Validation of an rpoB gene PCR assay for detection of Tropheryma whipplei: 10 years' experience in a National Reference Laboratory.

The performance of a real-time PCR assay targeting the Tropheryma whipplei rpoB gene was evaluated using test strains and 1,236 clinical specimens in a national reference laboratory. The novel rpoB-PCR assay proved to be specific, revealed improved analytical sensitivity, and substantially accelerated detection of T. whipplei DNA in clinical specimens.

Use of a commercial PCR-based line blot method for identification of bacterial pathogens and the mecA and van genes from BacTAlert blood culture bottles.

In this study, the PCR-based DNA strip assay GenoType BC for the identification of bacteria and the resistance genes mecA, vanA, vanB, vanC1, and vanC2/3 directly from positive BacTAlert blood culture bottles was evaluated in a multicenter study. Of a total of 511 positive blood cultures, correct identification percentages for Gram-negative bacteria, Gram-positive bacteria, and the mecA gene were 96.1%, 89.9%, and 92.9%, respectively. Results were available 4 h after growth detection.

MyD88/TLR9 mediated immunopathology and gut microbiota dynamics in a novel murine model of intestinal graft-versus-host disease.

BACKGROUND: The bacterial microflora aggravates graft-versus-host-disease (GvHD) after allogeneic stem cell transplantation, but the underlying mechanisms of manifestations of intestinal GvHD (iGvHD) in the gut remain poorly understood. AIM: To analyse the gut flora composition and the impact of bacterial sensing via Toll-like receptors (TLRs) in iGvHD. METHODS: By mimicking clinical low-intensity conditioning regimens used in humans, a novel irradiation independent, treosulfan and cyclophosphamide-based murine allogeneic transplantation model was established. A global survey of the intestinal microflora by cultural and molecular methods was performed, the intestinal immunopathology in TLR-deficient recipient mice with iGvHD investigated and finally, the impact of anti-TLR9 treatment on iGvHD development assessed. RESULTS: The inflammatory responses in iGvHD were accompanied by gut flora shifts towards enterobacteria, enterococci and Bacteroides/Prevotella spp. Analysis of iGvHD in MyD88(-/-), TRIF(-/-), TLR2/4(-/-), and TLR9(-/-) recipient mice showed that bacterial sensing via TLRs was essential for iGvHD development. Acute iGvHD was characterised by increasing numbers of apoptotic cells, proliferating cells, T cells and neutrophils within the colon. These responses were significantly reduced in MyD88(-/-), TLR2/4(-/-), TRIF(-/-) and TLR9(-/-) mice, as compared with wild-type controls. However, TRIF(-/-) and TLR2/4(-/-) mice were not protected from mortality, whereas TLR9(-/-) mice displayed increased survival rates. The important role of TLR9-mediated immunopathology was independently confirmed by significantly reduced macroscopic disease symptoms and colonic apoptosis as well as by reduced T-cell and neutrophil numbers within the colon after treatment with a synthetic inhibitory oligonucleotide. CONCLUSIONS: These results emphasise the critical role of gut microbiota, innate immunity and TLR9 in iGvHD and highlight anti-TLR9 strategies as novel therapeutic options.

Filifactor alocis--involvement in periodontal biofilms.

