Evidence for acquisition of the lipooligosaccharide biosynthesis locus in Campylobacter jejuni GB11, a strain isolated from a patient with Guillain-Barré syndrome, by horizontal exchange

Molecular and in silico typing of the lipooligosaccharide biosynthesis gene cluster in Campylobacter jejuni and Campylobacter coli

The extensive genetic variation in the lipooligosaccharide (LOS) core biosynthesis gene cluster has led to the development of a classification system; with 8 classes (I-VIII) for Campylobacter coli (C. coli) LOS region and with 23 classes (A-W) or four groups (1–4) for Campylobacter jejuni (C. jejuni) LOS region. PCR based LOS locus type identification for C. jejuni clinical isolates from a UK hospital as well as in silico LOS locus analysis for C. jejuni and C. coli genome sequences from GenBank was carried out to determine the frequencies of various LOS genotypes in C. jejuni and C. coli. Analysis of LOS gene content in 60 clinical C. jejuni isolates and 703 C. jejuni genome sequences revealed that class B (Group 1) was the most abundant LOS class in C. jejuni. The hierarchy of C. jejuni LOS group prevalence (group 1 > group 2 > group 3 > group 4) as well as the hierarchy of the frequency of C. jejuni LOS classes present within the group 1 (B > C > A > R > M > V), group 2 (H/P > O > E > W), group 3 (F > K > S) and group 4 (G > L) was identified. In silico analysis of LOS gene content in 564 C. coli genome sequences showed class III as the most abundant LOS locus type in C. coli. In silico analysis of LOS gene content also identified three novel LOS types of C. jejuni and previously unknown LOS biosynthesis genes in C. coli LOS locus types I, II, III, V and VIII. This study provides C. jejuni and C. coli LOS loci class frequencies in a smaller collection of C. jejuni clinical isolates as well as within the larger, worldwide database of C. jejuni and C. coli.

Murine Models for the Investigation of Colonization Resistance and Innate Immune Responses in Campylobacter Jejuni Infections

Human infections with the food-borne pathogen Campylobacter jejuni are progressively increasing worldwide and constitute a significant socioeconomic burden to mankind. Intestinal campylobacteriosis in humans is characterized by bloody diarrhea, fever, abdominal pain, and severe malaise. Some individuals develop chronic post-infectious sequelae including neurological and autoimmune diseases such as reactive arthritis and Guillain-Barré syndrome. Studies unraveling the molecular mechanisms underlying campylobacteriosis and post-infectious sequelae have been hampered by the scarcity of appropriate experimental in vivo models. Particularly, conventional laboratory mice are protected from C. jejuni infection due to the physiological colonization resistance exerted by the murine gut microbiota composition. Additionally, as compared to humans, mice are up to 10,000 times more resistant to C. jejuni lipooligosaccharide (LOS) constituting a major pathogenicity factor responsible for the immunopathological host responses during campylobacteriosis. In this chapter, we summarize the recent progress that has been made in overcoming these fundamental obstacles in Campylobacter research in mice. Modification of the murine host-specific gut microbiota composition and sensitization of the mice to C. jejuni LOS by deletion of genes encoding interleukin-10 or a single IL-1 receptor-related molecule as well as by dietary zinc depletion have yielded reliable murine infection models resembling key features of human campylobacteriosis. These substantial improvements pave the way for a better understanding of the molecular mechanisms underlying pathogen-host interactions. The ongoing validation and standardization of these novel murine infection models will provide the basis for the development of innovative treatment and prevention strategies to combat human campylobacteriosis and collateral damages of C. jejuni infections.

Guide-free Cas9 from pathogenic Campylobacter jejuni bacteria causes severe damage to DNA

CRISPR-Cas9 systems are enriched in human pathogenic bacteria and have been linked to cytotoxicity by an unknown mechanism. Here, we show that upon infection of human cells, Campylobacter jejuni secretes its Cas9 (CjeCas9) nuclease into their cytoplasm. Next, a native nuclear localization signal enables CjeCas9 nuclear entry, where it catalyzes metal-dependent nonspecific DNA cleavage leading to cell death. Compared to CjeCas9, native Cas9 of Streptococcus pyogenes (SpyCas9) is more suitable for guide-dependent editing. However, in human cells, native SpyCas9 may still cause some DNA damage, most likely because of its ssDNA cleavage activity. This side effect can be completely prevented by saturation of SpyCas9 with an appropriate guide RNA, which is only partially effective for CjeCas9. We conclude that CjeCas9 plays an active role in attacking human cells rather than in viral defense. Moreover, these unique catalytic features may therefore make CjeCas9 less suitable for genome editing applications.

