dual Lifestyle of an Intracellular, Facultative Symbiont

"Candidatus Synechococcus feldmannii" is a facultative intracellular symbiont of the Atlanto-Mediterranean sponge Petrosia ficiformis. Genomic information of sponge-associated cyanobacteria derives thus far from the obligate and extracellular symbiont "Candidatus Synechococcus spongiarum." Here we utilized a differential methylation-based approach for bacterial DNA enrichment combined with metagenomics to obtain the first draft genomes of "Ca. Synechococcus feldmannii." By comparative genomics, we revealed that some genomic features (e.g., iron transport mediated by siderophores, eukaryotic-like proteins, and defense mechanisms, like CRISPR-Cas [clustered regularly interspaced short palindromic repeats-associated proteins]) are unique to both symbiont types and absent or rare in the genomes of taxonomically related free-living cyanobacteria. These genomic features likely enable life under the conditions found inside the sponge host. Interestingly, there are many genomic features that are shared by "Ca. Synechococcus feldmannii" and free-living cyanobacteria, while they are absent in the obligate symbiont "Ca. Synechococcus spongiarum." These include genes related to cell surface structures, genetic regulation, and responses to environmental stress, as well as the composition of photosynthetic genes and DNA metabolism. We speculate that the presence of these genes confers on "Ca. Synechococcus feldmannii" its facultative nature (i.e., the ability to respond to a less stable environment when free-living). Our comparative analysis revealed that distinct genomic features depend on the nature of the symbiotic interaction: facultative and intracellular versus obligate and extracellular. IMPORTANCE Given the evolutionary position of sponges as one of the earliest phyla to depart from the metazoan stem lineage, studies on their distinct and exceptionally diverse microbial communities should yield a better understanding of the origin of animal-bacterium interactions. While genomes of several extracellular sponge symbionts have been published, the intracellular symbionts have, so far, been elusive. Here we compare the genomes of two unicellular cyanobacterial sponge symbionts that share an ancestor but followed different evolutionary paths-one became intracellular and the other extracellular. Counterintuitively, the intracellular cyanobacteria are facultative, while the extracellular ones are obligate. By sequencing the genomes of the intracellular cyanobacteria and comparing them to the genomes of the extracellular symbionts and related free-living cyanobacteria, we show how three different cyanobacterial lifestyles are reflected by adaptive genomic features.

Campylobacter jejuni Demonstrates Conserved Proteomic and Transcriptomic Responses When Co-cultured With Human INT 407 and Caco-2 Epithelial Cells

Major foodborne bacterial pathogens, such as Campylobacter jejuni, have devised complex strategies to establish and foster intestinal infections. For more than two decades, researchers have used immortalized cell lines derived from human intestinal tissue to dissect C. jejuni-host cell interactions. Known from these studies is that C. jejuni virulence is multifactorial, requiring a coordinated response to produce virulence factors that facilitate host cell interactions. This study was initiated to identify C. jejuni proteins that contribute to adaptation to the host cell environment and cellular invasion. We demonstrated that C. jejuni responds to INT 407 and Caco-2 cells in a similar fashion at the cellular and molecular levels. Active protein synthesis was found to be required for C. jejuni to maximally invade these host cells. Proteomic and transcriptomic approaches were then used to define the protein and gene expression profiles of C. jejuni co-cultured with cells. By focusing on those genes showing increased expression by C. jejuni when co-cultured with epithelial cells, we discovered that C. jejuni quickly adapts to co-culture with epithelial cells by synthesizing gene products that enable it to acquire specific amino acids for growth, scavenge for inorganic molecules including iron, resist reactive oxygen/nitrogen species, and promote host cell interactions. Based on these findings, we selected a subset of the genes involved in chemotaxis and the regulation of flagellar assembly and generated C. jejuni deletion mutants for phenotypic analysis. Binding and internalization assays revealed significant differences in the interaction of C. jejuni chemotaxis and flagellar regulatory mutants. The identification of genes involved in C. jejuni adaptation to culture with host cells provides new insights into the infection process.

