Virulence characteristics of hcp (+) Campylobacter jejuni and Campylobacter coli isolates from retail chicken

Campylobacter jejuni from no antibiotics ever (NAE) broilers: prevalence, antibiotic resistance, and virulence genes analysis

Campylobacter jejuni (C. jejuni) is a leading foodborne illness causing bacteria, and poultry is a major reservoir of this pathogen. With the recent increase in broiler production under the "no antibiotics ever" (NAE) system, this study aimed to assess the prevalence, antibiotic resistance, and virulence characteristics of C. jejuni isolated from NAE raised broilers. A total of 270 cloacal swabs were collected from the live-hang areas of 3 commercial processing plants over 9 wk. Each processing plant was visited 3 times at a 1-wk interval, and 30 samples were collected per visit. Among the total 270 cloacal swab samples, C. jejuni was isolated from 44 (16.3%) samples . Of these isolates, 65.9% possessed toxin-producing genes cdtA, cdtB, and cdtC, and invasion gene ciaB. The prevalence of antibioitc resistance genes aph (3')-IIIa, erm(B) were 59.1%, and 50%, respectively. Nine (20.45%) C. jejuni isolates were identified as multidrug resistant (MDR), and 18 (40.9%) isolates showed resistance to at least 1 tested antibiotic. The highest resistance was observed against tetracycline (29.5%), followed by nalidixic acid (25%), whereas 22.7% of isolates were resistant to 2 clinically important antibiotics, azithromycin and ciprofloxacin. These results suggest that there ishigh prevalence level of multi-drug resistant C. jejuni with toxin producing virulence genes in the NAE-raised broilers sampled in this study, indicating the potential for serious human illnesses if transmitted through the food chain.

The Missing Pieces: The Role of Secretion Systems in Campylobacter jejuni Virulence

Campylobacter jejuni is likely the most common bacterial cause of gastroenteritis worldwide, responsible for millions of cases of inflammatory diarrhea characterized by severe abdominal cramps and blood in the stool. Further, C. jejuni infections are associated with post-infection sequelae in developed countries and malnutrition and growth-stunting in low- and middle-income countries. Despite the increasing prevalence of the disease, campylobacteriosis, and the recognition that this pathogen is a serious health threat, our understanding of C. jejuni pathogenesis remains incomplete. In this review, we focus on the Campylobacter secretion systems proposed to contribute to host-cell interactions and survival in the host. Moreover, we have applied a genomics approach to defining the structural and mechanistic features of C. jejuni type III, IV, and VI secretion systems. Special attention is focused on the flagellar type III secretion system and the prediction of putative effectors, given that the proteins exported via this system are essential for host cell invasion and the inflammatory response. We conclude that C. jejuni does not possess a type IV secretion system and relies on the type III and type VI secretion systems to establish a niche and potentiate disease.

In silico investigation of the genus Campylobacter type VI secretion system reveals genetic diversity in organization and putative effectors

Bacterial type VI secretion systems (T6SSs) are contractile nanomachines that deliver proteinic substrates into target prokaryotic or eukaryotic cells and the surrounding milieu. The genus Campylobacter encompasses 39 recognized species and 13 subspecies, with many belonging to a group known as ‘emerging Campylobacter pathogens’. Within Campylobacter , seven species have been identified to harbour a complete T6SS cluster but have yet to be comparatively assessed. In this study, using systematic bioinformatics approaches and the T6SS-positive Campylobacter jejuni 488 strain as a reference, we explored the genus-wide prevalence, similarity and make-up of the T6SS amongst 372 publicly available ‘complete’ Campylobacter genomes. Our analyses predict that approximately one-third of Campylobacter species possess a T6SS. We also putatively report the first identification of a T6SS in four species: Campylobacter cuniculorum, Campylobacter helveticus, Campylobacter armoricus and Campylobacter ornithocola . The Campylobacter T6SSs cluster into three distinct organizations (I–III), of which two break down into further variants. Thirty T6SS-containing genomes were found to harbour more than one vgrG gene, with Campylobacter lari strain NCTC 11845 possessing five. Analysis of the C. jejuni Pathogenicity Island-1 confirmed its conservation amongst T6SS-positive C. jejuni strains, as well as highlighting its diverse genetic composition, including additional putative effector–immunity pairs (e.g. PoNe and DUF1911 domains). Effector–immunity pairs were also observed neighbouring vgrG s in several other Campylobacter species, in addition to putative genes encoding nucleases, lysozymes, ATPases and a ferric ATP-binding cassette uptake system. These observations highlight the diverse genetic make-up of the T6SS within Campylobacter and provide further evidence of its role in pathogenesis.

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.

Zoonotic Campylobacter spp. and Salmonella spp. carried by wild boars in a metropolitan area: occurrence, antimicrobial susceptibility and public health relevance

Campylobacter spp. and Salmonella spp. are the most reported zoonotic agents in Europe. They can be transmitted from wildlife to humans, and wild boars (Sus scrofa) can harbour them. In the Metropolitan Area of Barcelona (MAB, NE Spain) wild boars are found in urbanized areas. To assess the potential public health risk of this increasing wild boar population, we collected stool samples from 130 wild boars from the MAB (June 2015 - February 2016), to determine the Campylobacter and Salmonella occurrence and the antimicrobial susceptibility of the isolates. We also investigated the genetic diversity and virulence potential of Campylobacter. Campylobacter prevalence in wild boars was 61%. Forty six percent of wild boars carried Campylobacter lanienae, 16% carried Campylobacter coli, and 1% carried Campylobacter hyointestinalis; 4% carried both C. lanienae and C. coli, and 1% carried both C. lanienae and C. hyointestinalis. This is the first report of C. hyointestinalis in wildlife in Spain. Using pulse-field gel electrophoresis and multilocus sequence typing, we observed a high genetic diversity of Campylobacter and identified new sequence types. Thirty-three percent of C. coli and 14% of C. lanienae isolates showed a high virulence potential. All of the Campylobacter isolates analysed were resistant to at least one antimicrobial agent. Multidrug resistance was only detected in C. coli (67%). Salmonella enterica subsp. enterica was detected in four wild boars (3%) and included a S. Enteritidis serovar (1/4 wild boars) and a multidrug-resistant (ASSuT) monophasic S. Typhimurium serovar (1/4 wild boars) which is associated with human infections and pig meat in Europe. The characteristics of some of the Campylobacter and Salmonella isolates recovered suggest an anthropogenic origin. Wild boars are a reservoir of Campylobacter and have the potential to spread antimicrobial resistant Campylobacter and Salmonella in urbanized areas in the MAB.