An Updated Classification System and Review of the Lipooligosaccharide Biosynthesis Gene Locus in Campylobacter jejuni

Lipooligosaccharide (LOS) is an integral component of the Campylobacter cell membrane with a structure of core oligosaccharides forming inner and outer core regions and a lipid A moiety. The gene content of the LOS core biosynthesis cluster exhibits extensive sequence variation, which leads to the production of variable cell surface LOS structures in Campylobacter. Some LOS outer core molecules in Campylobacter jejuni are molecular mimics of host structures (such as neuronal gangliosides) and are thought to trigger neuronal disorders (particularly Guillain–Barré syndrome and Miller Fisher syndrome) in humans. The extensive genetic variation in the LOS biosynthesis gene cluster, a majority of which occurs in the LOS outer core biosynthesis gene content present between lgtF and waaV, has led to the development of a classification system with 23 classes (A–W) and four groups (1–4) for the C. jejuni LOS region. This review presents an updated and simplified classification system for LOS typing alongside an overview of the frequency of C. jejuni LOS biosynthesis genotypes and structures in various C. jejuni populations.

Novel Clinical Campylobacter jejuni Infection Models Based on Sensitization of Mice to Lipooligosaccharide, a Major Bacterial Factor Triggering Innate Immune Responses in Human Campylobacteriosis

: Human Campylobacter jejuni infections inducing campylobacteriosis including post-infectious sequelae such as Guillain-Barré syndrome and reactive arthritis are rising worldwide and progress into a global burden of high socioeconomic impact. Intestinal immunopathology underlying campylobacteriosis is a classical response of the innate immune system characterized by the accumulation of neutrophils and macrophages which cause tissue destruction, barrier defects and malabsorption leading to bloody diarrhea. Clinical studies revealed that enteritis and post-infectious morbidities of human C. jejuni infections are strongly dependent on the structure of pathogenic lipooligosaccharides (LOS) triggering the innate immune system via Toll-like-receptor (TLR)-4 signaling. Compared to humans, mice display an approximately 10,000 times weaker TLR-4 response and a pronounced colonization resistance (CR) against C. jejuni maintained by the murine gut microbiota. In consequence, investigations of campylobacteriosis have been hampered by the lack of experimental animal models. We here summarize recent progress made in the development of murine C. jejuni infection models that are based on the abolishment of CR by modulating the murine gut microbiota and by sensitization of mice to LOS. These advances support the major role of LOS driven innate immunity in pathogenesis of campylobacteriosis including post-infectious autoimmune diseases and promote the preclinical evaluation of novel pharmaceutical strategies for prophylaxis and treatment.

Effects of antibiotic resistance (AR) and microbiota shifts on Campylobacter jejuni-mediated diseases

Campylobacter jejuni is an important zoonotic pathogen recently designated a serious antimicrobial resistant (AR) threat. While most patients with C. jejuni experience hemorrhagic colitis, serious autoimmune conditions can follow including inflammatory bowel disease (IBD) and the acute neuropathy Guillain Barré Syndrome (GBS). This review examines inter-relationships among factors mediating C. jejuni diarrheal versus autoimmune disease especially AR C. jejuni and microbiome shifts. Because both susceptible and AR C. jejuni are acquired from animals or their products, we consider their role in harboring strains. Inter-relationships among factors mediating C. jejuni colonization, diarrheal and autoimmune disease include C. jejuni virulence factors and AR, the enteric microbiome, and host responses. Because AR C. jejuni have been suggested to affect the severity of disease, length of infections and propensity to develop GBS, it is important to understand how these interactions occur when strains are under selection by antimicrobials. More work is needed to elucidate host-pathogen interactions of AR C. jejuni compared with susceptible strains and how AR C. jejuni are maintained and evolve in animal reservoirs and the extent of transmission to humans. These knowledge gaps impair the development of effective strategies to prevent the emergence of AR C. jejuni in reservoir species and human populations.

Milk Modulates Campylobacter Invasion into Caco-2 Intestinal Epithelial Cells

Raw milk is a recognized source of Campylobacter outbreaks, but pasteurization is an effective way to eliminate the causative agent of Campylobacteriosis. Whereas breastfeeding is protective against infectious diseases, consumption of formula milk is thought to be not. However, in relation to Campylobacter, such data is currently unavailable. Although both pasteurized and formula milk are pathogen free and prepared in a quality controlled manner, the effect they have on the virulence of Campylobacter species is unknown. Here, we studied the effect of cow, goat, horse, and formula milk on Campylobacter invasion into intestinal epithelial Caco-2 cells, a pathogenic feature of this bacterial species, using a gentamicin exclusion invasion assay. We found that all milk products modulated the invasion of Campylobacter species into the Caco-2 cells in a dose-dependent manner. Control experiments showed that the milks were not toxic for the Caco-2 cells and that the effect on invasion is caused by heat labile (e.g., milk proteins) or heat stable (e.g., sugar/lipids) components depending on the Campylobacter species studied. This in vitro study shows for the first time that pasteurized and formula milk affect the invasion of Campylobacter. We recommend a prospective study to examine whether pasteurized and formula milk affect Campylobacteriosis.

