Improved serological diagnosis stresses the major role of Campylobacter jejuni in triggering Guillain-Barré syndrome

Considerations for unblinding individual study participants during vaccine trials

Premature unblinding of individual participants is rarely reported in publications, but such unblinding can disrupt vaccine trials by causing worry and drop-out of other participants or "pseudo unblinding," in which participants or investigators over-interpret certain symptoms as being related to receiving an investigational product. This review summarizes appropriate reasons for unblinding in vaccine trials. Regulatory guidance could be improved by distinguishing guidance for vaccine trials from drug trials, with the recognition that unblinding individual participants in vaccine studies is rarely needed for management of adverse events following immunization.

Genomic adaptations of Campylobacter jejuni to long-term human colonization

BACKGROUND

Campylobacter is a genus of bacteria that has been isolated from the gastrointestinal tract of humans and animals, and the environments they inhabit around the world. Campylobacter adapt to new environments by changes in their gene content and expression, but little is known about how they adapt to long-term human colonization. In this study, the genomes of 31 isolates from a New Zealand patient and 22 isolates from a United Kingdom patient belonging to Campylobacter jejuni sequence type 45 (ST45) were compared with 209 ST45 genomes from other sources to identify the mechanisms by which Campylobacter adapts to long-term human colonization. In addition, the New Zealand patient had their microbiota investigated using 16S rRNA metabarcoding, and their level of inflammation and immunosuppression analyzed using biochemical tests, to determine how Campylobacter adapts to a changing gastrointestinal tract.

RESULTS

There was some evidence that long-term colonization led to genome degradation, but more evidence that Campylobacter adapted through the accumulation of non-synonymous single nucleotide polymorphisms (SNPs) and frameshifts in genes involved in cell motility, signal transduction and the major outer membrane protein (MOMP). The New Zealand patient also displayed considerable variation in their microbiome, inflammation and immunosuppression over five months, and the Campylobacter collected from this patient could be divided into two subpopulations, the proportion of which correlated with the amount of gastrointestinal inflammation.

CONCLUSIONS

This study demonstrates how genomics, phylogenetics, 16S rRNA metabarcoding and biochemical markers can provide insight into how Campylobacter adapts to changing environments within human hosts. This study also demonstrates that long-term human colonization selects for changes in Campylobacter genes involved in cell motility, signal transduction and the MOMP; and that genetically distinct subpopulations of Campylobacter evolve to adapt to the changing gastrointestinal environment.

Structure-Activity Relationship Study Reveals the Molecular Basis for Specific Sensing of Hydrophobic Amino Acids by the Campylobacter jejuni Chemoreceptor Tlp3

Chemotaxis is an important virulence factor of the foodborne pathogen Campylobacter jejuni. Inactivation of chemoreceptor Tlp3 reduces the ability of C. jejuni to invade human and chicken cells and to colonise the jejunal mucosa of mice. Knowledge of the structure of the ligand-binding domain (LBD) of Tlp3 in complex with its ligands is essential for a full understanding of the molecular recognition underpinning chemotaxis. To date, the only structure in complex with a signal molecule is Tlp3 LBD bound to isoleucine. Here, we used in vitro and in silico screening to identify eight additional small molecules that signal through Tlp3 as attractants by directly binding to its LBD, and determined the crystal structures of their complexes. All new ligands (leucine, valine, α-amino-N-valeric acid, 4-methylisoleucine, β-methylnorleucine, 3-methylisoleucine, alanine, and phenylalanine) are nonpolar amino acids chemically and structurally similar to isoleucine. X-ray crystallographic analysis revealed the hydrophobic side-chain binding pocket and conserved protein residues that interact with the ammonium and carboxylate groups of the ligands determine the specificity of this chemoreceptor. The uptake of hydrophobic amino acids plays an important role in intestinal colonisation by C. jejuni, and our study suggests that C. jejuni seeks out hydrophobic amino acids using chemotaxis.