A Campylobacter integrative and conjugative element with a CRISPR-Cas9 system targeting competing plasmids: a history of plasmid warfare?

Microbial genomes are highly adaptable, with mobile genetic elements (MGEs) such as integrative conjugative elements (ICEs) mediating the dissemination of new genetic information throughout bacterial populations. This is countered by defence mechanisms such as CRISPR-Cas systems, which limit invading MGEs by sequence-specific targeting. Here we report the distribution of the pVir, pTet and PCC42 plasmids and a new 70–129 kb ICE (CampyICE1) in the foodborne bacterial pathogens Campylobacter jejuni and Campylobacter coli. CampyICE1 contains a degenerated Type II-C CRISPR system consisting of a sole Cas9 protein, which is distinct from the previously described Cas9 proteins from C. jejuni and C. coli. CampyICE1 is conserved in structure and gene order, containing blocks of genes predicted to be involved in recombination, regulation and conjugation. CampyICE1 was detected in 134/5829 (2.3 %) C. jejuni genomes and 92/1347 (6.8 %) C. coli genomes. Similar ICEs were detected in a number of non-jejuni/coli Campylobacter species, although these lacked a CRISPR-Cas system. CampyICE1 carries three separate short CRISPR spacer arrays containing a combination of 108 unique spacers and 16 spacer-variant families. A total of 69 spacers and 10 spacer-variant families (63.7 %) were predicted to target Campylobacter plasmids. The presence of a functional CampyICE1 Cas9 protein and matching anti-plasmid spacers was associated with the absence of the pVir, pTet and pCC42 plasmids (188/214 genomes, 87.9 %), suggesting that the CampyICE1-encoded CRISPR-Cas has contributed to the exclusion of competing plasmids. In conclusion, the characteristics of the CRISPR-Cas9 system on CampyICE1 suggests a history of plasmid warfare in Campylobacter.

Phosphorylation of Extracellular Proteins in Acinetobacter baumannii in Sessile Mode of Growth

Acinetobacter baumannii is a problematic nosocomial pathogen owing to its increasing resistance to antibiotics and its great ability to survive in the hospital environment, which is linked to its capacity to form biofilms. Structural and functional investigations of post-translational modifications, such as phosphorylations, may lead to identification of candidates for therapeutic targets against this pathogen. Here, we present the first S/T/Y phosphosecretome of two A. baumannii strains, the reference strain ATCC 17978 and the virulent multi-drug resistant strain AB0057, cultured in two modes of growth (planktonic and biofilm) using TiO2 chromatography followed by high resolution mass spectrometry. In ATCC 17978, we detected a total of 137 (97 phosphoproteins) and 52 (33 phosphoproteins) phosphosites in biofilm and planktonic modes of growth, respectively. Similarly, in AB0057, 155 (119 phosphoproteins) and 102 (74 phosphoproteins) phosphosites in biofilm and planktonic modes of growth were identified, respectively. Both strains in the biofilm mode of growth showed a higher number of phosphosites and phosphoproteins compared to planktonic growth. Several phosphorylated sites are localized in key regions of proteins involved in either drug resistance (β-lactamases), adhesion to host tissues (pilins), or protein secretion (Hcp). Site-directed mutagenesis of the Hcp protein, essential for type VI secretion system-mediated interbacterial competition, showed that four of the modified residues are essential for type VI secretion system activity.

Hyper-Aerotolerant Campylobacter coli From Swine May Pose a Potential Threat to Public Health Based on Its Quinolone Resistance, Virulence Potential, and Genetic Relatedness

Campylobacter, a major foodborne pathogen, is susceptible to oxygen. Recently, aerotolerant Campylobacter with enhanced tolerance to aerobic stress has become a major concern in food safety. However, the aerotolerance of Campylobacter coli from pigs has not been studied extensively. Here, we sought to investigate the prevalence of C. coli across multiple swine groups in farms, including weaning, growing, and fattening pigs in production stages and pregnant sows. Additionally, we analyzed C. coli aerotolerance, quinolone resistance, virulence potential, and multilocus sequence typing (MLST) genotypes. Finally, we compared the characteristics of C. coli according to the aerotolerance levels. In total, we obtained 124 (66.3%) C. coli isolates from 187 swine fecal samples across six swine farms. The pathogen was prevalent in weaning (45.5%), growing (68.3%), and fattening (75.4%) pigs, and pregnant sows (66.7%). Hyper-aerotolerant HAT C. coli (13.7% of 124 isolates) was present in all swine groups, with the highest proportion in the pregnant sows (27.3%). All HAT isolates possessed diverse virulence-related genes such as flaA, cadF, pldA, ceuE, and cdtA. All C. coli isolates were resistant to quinolones, and 12 (10%) presented high-level ciprofloxacin resistance (MIC ≥ 32 μg/mL). The proportion of C. coli isolates with a high-level ciprofloxacin resistance was the highest in HAT C. coli (18.8%). Furthermore, six MLST sequence types (STs) (ST827, ST830, ST854, ST1016, ST1068, and ST1096) of swine-derived C. coli were in common with human-derived C. coli (PubMLST). The proportion of C. coli belonging to such shared STs at each aerotolerance level was the highest in HAT C. coli (HAT vs. oxygen-sensitive; OR = 3.13). In conclusion, quinolone resistance of C. coli may be distributed throughout in all swine groups in farms. HAT C. coli is likely to remain in pig farms and re-infect other pigs in the farms. Furthermore, swine-derived HAT C. coli could be transmitted to humans easily through the food chain owing to its aerotolerance, and it could pose a threat to public health owing to its high-level ciprofloxacin resistance and virulence. This study highlights the need to develop management practices that prevent the transmission of swine-derived HAT C. coli to humans.