Campylobacter jejuni capsular genotypes are related to Guillain-Barré syndrome

In about one in a thousand cases, a Campylobacter jejuni infection results in the severe polyneuropathy Guillain-Barré syndrome (GBS). It is established that sialylated lipo-oligosaccharides (LOS) of C. jejuni are a crucial virulence factor in GBS development. Frequent detection of C. jejuni with sialylated LOS in stools derived from patients with uncomplicated enteritis implies that additional bacterial factors should be involved. To assess whether the polysaccharide capsule is a marker for GBS, the capsular genotypes of two geographically distinct GBS-associated C. jejuni strain collections and an uncomplicated enteritis control collection were determined. Capsular genotyping of C. jejuni strains from the Netherlands revealed that three capsular genotypes, HS1/44c, HS2 and HS4c, were dominant in GBS-associated strains and capsular types HS1/44c and HS4c were significantly associated with GBS (p 0.05 and p 0.01, respectively) when compared with uncomplicated enteritis. In a GBS-associated strain collection from Bangladesh, capsular types HS23/36c, HS19 and HS41 were most prevalent and the capsular types HS19 and HS41 were associated with GBS (p 0.008 and p 0.02, respectively). Next, specific combinations of the LOS class and capsular genotypes were identified that were related to the occurrence of GBS. Multilocus sequence typing revealed restricted genetic diversity for strain populations with the capsular types HS2, HS19 and HS41. We conclude that capsular types HS1/44c, HS2, HS4c, HS19, HS23/36c and HS41 are markers for GBS. Besides a crucial role for sialylated LOS of C. jejuni in GBS pathogenesis, the identified capsules may contribute to GBS susceptibility.

Natural transformation of Campylobacter jejuni occurs beyond limits of growth

Campylobacter jejuni is a human bacterial pathogen. While poultry is considered to be a major source of food borne campylobacteriosis, C. jejuni is frequently found in the external environment, and water is another well-known source of human infections. Natural transformation is considered to be one of the main mechanisms for mediating transfer of genetic material and evolution of the organism. Given the diverse habitats of C. jejuni we set out to examine how environmental conditions and physiological processes affect natural transformation of C. jejuni. We show that the efficiency of transformation is correlated to the growth conditions, but more importantly that transformation occurs at growth-restrictive conditions as well as in the late stationary phase; hence revealing that growth per se is not required for C. jejuni to be competent. Yet, natural transformation of C. jejuni is an energy dependent process, that occurs in the absence of transcription but requires an active translational machinery. Moreover, we show the ATP dependent ClpP protease to be important for transformation, which possibly could be associated with reduced protein glycosylation in the ClpP mutant. In contrast, competence of C. jejuni was neither found to be involved in DNA repair following DNA damage nor to provide a growth benefit. Kinetic studies revealed that several transformation events occur per cell cycle indicating that natural transformation of C. jejuni is a highly efficient process. Thus, our findings suggest that horizontal gene transfer by natural transformation takes place in various habitats occupied by C. jejuni.

[Campylobacteriosis of man : livestock as reservoir for Campylobacter species]

Over the last few years, infections with Campylobacter have significantly increased in Europe and Germany and these bacteria have even surpassed Salmonella as the most prevalent bacteria, causing gastroenteritis. Especially contamination during the handling and consumption of meat products seems to be the most important risk factor which plays a prominent role for transmission to man. In addition, contact with pets and other animals, drinking raw or improperly pasteurized milk, and the tenacity of Campylobacter in different environments, especially water, have also to be considered for an adequate risk assessment. Besides gastroenteritis, arthralgia, and Guillain-Barré syndrome are important clinical complications of Campylobacter infections in man. At the same time, it is mostly unclear why the course of infection in man and in reservoir animals differs significantly, especially as only a few classical bacterial virulence factors have been identified so far. For these reasons, the development of efficient prevention strategies is of utmost importance in order to control campylobacteriosis.

Characterization of the specific interaction between sialoadhesin and sialylated Campylobacter jejuni lipooligosaccharides

In Campylobacter jejuni-induced Guillain-Barré syndrome (GBS), molecular mimicry between C. jejuni lipooligosaccharide (LOS) and host gangliosides leads to the production of cross-reactive antibodies directed against the peripheral nerves of the host. Currently, the presence of surface exposed sialylated LOS in C. jejuni is the single known bacterial pathogenesis factor associated with the development of GBS. Using a unique, well-characterized strain collection, we demonstrate that GBS-associated C. jejuni strains bind preferentially to sialoadhesin (Sn, Siglec-1, or CD169), a sialic acid receptor found on a subset of macrophages. In addition, using a whole-cell enzyme-linked immunosorbent assay (ELISA), C. jejuni strains with sialylated LOS bound exclusively to soluble Sn. Mass spectrometry revealed that binding was sialic acid-linkage specific with a preference for alpha(2,3)-linked sialic acid attached to the terminal galactose of the LOS chain as seen in the gangliosides GD1a, GM1b, and GM3. This molecular interaction was also related to functional consequences as a GBS-associated C. jejuni strain that bound Sn in a whole-cell ELISA adhered to surface-expressed Sn of Sn-transfected CHO cells but was unable to adhere to wild-type CHO cells. Moreover, a sialic acid-negative mutant of the same C. jejuni strain was unable to bind Sn-transfected CHO cells. This is the first report of the preferential binding of GBS-associated C. jejuni strains to the Sn immune receptor (P = 0.014). Moreover, because this binding is dependent on sialylated LOS, the main pathogenic factor in GBS progression, the present findings bring us closer to unraveling the mechanisms that lead to formation of cross-reactive antibodies in GBS disease.