Serological Markers of Recent Campylobacter jejuni Infection in Patients with Guillain-Barré Syndrome in the State of Piauí, Brazil, 2014-2016

In countries where poliomyelitis has been eradicated, Guillain-Barré syndrome (GBS) is the leading cause of acute flaccid paralysis. The range of infections that precede GBS in Brazil is unknown. Campylobacter jejuni infection is the most frequent trigger of GBS worldwide. Given the lack of systematic surveillance of diarrheal diseases, particularly in adults, the incidence of enteritis caused by C. jejuni in developing countries is unknown. From 2014 to 2016, pretreatment serum samples from 63 GBS patients were tested by immunoglobulin M (IgM) enzyme-linked immunosorbent assay for C. jejuni. Campylobacter jejuni IgM antibodies were detected in 17% (11/63) of the samples. There was no association between serological positivity (IgM) for C. jejuni and the occurrence of diarrhea among the investigated cases (P = 0.36). Hygiene measures, basic sanitation, and precautions during handling and preparation of food of animal origin may help prevent acute flaccid paralysis.

The crystal structure of the tandem-PAS sensing domain of Campylobacter jejuni chemoreceptor Tlp1 suggests indirect mechanism of ligand recognition

Chemotaxis and motility play an important role in the colonisation of avian and human hosts by Campylobacter jejuni. Chemotactic recognition of extracellular signals is mediated by the periplasmic sensing domain of methyl-accepting chemotactic proteins (membrane-embedded receptors). In this work, we report a high-resolution structure of the periplasmic sensing domain of transducer-like protein 1 (Tlp1), an aspartate receptor of C. jejuni. Crystallographic analysis revealed that it contains two Per-Arnt-Sim (PAS) subdomains. An acetate and chloride ions (both from the crystallisation buffer) were observed bound to the membrane-proximal and membrane-distal PAS subdomains, respectively. Surprisingly, despite being crystallised in the presence of aspartate, the structure did not show any electron density corresponding to this amino acid. Furthermore, no binding between the sensing domain of Tlp1 and aspartate was detected by microcalorimetric experiments. These structural and biophysical data suggest that Tlp1 does not sense aspartate directly; instead, ligand recognition is likely to occur indirectly via an as yet unidentified periplasmic binding protein.

Cloning, refolding, purification and preliminary crystallographic analysis of the sensory domain of the Campylobacter chemoreceptor for multiple ligands (CcmL)

A periplasmic sensory domain of the Campylobacter jejuni chemoreceptor for multiple ligands (CcmL) has been crystallized by the hanging-drop vapour-diffusion method using polyethylene glycol 3350 as a precipitating agent. A complete data set was collected to 1.3 Å resolution using cryocooling conditions and synchrotron radiation. The crystals belonged to space group P21, with unit-cell parameters a = 42.6, b = 138.0, c = 49.0 Å, β = 94.3°.

Cloning, expression, refolding, purification and preliminary crystallographic analysis of the sensory domain of the Campylobacter chemoreceptor for aspartate A (CcaA)

In Campylobacter jejuni, chemotaxis and motility have been identified as important virulence factors that are required for host colonization and invasion. Chemotactic recognition of extracellular signals is mediated by the periplasmic sensory domains of its transducer-like proteins (Tlps). In this study, the sensory domain of the C. jejuni chemoreceptor for aspartate A (CcaA) has been expressed in Escherichia coli and purified from inclusion bodies. The urea-denatured protein was refolded and then crystallized by the hanging-drop vapour-diffusion method using PEG 3350 as a precipitating agent. A complete data set has been collected to 1.4 Å resolution using cryocooling conditions and synchrotron radiation. The crystals belonged to space group P1, with unit-cell parameters a=39.3, b=43.3, c=50.9 Å, α=92.5, β=111.4, γ=114.7°.

Is the Campylobacter jejuni secretory protein Cj0069 a suitable antigen for serodiagnostics?

Campylobacter spp. is the most common bacterial pathogen of gastroenteritis worldwide. Poultry is the main reservoir and consequently the main origin of infections for humans. As a consequence of a primary Campylobacter infection which typically manifests as diarrhea, there is an increased risk to suffer from post-infectious complications such as reactive arthritis, neuropathia, myositis or a Guillain-Barré Syndrome. Usually the verification of acute campylobacteriosis is made by stool culture. In contrast, post-infectious complications can be diagnosed by serological assays. Since most of them are based on whole cell lysates, an insufficient specificity results from cross-reactions between related species. Therefore, the use of recombinant antigens becomes more and more favorable. Campylobacter is able to secrete a number of proteins, which are amongst others necessary for cell invasion and therefore play a crucial role for virulence. One of these, Cj0069, has a similar specificity and sensitivity in the detection of anti-Campylobacter jejuni IgG compared to the well-established antigens OMP18 and P39. This makes it a suitable antigen for diagnosing C. jejuni post-infectious complications.

