Summary
Campylobacter jejuni is a major cause of bacterial gastroenteritis worldwide, primarily associated with the consumption of contaminated poultry. C. jejuni lineages vary in host range and ...prevalence in human infection, suggesting differences in survival throughout the poultry processing chain. From 7343 MLST‐characterised isolates, we sequenced 600 C. jejuni and C. coli isolates from various stages of poultry processing and clinical cases. A genome‐wide association study (GWAS) in C. jejuni ST‐21 and ST‐45 complexes identified genetic elements over‐represented in clinical isolates that increased in frequency throughout the poultry processing chain. Disease‐associated SNPs were distinct in these complexes, sometimes organised in haplotype blocks. The function of genes containing associated elements was investigated, demonstrating roles for cj1377c in formate metabolism, nuoK in aerobic survival and oxidative respiration, and cj1368‐70 in nucleotide salvage. This work demonstrates the utility of GWAS for investigating transmission in natural zoonotic pathogen populations and provides evidence that major C. jejuni lineages have distinct genotypes associated with survival, within the host specific niche, from farm to fork.
produces a genotoxin, cytolethal distending toxin (CDT), which has DNAse activity and causes DNA double-strand breaks. Although
infection has been shown to promote intestinal inflammation, the impact ...of this bacterium on carcinogenesis has never been examined.
Germ-free (GF)
mice, fed with 1% dextran sulfate sodium, were used to test tumorigenesis potential of CDT-producing
. Cells and enteroids were exposed to bacterial lysates to determine DNA damage capacity via γH2AX immunofluorescence, comet assay and cell cycle assay. To examine the interplay of CDT-producing
, gut microbiome and host in tumorigenesis, colonic RNA-sequencing and faecal 16S rDNA sequencing were performed. Rapamycin was administrated to investigate the prevention of CDT-producing
-induced tumorigenesis.
GF
mice colonised with human clinical isolate
81-176 developed significantly more and larger tumours when compared with uninfected mice.
with a mutated
subunit, mut
, attenuated
-induced tumorigenesis in vivo and decreased DNA damage response in cells and enteroids.
infection induced expression of hundreds of colonic genes, with 22 genes dependent on the presence of c
The
-infected group had a significantly different microbial gene expression profile compared with the mut
group as shown by metatranscriptomic data, and different microbial communities as measured by 16S rDNA sequencing. Finally, rapamycin could diminish the tumorigenic capability of
.
Human clinical isolate
81-176 promotes colorectal cancer and induces changes in microbial composition and transcriptomic responses, a process dependent on CDT production.
In response to changes in their environment bacteria need to change both their protein and phospholipid repertoire to match environmental requirements, but the dynamics of bacterial phospholipid ...composition under different growth conditions is still largely unknown. In the present study, we investigated the phospholipidome of the bacterial pathogen Campylobacter jejuni. Transcription profiling on logarithmic and stationary phase grown cells of the microaerophilic human pathogen C. jejuni using RNA-seq revealed differential expression of putative phospholipid biosynthesis genes. By applying high-performance liquid chromatography tandem–mass spectrometry, we identified 203 phospholipid species representing the first determination of the phospholipidome of this pathogen. We identified nine different phospholipid classes carrying between one and three acyl chains. Phospholipidome analysis on bacteria of different ages (0–5 days) showed rapid changes in the ratio of phospholipids containing ethanolamine, or glycerol as phospholipid head group and in the number of cyclopropane bond containing fatty acids. Oxygen concentration influenced the percentage of lysophospholipids, and cyclo-propane bonds containing acyl chains. We show that large amounts of the phospholipids are lysophospholipids (30–45%), which mutant studies reveal are needed for normal C. jejuni motility at low oxygen conditions. C. jejuni possesses an unusual phospholipidome that is highly dynamic in response to environmental changes.