Bioinformatic Analysis of the Campylobacter jejuni Type VI Secretion System and Effector Prediction

The Type VI Secretion System (T6SS) has important roles relating to bacterial antagonism, subversion of host cells, and niche colonisation. Campylobacter jejuni is one of the leading bacterial causes of human gastroenteritis worldwide and is a commensal coloniser of birds. Although recently discovered, the T6SS biological functions and identities of its effectors are still poorly defined in C. jejuni. Here, we perform a comprehensive bioinformatic analysis of the C. jejuni T6SS by investigating the prevalence and genetic architecture of the T6SS in 513 publicly available genomes using C. jejuni 488 strain as reference. A unique and conserved T6SS cluster associated with the Campylobacter jejuni Integrated Element 3 (CJIE3) was identified in the genomes of 117 strains. Analyses of the T6SS-positive 488 strain against the T6SS-negative C. jejuni RM1221 strain and the T6SS-positive plasmid pCJDM202 carried by C. jejuni WP2-202 strain defined the “T6SS-containing CJIE3” as a pathogenicity island, thus renamed as Campylobacter jejuni Pathogenicity Island-1 (CJPI-1). Analysis of CJPI-1 revealed two canonical VgrG homologues, CJ488_0978 and CJ488_0998, harbouring distinct C-termini in a genetically variable region downstream of the T6SS operon. CJPI-1 was also found to carry a putative DinJ-YafQ Type II toxin-antitoxin (TA) module, conserved across pCJDM202 and the genomic island CJIE3, as well as several open reading frames functionally predicted to encode for nucleases, lipases, and peptidoglycan hydrolases. This comprehensive in silico study provides a framework for experimental characterisation of T6SS-related effectors and TA modules in C. jejuni.

Mixtures of natural antimicrobials can reduce Campylobacter jejuni, Salmonella enterica and Clostridium perfringens infections and cellular inflammatory response in MDCK cells

Background

The classification of natural antimicrobials as potential antibiotic replacements is still hampered by the absence of clear biological mechanisms behind their mode of action. This study investigated the mechanisms underlying the anti-bacterial effect of a mixture of natural antimicrobials (maltodextrin, citric acid, sodium citrate, malic acid, citrus extract and olive extract) against Campylobacter jejuni RC039, Salmonella enterica SE 10/72 and Clostridium perfringens ATCC® 13124 invasion of Madin–Darby Canine Kidney cells (MDCK).

Results

Minimum sub-inhibitory concentrations were determined for Campylobacter jejuni (0.25%), Salmonella enterica (0.50%) and Clostridium perfringens (0.50%) required for the in vitro infection assays with MDCK cells. The antimicrobial mixture significantly reduced the virulence of all three pathogens towards MDCK cells and restored the integrity of cellular tight junctions through increased transepithelial resistance (TEER) and higher expression levels of ZO-1 (zonula occludens 1) and occludin. This study also identified the ERK (external regulated kinase) signalling pathway as a key mechanism in blocking the pro-inflammatory cytokine production (IL-1β, IL-6, IL-8, TNF-α) in infected cells. The reduction in hydrogen peroxide (H₂O₂) production and release by infected MDCK cells, in the presence of the antimicrobial mixture, was also associated with less tetrathionate formed by oxidation of thiosulphate (p < 0.0001).

Conclusion

The present study describes for the first time that mixtures of natural antimicrobials can prevent the formation of substrates used by bacterial pathogens to grow and survive in anaerobic environments (e.g. tetrathionate). Moreover, we provide further insights into pathogen invasion mechanisms through restoration of cellular structures and describe their ability to block the ERK–MAPK kinase pathway responsible for inflammatory cytokine release

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.

The effect of natural antimicrobials on the Campylobacter coli T6SS+/- during in vitro infection assays and on their ability to adhere to chicken skin and carcasses

Reducing the Campylobacter load on poultry carcasses represents a major tasks for the industry as its ability to reduce their presence is of major interest aiming to increase consumer safety. This study investigated the ability of a mixture of natural antimicrobials (A3001) to reduce the adherence of the T6SS^+/-C. coli isolates (NC1^hcp-, NC2 ^hcp- and NC3 ^hcp+) to chicken neck skin and whole carcasses. Overall, the antimicrobial mixture induced a significant reduction in the capability of our C. coli isolates to colonise the chicken skin (p < 0.05) and carcasses (p < 0.0001) but with a greater effect (≈3 log reduction) on the NC3 isolate. Using the HCT-8 in vitro infection model we also show that at a concentration of 0.5% A3001, the impact on the NC3 isolate is accompanied by the downregulation of the hcp gene (p = 0.0001), and indicator of the T6SS presence. The results described herein also indicated that these isolates are highly resistant to H₂O₂, up to 20 mM, suggesting a high resilience to environmental stresses. In summary our study shows that natural antimicrobials can reduce the ability of T6SS positive chicken C. coli isolates to adhere to chicken skin or to the whole carcass and to infect epithelial cells in vitro and could be considered a potential intervention at processor level.