Seroprevalence of campylobacteriosis and relevant post-infectious sequelae

Post-infectious sequelea such as Guillain Barré syndrome (GBS), reactive arthritis (RA), and inflammatory bowel disease (IBD) may arise as a consequence of acute Campylobacter-enteritis (AE). However, reliable seroprevalence data of Campylobacter-associated sequelae has not been established. The objectives of this study were, first, to identify the most specific and sensitive test antigen in an optimized ELISA assay for diagnosing a previous Campylobacter-infection and, second, to compare the prevalence of anti-Campylobacter antibodies in cohorts of healthy blood donors (BD), AE, GBS, RA, and IBD patients with antibodies against known GBS, RA and IBD triggering pathogens. Optimized ELISAs of single and combined Campylobacter-proteins OMP18 and P39 as antigens were prepared and sera from AE, GBS, RA and IBD patients and BD were tested for Campylobcter-specific IgA and IgG antibodies. The results were compared with MIKROGEN™-recomLine Campylobacter IgA/IgG and whole cell lysate-immunoblot. Antibodies specific for Helicobacter pylori, Mycoplasma pneumoniae, Yersinia enterocolitica, and Borrelia afzelii were tested with commercial immunoblots. ROC plot analysis revealed AUC maxima in the combination of OMP18 and P39 for IgA and in the P39-antigen for IgG. As a result, 34–49 % GBS cases, 44–62 % RA cases and 23–40 % IBD cases were associated with Campylobacter-infection. These data show that Campylobcater-seropositivity in these patient groups is significantly higher than other triggering pathogens suggesting that it plays an important role in development of GBS and RA, and supports the hypothesis that recurrent acute campylobacteriosis triggers IBD.

Characterisation of a multi-ligand binding chemoreceptor CcmL (Tlp3) of Campylobacter jejuni

Campylobacter jejuni is the leading cause of human gastroenteritis worldwide with over 500 million cases annually. Chemotaxis and motility have been identified as important virulence factors associated with C. jejuni colonisation. Group A transducer-like proteins (Tlps) are responsible for sensing the external environment for bacterial movement to or away from a chemical gradient or stimulus. In this study, we have demonstrated Cj1564 (Tlp3) to be a multi-ligand binding chemoreceptor and report direct evidence supporting the involvement of Cj1564 (Tlp3) in the chemotaxis signalling pathway via small molecule arrays, surface plasmon and nuclear magnetic resonance (SPR and NMR) as well as chemotaxis assays of wild type and isogenic mutant strains. A modified nutrient depleted chemotaxis assay was further used to determine positive or negative chemotaxis with specific ligands. Here we demonstrate the ability of Cj1564 to interact with the chemoattractants isoleucine, purine, malic acid and fumaric acid and chemorepellents lysine, glucosamine, succinic acid, arginine and thiamine. An isogenic mutant of cj1564 was shown to have altered phenotypic characteristics of C. jejuni, including loss of curvature in bacterial cell shape, reduced chemotactic motility and an increase in both autoagglutination and biofilm formation. We demonstrate Cj1564 to have a role in invasion as in in vitro assays the tlp3 isogenic mutant has a reduced ability to adhere and invade a cultured epithelial cell line; interestingly however, colonisation ability of avian caeca appears to be unaltered. Additionally, protein-protein interaction studies revealed signal transduction initiation through the scaffolding proteins CheV and CheW in the chemotaxis sensory pathway. This is the first report characterising Cj1564 as a multi-ligand receptor for C. jejuni, we therefore, propose to name this receptor CcmL, Campylobacterchemoreceptor for multiple ligands. In conclusion, this study identifies a novel multifunctional role for the C. jejuni CcmL chemoreceptor and illustrates its involvement in the chemotaxis pathway and subsequent survival of this organism in the host.

Bacterial chemotaxis is an important part in initiation of colonisation and subsequent pathogenicity. In this study, we report direct evidence supporting the involvement of C. jejuni transducer-like protein Cj1564 (Tlp3) in the chemotaxis signalling pathway via small molecule arrays, surface plasmon and nuclear magnetic resonance (SPR and NMR) as well as chemotaxis assays of wild type and isogenic mutants. We further demonstrate its ability to interact with chemoattractants isoleucine, purine, malic acid and fumaric acid and chemorepellents lysine, glucosamine, succinic acid, arginine and thiamine. This is the first report identifying Cj1564 as a multi-ligand receptor for Campylobacter jejuni and its signal transduction initiation through the CheV and CheW proteins. Finally, our characterisation of C. jejuni Cj1564 provides additional basis for elucidating the roles of other group A chemoreceptors and their importance in the chemotaxis signalling pathway.