Campylobacter coli Clade 3 Isolates Induce Rapid Cell Death In Vitro

Campylobacter bacteria are major human enteropathogens. Campylobacter coli shows less genetic diversity than C. jejuni and clusters into three clades, of which clade 1 includes most human and farm animal isolates, while environmental C. coli isolates mainly belong to clades 2 and 3. Recently, we sequenced the whole genomes of eight C. coli clade 2 and 3 isolates cultivated from water, and here we studied their interaction with human HT-29 colon cancer cells compared to that of clinical clade 1 isolates. All C. coli clade 3 isolates already caused cell necrosis 1 to 2 h after inoculation, whereas none of the clade 1 and 2 isolates analyzed induced cell death. Isolates from clades 2 and 3 adhered to epithelial cells better than clade 1 isolates, but all isolates induced similar levels of interleukin-8 (IL-8). Alignment and phylogenetic analysis of the translated putative virulence genes cadF, flpA, iamA, ciaB, and ceuE revealed clade-specific protein sequence variations, with clade 1 and 2 sequences being more closely related and clade 3 sequences being further apart, in general. Moreover, when RNA levels were measured, clade 3 isolates showed significantly lower levels of expression of cadF, iamA, and ceuE than clade 2 isolates, while flpA expression levels were higher in clade 3 isolates. The cytolethal distending toxin genes were also expressed in clades 2 and 3, although there was no difference between clades. Our findings demonstrate differences between the effects of C. coli clade 1, 2, and 3 isolates on human cells and suggest that C. coli clade 3 might be more virulent than clade 2 due to the observed cytotoxicity.IMPORTANCECampylobacter coli is a common zoonotic cause of gastroenteritis in humans worldwide. The majority of infections are caused by C. coli clade 1 isolates, whereas infections due to clade 2 and 3 isolates are rare. Whether this depends on a low prevalence of clade 2 and 3 isolates in reservoirs important for human infections or their lower ability to cause human disease is unknown. Here, we studied the effects of C. coli clade 2 and 3 isolates on a human cell line. These isolates adhered to human cells to a higher degree than clinical clade 1 isolates. Furthermore, we could show that C. coli clade 3 isolates rapidly induced cell death, suggesting differences in the virulence of C. coli The exact mechanism of cell death remains to be revealed, but selected genes showed interesting clade-specific expression patterns.

Presence of genes associated with adhesion, invasion, and toxin production in Campylobacter jejuni isolates and effect of temperature on their expression

The aims of this study were to evaluate the presence of genes associated with adhesion (cadF), invasion (ciaB), and cytotoxin production (cdtA, cdtB, and cdtC) among Campylobacter jejuni isolates from a poultry slaughterhouse and to investigate the effect of different temperatures on the expression of these virulence-associated genes. A total of 88 C. jejuni isolates from cecum, liver, chicken carcasses, chilled water, and scalding water were submitted to PCR assay for detection of virulence genes. Representative isolates were selected for gene expression evaluation at 37 and 42 °C, according to their virulence gene profile and genotypic typing. All C. jejuni isolates carried the five virulence-associated genes, which play an important role in the infectious process. Differential gene expression by RT-qPCR was observed among C. jejuni isolates at 37 and 42 °C. The expression levels at 37 °C showed upregulation of the ciaB, cdtA, cdtB, and cdtC genes in five isolates, with the exception of ciaB for isolate 4. At 42 °C, upregulation was observed for ciaB and cdtC, cdtA and cdtB, and cadF in four, three, and two isolates, respectively. The C. jejuni isolates expressed the virulence genes evaluated, and the expression is gene- and isolate-dependent and varied according the temperature.

Insights into the impact of flhF inactivation on Campylobacter jejuni colonization of chick and mice gut

Background

Campylobacter jejuni (C. jejuni) is a leading cause of foodborne gastroenteritis worldwide. This bacterium lacks many of the classical virulence factors, and flagellum-associated persistent colonization has been shown to be crucial for its pathogenesis. The flagellum plays a multifunctional role in C. jejuni pathogenesis, and different flagellar elements make diverse contributions. The flhF gene encodes the flagellar biosynthesis regulator, which is important for flagellar biosynthesis. In this study, the influence of flhF on C. jejuni colonization was systematically studied, and the possible mechanisms were also analyzed.

