Localization of the sapA gene on a physical map of Campylobacter fetus chromosomal DNA

Bacterial Pericarditis Caused by Campylobacter fetus subsp. fetus After Mutton Consumption

Campylobacter fetus subsp. fetus causes systemic diseases including bacteremia and meningitis. However, it rarely causes bacterial pericarditis. We present a rare case of bacterial pericarditis caused by Campylobacter fetus subsp. fetus. A man in his 60s presented with a fever and dyspnea. Electrocardiography revealed ST segment elevation in all leads except augmented vector right (aVR), and contrast-enhanced computed tomography of the chest revealed a large pericardial effusion. Campylobacter fetus subsp. fetus, appearing as curved, gull-wing-shaped gram-negative rods on microscopy, was identified on blood culture. The patient was diagnosed with acute pericarditis caused by Campylobacter fetus subsp. fetus. Further, history-taking revealed that he had consumed undercooked mutton before the onset of his illness. He recovered after treatment with antibiotics (ceftriaxone, ampicillin, and amoxicillin) for four weeks. With a blood culture revealing gull-wing shaped gram-negative rods, and the patient's history including potential contact with animals or the consumption of raw or undercooked meat, Campylobacter fetus subsp. fetus infection should be suspected.

Phenotypic and molecular characterization of bovine Campylobacter fetus strains isolated in Brazil

The objective of the present study was to characterize the phenotypic and molecular aspects of Campylobacter fetus strains isolated from bovine herds with reproductive problems. Thirty-one Brazilian field isolates, together with one reference strain of each subspecies of C. fetus, were analyzed. The strains were submitted to phenotypic identification followed by subspecies characterization using the polymerase chain reaction (PCR) and numeric evaluation of restriction fragment length polymorphism (RFLP) separated by pulsed-field gel electrophoresis (PFGE). Phenotypically, 4 isolates (12.1%) were classified as C. fetus subsp. fetus, and 29 isolates (87.9%) were classified as C. fetus subsp. venerealis. However, according to molecular analysis, only 1 isolate (3.0%) was classified as C. fetus subsp. fetus (the reference strain), whereas 32 isolates (97.0%) were considered C. fetus subsp. venerealis. SalI digestion of C. fetus genomic DNA, obtained from the 33 strains, yielded 7-10 DNA fragments ranging in size from 40 to 373kb, with 12 distinct patterns. Furthermore, the numeric analysis by neighbor-joining of the DNA from the 33 strains resulted in a dendrogram in which 2 distinct groups were identified. It was concluded that phenotypic characterization of C. fetus subspecies might lead to erroneous classification of field isolates. Although RFLP-PFGE is a powerful and reliable technique to characterize C. fetus, it has the inconvenience of being time consuming and laborious. Whereas PCR, besides providing rapid results, was found to be reliable and convenient for the characterization of field isolates of C. fetus.

Structure and genotypic plasticity of the Campylobacter fetus sap locus

The Campylobacter fetus surface layer proteins (SLPs), encoded by five to nine sapA homologues, are major virulence factors. To characterize the sapA homologues further, a 65.9 kb C. fetus genomic region encompassing the sap locus from wild-type strain 23D was completely sequenced and analysed; 44 predicted open reading frames (ORFs) were recognized. The 53.8 kb sap locus contained eight complete and one partial sapA homologues, varying from 2769 to 3879 bp, sharing conserved 553-2622 bp 5' regions, with partial sharing of 5' and 3' non-coding regions. All eight sapA homologues were expressed in Escherichia coli as antigenic proteins and reattached to the surface of SLP- strain 23B, indicating their conserved function. Analysis of the sap homologues indicated three phylogenetic groups. Promoter-specific polymerase chain reactions (PCRs) and sapA homologue-specific reverse transcription (RT)-PCRs showed that the unique sapA promoter can potentially express all eight sapA homologues. Reciprocal DNA recombination based on the 5' conserved regions can involve each of the eight sapA homologues, with frequencies from 10(-1) to 10(-3). Intragenic recombination between sapA7 and sapAp8, mediated by their conserved regions with a 10(-1)-10(-2) frequency, allows the formation of new sap homologues. As divergent SLP C-termini possess multiple antigenic sites, their reciprocal recombination behind the unique sap promoter leads to continuing antigenic variation.

Campylobacter surface-layers (S-layers) and immune evasion

Many pathogenic bacteria have evolved mechanisms for evading host immune systems. One evasion mechanism is manifest by the surface layer (S-layer), a paracrystalline protein structure composed of S-layer proteins (SLPs). The S-layer, possessed by 2 Campylobacter species (C. fetus and C. rectus), is external to the bacterial outer membrane and can have multiple functions in immune avoidance. C. fetus is a pathogen of ungulates and immunocompromised humans, in whom it causes disseminated bloodstream disease. In C. fetus, the S-layer is required for dissemination and is involved in 2 mechanisms of evasion. First, the S-layer confers resistance to complement-mediated killing in non-immune serum by preventing the binding of complement factor C3b to the C. fetus cell surface. S-layer expressing C. fetus strains remain susceptible to complement-independent killing, utilizing opsonic antibodies directed against the S-layer. However, C. fetus has also evolved a mechanism for avoiding antibody-mediated killing by high-frequency antigenic variation of SLPs. Antigenic variation is accomplished by complex DNA inversion events involving a family of multiple SLP-encoding genes and a single SLP promoter. Inversion events result in the expression of antigenically variant S-layers, which require distinct antibody responses for killing. C. rectus is implicated in the pathogenesis of periodontal disease and also possesses an S-layer that appears to be involved in evading the human system. Although studied less extensively than its C. fetus counterpart, the C. rectus S-layer appears to confer resistance to complement-mediated killing and to cause the down-regulation of proinflammatory cytokines.

Epidemiologic application of pulsed-field gel electrophoresis to an outbreak of Campylobacter fetus meningitis in a neonatal intensive care unit

An outbreak of nosocomial Campylobacter fetus meningitis occurred in a neonatal intensive care unit (NICU). Eight C. fetus strains were isolated from 4 infants with meningitis, the mother of the index patient and 2 infants who were asymptomatic intestinal carriers. The pulsed-field gel electrophoresis (PFGE) pattern with the restriction endonucleases Smal and Sall were found to be identical for the nosocomial C. fetus isolates, but the patterns were different from those of sporadic strains. These nosocomial strains were strongly suspected to be a single strain. The finding revealed that the index patient was infected by the mother, and that the outbreak developed from this patient by cross-infection. This is the first confirmed nosocomial C. fetus meningitis outbreak spread by cross-infection in a NICU.

Southern blotting analyses of strains of Campylobacter fetus using the conserved region of sapA

Chromosomal DNA of 27 strains of Campylobacter fetus was analyzed by Southern blotting with a probe of the conserved region of sapA. The probe hybridized with 23 strains that produced type A lipopolysaccharide. These strains had more than six sapA homologs. In Southern blots of SalI-digested chromosomal DNA separated by pulsed-field gel electrophoresis, one fragment from 19 strains and two fragments from 4 strains hybridized. These data indicate that multiple sapA homologs are localized to a limited region on the chromosomal DNA of C. fetus and thus suggest the possibility of developing a typing system using this method.

Analysis of strains of Campylobacter fetus by pulsed-field gel electrophoresis

Campylobacter fetus chromosomal DNA from 21 strains was analyzed by pulsed-field gel electrophoresis. The fingerprint patterns generated with SmaI and SalI were distinctive. Using the profiles obtained by pulsed-field gel electrophoresis, we established the phylogenetic dendrogram of C. fetus to identify the genetic relationship of the strains.