BACKGROUND: Bacteria in periodontal pockets develop complex sessile communities that attach to the tooth surface. These highly dynamic microfloral environments challenge both clinicians and researchers alike. The exploration of structural organisation and bacterial interactions within these biofilms is critically important for a thorough understanding of periodontal disease. In recent years, Filifactor alocis, a fastidious, Gram-positive, obligately anaerobic rod was repeatedly identified in periodontal lesions using DNA-based methods. It has been suggested to be a marker for periodontal deterioration. The present study investigated the epidemiology of F. alocis in periodontal pockets and analysed the spatial arrangement and architectural role of the organism in in vivo grown subgingival biofilms. RESULTS: A species-specific oligonucleotide probe, FIAL, was designed and evaluated. A total of 490 subgingival plaque samples were submitted to PCR and subsequent dot blot hybridization to compare the prevalence of F. alocis in patients suffering from generalized aggressive periodontitis (GAP), chronic periodontitis (CP), and control subjects resistant to periodontitis. Moreover, a specially designed carrier system was used to collect in vivo grown subgingival biofilms from GAP patients. Subsequent topographic analysis was performed using fluorescence in situ hybridization.While the majority of patients suffering from GAP or CP harboured F. alocis, it was rarely detected in the control group. In the examined carrier-borne biofilms the organism predominantly colonized apical parts of the pocket in close proximity to the soft tissues and was involved in numerous structures that constitute characteristic architectural features of subgingival periodontal biofilms. CONCLUSIONS: F. alocis is likely to make a relevant contribution to the pathogenetic structure of biofilms accounting for periodontal inflammation and can be considered an excellent marker organism for periodontal disease.

Molecular epidemiology and spatial distribution of Selenomonas spp. in subgingival biofilms.

The aetiology of periodontal disease has been a field of intensive research in the past decades. Along with a variety of other putative pathogens, different members of the genus Selenomonas have repeatedly been associated with both generalized aggressive periodontitis and chronic periodontitis. For the present study, a specific oligonucleotide probe targeting the majority of all oral Selenomonas spp. was designed. Their prevalence was determined, using dot-blot hybridization, in a total of 742 subgingival samples collected from patients with generalized aggressive (n=62) and chronic periodontitis (n=82), and from periodontitis-resistant subjects (n=19). In addition, fluorescence in situ hybridization (FISH) and electron microscopy were performed to analyze the spatial arrangement of Selenomonas in subgingival biofilms collected from patients with generalized aggressive periodontitis. In the samples from patients, Selenomonas spp. showed a lower prevalence in both diseased groups compared with other putative pathogens, and a relatively high prevalence in the periodontitis-resistant group. Consequently, Selenomonas spp. do not seem to be suitable diagnostic marker organisms for periodontal disease. By contrast, FISH and electron microscopic analysis of periodontal carriers revealed that Selenomonas spp. appeared in large numbers in all parts of the collected biofilms and seemed, if present in a site from patients, to make a relevant contribution to their structural organization.

Investigation of the intestinal microbiota in preterm infants using different methods.

Modifications in microbial colonization of the human gut are believed to affect intestinal homeostasis and increase the risk of gastrointestinal diseases. The present study examined different methods for investigating the dynamic characterization of the intestinal microbiota in preterm infants. Fecal samples were collected weekly from ten preterm infants during their stay in a neonatal intensive care unit. The infants had a mean gestational age of 29 weeks (range: 28-32 weeks) and a mean birth weight of 1233g (range: 935-1450g). Bacterial colonization was assessed using conventional culture techniques and molecular biological methods. More specifically, the recently developed denaturing high performance liquid chromatography (dHPLC) technique was compared to established methods such as temporal temperature gradient gel electrophoresis (TTGE) and rRNA gene library sequencing. Our results indicate that the gastrointestinal tract of preterm infants, born at a gestational age of less than 33 weeks, has a low biodiversity of mainly, culturable bacteria. Finally, dHPLC was evaluated in terms of speed, labor and sensitivity for its use as a tool to analyze microbial colonization in preterm infants. We found that this technique provided major improvements over gel-based fingerprinting methods, such as TTGE, that are commonly used for studying microbial ecology. As such, it may become a common analytical tool for this purpose.

Rapid and accurate diagnosis of human intestinal spirochetosis by fluorescence in situ hybridization.