The Campylobacter jejuni Cj0268c protein is required for adhesion and invasion in vitro

Adherence of Campylobacter jejuni to its particular host cells is mediated by several pathogen proteins. We screened a transposon-based mutant library of C. jejuni in order to identify clones with an invasion deficient phenotype towards Caco2 cells and detected a mutant with the transposon insertion in gene cj0268c. In vitro characterization of a generated non-random mutant, the mutant complemented with an intact copy of cj0268c and parental strain NCTC 11168 confirmed the relevance of Cj0268c in the invasion process, in particular regarding adherence to host cells. Whereas Cj0268c does not impact autoagglutination or motility of C. jejuni, heterologous expression in E. coli strain DH5α enhanced the potential of the complemented E. coli strain to adhere to Caco2 cells significantly and, thus, indicates that Cj0268c does not need to interact with other C. jejuni proteins to develop its adherence-mediating phenotype. Flow cytometric measurements of E. coli expressing Cj0268c indicate a localization of the protein in the periplasmic space with no access of its C-terminus to the bacterial surface. Since a respective knockout mutant possesses clearly reduced resistance to Triton X-100 treatment, Cj0268c contributes to the stability of the bacterial cell wall. Finally, we could show that the presence of cj0268c seems to be ubiquitous in isolates of C. jejuni and does not correlate with specific clonal groups regarding pathogenicity or pathogen metabolism.

Cloning, expression, and antigenicity of 14 proteins from Campylobacter jejuni

Fourteen Campylobacter jejuni genes--porA, cadF, omp18, dnaK, flaC, peb1, peb2, peb3, peb4, ahpC, groEL, tuF, hipO, and Cj0069--were cloned and expressed in Escherichia coli BL21. The recombinant proteins were purified on histidine (His) and glutathione S-transferase (GST) trap columns using the ÄKTA Explorer 100 System. Recombinant proteins were visualized using sodium dodecyl sulfate-polyacrylamide gel electrophoresis and identified using matrix-assisted laser desorption ionization time-of-flight mass spectrometry. The antigenicities of these recombinant proteins were assessed by Western blotting and enzyme-linked immunosorbent assays with anti-C. jejuni immune rabbit sera. Four recombinant proteins, including rGST-PorA, rHis-CadF, rGST-GroEL, and rGST-TuF, demonstrated reactions with both anti-serum and preimmune serum, while rHis-DnaK, rGST-FlaC, rGST-PEB2, rGST-PEB3, rGST-PEB4, and rGST-HipO showed variable antigenicity characteristics to the anti-sera derived from different C. jejuni strains. rHis-Omp18, rHis-PEB1, and rGST-AhpC demonstrated universal and specific antigenities with the entire anti-sera panel tested in this present study, while recombinant rGST-Cj0069 and rHis-DnaK did not react with any of the anti-C. jejuni sera tested. In conclusion, rGST-AhpC may be useful as a potential serodiagnostic antigen for C. jejuni infection.

Gene expression profile of Campylobacter jejuni-induced GBS in Bama miniature pigs

Our aim was to investigate the in vivo gene expression pattern of the Guillain-Barre syndrome (GBS) with DNA microarrays and bioinformatics tools. Oral-infusion model animals mimicking human infection of GBS were analyzed. Tissue samples and body fluids were collected to perform antibody tests and biopsy assays. Gene-expression microarray was conducted with nerve tissues and GBS-related genes were elucidated via bioinformatics tools. Model animals showed typical symptoms of GBS in that mild demyelination was shown by cerebellar white matter and by lumbar enlargement of model animals. Then, 81.25% of the model animals were positive with GM1-IgG antibodies by ELISA. In the microarray analysis, 1,261 genes were identified with statistically different expression (P < 0.05), 21 of which were associated with gene function analysis, gene pathway identification, signal transduction and co-expression network construction. Furthermore, quantitative PCR was used to characterize the gene expression level. We found that genes of HPRT1, PKC and PPARGC-1 were in the core of the network, while the expression of PPARGC-1, SUS2DD and AMPKA2 were significantly inhibited. A total of 21 genes were found to be actively involved in the process of protein transportation, transcriptional regulation, antigen identification and cell cycle regulation during the GBS infection period. The co-expression network indicated an important association between GBS and the 21 genes, especially the down-regulated ones. In conclusion, we demonstrated that GBS-affected hosts had a specific gene expression profile, which may guide the direction of GBS research and therapy.