Host factors determine anti-GM1 response following oral challenge of chickens with Guillain-Barré syndrome derived Campylobacter jejuni strain GB11

Background

Anti-ganglioside antibodies with a pathogenic potential are present in C. jejuni-associated Guillain-Barré syndrome (GBS) patients and are probably induced by molecular mimicry. Immunization studies in rabbits and mice have demonstrated that these anti-ganglioside antibodies can be induced using purified lipo-oligosaccharides (LOS) from C. jejuni in a strong adjuvant.

Methodology/Principal Findings

To investigate whether natural colonization of chickens with a ganglioside-mimicking C. jejuni strain induces an anti-ganglioside response, and to investigate the diversity in anti-ganglioside response between and within genetically different chicken lines, we orally challenged chickens with different C. jejuni strains. Oral challenge of chickens with a C. jejuni strain from a GBS patient, containing a LOS that mimics ganglioside GM1, induced specific IgM and IgG anti-LOS and anti-GM1 antibodies. Inoculation of chickens with the Penner HS:3 serostrain, without a GM1-like structure, induced anti-LOS but no anti-ganglioside antibodies. We observed different patterns of anti-LOS/ganglioside response between and within the five strains of chickens.

Conclusions

Natural infection of chickens with C. jejuni induces anti-ganglioside antibodies. The production of antibodies is governed by both microbial and host factors.

Never take candy from a stranger: the role of the bacterial glycome in host–pathogen interactions

With the comprehensive study and complete sequencing of the Haemophilus influenzae genome in 1995 came the term ‘genomics’ and the beginning of the ‘omics’ era. Since this time, several analogous fields, such as transcriptomics and proteomics, have emerged. While growth and advancement in these fields have increased understanding of microbial virulence, the study of bacterial glycomes is still in its infancy and little is known concerning their role in host–pathogen interactions. Bacterial glycomics is challenging owing to the diversity of glyco-conjugate molecules, vast array of unusual sugars and limited number of analytical approaches available. However, recent advances in glycomics technologies offer the potential for exploration and characterization of both the structures and functions of components of bacterial glycomes in a systematic manner. Such characterization is a prerequisite for discerning the role of bacterial glycans in the interaction between host defences and bacterial virulence factors.

Sialylation of Campylobacter jejuni lipo-oligosaccharides is associated with severe gastro-enteritis and reactive arthritis

We used various genotyping methods to identify bacterial genetic markers for development of arthritic symptoms following Campylobacter enteritis. We genotyped a collection of population derived Campylobacter strains, with detailed information on clinical characteristics, including arthritic symptoms. Besides using whole genome screening methods, we focused on the lipo-oligosaccharide (LOS) gene locus in which marker genes for developing post-Campylobacter neurological disease are present. Patients with arthritic symptoms were more frequently infected with Campylobacter jejuni strains with a class A LOS locus. We also found that patients who were infected with a C. jejuni strain containing sialic acid-positive LOS (class A, B or C) more frequently had bloody diarrhoea and a longer duration of symptoms. Furthermore, the IgM antibody response against Campylobacter was stronger in patients with a sialic acid containing LOS. Ganglioside auto-antibodies were observed in a small number of patients following infection with a class C strain. We conclude that sialylation of C. jejuni LOS is not only a risk factor for development of post-infectious symptoms, but is also associated with increased severity of enteric disease.

The sialylated lipooligosaccharide outer core in Campylobacter jejuni is an important determinant for epithelial cell invasion

Campylobacter jejuni is a frequent cause of bacterial gastroenteritis worldwide. Lipooligosaccharide (LOS) has been identified as an important virulence factor that may play a role in microbial adhesion and invasion. Here we specifically address the question of whether LOS sialylation affects the interaction of C. jejuni with human epithelial cells. For this purpose, 14 strains associated with Guillain-Barré syndrome (GBS), 34 enteritis-associated strains, the 81-176 reference strain, and 6 Penner serotype strains were tested for invasion of two epithelial cell lines. C. jejuni strains expressing sialylated LOS (classes A, B, and C) invaded cells significantly more frequently than strains expressing nonsialylated LOS (classes D and E) (P < 0.0001). To further explore this observation, we inactivated the LOS sialyltransferase (Cst-II) via knockout mutagenesis in three GBS-associated C. jejuni strains expressing sialylated LOS (GB2, GB11, and GB19). All knockout strains displayed significantly lower levels of invasion than the respective wild types. Complementation of a Deltacst-II mutant strain restored LOS sialylation and reset the invasiveness to wild-type levels. Finally, formalin-fixed wild-type strains GB2, GB11 and GB19, but not the isogenic Deltacst-II mutants that lack sialic acid, were able to inhibit epithelial invasion by viable GB2, GB11, and GB19 strains. We conclude that sialylation of the LOS outer core contributes significantly to epithelial invasion by C. jejuni and may thus play a role in subsequent postinfectious pathologies.