Human intestinal spirochetosis (HIS) is associated with overgrowth of the large intestine by spirochetes of the genus Brachyspira. The microbiological diagnosis of HIS is hampered by the fastidious nature and slow growth of Brachyspira spp. In clinical practice, HIS is diagnosed histopathologically, and a significant portion of cases may be missed. Fluorescence in situ hybridization (FISH) is a molecular method that allows the visualization and identification of single bacteria within tissue sections. In this study, we analyzed intestinal biopsy samples from five patients with possible HIS. All specimens yielded positive results by histopathological techniques. PCR amplification and sequencing of the 16S rRNA gene were performed. Sequences of two isolates clustered in the group of Brachyspira aalborgi, whereas in three cases, the sequences were highly similar to that of Brachyspira pilosicoli. Three phylotypes showed mismatches at distinct nucleotide positions with Brachyspira sp. sequences published previously. In addition, culture for Brachyspira was successful in three cases. On the basis of these data, we designed and evaluated a Brachyspira genus-specific 16S rRNA-directed FISH probe that detects all of the Brachyspira spp. published to date. FISH of biopsy samples resulted in strong, unequivocal signals of brush-like formations at the crypt surfaces. This technique allowed simultaneous visualization of single spirochetes and their identification as Brachyspira spp. In conclusion, FISH provides a fast and accurate technique for the visualization and identification of intestinal spirochetes in tissue sections. It therefore represents a valuable tool for routine diagnosis of HIS.

Are putative periodontal pathogens reliable diagnostic markers?

Periodontitis is one of the most common chronic inflammatory diseases. A number of putative bacterial pathogens have been associated with the disease and are used as diagnostic markers. In the present study, we compared the prevalence of oral bacterial species in the subgingival biofilm of generalized aggressive periodontitis (GAP) (n = 44) and chronic periodontitis (CP) (n = 46) patients with that of a periodontitis-resistant control group (PR) (n = 21). The control group consisted of subjects at least 65 years of age with only minimal or no periodontitis and no history of periodontal treatment. A total of 555 samples from 111 subjects were included in this study. The samples were analyzed by PCR of 16S rRNA gene fragments and subsequent dot blot hybridization using oligonucleotide probes specific for Aggregatibacter (Actinobacillus) actinomycetemcomitans, Porphyromonas gingivalis, Prevotella intermedia, Tannerella forsythia, a Treponema denticola-like phylogroup (Treponema phylogroup II), Treponema lecithinolyticum, Campylobacter rectus, Fusobacterium spp., and Fusobacterium nucleatum, as well as Capnocytophaga ochracea. Our data confirm a high prevalence of the putative periodontal pathogens P. gingivalis, P. intermedia, and T. forsythia in the periodontitis groups. However, these species were also frequently detected in the PR group. For most of the species tested, the prevalence was more associated with increased probing depth than with the subject group. T. lecithinolyticum was the only periodontopathogenic species showing significant differences both between GAP and CP patients and between GAP patients and PR subjects. C. ochracea was associated with the PR subjects, regardless of the probing depth. These results indicate that T. lecithinolyticum may be a diagnostic marker for GAP and C. ochracea for periodontal health. They also suggest that current presumptions of the association of specific bacteria with periodontal health and disease require further evaluation.

The missing link: Bordetella petrii is endowed with both the metabolic versatility of environmental bacteria and virulence traits of pathogenic Bordetellae.

BACKGROUND: Bordetella petrii is the only environmental species hitherto found among the otherwise host-restricted and pathogenic members of the genus Bordetella. Phylogenetically, it connects the pathogenic Bordetellae and environmental bacteria of the genera Achromobacter and Alcaligenes, which are opportunistic pathogens. B. petrii strains have been isolated from very different environmental niches, including river sediment, polluted soil, marine sponges and a grass root. Recently, clinical isolates associated with bone degenerative disease or cystic fibrosis have also been described. RESULTS: In this manuscript we present the results of the analysis of the completely annotated genome sequence of the B. petrii strain DSMZ12804. B. petrii has a mosaic genome of 5,287,950 bp harboring numerous mobile genetic elements, including seven large genomic islands. Four of them are highly related to the clc element of Pseudomonas knackmussii B13, which encodes genes involved in the degradation of aromatics. Though being an environmental isolate, the sequenced B. petrii strain also encodes proteins related to virulence factors of the pathogenic Bordetellae, including the filamentous hemagglutinin, which is a major colonization factor of B. pertussis, and the master virulence regulator BvgAS. However, it lacks all known toxins of the pathogenic Bordetellae. CONCLUSION: The genomic analysis suggests that B. petrii represents an evolutionary link between free-living environmental bacteria and the host-restricted obligate pathogenic Bordetellae. Its remarkable metabolic versatility may enable B. petrii to thrive in very different ecological niches.