Chemotaxis in Campylobacter jejuni

Chemotaxis is the common way of flagellated bacteria to direct their locomotion to sites of most favourable living conditions, that are sites with the highest concentrations of energy sources and the lowest amounts of bacteriotoxic substances. The general prerequisites for chemotaxis are chemoreceptors, a chemosensory signal-transduction system and the flagellar apparatus. Epsilonproteobacteria like Campylobacter sp. show specific variations of the common chemotaxis components. CheV, a CheW-like linking-protein with an additional response regulator (RR) domain, was identified as commonly used coupling scaffold protein of Campylobacter jejuni. It attaches the histidine autokinase (CheAY), which also has an additional RR-domain, to the chemoreceptors signalling domains. These additional RR-domains seem to play an important role in the regulation of the CheAY-phosphorylation state and thereby in sensory adaptation. The Campylobacter-chemoreceptors are arranged into the three groups A, B, and C. Group A contains membrane-anchored receptors sensing periplasmic signals, group B consists only of one receptor with two cytoplasmic ligand-proteins representing a bipartite energy taxis system that senses pyruvate and fumarate, and group C receptors are cytoplasmic signalling domains with mostly unknown cytoplasmic ligand-binding proteins as sensory constituents. Recent findings demonstrating different alleles of the TLP7 chemoreceptor, specific for formic acid, led to an amendment of this grouping.

[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.

Quantifying the association between Campylobacter infection and Guillain-Barré syndrome: a systematic review

Guillain-Barré Syndrome (GBS) is a neurologic disease that causes ascending paralysis and is triggered by a preceding bacterial or viral infection. Several studies have shown that patients with GBS have a recent history of infection due to Campylobacter jejuni. A literature review of published studies that reported rates of Campylobacter infection before or in conjunction with GBS was done. These reported data were used for calculating the proportion of GBS cases who tested positive for Campylobacter compared to the control population and the incidence of GBS among patients infected with Campylobacter. Results of the analysis suggest that 31% of 2,502 GBS cases included in these papers are attributable to Campylobacter infection.

Immunity to Campylobacter: its role in risk assessment and epidemiology

Acquired immunity is an important factor in the epidemiology of campylobacteriosis in the developing world, apparently limiting symptomatic infection to children of less than two years. However, also in developed countries the highest incidence is observed in children under five years and the majority of Campylobacter infections are asymptomatic, which may be related to the effects of immunity and/or the ingested doses. Not accounting for immunity in epidemiological studies may lead to biased results due to the misclassification of Campylobacter-exposed but apparently healthy persons as unexposed. In risk assessment studies, health risks may be overestimated when immunity is neglected.

[Diarrhea from the infectologist's point of view]

Gastroenteritis is a nonspecific term for various pathologic states of the gastrointestinal tract. Gastroenteritis causing pathogens are the second leading cause of morbidity and mortality worldwide. In the developed countries diarrhea is the most common reason for missing work, while in the developing world, it is a leading cause of death. Internationally, the mortality rate is 5-10 million deaths each year. "Traveller's diarrhea" is a polyetiologic common health problem of international travellers which affects travellers generally for days, but it can result in chronic postinfectious irritable bowel syndrome as well. Infectious agents usually cause acute gastroenteritis either by adherence of the intestinal mucosa, or by mucosal invasion, enterotoxin production, and/or cytotoxin production. The incubation period can often suggest the cause of etiology. When symptoms occur within 6 hours of eating, ingestion of preformed toxin of S. aureus or Bacillus cereus should be suspected. The incidence of hypervirulent C. difficile associated colitis is an emerging problem as a healthcare system associated infection. While infectious agents do not commonly cause chronic diarrhea, those that do include C. difficile, Giardia lamblia, Entamoeba histolytica, Cryptosporidium, Aeromonas and Yersinia . Amoebiasis is the second to malaria as a protozoal cause of death. Infection with HIV is also a common cause of diarrhea.