Antimicrobial Resistance and Virulence-Associated Markers in Campylobacter Strains From Diarrheic and Non-diarrheic Humans in Poland

Campylobacteriosis is one of the most common causes of bacterial gastroenteritis. However, the clinical course of the illness varies in symptoms and severity. The aim of this study was to characterize Campylobacter jejuni (34 isolates) and C. coli (9 isolates) from persons with diarrheal and non-diarrheal stools at the time of examination and fecal sampling, in Poland by using whole-genome sequencing (WGS). Multilocus sequence typing (MLST) analysis revealed a high diversity with a total of 20 sequence types (STs) among 26 Campylobacter isolates from diarrheic and 13 STs among 17 isolates from non-diarrheic persons. ST-50 and ST-257 were most common in both groups. The phenotypic resistance rate was 74.4% for ciprofloxacin, 67.4% for sulfamethoxazole/trimethoprim, 58.1% for amoxicillin, 48.8% for tetracycline, and 46.5% for ceftriaxone. Only single isolates were resistant to erythromycin, gentamicin, and amoxicillin/clavulanic acid. Overall genotypic resistance toward amoxicillin, fluoroquinolones, tetracyclines, and aminoglycosides was predicted to occur in 93.1, 67.4, 48.8, and 11.6% of the isolates, respectively. None of the isolates showed the presence of the erm(B) gene or mutation in 23S rRNA. Neither was variation found in the important target region in L4 and L22 ribosomal proteins. In regard to the CmeABC efflux pump, a set of variable mutations affecting the regulatory region was noted. All Campylobacter isolates possessed genes associated with adhesion (cadF, jlpA, porA, and pebA) and invasion (ciaB, pldA, and flaC). The type IV secretion system (T4SS) was found in isolates from both diarrheic (15.4%, CI 95%: 6.1–33.5%) and non-diarrheic (23.5%, CI 95%: 9.6–47.3%) persons. The rates of the presence of cytolethal distending toxin cdtABC gene cluster and type VI secretion system (T6SS) were higher in Campylobacter isolates obtained from persons with diarrhea (96.2%, CI 95%: 81.7–99.3% and 26.9%, CI 95%: 13.7–46.1%) compared to isolates from non-diarrheic persons (76.5%, CI 95%: 52.7–90.4% and 11.8%, CI 95%: 3.3–34.3%). The lack of statistically significant differences between two groups in tested virulence factors suggests that individual susceptibility of the host might play more determining role in the disease outcome than characteristics of the infecting strain.

Molecular characterization of megaplasmids encoding the type VI secretion system in Campylobacter jejuni isolated from chicken livers and gizzards

Megaplasmids in Campylobacter spp. likely play important roles in antibiotic resistance, virulence, and horizontal gene transfer. In this study, megaplasmids pCJDM202 (119 kb) and pCJDM67L (116 kb) from C. jejuni strains WP2-202 and OD2-67, respectively, were sequenced and characterized. These megaplasmids contained genes for tetracycline resistance [tet(O)], the Type IV secretion system, conjugative transfer and the Type VI secretion system (T6SS). The T6SS genes in Campylobacter plasmids encoded genes and proteins that were similar to those identified in Campylobacter chromosomal DNA. When the megaplasmid pCJDM202 from C. jejuni WP2-202 was transferred via conjugation to C. jejuni NCTC11168 Nal⁺, transconconjugants acquired tetracycline resistance and enhanced cytotoxicity towards red blood cells. A T6SS mutant of strain WP2-202 was generated and designated Δhcp3; the mutant was significantly impaired in its ability to lyse red blood cells and survive in defibrinated blood. The cytotoxicity of Campylobacter strains towards the human embryonic kidney cell line HEK 293 was not impacted by the T6SS. In summary, the T6SS encoded by Campylobacter megaplasmids mediates lysis of RBCs and likely contributes to survival on retail meats where blood cells are abundant.

Characterization and Prevalence of Campylobacter spp. From Broiler Chicken Rearing Period to the Slaughtering Process in Eastern China

Campylobacter is one of the most important foodborne pathogens worldwide, and poultry is regarded as the main reservoir of Campylobacter. The contamination of Campylobacter in broiler chickens at the farm level is closely related to the transmission of Campylobacter in the poultry production chain. This study identified 464 Campylobacter isolates from 1,534 samples from broiler rearing period and slaughtering process including 233 Campylobacter jejuni isolates and 231 Campylobacter coli isolates. We have observed a dynamic distribution of Campylobacter during broiler chicken production, that 66.3% of Campylobacter isolates were C. jejuni during broiler rearing period, while C. coli occupied 60.4% of Campylobacter isolates during the broiler slaughtering process. A tag-label method allowed us to track the dynamic of Campylobacter in each broiler chicken from 31-day age at rearing to the partition step in the slaughterhouse. At the 31-day during rearing, 150 broiler chicken were labeled, and was tracked for Campylobacter positive from rearing period to slaughtering process. Among the labeled broiler, 11 of the tracking broiler samples were able to detect Campylobacter from rearing period to slaughtering. All Campylobacter isolates from the 11 tracking samples were sequenced and analyzed. C. jejuni isolates were divided into four STs and C. coli isolates were divided into six STs. Isolates with identical core genome were observed from the same tag-labeled samples at different stages indicating a vertical transmission of Campylobacter in the early broiler meat production. Meanwhile, the core genome analysis elucidated the cross-contamination of Campylobacter during the rearing period and the slaughtering process. The virulotyping analysis revealed that all C. jejuni isolates shared the same virulotypes, while C. coli isolates were divided into three different virulotypes. The antimicrobial resistance gene analysis demonstrated that all Campylobacter isolates contained at least two antibiotic resistance genes (ARGs), and the ARG profiles were well-corresponding to each ST type. Our study observed a high prevalence of Campylobacter during the early chicken meat production, and further studies will be needed to investigate the diversity and transmission of Campylobacter in the poultry production chain.

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.