Occurrence and clinical relevance of Mycobacterium chimaera sp. nov., Germany.

Retrospective molecular genetic analysis of 166 Mycobacterium intracellulare isolates showed that 143 (86%) strains could be assigned to Mycobacterium chimaera sp. nov. Of 97 patients from whom M. chimaera sp. nov. was isolated, only 3.3% exhibited mycobacterial lung disease, whereas all M. intracellulare isolates caused severe pulmonary infections.

A view on Bartonella quintana endocarditis--confirming the molecular diagnosis by specific fluorescence in situ hybridization.

Culture-negative endocarditis is a frequent problem in cardiology, especially if caused by fastidious organisms. Among these, the diagnostic tools for the detection of Bartonella quintana are still unsatisfactory. In a culture-negative case of suspected endocarditis undergoing aortic valve replacement, polymerase chain reaction amplification and sequencing of the 16S rRNA gene indicated B. quintana infection. To develop a new diagnostic tool, independent from culture and amplification techniques, we designed and optimized an oligonucleotide fluorescence in situ hybridization (FISH) probe specific for B. quintana and suitable for FISH. FISH succeeded in simultaneous visualization and identification of vital microorganisms directly within the aortic valve tissue and in fast and univocal diagnosis of B. quintana endocarditis.

Fluorescence in situ hybridisation (FISH) accelerates identification of Gram-positive cocci in positive blood cultures.

Sepsis is a life-threatening disease with a high mortality rate. Rapid identification of blood culture isolates plays a crucial role in adequate antimicrobial therapy in sepsis patients. To accelerate microbiological diagnosis, a comprehensive panel of oligonucleotide probes for fluorescence in situ hybridisation (FISH) targeting Gram-positive cocci was compiled and evaluated on 428 positive blood culture specimens. By combining genus-specific and species-specific probes, the assay allowed discrimination of staphylococci, streptococci and enterococci as well as differentiation of therapy-relevant pathogens such as Staphylococcus aureus and Enterococcus faecium/durans. Furthermore, the newly designed FISH probes STREP2, ENCO and GRANU targeted Streptococcus pneumoniae/mitis, Enterococcus spp. (except E. faecalis) and Granulicatella adiacens group, respectively. The FISH assay achieved an overall sensitivity of 98.65% and a specificity of 99.0% and therefore allowed rapid and reliable molecular identification of Gram-positive cocci in blood culture specimens.

Aetiology of community-acquired, acute gastroenteritis in hospitalised adults: a prospective cohort study.

BACKGROUND: The aetiology of severe gastroenteritis leading to hospitalisation in adults frequently remains unclear. Our objective was to study the causes and characteristics of community-acquired, acute gastroenteritis in adult hospitalized patients to support the clinical management of these patients. METHODS: From August 2005 to August 2007, we conducted a prospective cohort study among patients > or =18 y hospitalized with community-acquired gastroenteritis in a university hospital in Berlin, Germany. Stool specimens were examined for 26 gastrointestinal pathogens, supplemented by serologic tests for antibodies to Campylobacter spp., Yersinia spp., and Entamoeba histolytica. Patient data on demographics and clinical presentation were recorded and analyzed. Coexisting medical conditions were assessed using the Charlson Comorbidity Index score. RESULTS: Of 132 patients presenting with acute community-acquired gastroenteritis, 104 were included in the study. A non-infectious aetiology was diagnosed in 8 patients (8%). In 79 (82%) of the remaining 96 patients at least one microorganism was identified. Campylobacter spp. (35%) was detected most frequently, followed by norovirus (23%), Salmonella spp. (20%), and rotavirus (15%). In 46% of the patients with Campylobacter spp. infection, the diagnosis was made solely by serology. More than one pathogen was found in seventeen (22%) patients. Simultaneous infection was significantly more likely in patients with rotavirus and salmonella infections (RR 3.6; 95% CI: 1.8-7.4; RR 2.5; 95%CI: 1.2-5.5). Length of hospital stay (median: 5.5 days) was independent of the pathogen, but was associated with coexisting medical conditions (OR 4,8; 95%CI:2,0-11,6). CONCLUSION: Known enteric pathogens were detected in 82% of adult patients who were hospitalized with acute gastroenteritis. We found that currently used culture-based methods may miss a substantial proportion of Campylobacter infections, and additional serological testing for Campylobacter should be considered. Viral infections emerged as an important cause of severe gastroenteritis in adults, and viral-bacterial co-infections in adults are probably underrecognized so far. The presence of coexisting medical conditions--but not the etiological agent--was a predictor for the duration of the hospital stay.

