Differentiation of Campylobacter jejuni serotype O19 strains from non-O19 strains by PCR

[Campylobacter jejuni O:19 serotype in Argentine poultry meat supply chain]

Thermotolerant species of Campylobacter have been focus of attention in the last years because they are the major agent causing zoonotic foodborne diseases. In addition, Campylobacter jejuni O:19 serotype was associated with Guillain Barré syndrome. The aim of this study was to determine the proportion of C. jejuni O:19 serotype isolated at different stages of three poultry meat supply chain in Santa Fe, Argentina. The analysis showed that 18% of isolated C. jejuni belong to serotype O:19. It was also determined that the presence of these strains is given in almost all production stages. These results reflect a significant risk to public health of consumers. Epidemiological studies of Campylobacter should be considered to establish a risk manager policy.

DNA diversity of the wla gene cluster among serotype HS:19 and non-HS:19 Campylobacter jejuni strains

Campylobacter jejuni infection is an important trigger of Guillain-Barré syndrome (GBS), and serotype HS:19 strains are over-represented among GBS-associated isolates. Structures in C. jejuni lipooligosaccharide (LOS) resemble human gangliosides, suggesting that molecular mimicry could be important in triggering the neural injury. We assessed the genetic diversity among 36 C. jejuni serotype HS:19 and non-HS:19 strains by analysis of PCR-based restriction fragment length polymorphism (RFLP) patterns of 12 LOS biosynthesis-related genes ( wla cluster). PCR amplification revealed that the size, order, and direction of each wla gene was identical among all strains tested. However, an additional ORF, located between wlaI and wlaK, was detected in 28 of the 36 isolates examined, and nucleotide sequence analysis revealed that the gene was identical to orfE in C. jejuni strain NCTC 11168. An inverted repeat motif was found downstream of the wlaI stop codon and upstream of the orfE stop codon, an organization allowing pairing of repeated sequences that could lead to deletion of the internal segment. Digestion of the PCR products with restriction endonuclease DdeI or AluI and cluster analysis of RFLP banding patterns showed that all HS:19 strains were closely related and distinct from non-HS:19 strains, consistent with earlier analyses, suggesting that HS:19 strains represent a highly clonal population. RFLP analysis of wla genes also may be useful for epidemiological studies.

Nucleases encoded by the integrated elements CJIE2 and CJIE4 inhibit natural transformation of Campylobacter jejuni

The species Campylobacter jejuni is naturally competent for DNA uptake; nevertheless, nonnaturally transformable strains do exist. For a subset of strains we previously showed that a periplasmic DNase, encoded by dns, inhibits natural transformation in C. jejuni. In the present study, genetic factors coding for DNase activity in the absence of dns were identified. DNA arrays indicated that nonnaturally transformable dns-negative strains contain putative DNA/RNA nonspecific endonucleases encoded by CJE0566 and CJE1441 of strain RM1221. These genes are located on C. jejuni integrated elements 2 and 4. Expression of CJE0566 and CJE1441 from strain RM1221 and a homologous gene from strain 07479 in DNase-negative Escherichia coli and C. jejuni strains indicated that these genes code for DNases. Genetic transfer of the genes to a naturally transformable C. jejuni strain resulted in a decreased efficiency of natural transformation. Modeling suggests that the C. jejuni DNases belong to the Serratia nuclease family. Overall, the data indicate that the acquisition of prophage-encoded DNA/RNA nonspecific endonucleases inhibits the natural transformability of C. jejuni through hydrolysis of DNA.

The role of respiratory donor enzymes in Campylobacter jejuni host colonization and physiology

The human pathogen Campylobacter jejuni utilizes oxidative phosphorylation to meet all of its energy demands. The genome sequence of this bacterium encodes a number of respiratory enzymes in a branched electron transport chain that predicts the utilization of a number of electron transport chain donor and acceptor molecules. Three of these electron donor enzymes: hydrogenase, formate dehydrogenase, and 2-oxoglutarate:acceptor oxidoreductase (OOR), oxidize hydrogen, formate and alpha-ketoglutarate as electron donors, respectively. Mutations were created in these donor enzymes to isolate mutants in hydrogenase (HydB::CM), formate dehydrogenase (Fdh::CM), and OOR (OorB::CM), as well as a strain with insertions in both hydrogenase and formate dehydrogenase (Hyd::Fdh). These mutants are deficient in their respective enzyme activities and do not reduce the components of the electron transport chain when provided with their respective substrates. The presence of either hydrogen or formate in the media stimulated the growth of wild type (WT) C. jejuni (but not the associated mutant strains) and at least one of these alternative substrates is required for growth of the OOR mutant strain OorB::CM. Finally, the importance of hydrogenase, formate dehydrogenase and OOR as well as the complex I of C. jejuni are elucidated by chicken colonization assays, where the double mutant Hyd::Fdh, OorB::CM and nuo mutants are severely impaired in host colonization.

A DNase encoded by integrated element CJIE1 inhibits natural transformation of Campylobacter jejuni

The species Campylobacter jejuni is considered naturally competent for DNA uptake and displays strong genetic diversity. Nevertheless, nonnaturally transformable strains and several relatively stable clonal lineages exist. In the present study, the molecular mechanism responsible for the nonnatural transformability of a subset of C. jejuni strains was investigated. Comparative genome hybridization indicated that C. jejuni Mu-like prophage integrated element 1 (CJIE1) was more abundant in nonnaturally transformable C. jejuni strains than in naturally transformable strains. Analysis of CJIE1 indicated the presence of dns (CJE0256), which is annotated as a gene encoding an extracellular DNase. DNase assays using a defined dns mutant and a dns-negative strain expressing Dns from a plasmid indicated that Dns is an endogenous DNase. The DNA-hydrolyzing activity directly correlated with the natural transformability of the knockout mutant and the dns-negative strain expressing Dns from a plasmid. Analysis of a broader set of strains indicated that the majority of nonnaturally transformable strains expressed DNase activity, while all naturally competent strains lacked this activity. The inhibition of natural transformation in C. jejuni via endogenous DNase activity may contribute to the formation of stable lineages in the C. jejuni population.