Characterization of lipooligosaccharide-biosynthetic loci of Campylobacter jejuni reveals new lipooligosaccharide classes: evidence of mosaic organizations

The lipooligosaccharide (LOS) biosynthesis region is one of the more variable genomic regions between strains of Campylobacter jejuni. Indeed, eight classes of LOS biosynthesis loci have been established previously based on gene content and organization. In this study, we characterize additional classes of LOS biosynthesis loci and analyze various mechanisms that result in changes to LOS structures. To gain further insights into the genomic diversity of C. jejuni LOS biosynthesis region, we sequenced the LOS biosynthesis loci of 15 strains that possessed gene content that was distinct from the eight classes. This analysis identified 11 new classes of LOS loci that exhibited examples of deletions and insertions of genes and cassettes of genes found in other LOS classes or capsular biosynthesis loci leading to mosaic LOS loci. The sequence analysis also revealed both missense mutations leading to "allelic" glycosyltransferases and phase-variable and non-phase-variable gene inactivation by the deletion or insertion of bases. Specifically, we demonstrated that gene inactivation is an important mechanism for altering the LOS structures of strains possessing the same class of LOS biosynthesis locus. Together, these observations suggest that LOS biosynthesis region is a hotspot for genetic exchange and variability, often leading to changes in the LOS produced.

Bacteriophage influence Campylobacter jejuni types populating broiler chickens

The characteristics that allow one Campylobacter jejuni genotype to succeed over another under the influence of bacteriophage predation have been examined in experimental broiler chickens following the observation that this succession appeared to occur in naturally colonized broiler chicken flocks. Examination of three C. jejuni strains from a single flock indicated that horizontal transfer of at least 112 kb of genomic DNA from strain F2C10 (bacteriophage sensitive) to strain F2E1 (bacteriophage insensitive) had created strain F2E3. Transfer of this DNA was associated with acquisition of sensitivity to 6 of 25 lytic bacteriophage isolated from the same flock. All strains tested were capable of colonizing broiler chickens but cocolonization revealed that the bacteriophage sensitive strains F2E3 and F2C10 had a competitive advantage over the bacteriophage insensitive strain F2E1. With the addition of lytic bacteriophage the situation was completely reversed, with F2E1 dominating. The inability to replicate bacteriophage is associated with a significant fitness cost that renders the insensitive strain competitive only in the presence of bacteriophage. We demonstrate that interstrain recombination in vivo can generate genome diversity in C. jejuni and that bacteriophage predation is a strong selective pressure that influences the relative success of emergent strains in broiler chickens.

Comparative genomic analysis of Campylobacter jejuni associated with Guillain-Barré and Miller Fisher syndromes: neuropathogenic and enteritis-associated isolates can share high levels of genomic similarity

Background

Campylobacter jejuni infection represents the most frequent antecedent infection triggering the onset of the neuropathic disorders Guillain-Barré syndrome (GBS) and Miller Fisher syndrome (MFS). Although sialylated ganglioside-mimicking lipo-oligosaccharide (LOS) structures are the strongest neuropathogenic determinants in C. jejuni, they do not appear to be the only requirement for a neuropathic outcome since strains capable of their production have been isolated from patients with uncomplicated cases of enteritis. Consequently, other pathogen and/or host-related factors contribute to the onset of neurological complications. We have used comparative genomic hybridization to perform a detailed genomic comparison of strains isolated from GBS/MFS and enteritis-only patients. Our dataset, in which the gene conservation profile for 1712 genes was assayed in 102 strains, including 56 neuropathogenic isolates, represents the largest systematic search for C. jejuni factors associated with GBS/MFS to date and has allowed us to analyze the genetic background of neuropathogenic C. jejuni strains with an unprecedented level of resolution.

Results

The majority of GBS/MFS strains can be assigned to one of six major lineages, suggesting that several genetic backgrounds can result in a neuropathogenic phenotype. A statistical analysis of gene conservation rates revealed that although genes involved in the sialylation of LOS structures were significantly associated with neuropathogenic strains, still many enteritis-control strains both bear these genes and share remarkable levels of genomic similarity with their neuropathogenic counterparts. Two capsule biosynthesis genes (Cj1421c and Cj1428c) showed higher conservation rates among neuropathogenic strains compared to enteritis-control strains. Any potential involvement of these genes in neuropathogenesis must be assessed. A single gene (HS:3 Cj1135) had a higher conservation rate among enteritis-control strains. This gene encodes a glucosyltransferase that is found in some of the LOS classes that do not express ganglioside mimics.

Conclusion

Our findings corroborate that neuropathogenic factors may be transferred between unrelated strains of different genetic background. Our results would also suggest that the failure of some strains isolated from uncomplicated cases of enteritis to elicit a neuropathic clinical outcome may be due to subtle genetic differences that silence their neuropathogenic potential and/or due to host-related factors.

The microarray data has been deposited in NCBI's Gene Expression Omnibus under accession number GSE3579.