Results

The flhF gene has a significant influence on C. jejuni colonization, and its inactivation resulted in severe defects in the commensal colonization of chicks, with approximately 10⁴- to 10⁷-fold reductions (for NCTC 11168 and a C. jejuni isolate respectively) observed in the bacterial caecal loads. Similar effects were observed in mice where the flhF mutant strain completely lost the ability to continuously colonize mice, which cleared the isolate at 7 days post inoculation. Characterization of the phenotypic properties of C. jejuni that influence colonization showed that the adhesion and invasion abilities of the C. jejuni flhF mutant were reduced to approximately 52 and 27% of that of the wild-type strain, respectively. The autoagglutination and biofilm-formation abilities of the flhF mutant strain were also significantly decreased. Further genetic investigation revealed that flhF is continuously upregulated during the infection process, which indicates a close association of this gene with C. jejuni pathogenesis. The transcription of some other infection-related genes that are not directly involved in flagellar assembly were also influenced by its inactivation, with the flagellar coexpressed determinants (Feds) being apparently affected.

Conclusions

Inactivation of flhF has a significant influence on C. jejuni colonization in both birds and mammals. This defect may be caused by the decreased adhesion, invasion, autoagglutination and biofilm-formation abilities of the flhF mutant strain, as well as the influence on the transcription of other infection related genes, which provides insights into this virulence factor and the flagellum mediated co-regulation of C. jejuni pathogenesis.

Electronic supplementary material

The online version of this article (10.1186/s12866-018-1318-1) contains supplementary material, which is available to authorized users.

In planta expression of nanobody-based designer chicken antibodies targeting Campylobacter

Campylobacteriosis is a widespread infectious disease, leading to a major health and economic burden. Chickens are considered as the most common infection source for humans. Campylobacter mainly multiplies in the mucus layer of their caeca. No effective control measures are currently available, but passive immunisation of chickens with pathogen-specific maternal IgY antibodies, present in egg yolk of immunised chickens, reduces Campylobacter colonisation. To explore this strategy further, anti-Campylobacter nanobodies, directed against the flagella and major outer membrane proteins, were fused to the constant domains of chicken IgA and IgY, combining the benefits of nanobodies and the effector functions of the Fc-domains. The designer chimeric antibodies were effectively produced in leaves of Nicotiana benthamiana and seeds of Arabidopsis thaliana. Stable expression of the chimeric antibodies in seeds resulted in production levels between 1% and 8% of the total soluble protein. These in planta produced antibodies do not only bind to their purified antigens but also to Campylobacter bacterial cells. In addition, the anti-flagellin chimeric antibodies are reducing the motility of Campylobacter bacteria. These antibody-containing Arabidopsis seeds can be tested for oral passive immunisation of chickens and, if effective, the chimeric antibodies can be produced in crop seeds.

The Novel Protein Cj0371 Inhibits Chemotaxis of Campylobacter jejuni

cj0371 is a novel gene that is associated with Campylobacter jejuni virulence, and an isogenic mutant of cj0371 showed hyper chemotaxis and motility. Chemotactic motility is an important virulence factor and is involved in C. jejuni pathogenesis. Campylobacter sp. has specific variations of the common chemotaxis components, including histidine autokinase CheA, coupling scaffold protein CheV, chemotaxis response regulator protein CheY and several chemoreceptor proteins. In this study, we used immunoprecipitation combined with LC-MS/MS analyses to screen six chemotaxis pathway proteins that potentially interact with the putative protein Cj0371. qRT-PCR was used to quantitatively analyze the expression of these chemotaxis genes and basic flagella genes. The results showed that the expression of cheV, cj1110c, and cj0262c was significantly up-regulated, and four flagella genes also had up-regulated expression in the cj0371 mutant. GST pull-down analyses found that Cj0371 interacted with the receiver domain of the CheV protein. Enzyme-coupled spectrophotometric assays showed that the ATPase activity of CheA was higher when Cj0371 was not present in the chemotaxis reaction medium. Therefore, we concludes that cj0371 has a negative influence on C. jejuni chemotaxis, which may occur by adjusting the receiver domain of CheV to influence chemotaxis. This paper provides a new component in the chemotaxis pathway of C. jejuni for the first time and highlight the complexity of this remarkable pathway.

