The Campylobacter jejuni Response Regulator and Cyclic-Di-GMP Binding CbrR Is a Novel Regulator of Flagellar Motility

A leading cause of bacterial gastroenteritis, Campylobacter jejuni is also associated with broad sequelae, including extragastrointestinal conditions such as reactive arthritis and Guillain-Barré Syndrome (GBS). CbrR is a C. jejuni response regulator that is annotated as a diguanylate cyclase (DGC), an enzyme that catalyzes the synthesis of c-di-GMP, a universal bacterial second messenger, from GTP. In C. jejuni DRH212, we constructed an unmarked deletion mutant, cbrR^-, and complemented mutant, cbrR⁺. Motility assays indicated a hyper-motile phenotype associated with cbrR^-, whereas motility was deficient in cbrR⁺. The overexpression of CbrR in cbrR⁺ was accompanied by a reduction in expression of FlaA, the major flagellin. Biofilm assays and scanning electron microscopy demonstrated similarities between DRH212 and cbrR^-; however, cbrR⁺ was unable to form significant biofilms. Transmission electron microscopy showed similar cell morphology between the three strains; however, cbrR⁺ cells lacked flagella. Differential radial capillary action of ligand assays (DRaCALA) showed that CbrR binds GTP and c-di-GMP. Liquid chromatography tandem mass spectrometry detected low levels of c-di-GMP in C. jejuni and in E. coli expressing CbrR. CbrR is therefore a negative regulator of FlaA expression and motility, a critical virulence factor in C. jejuni pathogenesis.

Chemotactic behavior of Campylobacter fetus subspecies towards cervical mucus, bovine placenta and selected substances and ion

The chemotaxis of C. fetus subsp. venerealis and C. fetus subsp. fetus was determined in the presence of bovine cervical mucus and bovine placental extract. Some reported substances and ion in those materials, such amino acids, ferrous iron, hormones, sugars and organic acids were also investigated. Bovine cervical mucus, bovine placenta extracts and some substances and ion of these materials namely L–fucose, L– aspartate, L–glutamate, L–serine, ferrous iron, fumarate, pyruvate and succinate were chemoattractants. The chemottraction was significantly larger in higher concentrations of the tested substances and ion and significant differences among tested strains were also observed. Meso-erythritol and hormones bovine placental lactogen, 17β-estradiol, and progesterone did not elicit chemotactical response. In conclusion, this chemotactic behavior may guide the C. fetus navigation in the bovine host's genital tract and be an important cofactor of tissue tropism for this bacterium.

Histopathology and Spatial Distribution of Putative Growth Factors in Relation to Bacterial Localization of Campylobacter jejuni Within the Ovine Gallbladder

Campylobacter jejuni is an important zoonotic pathogen that is the leading cause of both human foodborne bacterial gastroenteritis worldwide and ovine abortion in the United States. Previous studies have demonstrated that the gallbladder of ruminants is often positive on culture for Campylobacter sp., suggesting that this environment may serve as a chronic nidus of infection for maintenance of disease within populations. The objective of this study was to determine if previously identified putative growth promoting factors of C. jejuni are present within the gallbladder mucosa of sheep and to evaluate for bacterial co-localization of C. jejuni with these compounds following experimental inoculation. Direct gallbladder inoculation with C. jejuni sheep abortion (SA) clone clinical isolate IA3902 followed by immunohistochemical analysis and scanning electron microscopy allowed for identification of C. jejuni at the gallbladder mucosal surface and within the gallbladder submucosal glands. Histochemistry identified several putative Campylobacter growth promoting factors including neutral and acid mucins as well as L-fucose to be present both on the mucosal surface as well as in the gallbladder submucosal glands. In summary, following experimental inoculation of the ovine gallbladder, C. jejuni IA3902 was identified in direct contact with the gallbladder mucosal surface and deep mucosal glands in the same location as several putative growth promoting factors. This suggests the yet to be tested hypothesis that under natural conditions of infection, the gallbladder submucosal glands have the potential to provide a protected niche for chronic carriage of C. jejuni in animal hosts.

Investigating the Suitability of a Laboratory Mouse Model to Study the Pathogenesis of Abortifacient Campylobacter jejuni

The aim of this study was to assess whether pregnant mice represent a useful model to study the reproductive pathology of Campylobacter jejuni IA3902 using the end point of positive microbial culture of the organism from the fetoplacental unit. Pregnant BALB/c and CD-1 mice (14 days' gestation) were inoculated orally and intraperitoneally (IP) with 1 × 10⁹ colony-forming units/ml of C. jejuni IA3902. The organism was recovered by microbial culture from the fetoplacental unit in 10 of 10 BALB/c and 10 of 10 CD-1 IP-inoculated pregnant mice and in 29% (2/7) BALB/c and 38% (3/8) CD-1 orally inoculated pregnant mice. Gross reproductive lesions included necrosuppurative placentitis, fetal resorption, intrauterine fetal death, stillborn pups (dead neonates), and multifocal hepatitis. Histological changes consisted of locally extensive neutrophilic and necrotizing placentitis with intralesional bacterial colonies of C. jejuni, ulcerative endometritis, random multifocal hepatitis, and rare cholecystitis. Immunohistochemistry for the major outer membrane protein of C. jejuni revealed moderate to large numbers of the organism at the periphery of the placental discs, within trophoblasts and extracellularly, with invasion into the placental disc largely via the vascular network. The organism is trophic for neutral mucin, iron, and L-fucose within the murine placenta. C. jejuni IA3902 has affinity for the murine reproductive tract, specifically the fetoplacental unit, where it results in a necrotizing placentitis with positive microbial recovery after both IP and oral challenge in BALB/c and CD-1 pregnant mice.