Application of capillary electrophoresis mass spectrometry to the characterization of bacterial lipopolysaccharides

Capillary electrophoresis (CE) is a high-resolution technique for the separation of complex biological mixtures and has been widely applied to biological analyses. The coupling of capillary electrophoresis with mass spectrometry (MS) provides a powerful approach for rapid identification of target analytes present at trace levels in biological matrices, and for structural characterization of complex biomolecules. Here we review the analytical potential of combined capillary electrophoresis electrospray mass spectrometry (CE-MS) for the analysis of bacterial lipopolysaccharides (LPS). This hyphened methodology facilitates the determination of closely related LPS glycoform and isoform families by exploiting differences in their unique molecular conformations and ionic charge distributions by electrophoretic separation. On-line CE-MS also provides an additional avenue to improve detection limits, which has been successfully applied to directly probe oligosaccharide LPS glycoform populations of bacteria isolated from infected animal models without the need for further passage.

A role for the tet(O) plasmid in maintaining Campylobacter plasticity

Genomic sequencing projects are beginning to reveal regions of extensive DNA homology between bacterial genera. Public fears of the spread of genetically modified organisms into the food chain and the increasing prevalence of multi-drug resistant disease in humans highlight the implications of horizontal gene transfer. The striking DNA sequence similarity between the two uniquely identified tetracycline resistant (Tc(R)) Campylobacter plasmids, pCC31 and pTet, suggests their conserved acquisition and maintenance within Campylobacter [Batchelor, R.A., Pearson, B.M., Friis, L.M., Guerry, P., Wells, J.M. 2004. Nucleotide sequences and comparison of two large conjugative plasmids from different Campylobacter species. Microbiology 150, 3507-3517]. It is thus likely that these and other conjugative plasmids are highly prevalent and broadly distributed across several continents. Microarray technology is now enabling fast and extensive genomic comparisons to be made and allows us to investigate intra- and inter-genetic conservation and variability. This study details the development of a microarray specific for genes from Campylobacter plasmids pCC31, pTet and pVir and its application to the analysis of Campylobacter plasmid gene presence and preservation throughout environmental and clinical isolates. Application of the iterative algorithm GENCOM (freely available at ) is used as a rapid and effective way of comparing the content and conservation of plasmids in bacteria and provides details of the Campylobacter flexible gene pool and its contribution to genomic plasticity.

Identification of DNA sequence variation in Campylobacter jejuni strains associated with the Guillain-Barré syndrome by high-throughput AFLP analysis

BACKGROUND

Campylobacter jejuni is the predominant cause of antecedent infection in post-infectious neuropathies such as the Guillain-Barré (GBS) and Miller Fisher syndromes (MFS). GBS and MFS are probably induced by molecular mimicry between human gangliosides and bacterial lipo-oligosaccharides (LOS). This study describes a new C. jejuni-specific high-throughput AFLP (htAFLP) approach for detection and identification of DNA polymorphism, in general, and of putative GBS/MFS-markers, in particular.

RESULTS

We compared 6 different isolates of the "genome strain" NCTC 11168 obtained from different laboratories. HtAFLP analysis generated approximately 3000 markers per stain, 19 of which were polymorphic. The DNA polymorphisms could not be confirmed by PCR-RFLP analysis, suggesting a baseline level of 0.6% AFLP artefacts. Comparison of NCTC 11168 with 4 GBS-associated strains revealed 23 potentially GBS-specific markers, 17 of which were identified by DNA sequencing. A collection of 27 GBS/MFS-associated and 17 enteritis control strains was analyzed with PCR-RFLP tests based on 11 of these markers. We identified 3 markers, located in the LOS biosynthesis genes cj1136, cj1138 and cj1139c, that were significantly associated with GBS (P = 0.024, P = 0.047 and P < 0.001, respectively). HtAFLP analysis of 13 highly clonal South African GBS/MFS-associated and enteritis control strains did not reveal GBS-specific markers.

CONCLUSION

This study shows that bacterial GBS markers are limited in number and located in the LOS biosynthesis genes, which corroborates the current consensus that LOS mimicry may be the prime etiologic determinant of GBS. Furthermore, our results demonstrate that htAFLP, with its high reproducibility and resolution, is an effective technique for the detection and subsequent identification of putative bacterial disease markers.

Exchange of lipooligosaccharide synthesis genes creates potential Guillain-Barre syndrome-inducible strains of Campylobacter jejuni

Human ganglioside-like structures, such as GM1, found on some Campylobacter jejuni strains have been linked to inducing the Guillain-Barré Syndrome (GBS). This study shows that a C. jejuni strain without GM1-like molecules acquired large DNA fragments, including lipooligosaccharide synthesis genes, from a strain expressing GM1-like molecules and consequently transformed into a number of potential GBS-inducible transformants, which exhibited a high degree of genetic and phenotypic diversity.