Involvement of Guggenheimella bovis in digital dermatitis lesions of dairy cows.

Digital dermatitis (DD) of cattle leads to lameness and a decrease of milk production and is responsible for major economic losses worldwide. Although a bacterial aetiology is generally accepted, it still is unclear which microorganisms cause and/or maintain the disease. Recently, a previously undiscovered bacterial species, Guggenheimella bovis, has been isolated from the front of two DD lesions in Swiss cattle and suggested as a potential pathogen. The aims of the present study were to determine the prevalence of G. bovis in 58 German cows suffering from DD via dot blot hybridization, and to analyse the spatial distribution of G. bovis within the affected tissue by fluorescence in situ hybridization (FISH). A species-specific probe, GUBO1, was designed and evaluated. In none of the 58 samples Guggenheimella could be detected, while cultured G. bovis was reliably identified by GUBO1. Further FISH experiments were carried out on two additional biopsies of Swiss cattle tested positive for G. bovis by quantitative PCR and permitted visualization of the newly discovered bacteria in situ. In these biopsies G. bovis proved to be tissue invasive forming characteristic spherical microcolonies not only within the bacterial biofilm but also in seemingly unaffected parts of the tissue not yet reached by the advancing bacterial front. Although the presence of G. bovis does not constitute an essential premise for DD, it seems likely that the bacterial species involved in DD vary, and that in some cases G. bovis is crucial for the development of DD lesions.

Molecular monitoring of the intestinal flora by denaturing high performance liquid chromatography.

Gut flora analysis is hampered by the complexity of the intestinal microbiota and by inherent limitations of culture-based approaches. Therefore, culture-independent molecular methods based upon 16S rRNA gene analysis were applied successfully for the analysis of complex microbial communities. However, generally accepted and validated profiling methods such as denaturing and temperature gradient gel electrophoresis (DGGE/TGGE) are still laborious and time consuming. Thus, we adapted the separation of amplified bacterial 16S rRNA gene fragments by denaturing high performance liquid chromatography (DHPLC) using the WAVE Microbial Analysis System as a rapid and convenient means to display complex intestinal bacterial communities and to monitor changes in the gut flora. The separation of 16S rRNA gene fragments amplified from reference strains representing main gut bacterial populations and from human stool samples revealed that DHPLC analysis effectively detects bacterial groups predominant in the human gut flora. The investigation of faecal samples from hospitalized patients before, during and after antibiotic therapy showed that PCR-based DHPLC can be used to monitor gut flora changes. Results from DHPLC analysis were comparable with DGGE profiles generated from the same samples, demonstrating that the adapted DHPLC protocol is well suited for the analysis of complex microbial communities.

Vaccination prevents Helicobacter pylori-induced alterations of the gastric flora in mice.

Molecular analysis of the gastric microflora in mice revealed that Helicobacter pylori infection causes an increase in microbial diversity. The stomachs of H. pylori-infected animals were colonized by bacteria which are naturally restricted to the lower intestinal tract. Clostridia, Bacteroides/Prevotella spp., Eubacterium spp., Ruminococcus spp., streptococci and Escherichia coli were detected exclusively in the stomachs of infected animals, whereas lactobacilli dominated the gastric flora in noninfected mice. The H. pylori-induced shifts in the gastric microbiota were independent from histological pathology and from changes in the gastric pH but were prevented by immunization of mice with live Salmonella expressing H. pylori urease. Immunized mice displayed reduced H. pylori levels in the gastric epithelium and developed a normal gastric microflora, indicating that vaccination may be protective against H. pylori-induced changes in the gastric flora.