Antiganglioside antibodies and their pathophysiological effects on Guillain-Barré syndrome and related disorders--a review

Guillain-Barré syndrome (GBS) is an acute immune-mediated polyradiculoneuropathy which can cause acute quadriplegia. Infection with micro-organisms, including Campylobacter jejuni (C. jejuni), Haemophilus influenzae, and Cytomegalovirus (CMV), is recognized as a main triggering event for the disease. Lipooligosaccharide (LOS) genes are responsible for the formation of human ganglioside-like LOS structures in infectious micro-organisms that can induce GBS. Molecular mimicry of LOSs on the surface of infectious agents and of ganglioside antigens on neural cells is thought to induce cross-reactive humoral and cellular immune responses. Patients with GBS develop antibodies against those gangliosides, resulting in autoimmune targeting of peripheral nerve sites, leading to neural damage. Heterogeneity of ganglioside expression in the peripheral nervous system (PNS) may underlie the differential clinical manifestation of the GBS variants. Recent studies demonstrate that some GBS sera react with ganglioside complexes consisting of two different gangliosides, such as GD1a and GD1b, or GM1 and GD1a, but not with each constituent ganglioside alone. The discovery of antiganglioside complex antibodies not only improves the detection rate of autoantibodies in GBS, but also provides a new concept in the antibody-antigen interaction through clustered carbohydrate epitopes. Although ganglioside mimicry is one of the possible etiological causes of GBS, unidentified factors may also contribute to the pathogenesis of GBS. While GBS is not considered a genetic disease, host factors, particularly human lymphocyte antigen type, appear to have a role in the pathogenesis of GBS following C. jejuni infection.

Continued decline in the incidence of Campylobacter infections, FoodNet 1996-2006

Campylobacter is a leading cause of foodborne illness worldwide. In the United States, changes in the incidence of culture-confirmed Campylobacter infections have been monitored by the Foodborne Diseases Active Surveillance Network (FoodNet) since 1996. In 2006, the incidence of culture-confirmed Campylobacter infection in the FoodNet sites was 12.7 per 100,000 persons. This represents a 30% decline (95% confidence = 35% to 24% decrease) compared to the 1996-1998 illness baseline; however, most of the decline occurred between 1996 and 1999 and the incidence still remains above the national health objective. Important declines were observed in four FoodNet sites (California, Connecticut, Georgia, and Maryland), all age groups, and both sexes. To promote continued progress towards achieving the national health objective, the epidemiology of Campylobacter infections in the United States, including geographic variation and higher incidence among the very young, warrants further study.

Validation of an ELISA for the diagnosis of recent Campylobacter infections in Guillain–Barré and reactive arthritis patients

Weeks or months following Campylobacter infection, a small proportion of infected individuals develop Guillain-Barré syndrome (GBS) or reactive arthritis (ReA). Stool culture for Campylobacter is often negative in these patients, and serology is therefore the method of choice for diagnosing a recent infection with Campylobacter. This study developed a capture ELISA system to detect anti-Campylobacter IgA and IgM antibodies indicative of a recent infection. The sensitivity of the assay was 82.0% in uncomplicated Campylobacter enteritis patients, 96.2% in GBS patients who were culture-positive for Campylobacter, and 93.1% in culture-positive ReA patients, with a specificity of 93.0%. The assay allows identification of Campylobacter infection in patients with post-infectious neurological and rheumatological complications.

Role of the plasmid-encoded tet(O) gene in tetracycline-resistant clinical isolates of Campylobacter jejuni and Campylobacter coli

The prevalence of tetracycline resistance, tetracycline MICs and tet(O) gene localization were investigated in 83 Campylobacter isolates from patients suffering from acute gastroenteritis in Germany. Combined biochemical and molecular markers identified 74 isolates (89 %) as Campylobacter jejuni, including seven atypical isolates that failed to hydrolyse hippurate, and nine isolates (11 %) as Campylobacter coli. Tetracycline resistance was detected in six out of nine Campylobacter coli isolates (67 %) and 13 out of 74 C. jejuni isolates (18 %). Low-level tetracycline resistance was observed for C. coli (MIC 16 microg ml(-1) for all strains), whereas C. jejuni showed high-level resistance (MIC >256 microg ml(-1) for all strains). Both low- and high-level tetracycline resistance was associated with the presence of the tet(O) gene. In C. jejuni, tet(O) was plasmid-encoded in 54 % of tetracycline-resistant isolates, whereas in C. coli, tet(O) appeared to be located on the chromosome.