Electrophoresis-assisted open-tubular liquid chromatography/mass spectrometry for the analysis of lipooligosaccharide expressed by Campylobacter jejuni

Lipooligosaccharide (LOS) is the major component of the external membrane of Campylobacter jejuni. LOS contains a hydrophobic moiety, lipid A, and a hydrophilic moiety, oligosaccharide. Due to the unique mimicry of human ganglioside structures and potential involvement in the induction of the autoimmune polyneuropathies, Guillain-Barré and Miller Fisher syndromes, the structural characterization of C. jejuni LOS has received much attention. We have been using capillary zone electrophoresis-mass spectrometry to analyze O-deacylated LOS from C. jejuni. In an attempt to optimize the separation conditions, the effect of methanol on the separation of LOS was investigated. It was found that methanol resulted in stronger adsorption of LOS onto the wall of fused-silica capillary. In this paper, we applied this adsorption to perform electrophoresis-assisted open-tubular liquid chromatography electrospray mass spectrometry for the analysis of O-deacylated LOS mixtures from C. jejuni. The analytical potential of the proposed strategy for the analysis of O-deacylated LOS glycoforms from five bacterial colonies is demonstrated. Online tandem mass spectrometry is shown to provide a powerful tool for characterization of variations in the hexosamine backbone, phosphorylation of the lipid A, and sialic acid sequence information.

Co-infection with two different Campylobacter jejuni strains in a patient with the Guillain-Barré syndrome

Campylobacter jejuni is the predominant cause of antecedent infection in Guillain-Barré syndrome (GBS) or Miller Fisher syndrome (MFS). C. jejuni probably triggers GBS or MFS through molecular mimicry between bacterial sialylated lipo-oligosaccharides (LOS) and gangliosides in peripheral nerve tissue. We investigated whether co-infections with multiple C. jejuni strains occur in GBS or MFS patients and we further characterized these strains. PFGE analysis of 83 C. jejuni isolates from single primary colonies from stool cultures of 13 patients with GBS or MFS revealed co-infection with two different strains in one patient (8%). We showed that only strain GB5.1 contained an LOS biosynthesis gene locus that is associated with neuropathy. The patient serum strongly reacted with the LOS of strain GB5.1 and not with the LOS of strain GB5.2. Mass spectrometry revealed that both strains expressed a non-sialylated outer core structure in their LOS. The patient serum contained anti-asialo-GM2 antibodies that cross-reacted with the LOS of strain GB5.1. This study demonstrates that co-infection with multiple C. jejuni strains occurs in GBS patients. Consequently, not all C. jejuni strains isolated from the faeces of a GBS patient are involved in the pathogenesis of GBS per se. Furthermore, this is the first report in which cross-reactivity of antibodies to asialo-GM2 and to the LOS of a C. jejuni strain from a GBS patient has been demonstrated. This finding suggests that molecular mimicry with non-sialylated structures may also be involved in the pathogenesis of GBS.

Comparison of Campylobacter jejuni lipooligosaccharide biosynthesis loci from a variety of sources

Campylobacter jejuni strains exhibit significant variation in the genetic content of the lipooligosaccharide (LOS) biosynthesis loci with concomitant differences in LOS structure. The C. jejuni LOS loci have been grouped into six classes based on gene content and organization. Utilizing PCR amplifications of genes from these loci, we were able to classify a majority (80%) of the LOS biosynthesis loci from 123 strains of C. jejuni that included 39 of the Penner serotype reference strains. We found that a particular LOS class was not always associated with a specific Penner serotype, and 14 of 16 Guillain-Barré syndrome-associated isolates tested in this study shared the same LOS class. The remaining isolates that could not be classified were often distinguishable from each other based on the results of gene-specific PCR and the lengths of their LOS biosynthesis loci as determined by long (XL) PCR. Sequence analysis of two of these unique XL PCR products demonstrated two new LOS classes. These results support the hypothesis that the LOS locus is a hot spot for genetic exchange and rearrangements. Analysis of the LOS biosynthesis genes by PCR assays can be used for typing C. jejuni and offers the advantage of inferring potential LOS structures.

Brucella melitensis infection associated with Guillain-Barré syndrome through molecular mimicry of host structures

Brucella melitensis is a facultative intracellular bacterium that can survive inside macrophages and the causative agent of brucellosis. In the present study, we found that a lipooligosaccharide of B. melitensis has a GM1 ganglioside-like structure and shows a strong antibody response in mice. The cholera toxin B subunit, which binds to GM1 ganglioside specifically, reacted with the surface of B. melitensis. Immunization with B. melitensis induced the production of anti-GM1 ganglioside antibodies in mice and serum from immunized mice showed a cross-reaction with Guillain-Barré syndrome (GBS)-associated Campylobacter jejuni, but not non-GBS-associated C. jejuni. When B. melitensis was treated with a neuraminidase, antibody responses disappeared. B. melitensis immunization induced the production of anti-GM1 ganglioside antibodies in BALB/c mice but not in C57BL/6 and ddY mice, and for BALB/c mice, immunization with B. melitensis induced much greater production of anti-GM1 ganglioside than GBS-associated C. jejuni. Flaccid limb weakness was observed in B. melitensis immunized mice. These results suggest that B. melitensis is a new etiological agent for GBS and that immunological responses between it and GBS-associated C. jejuni in the mouse model may be different.