Intracellular Survival and Translocation Ability of Human and Avian Campylobacter jejuni and Campylobacter coli Strains

Campylobacter acts using complex strategies to establish and promote intestinal infections. After ingestion via contaminated foods, this bacterium invades and can survive within the intestinal cells, also inducing epithelial translocation of non-invasive intestinal bacteria. In this investigation, the ability of human and avian C. jejuni and C. coli isolates to survive within two different intestinal epithelial cells lines, Caco-2 and INT 407, as well as the intestinal translocation phenomenon, was assessed. Our data demonstrated that both C. jejuni and C. coli strains survived in Caco-2 (81.8% and 100% respectively) and INT 407 monolayers (72.7% and 100% respectively) within the first 24 h post-infection period, with a progressive reduction in the prolonged period of 48 h and 72 h post-infection. The translocation of the non-invasive E. coli 60/06 FB was remarkably increased in C. jejuni treated Caco-2 monolayers (2.36 ± 0.42 log cfu/mL) (P < 0.01) and less in those treated with C. coli (1.2 ± 0.34 log cfu/mL), compared to E. coli 60/06 FB alone (0.37 ± 0.14 log cfu/mL). Our results evidenced the ability of both human and avian strains of C. jejuni and C. coli to efficiently survive within intestinal cells and induce the translocation of a non-invasive pathogen. Overall, these findings stress how this pathogen can interact with host cells and support the hypothesis that defects in the intestinal barrier function induced by Campylobacter spp. could have potentially negative implications for human health.

Regulation of gene expression of hcp, a core gene of the type VI secretion system in Acinetobacter baumannii causing respiratory tract infection

Purpose. The objective of the current study was to investigate whether hcp plays a role in the process of Acinetobacter baumannii infection and to examine clinically relevant factors that may affect hcp expression.Methodology. Seventy-seven A. baumannii isolates from patients with a respiratory infection at the Second Affiliated Hospital and Yuying Childrens Hospital of Wenzhou Medical University (Wenzhou, China) were included in this study. PCR was performed to screen for the presence of hcp. Quantitative real time polymerase chain reaction (qRT-PCR) was carried out to examine the expression of hcp.Results. A total of 77.9 % (60 of 77) of the A. baumannii clinical isolates possessed the hcp gene. Expression of hcp was found to be strain-specific and associated with the infection status. Higher gene expression of hcp was found for invasive A. baumannii isolates causing an infection relative to the colonization group, and for the same strain at a post-infection status compared with that prior to infection. Acid environment was also found to be a trigger of hcp gene expression.Conclusion. The type VI secretion system and hcp predominate in A. baumannii causing respiratory infections. Expression of hcp is regulated by the infection status and acid environment, and might play a role in the process of triggering infection by the colonizer.

The Campylobacter jejuni Type VI Secretion System Enhances the Oxidative Stress Response and Host Colonization

The role of the Type VI secretion system (T6SS) in Campylobacter jejuni is poorly understood despite an increasing prevalence of the T6SS in recent C. jejuni isolates in humans and chickens. The T6SS is a contractile secretion machinery capable of delivering effectors that can play a role in host colonization and niche establishment. During host colonization, C. jejuni is exposed to oxidative stress in the host gastrointestinal tract, and in other bacteria the T6SS has been linked with the oxidative stress response. In this study, comparisons of whole genome sequences of a novel human isolate 488 with previously sequenced strains revealed a single highly conserved T6SS cluster shared between strains isolated from humans and chickens. The presence of a functional T6SS in the 488 wild-type strain is indicated by expression of T6SS genes and secretion of the effector TssD. Increased expression of oxidative stress response genes katA, sodB, and ahpC, and increased oxidative stress resistance in 488 wild-type strain suggest T6SS is associated with oxidative stress response. The role of the T6SS in interactions with host cells is explored using in vitro and in vivo models, and the presence of the T6SS is shown to increase C. jejuni cytotoxicity in the Galleria mellonella infection model. In biologically relevant models, the T6SS enhances C. jejuni interactions with and invasion of chicken primary intestinal cells and enhances the ability of C. jejuni to colonize chickens. This study demonstrates that the C. jejuni T6SS provides defense against oxidative stress and enhances host colonization, and highlights the importance of the T6SS during in vivo survival of T6SS-positive C. jejuni strains.

Attenuation of Vibrio parahaemolyticus Virulence Factors by a Mixture of Natural Antimicrobials

Reducing acute mortality in aquatic crustaceans using natural alternatives to antibiotics has become a necessity, firstly for its positive impact on the aquaculture industry and, secondly, because the extensive use of antibiotics may lead to increased levels of drug resistance in pathogenic microorganisms. This study aimed to investigate the effect of a mixture of natural antimicrobials on the in vitro and in vivo virulence abilities of Type VI secretion system (T6SS)-positive Vibrio parahaemolyticus (A3 and D4), strains known as having potentially harmful health consequences for aquatic crustaceans and consumers. Herein, we report that a natural antimicrobial mixture (A3009) was capable of significantly reducing the virulence of V. parahaemolyticus strains A3 and D4 in an in vitro infection model, using the fish cell line CHSE-214, an effect which correlates with the bacterial downregulation of hcp1 and hcp2 gene expression and with the ability of the antimicrobial to efficiently retain low cytotoxic levels (p < 0.001). We show for the first time that a natural antimicrobial is able to significantly reduce the mortality of shrimps in a challenge experiment and is able to significantly attenuate H₂O₂ release during infection (p < 0.001), indicating that it could harbor positive intestinal redox balance effects.