CapC, a Novel Autotransporter and Virulence Factor of Campylobacter jejuni

Campylobacter jejuni is recognized as an important causative agent of bacterial gastroenteritis in the developed world. Despite the identification of several factors contributing to infection, characterization of the virulence strategies employed by C. jejuni remains a significant challenge. Bacterial autotransporter proteins are a major class of secretory proteins in Gram-negative bacteria, and notably, many autotransporter proteins contribute to bacterial virulence. The aim of this study was to characterize the C. jejuni 81116 C8J_1278 gene (capC), predicted to encode an autotransporter protein, and examine the contribution of this factor to virulence of C. jejuni The predicted CapC protein has a number of features that are consistent with autotransporters, including the N-terminal signal sequence and the C-terminal β-barrel domain and was determined to localize to the outer membrane. Inactivation of the capC gene in C. jejuni 81116 and C. jejuni M1 resulted in reduced insecticidal activity in Galleria mellonella larvae. Furthermore, C. jejuni capC mutants displayed significantly reduced adherence to and invasion of nonpolarized, partially differentiated Caco-2 and T84 intestinal epithelial cells. Gentamicin treatment showed that the reduced invasion of the capC mutant is primarily caused by reduced adherence to intestinal epithelial cells, not by reduced invasion capability. C. jejuni capC mutants caused reduced interleukin 8 (IL-8) secretion from intestinal epithelial cells and elicited a significantly diminished immune reaction in Galleria larvae, indicating that CapC functions as an immunogen. In conclusion, CapC is a new virulence determinant of C. jejuni that contributes to the integral infection process of adhesion to human intestinal epithelial cells.IMPORTANCECampylobacter jejuni is a major causative agent of human gastroenteritis, making this zoonotic pathogen of significant importance to human and veterinary public health worldwide. The mechanisms by which C. jejuni interacts with intestinal epithelial cells and causes disease are still poorly understood due, in part, to the heterogeneity of C. jejuni infection biology. Given the importance of C. jejuni to public health, the need to characterize novel and existing virulence mechanisms is apparent. The significance of our research is in demonstrating the role of CapC, a novel virulence factor in C. jejuni that contributes to adhesion and invasion of the intestinal epithelium, thereby in part, addressing the dearth of knowledge concerning the factors involved in Campylobacter pathogenesis and the variation observed in the severity of human infection.

Genetic characterisation of virulence genes associated with adherence, invasion and cytotoxicity in Campylobacter spp. isolated from commercial chickens and human clinical cases

Virulence-associated genes have been recognised and detected in Campylobacter species. The majority of them have been proven to be associated with pathogenicity. This study aimed to detect the presence of virulence genes associated with pathogenicity and responsible for invasion, expression of adherence, colonisation and production of the cytolethal distending toxin (cdt) in Campylobacter jejuni and Campylobacter coli. Commercial chicken faecal samples were randomly sampled from chicken farms within the Durban metropolitan area in South Africa. Furthermore, human clinical Campylobacter spp. isolates were randomly sampled from a private pathology laboratory in South Africa. Out of a total of 100 chicken faecal samples, 78% (n = 78) were positive for Campylobacter growth on modified charcoal cefoperazone deoxycholate and from the random laboratory collection of 100 human clinical isolates, 83% (n = 83) demonstrated positive Campylobacter spp. growth following culturing methods. These samples were screened for the presence of the following virulence genes: cadF, hipO, asp, ciaB, dnaJ, pldA, cdtA, cdtB and cdtC. As expected, the cadF gene was present in 100% of poultry (n = 78) and human clinical isolates (n = 83). Campylobacter jejuni was the main species detected in both poultry and human clinical isolates, whilst C. coli were detected at a significantly lower percentage (p < 0.05). Eight per cent of the C. jejuni from human clinical isolates had all virulence genes that were investigated. Only one C. coli isolate demonstrated the presence of all the virulence genes investigated; however, the pldA virulence gene was detected in 100% of the C. coli isolates in poultry and a high percentage (71%) in human clinical C. coli isolates as well. The detection of cdt genes was found at higher frequency in poultry than human clinical isolates. The high prevalence rates of virulence genes detected in poultry and human clinical isolates demonstrate their significance in the pathogenicity of Campylobacter species.