The crucial role of Campylobacter jejuni genes in anti-ganglioside antibody induction in Guillain-Barre syndrome

Molecular mimicry of Campylobacter jejuni lipo-oligosaccharides (LOS) with gangliosides in nervous tissue is considered to induce cross-reactive antibodies that lead to Guillain-Barre syndrome (GBS), an acute polyneuropathy. To determine whether specific bacterial genes are crucial for the biosynthesis of ganglioside-like structures and the induction of anti-ganglioside antibodies, we characterized the C. jejuni LOS biosynthesis gene locus in GBS-associated and control strains. We demonstrated that specific types of the LOS biosynthesis gene locus are associated with GBS and with the expression of ganglioside-mimicking structures. Campylobacter knockout mutants of 2 potential GBS marker genes, both involved in LOS sialylation, expressed truncated LOS structures without sialic acid, showed reduced reactivity with GBS patient serum, and failed to induce an anti-ganglioside antibody response in mice. We demonstrate, for the first time, to our knowledge, that specific bacterial genes are crucial for the induction of anti-ganglioside antibodies.

The crucial role of Campylobacter jejuni genes in anti-ganglioside antibody induction in Guillain-Barre syndrome

Molecular mimicry of Campylobacter jejuni lipo-oligosaccharides (LOS) with gangliosides in nervous tissue is considered to induce cross-reactive antibodies that lead to Guillain-Barre syndrome (GBS), an acute polyneuropathy. To determine whether specific bacterial genes are crucial for the biosynthesis of ganglioside-like structures and the induction of anti-ganglioside antibodies, we characterized the C. jejuni LOS biosynthesis gene locus in GBS-associated and control strains. We demonstrated that specific types of the LOS biosynthesis gene locus are associated with GBS and with the expression of ganglioside-mimicking structures. Campylobacter knockout mutants of 2 potential GBS marker genes, both involved in LOS sialylation, expressed truncated LOS structures without sialic acid, showed reduced reactivity with GBS patient serum, and failed to induce an anti-ganglioside antibody response in mice. We demonstrate, for the first time, to our knowledge, that specific bacterial genes are crucial for the induction of anti-ganglioside antibodies.

Campylobacter, from obscurity to celebrity

After its successful isolation from stools in the 1970s, Campylobacter jejuni has rapidly become the most commonly recognised cause of bacterial gastroenteritis in man. Reported cases of human campylobacteriosis represent only a small fraction of the actual number. In industrialised countries, the incidence of C. jejuni/Campylobacter coli infections peaks during infancy, and again in young adults aged 15-44 years. Acute self-limited gastrointestinal illness, characterised by diarrhoea, fever and abdominal cramps, is the most common presentation of C. jejuni/C. coli infection. The introduction of selective media has made the diagnosis of Campylobacter enteritis a simple procedure. In general, Campylobacter enteritis is a self-limiting disease which seldom requires antimicrobial therapy, although one in 1000 infections may lead to the Guillain-Barré syndrome. In industrialised countries, most infections are acquired through the handling and consumption of poultry meat. In developing countries, where the disease is confined to young children, inadequately treated water and contact with farm animals are the most important risk factors. Many infections are acquired during travel. Fluoroquinolone resistance has been reported in C. jejuni since the late 1980s in Europe and Asia, and since 1995 in the USA. The use of fluoroquinolones to treat animals used for food has accelerated this trend of resistance. In Australia, where fluoroquinolones have not been licensed for use in food production animals, C. jejuni remains susceptible to fluoroquinolones. The public health burden of Campylobacter spp. other than C. jejuni/C. coli remains unmeasured. Better diagnostic methods may reveal the true health burden of these organisms.

Analysis of Campylobacter jejuni capsular loci reveals multiple mechanisms for the generation of structural diversity and the ability to form complex heptoses

We recently demonstrated that Campylobacter jejuni produces a capsular polysaccharide (CPS) that is the major antigenic component of the classical Penner serotyping system distinguishing Campylobacter into >60 groups. Although the wide variety of C. jejuni serotypes are suggestive of structural differences in CPS, the genetic mechanisms of such differences are unknown. In this study we sequenced biosynthetic cps regions, ranging in size from 15 to 34 kb, from selected C. jejuni strains of HS:1, HS:19, HS:23, HS:36, HS:23/36 and HS:41 serotypes. Comparison of the determined cps sequences of the HS:1, HS:19 and HS:41 strains with the sequenced strain, NCTC11168 (HS:2), provides evidence for multiple mechanisms of structural variation including exchange of capsular genes and entire clusters by horizontal transfer, gene duplication, deletion, fusion and contingency gene variation. In contrast, the HS:23, HS:36 and HS:23/36 cps sequences were highly conserved. We report the first detailed structural analysis of 81-176 (HS:23/36) and G1 (HS:1) and refine the previous structural interpretations of the HS:19, HS:23, HS:36 and HS:41 serostrains. For the first time, we demonstrate the commonality and function of a second heptose biosynthetic pathway for Campylobacter CPS independent of the pathway for lipooligosaccharide (LOS) biosynthesis and identify a novel heptosyltransferase utilized by this alternate pathway. Furthermore, we show the retention of two functional heptose isomerases in Campylobacter and the sharing of a phosphatase for both LOS and CPS heptose biosynthesis.