Display omitted
•First analysis of the complete phospholipidome of the bacterial pathogen C. jejuni•Nine phospholipid classes were discovered carrying between one and three acyl chains•C.jejuni phospholipidome possess an unusually high percentage of lysophospholipids.•Lysophospholipids are needed to allow C.jejuni to be motile under low O2 conditions.•The C.jejuni phospholipidome is highly dynamic in response to environmental changes.
spp., especially
and
, are leading bacterial foodborne pathogens worldwide. In the United States, an estimated 0.8 million cases of campylobacteriosis occur annually, mostly involving
...Campylobacteriosis is generally self-limiting, but in severe cases, treatment with antibiotics may be mandated. The increasing incidence of fluoroquinolone resistance in
has rendered macrolides such as erythromycin and azithromycin the drugs of choice for human campylobacteriosis. The prevalence of macrolide resistance in
remains low, but macrolide resistance can be common in
Substitutions in the 23S rRNA gene, specifically A2075G, and less frequently A2074C/G, remain the most common mechanism for high-level resistance to macrolides. In
, resistance mediated by such substitutions is accompanied by a reduced ability to colonize chickens and other fitness costs, potentially contributing to the low incidence of macrolide resistance. Interestingly, similar fitness impacts have not been noted in
Also noteworthy is a novel mechanism first reported in 2014 for a
isolate from China and mediated by
(B) harbored on multidrug resistance genomic islands. The incidence of
(B) appears to reflect clonal expansion of certain strains, and whole-genome sequencing has been critical to the elucidation of
(B)-associated macrolide resistance in
spp. With the exception of one report from Spain,
(B)-mediated macrolide resistance has been restricted to
spp., mostly
, of animal and human origin from China. If
(B)-mediated macrolide resistance does not confer fitness costs in
, the range of this gene may expand in
, threatening to compromise treatment effectiveness for severe campylobacteriosis cases.
Despite the importance of Campylobacter jejuni as a pathogen, little is known about the fundamental aspects of its peptidoglycan (PG) structure and factors modulating its helical morphology. A PG ...dl-carboxypeptidase Pgp1 essential for maintenance of C. jejuni helical shape was recently identified. Bioinformatic analysis revealed the CJJ81176_0915 gene product as co-occurring with Pgp1 in several organisms. Deletion of cjj81176_0915 (renamed pgp2) resulted in straight morphology, representing the second C. jejuni gene affecting cell shape. The PG structure of a Δpgp2 mutant showed an increase in tetrapeptide-containing muropeptides and a complete absence of tripeptides, consistent with ld-carboxypeptidase activity, which was confirmed biochemically. PG analysis of a Δpgp1Δpgp2 double mutant demonstrated that Pgp2 activity is required to generate the tripeptide substrate for Pgp1. Loss of pgp2 affected several pathogenic properties; the deletion strain was defective for motility in semisolid agar, biofilm formation, and fluorescence on calcofluor white. Δpgp2 PG also caused decreased stimulation of the human nucleotide-binding oligomerization domain 1 (Nod1) proinflammatory mediator in comparison with wild type, as expected from the reduction in muropeptide tripeptides (the primary Nod1 agonist) in the mutant; however, these changes did not alter the ability of the Δpgp2 mutant strain to survive within human epithelial cells or to elicit secretion of IL-8 from epithelial cells after infection. The pgp2 mutant also showed significantly reduced fitness in a chick colonization model. Collectively, these analyses enhance our understanding of C. jejuni PG maturation and help to clarify how PG structure and cell shape impact pathogenic attributes.
Background:C. jejuni helical shape is important to pathogenesis.
Results: Deletion of pgp2 results in loss of C. jejuni helical shape and change in peptidoglycan structure and pathogenic properties.
Conclusion: Pgp2 is a ld-carboxypeptidase cleaving peptidoglycan tetrapeptides to tripeptides.
Significance: Characterization of enzymes involved in C. jejuni peptidoglycan and cell shape maintenance is crucial to the understanding of fundamental properties of this organism.
Antibiotic resistance is a major health problem, as drugs that were once highly effective no longer cure bacterial infections. WGS has previously been shown to be an alternative method for detecting ...horizontally acquired antimicrobial resistance genes. However, suitable bioinformatics methods that can provide easily interpretable, accurate and fast results for antimicrobial resistance associated with chromosomal point mutations are still lacking.
Phenotypic antimicrobial susceptibility tests were performed on 150 isolates covering three different bacterial species: Salmonella enterica, Escherichia coli and Campylobacter jejuni. The web-server ResFinder-2.1 was used to identify acquired antimicrobial resistance genes and two methods, the novel PointFinder (using BLAST) and an in-house method (mapping of raw WGS reads), were used to identify chromosomal point mutations. Results were compared with phenotypic antimicrobial susceptibility testing results.