Hyper-Aerotolerant Campylobacter coli from Duck Sources and Its Potential Threat to Public Health: Virulence, Antimicrobial Resistance, and Genetic Relatedness

Campylobacter, a common foodborne human pathogen, is considered sensitive to oxygen. Recently, aerotolerant (AT) Campylobacter jejuni with the ability to survive under aerobic stress has been reported. Here, we investigated the prevalence of hyper-aerotolerant (HAT) Campylobacter coli from duck sources (118 carcasses and meat) and its characteristics to assess potential impacts on public health. Half of 56 C. coli isolates were HAT and most harbored various virulence genes including flaA, cadF, cdtA, ceuB, and wlaN. Moreover, 98.2% of C. coli isolates showed resistance to quinolones, including ciprofloxacin (CIP), and nine (16.1%) showed high-level resistance to ciprofloxacin (Minimum Inhibitory Concentration, MIC ≥ 32 μg/mL) and most of these were HAT. Based on genetic relatedness between C. coli from duck sources and those from human sources (PubMLST and NCBI), HAT isolates sharing the same MLST sequence types were significantly more prevalent than those not sharing the same sequence types as those from human sources. Therefore, HAT C. coli is prevalent in duck sources, and is most likely transmitted to humans through the food chain given its aerotolerance. This being so, it might pose a threat to public health given its virulence and antimicrobial resistance (AMR). This study will assist in improving control strategies to reduce farm-to-table HAT C. coli transmission to humans.

Immunogenicity and protective efficacy of mucosal delivery of recombinant hcp of Campylobacter jejuni Type VI secretion system (T6SS) in chickens

The type VI secretion system (T6SS) has recently emerged as a new pattern of protein secretions in Campylobacter jejuni (C. jejuni). Within the T6SS cluster, hemolysin co-regulated protein (hcp) is considered as a hallmark of functional T6SS and holds key role in bacterial virulence. As poultry is the primary reservoir of C. jejuni and the major sources for human infection, we evaluated the capacity of recombinant hcp (rhcp) immunization in blocking C. jejuni colonization in chickens with an aim to control bacterial transmission to humans via poultry food chain. Considering the mucosal route is the primary portal for C. jejuni entry and gut mucosa offers the apposite site for C. jejuni adherence, we investigated the immune-protective potential of intra-gastric administration of rhcp using chitosan-based nanoparticles. To achieve this goal, full length coding sequence of hcp gene from C. jejuni was cloned and expressed in E. coli. Purified rhcp was entrapped in chitosan-Sodium tripolyphosphate nanoparticles (CS-TPP NPs) and orally gavaged in chickens. Our results suggest that intra-gastric immunization of CS-TPP-rhcp induces consistent and steady increase in intestinal (sIgA) and systemic antibody (IgY) response against rhcp with significant reduction in cecal load of C. jejuni. The protection afforded by rhcp associated cellular responses with Th1 and Th17 profile in terms of increased expression of NFkB, IL-1β, IL-8, IL-6, IFN-γ and IL-17 A genes. Though systemic immunization of rhcp with IFA resulting in a robust systemic (IgY) and local (sIgA) antibody response, mucosal administration of rhcp loaded CS-TPP NPs was found to be superior in terms of bacterial clearance. Altogether, present study suggests that chitosan based intra-gastric delivery of rhcp have several advantages over the injectable composition and could be a promising vaccine approach to effectively control C. jejuni colonization in chickens.

Virulence of a T6SS Campylobacter jejuni chicken isolate from North Romania

Objectives

In this study we have investigated the in vitro and in vivo virulence characteristics of a new T6SS positive Campylobacter jejuni chicken isolate (SV12) originating from a poultry population in North Romania. A detailed phenotypic characterization was performed and compared to the T6SS negative C. jejuni 81–176 wild strain.

Results

Our results indicate that the significantly higher capacity to attach and invade HCT-8 cells of C. jejuni SV12 isolate is associated with increased motility, increased resistance to bile salts and serum resistance, when compared to C. jejuni strain 81–76. Mice infected with the SV12 isolate showed statistically higher levels of colonization at both 7- and 14-days post-inoculation and in the stomach, caecum, duodenum and large intestine. Infection with the SV12 strain induced a stronger immune response as the gene transcript levels of IL-17, TNFα and IFNγ were more pronouncedly up-regulated compared to the C. jejuni strain 81–176. The present study showed that the new isolate SV12 had an enhanced virulence capacity compared to the wild strain which was evident in vivo as well. This work also provides an insight on the colonization pattern and host immune response differences between T6SS positive and T6SS negative C. jejuni.

Clinical impact of the type VI secretion system on virulence of Campylobacter species during infection

BACKGROUND

The clinical course of Campylobacter infection varies in symptoms and severity depending on host factors, virulence of the pathogen and initiated therapy. The type VI secretion system (T6SS) has been identified as a novel virulence factor, which mediates contact-dependent injection of enzymes and toxins into competing bacteria or host cells and facilitates the colonisation of a host organism. We aimed to compare the clinical course of Campylobacter infection caused by strains with and without the T6SS and identify possible associations between this putative virulence factor and the clinical manifestations of disease.

METHODS

From April 2015 to January 2017, patients with detection of Campylobacter spp. were identified at the University Hospital of Basel and the University Children's Hospital of Basel and included in this case-control study. Presence of the T6SS gene cluster was assayed by PCR targeting the hcp gene, confirmed with whole genome sequencing. Pertinent clinical data was collected by medical record review. Differences in disease- and host-characteristics between T6SS-positive (case) and -negative (control) were compared in a uni- and multi-variable analysis. Hospital admission, antibiotic therapy, admission to intensive care unit, development of bacteraemia and in-hospital mortality were considered as clinical endpoints.

RESULTS

We identified 138 cases of Campylobacter jejuni infections and 18 cases of Campylobacter coli infections from a paediatric and adult population. Analyses were focused on adult patients with C. jejuni (n = 119) of which 16.8% were T6SS-positive. Comparisons between T6SS-positive and -negative C. jejuni isolates did not reveal significant differences regarding clinical manifestations or course of disease. All clinical endpoints showed a similar distribution in both groups. A higher score in the Charlson Comorbidity Index was associated with T6SS-positive C. jejuni isolates (p < 0.001) and patients were more likely to have a solid organ transplant and to be under immunosuppressive therapy.