Methods to Study Campylobacter jejuni Adherence to and Invasion of Host Epithelial Cells

Measuring bacterial adherence and invasion of cells in vitro has enabled researchers to dissect the interactions of Campylobacter jejuni with eukaryotic cells. Numerous C. jejuni virulence determinants and host cell factors that contribute to the process of adherence, invasion, and immune modulation have been identified utilizing in vitro adherence and invasion assays. In this chapter, we describe the evaluation of C. jejuni adherence to and invasion of HeLa cells using the gentamicin-protection assay.

Arcobacter: an emerging food-borne zoonotic pathogen, its public health concerns and advances in diagnosis and control - a comprehensive review

Arcobacter has emerged as an important food-borne zoonotic pathogen, causing sometimes serious infections in humans and animals. Newer species of Arcobacter are being incessantly emerging (presently 25 species have been identified) with novel information on the evolutionary mechanisms and genetic diversity among different Arcobacter species. These have been reported from chickens, domestic animals (cattle, pigs, sheep, horses, dogs), reptiles (lizards, snakes and chelonians), meat (poultry, pork, goat, lamb, beef, rabbit), vegetables and from humans in different countries. Arcobacters are implicated as causative agents of diarrhea, mastitis and abortion in animals, while causing bacteremia, endocarditis, peritonitis, gastroenteritis and diarrhea in humans. Three species including A. butzleri, A. cryaerophilus and A. skirrowii are predominantly associated with clinical conditions. Arcobacters are primarily transmitted through contaminated food and water sources. Identification of Arcobacter by biochemical tests is difficult and isolation remains the gold standard method. Current diagnostic advances have provided various molecular methods for efficient detection and differentiation of the Arcobacters at genus and species level. To overcome the emerging antibiotic resistance problem there is an essential need to explore the potential of novel and alternative therapies. Strengthening of the diagnostic aspects is also suggested as in most cases Arcobacters goes unnoticed and hence the exact epidemiological status remains uncertain. This review updates the current knowledge and many aspects of this important food-borne pathogen, namely etiology, evolution and emergence, genetic diversity, epidemiology, the disease in animals and humans, public health concerns, and advances in its diagnosis, prevention and control.

Genotypic diversity, antimicrobial resistance and biofilm-forming abilities of Campylobacter isolated from chicken in Central China

Background

Campylobacter is considered to be the leading cause of human bacterial gastroenteritis, of which poultry is the main reservoir. Campylobacter contaminated chicken products are a major cause of human Campylobacter infection. In this study, the prevalence of Campylobacter in chicken in central China was investigated, and the genotypic diversity, antimicrobial resistance and biofilm of these isolates were characterized.

Results

A total of 206 Campylobacter isolates, including 166 C. jejuni and 40 C. coli, were isolated from chicken farms and live poultry markets in central China. Multilocus sequence typing and phylogenetic analysis showed that the Campylobacter isolates had diverse genetic backgrounds, which covered most of the dominant clone complexes (CCs) reported throughout China. The most prevalent CCs were CC-464, CC-1150, CC-353, and CC-828. All the isolates showed resistance to norfloxacin, ciprofloxacin and Cefazolin, and a prevalent resistance to fluoroquinolones, β-lactams and tetracyclines was also observed. Among all the isolates, 133 strains showed the ability to form biofilm, thereinto, the isolates in two genetic branches, mainly including CC-21, CC-48, CC-677 and CC-45, showed a significantly lower ability to form biofilm than other genetic branches (p < 0.05). However, in general, the ability to form biofilm varied among different genetic branches, suggesting a complex genetic background to biofilm formation, but not only the genetic lineages. Compared with the strains unable to form biofilm, biofilm-producing strains possessed a significantly higher resistance to ampicillin, neomycin, sulfamethoxazole, amikacin, clindamycin and erythromycin (p < 0.05).

Conclusions

To the best of our knowledge, this is the first report on the relationship of the genotypic diversity, antimicrobial resistance and biofilm-forming abilities of Campylobacter isolated from chicken in Central China, which showed the potential importance of biofilm in antimicrobial resistance. This study will help us better understand the epidemiology and antimicrobial resistance of Campylobacter.