Colonic Expression of Genes Encoding Inflammatory Mediators and Gelatinases During Campylobacter Jejuni Infection of Conventional Infant Mice.

Within 1 week following peroral Campylobacter jejuni infection, infant mice develop acute enteritis resolving thereafter. We here assessed colonic expression profiles of mediators belonging to the IL-23/IL-22/IL-18 axis and of matrix-degrading gelatinases MMP-2 and MMP-9 at day 6 post C. jejuni strain 81-176 infection. Whereas the pathogen readily colonized the intestines of infant IL-18(-/-) mice only, colonic mucin-2 mRNA, a pivotal mucus constituent, was downregulated in IL-22(-/-) mice and accompanied by increased expression of pro-inflammatory cytokines including IFN-γ, TNF, IL-17A, and IL-1ß. Furthermore, in both naive and infected IL-22(-/-) mice, colonic expression of IL-23p19 and IL-18 was lower as compared to wildtype mice, whereas, conversely, colonic IL-22 mRNA levels were lower in IL-18(-/-) and colonic IL-18 expression lower in IL-23p19(-/-) as compared to wildtype mice. Moreover, colonic expression of MMP-2 and MMP-9 and their endogenous inhibitor TIMP-1 were lower in IL-22(-/-) as compared to wildtype mice at day 6 postinfection. In conclusion, mediators belonging of the IL-23/IL-22/IL-18 axis as well as the gelatinases MMP-2 and MMP-9 are involved in mediating campylobacteriosis of infant mice in a differentially regulated fashion.

The Role of IL-23, IL-22, and IL-18 in Campylobacter Jejuni Infection of Conventional Infant Mice.

We have recently shown that, within 1 week following peroral Campylobacter jejuni infection, conventional infant mice develop self-limiting enteritis. We here investigated the role of IL-23, IL-22, and IL-18 during C. jejuni strain 81-176 infection of infant mice. The pathogen efficiently colonized the intestines of IL-18(-/-) mice only, but did not translocate to extra-intestinal compartments. At day 13 postinfection (p.i.), IL-22(-/-) mice displayed lower colonic epithelial apoptotic cell numbers as compared to wildtype mice, whereas, conversely, colonic proliferating cells increased in infected IL-22(-/-) and IL-18(-/-) mice. At day 6 p.i., increases in neutrophils, T and B lymphocytes were less pronounced in gene-deficient mice, whereas regulatory T cell numbers were lower in IL-23p19(-/-) and IL-22(-/-) as compared to wildtype mice, which was accompanied by increased colonic IL-10 levels in the latter. Until then, colonic pro-inflammatory cytokines including TNF, IFN-γ, IL-6, and MCP-1 increased in IL-23p19(-/-) mice, whereas IL-18(-/-) mice exhibited decreased cytokine levels and lower colonic numbers of T and B cell as well as of neutrophils, macrophages, and monocytes as compared to wildtype controls. In conclusion, IL-23, IL-22, and IL-18 are differentially involved in mediating C. jejuni-induced immunopathology of conventional infant mice.

Interleukin-18 Mediates Immune Responses to Campylobacter jejuni Infection in Gnotobiotic Mice.