CONCLUSIONS

Our study does not provide evidence that T6SS is associated with a more severe clinical course. Interestingly, T6SS-positive isolates are more commonly found in immunocompromised patients: an observation which merits further investigation.

Genomic Epidemiology of Campylobacter jejuni Transmission in Israel

Objectives: Campylobacter jejuni is responsible for 80% of Campylobacter infections in Israel, a country with a high incidence reaching 91/100,000 population. We studied the phylogeny, diversity and prevalence of virulence factors using whole genome sequencing (WGS) of a national sample of C. jejuni clinical, food, and animal isolates collected over a 10-year period (2003-2012). Methods: C. jejuni isolates (n = 263) were subject to WGS using Illumina sequencing (PE 250bpx2). Raw reads and de novo assemblies were analyzed with the BioNumerics whole genome MLST (wgMLST) pipeline. Reads were screened for 71 virulence genes by the SRST2 script. Allelic profiles were analyzed to create minimum spanning trees and allelic core distances were investigated to determine a reliable cutoff for strain determination. Results: wgMLST analysis of 263 C. jejuni isolates indicated significant diversity among the prevalent clonal complexes (CCs) with CC-21 and CC-353 being the most diverse, and CC-574 the most clonal. Within CC-21, sequence type (ST)-1359 created a separate clade. Human, poultry and bovine isolates clustered together across the different STs. Forty four percent of studied isolates were assigned to 29 genetic clusters. Temporal and geographical relatedness were found among the minority of clusters, while most phylogenetically associated cases appeared diffuse and unassociated epidemiologically. The majority of virulence factors were highly prevalent across the dataset and not associated with genotype, source of isolation or invasiveness. Conversely, all 13 genes associated with type VI secretion system (T6SS) were lineage-related and identified in only 18% of the isolates. T6SS was detected in 95.2% of ST-1359, a common type in Israel. Conclusions: wgMLST supported the assessment that poultry and cattle are likely food sources of infection in Israel. Substantial genetic clustering among C. jejuni isolates suggested multiple point source and diffuse outbreaks that were previously unreported in Israel. The high prevalence of T6SS among ST-1359 isolates is unique to Israel, and requires further investigation. This study exemplifies the importance of studying foodborne pathogens using advanced genomic approaches across the entire spectrum of One Health.

A Novel Natural Antimicrobial Can Reduce the in vitro and in vivo Pathogenicity of T6SS Positive Campylobacter jejuni and Campylobacter coli Chicken Isolates

Human campylobacteriosis is considered one of the most common foodborne diseases worldwide with poultry identified as the main source of infection accounting for 50-80% of human cases. Highly virulent Campylobacter spp., positive for the Type VI secretion system (T6SS), which have an increased ability to adhere to and invade the host gastrointestinal epithelium are highly prevalent in poultry. Multidrug resistant strains of bacteria are rapidly evolving and therefore, new antimicrobials to supplement animal feed that are able to control Campylobacter species, are in great need. The work presented herein indicates that a novel phenolic antimicrobial, Auranta 3001, is able to reduce the adhesion and invasion of human intestinal epithelial cells (HCT-8) by two T6SS positive chicken isolates, C. jejuni RC039 (p < 0.05) and C. coli RC013 (p < 0.001). Exposure of C. jejuni RC039 and C. coli RC013 to Auranta 3001 downregulated the expression of hcp and cetB genes, known to be important in the functionality of T6SS. Furthermore, the reduced adhesion and invasion is associated with a significant decrease in bacterial motility of both isolates (p < 0.05-p < 0.001) in vitro. Most importantly our in vivo results show that Auranta 3001 is able to reduce cecum colonization levels from log 8 CFU/ml to log 2 CFU/ml for C. jejuni RC039 and from log 7 CFU/ml to log 2 CFU/ml for C. coli RC013. In conclusion, this novel antimicrobial is able to reduce the pathogenic properties of T6SS campylobacters in vitro and also to decrease colonization in vivo.

A Novel Natural Antimicrobial Can Reduce the in vitro and in vivo Pathogenicity of T6SS Positive Campylobacter jejuni and Campylobacter coli Chicken Isolates

Human campylobacteriosis is considered one of the most common foodborne diseases worldwide with poultry identified as the main source of infection accounting for 50-80% of human cases. Highly virulent Campylobacter spp., positive for the Type VI secretion system (T6SS), which have an increased ability to adhere to and invade the host gastrointestinal epithelium are highly prevalent in poultry. Multidrug resistant strains of bacteria are rapidly evolving and therefore, new antimicrobials to supplement animal feed that are able to control Campylobacter species, are in great need. The work presented herein indicates that a novel phenolic antimicrobial, Auranta 3001, is able to reduce the adhesion and invasion of human intestinal epithelial cells (HCT-8) by two T6SS positive chicken isolates, C. jejuni RC039 (p < 0.05) and C. coli RC013 (p < 0.001). Exposure of C. jejuni RC039 and C. coli RC013 to Auranta 3001 downregulated the expression of hcp and cetB genes, known to be important in the functionality of T6SS. Furthermore, the reduced adhesion and invasion is associated with a significant decrease in bacterial motility of both isolates (p < 0.05-p < 0.001) in vitro. Most importantly our in vivo results show that Auranta 3001 is able to reduce cecum colonization levels from log 8 CFU/ml to log 2 CFU/ml for C. jejuni RC039 and from log 7 CFU/ml to log 2 CFU/ml for C. coli RC013. In conclusion, this novel antimicrobial is able to reduce the pathogenic properties of T6SS campylobacters in vitro and also to decrease colonization in vivo.

