Search

Transposon mutagenesis has been applied to a hyper-invasive clinical isolate of Campylobacter jejuni, 01/51. A random transposon mutant library was screened in an in vitro assay of invasion and 26 mutants with a significant reduction in invasion were identified. Given that the invasion potential of C. jejuni is relatively poor compared to other enteric pathogens, the use of a hyper-invasive strain was advantageous as it greatly facilitated the identification of mutants with reduced invasion. The location of the transposon insertion in 23 of these mutants has been determined; all but three of the insertions are in genes also present in the genome-sequenced strain NCTC 11168. Eight of the mutants contain transposon insertions in one region of the genome (~14 kb), which when compared with the genome of NCTC 11168 overlaps with one of the previously reported plasticity regions and is likely to be involved in genomic variation between strains. Further characterization of one of the mutants within this region has identified a gene that might be involved in adhesion to host cells. DOI 10.1099/mic.0.033399-0

Despite being classically defined as non-pathogenic, there is growing evidence that biotype 1A Yersinia enterocolitica isolates may be aetiological agents of disease in humans. In previous studies, a potential link between motility and the ability of biotype 1A strains to invade cultured epithelial cells was observed. In an attempt to further investigate this finding, a flagella mutant was constructed in a human faecal Y. enterocolitica biotype 1A isolate. The flagella mutation abolished the ability of the strain to invade cultured human epithelial cells, although adherence was not affected. The aflagellate mutant was also attenuated in its ability to survive within cultured macrophages, being cleared after 3 h, whilst the wild-type persisted for 24 h after infection. Examination of cytokine secretion by infected macrophages also suggested that the flagella of biotype 1A strains act as anti-inflammatory agents, decreasing production of tumour necrosis factor (TNF)-[alpha] whilst increasing secretion of interleukin (IL)-10. Preliminary studies using porcine in vitro organ culture (IVOC) tissue suggested that the flagella mutant was also attenuated in its ability to colonize intestinal tissue. DOI 10.1099/mic.0.2006/000919.0

The genome sequence of the enteric bacterial pathogen Campylobacter jejuni NCTC 11168 (11168-GS) was published in 2000, providing a valuable resource for the identification of C.jejuni-specific colonization and virulence factors. Surprisingly, the 11168-GS clone was subsequently found to colonize 1-day-old chicks following oral challenge very poorly compared to other strains. In contrast, we have found that the original clinical isolate from which 11168-GS was derived, 11168-O, is an excellent colonizer of chicks. Other marked phenotypic differences were also identified: 11168-O invaded and translocated through tissue culture cells far more efficiently and rapidly than 11168-GS, was significantly more motile, and displayed a different morphology. Serotyping, multiple high-resolution molecular genotyping procedures, and subtractive hybridization did not yield observable genetic differences between the variants, suggesting that they are clonal. However, microarray transcriptional profiling of these strains under microaerobic and severely oxygen-limited conditions revealed dramatic expression differences for several gene families. Many of the differences were in respiration and metabolism genes and operons, suggesting that adaptation to different oxygen tensions may influence colonization potential. This correlates biologically with our observation that anaerobically priming 11168-GS or aerobically passaging 11168-O caused an increase or decrease, respectively, in colonization compared to the parent strain. Expression differences were also observed for several flagellar genes and other less well-characterized genes that may participate in motility. Targeted sequencing of the sigma factors revealed specific DNA differences undetected by the other genomic methods. These observations highlight the capacity of C. jejuni to adapt to multiple environmental niches, the likelihood that this adaptation involves genetic evolution, and provides the first whole-genome molecular exploration of the effect of laboratory culture and storage on colonization and virulence properties of this pathogen.

Research has been conducted on Campylobacter jejuni strains. The genetic material associated with the colonization present in C. jejuni strain 81116 but not present in the strain 11168 genome sequence has been investigated and the results are presented.

The various methods of genotyping Campylobacter species are described and their advantages and disadvantages are discussed. Fla typing is best for short-term limited-outbreaks but AFLP is best for global epidemiological studies.

The microaerophilic nature of Campylobacter species implies an inherent sensitivity towards oxygen and its reduction products, particularly the superoxide anion. The deleterious effects of exposure to superoxide radicals are counteracted by the activity of superoxide dismutase (SOD). Organisms harboring the inactivated sodB gene of Campylobacter coli failed to produce a biologically functional form of the enzyme. The survival of the mutant sodB gene of C. coli was severely compromised when non-growing cells were exposed to air.

Poultry isolates of Campylobacter jejuni, genotyped using pulsed-field gel electrophoresis (PFGE) of chromosomal DNA, were of clonal origin but had undergone genomic rearrangements. The diversity in PFGE banding patterns is believed to have originated from genomic rearrangements. For instance, there was an interesting variation in PFGE genotypes between isolates derived from one batch of poultry and these isolates were found to have identical fla genotypes and identical or similar Penner serotypes, biotypes and phage types.

Researchers studying the Campylobacter jejuni strain 81116, which has two flagellin genes, fla A and fla B, have identified the significance of flagella in the colonization of the avian caecum, which appears to be the natural environment for these bacteria. The pressure of flagellin A rather than motility is necessary for optimal bacterial colonization of chicken caeca.

The application of the short variable region (SVR) of flaA isolated from Campylobacter jejuni to develop a fluorescently labeled PCR oligonucleotide probe is described to detect the DNA of the strain colonizing a poultry flock in samples taken from the environment. The method could be used to study the epidemiology of campylobacters in poultry flocks and to facilitate targeted biosecurity interventions.

A novel molecule-based method was developed to detect and enumerate specific campylobacter strains in mixed populations. The method was observed be quantitative, sensitive, and highly specific and facilitates the identification and enumeration of selected strains among all of the campylobacters in environmental samples.

An amplified fragment length polymorphism (AFLP) method, developed to genotype Yersinia enterocolitica, is used to investigate 70 representative strains isolated from humans, pigs, sheep, and cattle in the UK. Results suggest that some strains causing human disease do not come from veterinary sources identifiable at this time

Multilocus sequence typing (MLST) is applied to 266 Campylobacter jejuni isolates, mainly from veterinary sources, including cattle, sheep, pigs, pets, poultry and the environment as well as isolates from human cases of campylobacteriosis. The populations of veterinary and human isolates overlap, suggesting that most veterinary sources should be considered reservoirs of pathogenic campylobacter.