BACKGROUND: Human Campylobacter jejuni infections are progressively rising worldwide. Information about the molecular mechanisms underlying campylobacteriosis, however, are limited. In the present study we investigated whether cytokines such as IL-23, IL-22 and IL-18, which share pivotal functions in host immunity, were involved in mediating intestinal and systemic immunopathological responses upon C. jejuni infection. METHODOLOGY/PRINCIPAL FINDINGS: To assure stable infection, gnotobiotic (i.e. secondary abiotic) IL-23p19-/-, IL-22-/- and IL-18-/- mice were generated by broad-spectrum antibiotic treatment. Following peroral C. jejuni strain 81-176 infection, mice of all genotypes harbored comparably high pathogenic loads in their intestines. As compared to wildtype controls, however, IL-18-/- mice displayed less distinct C. jejuni induced sequelae as indicated by less pronounced large intestinal shrinkage and lower numbers of apoptotic cells in the colonic epithelial layer at day 8 postinfection (p.i.). Furthermore, lower colonic numbers of adaptive immune cells including regulatory T cells and B lymphocytes were accompanied by less distinct secretion of pro-inflammatory cytokines such as TNF and IFN-γ and lower IL-17A mRNA expression levels in colonic ex vivo biopsies of infected IL-18-/- as compared to wildtype mice. Upon C. jejuni infection, colonic IL-23p19 expression was up-regulated in IL-18-/- mice only, whereas IL-22 mRNA levels were lower in uninfected and infected IL-23p19-/- as well as infected IL-18-/- as compared to respective wildtype control mice. Remarkably, not only intestinal, but also systemic infection-induced immune responses were less pronounced in IL-18-/- mice as indicated by lower TNF, IFN-γ and IL-6 serum levels as compared to wildtype mice. CONCLUSION/SIGNIFICANCE: We here show for the first time that IL-18 is essentially involved in mediating C. jejuni infection in the gnotobiotic mouse model. Future studies need to further unravel the underlying regulatory mechanisms orchestrating pathogen-host interaction.

The IL-23/IL-22/IL-18 axis in murine Campylobacter jejuni infection.

BACKGROUND: Human Campylobacter jejuni infections are worldwide on the rise. Information about the distinct molecular mechanisms underlying campylobacteriosis, however, are scarce. In the present study we investigated whether cytokines including IL-23, IL-22 and IL-18 sharing pivotal functions in host immunity were involved in mediating immunopathological responses upon C. jejuni infection. RESULTS: To address this, conventionally colonized IL-23p19(-/-), IL-22(-/-) and IL-18(-/-) mice were perorally infected with C. jejuni strain ATCC 43431. Respective gene-deficient, but not wildtype mice were susceptible to C. jejuni infection and could be readily colonized with highest pathogenic loads in the terminal ileum and colon at day 14 postinfection (p.i.). In IL-23p19(-/-), IL-22(-/-) and IL-18(-/-) mice viable C. jejuni were detected in MLNs, but did not translocate to spleen, liver, kidney and blood in the majority of cases. Susceptible IL-22(-/-), but neither IL-23p19(-/-), nor IL-18(-/-) mice harbored higher intestinal commensal E. coli loads when compared to resistant wildtype mice. Alike C. jejuni, commensal E. coli did not translocate from the intestinal to extra-intestinal tissue sites. Despite C. jejuni infection, mice lacking IL-23p19, IL-22 or IL-18 exhibited less apoptotic cells, but higher numbers of proliferating cells in their colonic epithelium as compared to wildtype mice at day 14 p.i. Less pronounced apoptosis was parallelled by lower abundance of neutrophils within the colonic mucosa and lamina propria of infected IL-23p19(-/-) and IL-22(-/-) as compared to wildtype control mice, whereas less distinct colonic TNF secretion could be measured in IL-22(-/-) and IL-18(-/-) than in wildtype mice at day 14 p.i. Notably, in infected IL-22(-/-) mice, colonic IL-23p19 mRNA levels were lower, whereas the other way round, colonic IL-22 expression rates were lower in IL-23p19(-/-) mice as compared to wildtype controls. Moreover, IL-18 mRNA was less distinctly expressed in large intestines of naive and infected IL-22(-/-) mice, but not vice versa, given that IL-22 mRNA levels did not differ between in IL-18(-/-) and wildtype mice. CONCLUSION: Cytokines belonging to the IL-23/IL-22/IL-18 axis mediate immunopathological responses upon murine C. jejuni infection in a differentially orchestrated manner. Future studies need to further unravel the underlying regulatory mechanisms orchestrating pathogenic-host interaction.