Genomic diversity in Mycobacterium avium: single nucleotide polymorphisms between the S and C strains of M. avium subsp. paratuberculosis and with M. a. avium

Following identification of large genomic polymorphisms in a previous study, a polymerase chain reaction and sequencing strategy was used to identify single nucleotide polymorphisms (SNPs) in 25 genes in the sheep (S) and cattle (C) strains of Mycobacterium avium subsp. paratuberculosis (M. a. paratuberculosis) and between M. a. paratuberculosis and M. a. avium. From 12,117 bp of sequence representing 26 loci across 25 genes, 11 SNPs were identified between the S and C strains in eight genes: hsp65, sodA, dnaA, dnaN, recF, gyrB, inhA, and pks8. An in silico comparison of these M. a. paratuberculosis sequences and the M. a. avium 104 genome revealed 86 SNPs, which corresponded well with similar studies of SNPs in the M. avium complex.

Specific detection and differentiation of two subspecies of Fusobacterium necrophorum by PCR

The phylogenic relationships of two subspecies of Fusobacterium necrophorum were investigated by randomly amplified polymorphism DNA-polymerase chain reaction (RAPD-PCR). With each of the 12 random primers, the DNA fingerprints generated were subjected to cluster analysis for dendrograms. The analysis indicated that twelve strains were organized into two major clusters, and that all strains of each subspecies were confined to one cluster. Furthermore, two of the random primers examined each generated a unique band in F. n. necrophorum strains. We cloned these specific bands and determined the nucleotide sequences. A search for amino acid sequence homologies revealed that the two specific fragments had significant homology to the rpoB gene of Lactococcus lactis subsp. lactis and the hemagglutinin-related protein gene of Ralstonia solanacearum, respectively. New specific primers designed for the rpoB gene were able to amplify 900bp fragments from both subspecies. However, the specific primers designed for the hemagglutinin-related protein gene amplified only a 250bp fragment of the genome of the F. n. necrophorum strains, suggesting that this gene is unique to F. n. necrophorum. These results were further confirmed by dot blot hybridization. Finally, a one-step duplex PCR technique in a single tube for the rapid detection and differentiation of the F. necrophorum subspecies was developed.

Chronic effects of Campylobacter infection

Campylobacter jejuni is one of the most common causes of bacterial gastroenteritis and chronic sequelae, such as reactive arthritis and Guillain-Barré syndrome (GBS), are known to follow uncomplicated infections. While little is known about reactive arthritis following Campylobacter infection, our knowledge on the pathogenesis of Campylobacter-induced GBS is expanding rapidly and is summarized in this review.

Molecular characterization of invasive and noninvasive Campylobacter jejuni and Campylobacter coli isolates

Campylobacter jejuni is one of the most common causes of bacterial diarrhea worldwide and is the primary bacterial cause of food-borne illness. Adherence to and invasion of epithelial cells are the most important pathogenic mechanisms of Campylobacter diarrhea. Molecular characterization of invasive and noninvasive Campylobacter isolates from children with diarrhea and symptom-free children was performed by random amplified polymorphic DNA techniques (RAPD). A distinct RAPD profile with a DNA band of 1.6 kb was observed significantly more frequently among invasive (63%) than among noninvasive (16%) Campylobacter isolates (P = 0.000005). The 1.6-kb band was named the invasion-associated marker (IAM). Using specifically designed primers, a fragment of 518 bp of the iam locus was amplified in 85% of invasive and 20% of noninvasive strains (P = 0.0000000). Molecular typing with a PCR-restriction fragment length polymorphism assay which amplified the entire iam locus showed a HindIII restriction fragment polymorphism pattern associated mainly with invasive strains. Although cluster analysis of the RAPD fingerprinting showed genetic diversity among strains, two main clusters were identified. Cluster I comprised significantly more pathogenic and invasive isolates, while cluster II grouped the majority of nonpathogenic, noninvasive isolates. These data indicate that most of the invasive Campylobacter strains could be differentiated from noninvasive isolates by RAPD analysis and PCR using specific primers that amplify a fragment of the iam locus.

Flagella as a potential marker for Campylobacter jejuni strains associated with Guillain-Barré syndrome

Campylobacter jejuni recovered from patients with Guillain-Barré syndrome (GBS) in different geographical locations and bearing different heat-labile and heat-stable antigens were found to have identical amino acid sequences in their flagellar flaA short variable region, suggesting that it may be a potentially useful marker for GBS association.

Genetic characterization of Campylobacter jejuni O:41 isolates in relation with Guillain-Barré syndrome

Campylobacter jejuni O:41 strains are found in association with Guillain-Barré syndrome in South Africa. Strains of this serotype collected over 17 years were characterized by amplified fragment length polymorphism and flagellin typing to determine their clonal nature. Despite minor variation in GM1 expression, all of the strains were genetically indistinguishable, indicating that they are representative of a genetically stable clone.

Pathophysiology of Campylobacter jejuni infections of humans

Campylobacter jejuni and closely related organisms are major causes of human bacterial enteritis. These infections can lead to extraintestinal disease and severe long-term complications. Of these, neurological damage, apparently due to the immune response of the host, is the most striking. This review examines current knowledge of the pathophysiology of the organism. Diversity of C. jejuni isolates in genotypic and phenotypic characteristics now is recognized and clinically relevant examples are presented. Expected future directions are outlined.