A total of 685 different phenotypic tests associated with chromosomal resistance to quinolones, polymyxin, rifampicin, macrolides and tetracyclines resulted in 98.4% concordance. Eleven cases of disagreement between tested and predicted susceptibility were observed: two C. jejuni isolates with phenotypic fluoroquinolone resistance and two with phenotypic erythromycin resistance and five colistin-susceptible E. coli isolates with a detected pmrB V161G mutation when assembled with Velvet, but not when using SPAdes or when mapping the reads.
PointFinder proved, with high concordance between phenotypic and predicted antimicrobial susceptibility, to be a user-friendly web tool for detection of chromosomal point mutations associated with antimicrobial resistance.
In 2014, antimicrobial drug-resistant Campylobacter jejuni sequence type 6964 emerged contemporaneously in poultry from 3 supply companies in the North Island of New Zealand and as a major cause of ...campylobacteriosis in humans in New Zealand. This lineage, not previously identified in New Zealand, was resistant to tetracycline and fluoroquinolones. Genomic analysis revealed divergence into 2 major clades; both clades were associated with human infection, 1 with poultry companies A and B and the other with company C. Accessory genome evolution was associated with a plasmid, phage insertions, and natural transformation. We hypothesize that the tetO gene and a phage were inserted into the chromosome after conjugation, leaving a remnant plasmid that was lost from isolates from company C. The emergence and rapid spread of a resistant clone of C. jejuni in New Zealand, coupled with evolutionary change in the accessory genome, demonstrate the need for ongoing Campylobacter surveillance among poultry and humans.
New approaches for the control of Campylobacter jejuni biofilms in the food industry are being studied intensively. Natural products are promising alternative antimicrobial substances to control ...biofilm production, with particular emphasis on plant extracts. Dried flowers of
were used to produce essential oil (LEO), an ethanol extract (LEF), and an ethanol extract of
postdistillation waste material (LEW). The chemical compositions determined for these
preparations included seven major compounds that were selected for further testing. These were tested against C. jejuni for biofilm degradation and removal. Next-generation sequencing was used to study the molecular mechanisms underlying LEO actions against C. jejuni adhesion and motility. Analysis of LEO revealed 1,8-cineol, linalool, and linalyl acetate as the main components. For LEF and LEW, the main components were phenolic acid glycosides, with flavonoids rarely present. The MICs of the
preparations and pure compounds against C. jejuni ranged from 0.2 mg/ml to 1 mg/ml. LEO showed the strongest biofilm degradation. The reduction of C. jejuni adhesion was ≥1 log
CFU/ml, which satisfies European Food Safety Authority recommendations.
preparations reduced C. jejuni motility by almost 50%, which consequently can impact biofilm formation. These data are in line with the transcriptome analysis of C. jejuni, which indicated that LEO downregulated genes important for biofilm formation. LEW also showed good antibacterial and antibiofilm effects, particularly against adhesion and motility mechanisms. This defines an innovative approach using alternative strategies and novel targets to combat bacterial biofilm formation and, hence, the potential to develop new effective agents with biofilm-degrading activities.
The
preparations used in this study are found to be effective against C. jejuni, a common foodborne pathogen. They show antibiofilm properties at subinhibitory concentrations in terms of promoting biofilm degradation and inhibiting cell adhesion and motility, which are involved in the initial steps of biofilm formation. These results are confirmed by transcriptome analysis, which highlights the effect of
essential oil on C. jejuni biofilm properties. We show that the waste material from the hydrodistillation of
has particular antibiofilm effects, suggesting that it has potential for reuse for industrial purposes. This study highlights the need for efforts directed toward such innovative approaches and alternative strategies against biofilm formation and maintenance by developing new naturally derived agents with antibiofilm activities.
Campylobacter jejuni is a foodborne bacterial pathogen that is common in the developed world. However, we know less about its biology and pathogenicity than we do about other less prevalent ...pathogens. Interest in C. jejuni has increased in recent years as a result of the growing appreciation of its importance as a pathogen and the availability of new model systems and genetic and genomic technologies. C. jejuni establishes persistent, benign infections in chickens and is rapidly cleared by many strains of laboratory mouse, but causes significant inflammation and enteritis in humans. Comparing the different host responses to C. jejuni colonization should increase our understanding of this organism.
PDF