Exploring the oxidative, antimicrobial and genomic properties of Campylobacter jejuni strains isolated from poultry

Campylobacter jejuni is the leading cause of food-borne bacterial enteritis in humans, with contaminated poultry products considered the main source of infection. To survive the food chain, C. jejuni utilizes multiple defense mechanisms that counter oxidative and aerobic stresses. In this study, we phenotypically characterised 63 C. jejuni strains with oxidative stress survival and antimicrobial susceptibility testing to investigate correlations between these two phenotypes against the source of the strains and the presence of the MarR regulators RrpA and RrpB which have a role in regulating the response to oxidative and aerobic stress. C. jejuni strains isolated from meat and neck skin displayed the highest resistance to oxidative stress. In addition, C. jejuni strains that have an rrpA⁺rrpB^- profile exhibit increased resistance to oxidative stress and to antimicrobials. Here we establish a preliminary link between the distribution of RrpA and RrpB and the increased resistance to antimicrobials. This study provides insight into how the genotypic make up of C. jejuni can influence the ability of the bacterium to survive within areas of high oxygen stress, such as the food chain, and subsequently can have a potential negative impact on human health.

Epidemiology of Campylobacter Infections among Children in Egypt

Campylobacter is a frequently isolated bacterial pathogen among children with diarrhea. Data are lacking on the distribution and spectrum of disease associated with Campylobacter species and Campylobacter jejuni capsular polysaccharide (CPS) types. This information is essential because current vaccine research seeks to target specific CPS types. An effective CPS-conjugate vaccine will need to cover CPS types that are both common and associated with severe disease. The US Naval Medical Research Unit-3 conducted several prospective cohort studies researching diarrheal disease in Egypt from 1995 to 2003. In total, 1,057 children were enrolled and followed to a maximum age of 36 months. We analyzed Campylobacter-positive stool samples that were collected while subjects were symptomatic, along with corresponding clinical data. Of 441 Campylobacter isolates, 322 represented primary infections (189 C. jejuni, 127 Campylobacter coli, six unspeciated). There were 19 C. jejuni CPS types identified; eight accounted for 63.5% of primary C. jejuni infections. We also screened for the presence of the type-6 secretion system (T6SS), a putative virulence determinant. The T6SS was found in 18.0% of C. coli isolates and 57.6% of C. jejuni isolates (P < 0.001), and was not uniformly distributed among CPS types (P < 0.001). Strains with the T6SS were not associated with more severe disease. Clinical presentations across species and CPS types appeared similar. This study adds to the growing epidemiological data and also provides some analysis of the clinical spectrum associated with infection by specific Campylobacter species, C. jejuni capsule types, and possible virulence determinants.

The In Vitro and In Vivo Effect of Carvacrol in Preventing Campylobacter Infection, Colonization and in Improving Productivity of Chicken Broilers

The current trend in reducing the antibiotic usage in animal production imposes urgency in the identification of novel biocides. The essential oil carvacrol, for example, changes the morphology of the cell and acts against a variety of targets within the bacterial membranes and cytoplasm, and our in vitro results show that it reduces adhesion and invasion of chicken intestinal primary cells and also biofilm formation. A trial was conducted to evaluate the effects of dietary supplementation of carvacrol at four concentrations (0, 120, 200, and 300 mg/kg of diet) on the performance of Lactobacillus spp., Escherichia coli, Campylobacter spp., and broilers. Each of the four diets was fed to three replicates/trial of 50 chicks each from day 0 to 35. Our results show that carvacrol linearly decreased feed intake, feed conversion rates and increased body weight at all levels of supplementation. Plate count analysis showed that Campylobacter spp. was only detected at 35 days in the treatment groups compared with the control group where the colonization occurred at 21 days. The absence of Campylobacter spp. at 21 days in the treatment groups was associated with a significant increase in the relative abundance of Lactobacillus spp. Also, carvacrol was demonstrated to have a significant effect on E. coli numbers in the cecum of the treatment groups, at all supplementation levels. In conclusion, this study shows for the first time that at different concentrations, carvacrol can delay Campylobacter spp., colonization of chicken broilers, by inducing changes in gut microflora, and it demonstrates promise as an alternative to the use of antibiotics.

Adhesion, Biofilm Formation, and Genomic Features of Campylobacter jejuni Bf, an Atypical Strain Able to Grow under Aerobic Conditions

Campylobacter jejuni is the leading cause of bacterial enteritis in Europe. Human campylobacteriosis cases are frequently associated to the consumption of contaminated poultry meat. To survive under environmental conditions encountered along the food chain, i.e., from poultry digestive tract its natural reservoir to the consumer's plate, this pathogen has developed adaptation mechanisms. Among those, biofilm lifestyle has been suggested as a strategy to survive in the food environment and under atmospheric conditions. Recently, the clinical isolate C. jejuni Bf has been shown to survive and grow under aerobic conditions, a property that may help this strain to better survive along the food chain. The aim of this study was to evaluate the adhesion capacity of C. jejuni Bf and its ability to develop a biofilm. C. jejuni Bf can adhere to abiotic surfaces and to human epithelial cells, and can develop biofilm under both microaerobiosis and aerobiosis. These two conditions have no influence on this strain, unlike results obtained with the reference strain C. jejuni 81-176, which harbors only planktonic cells under aerobic conditions. Compared to 81-176, the biofilm of C. jejuni Bf is more homogenous and cell motility at the bottom of biofilm was not modified whatever the atmosphere used. C. jejuni Bf whole genome sequence did not reveal any gene unique to this strain, suggesting that its unusual property does not result from acquisition of new genetic material. Nevertheless some genetic particularities seem to be shared only between Bf and few others strains. Among the main features of C. jejuni Bf genome we noticed (i) a complete type VI secretion system important in pathogenicity and environmental adaptation; (ii) a mutation in the oorD gene involved in oxygen metabolism; and (iii) the presence of an uncommon insertion of a 72 amino acid coding sequence upstream from dnaK, which is involved in stress resistance. Therefore, the atypical behavior of this strain under aerobic atmosphere may result from the combination of insertions and mutations. In addition, the comparison of mRNA transcript levels of several genes targeted through genome analysis suggests the modification of regulatory processes in this strain.