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Chapter 9 : Arcobacter: an Opportunistic Human Food-Borne Pathogen?
Category: Clinical Microbiology; Bacterial Pathogenesis
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Two recent European surveys of patient stool samples ranked Arcobacter as the fourth most frequently recovered Campylobacter-like microbe. Aerotolerant campylobacteria (Arcobacter spp.) were first described as occurring in aborted porcine and bovine fetuses. Handling and consuming raw or contaminated poultry meat are acknowledged potential sources of human Arcobacter infection. Due to the phylogenetic relationship between Campylobacter and Arcobacter, it is logical to assume that animal models, virulence factors (including adherence), invasion, cytotoxicity, and toxin production of the two organisms would be similar. Classification of arcobacters as free-living, environmental organisms should be reflected in the gene content of the Arcobacter genomes. The genomes of some Arcobacter species would be predicted to contain niche-related genes, e.g., osmoprotectant genes in A. halophilus and nitrogen fixation genes in A. nitrofigilis. An multilocus sequence typing (MLST) method that could be used to type five Arcobacter species was recently designed. Future MLST and DNA microarray analyses will provide further insights into Arcobacter divergence. MLST analysis has identified putative horizontal gene transfer (HGT) events in Arcobacter. Members of the genus Arcobacter can be generalized as free-living organisms found predominantly in aqueous environments, occasionally associated with food animals, and infrequently associated with humans. The publication of the complete 2.341-Mb Arcobacter genome sequence has facilitated identification of unique virulence factors and genetic markers to monitor its transmission through the food chain and which underlie its distinctive epidemiology.
Phylogenetic analysis of Arcobacter 16S rRNA gene sequences. 16S sequences were aligned using CLUSTAL X (version 2.09.5). The condensed dendrogram was constructed using the neighbor-joining algorithm and the Kimura two-parameter distance estimation method. Bootstrap values of >75%, generated from 500 replicates, are shown at the nodes. The scale bar represents substitutions per site. Sulfurospirillum deleyianum, H. pylori, C. fetus, and C. jejuni 16S sequences are included for comparison.
Condensed dendrogram of unique Arcobacter sequence types (STs). For each unique sequence type, the profile allele sequences were extracted and concatenated. The concatenated allele sequences were aligned using CLUSTAL X (version 2.09.5). The dendrogram was constructed using the neighbor-joining algorithm and the Kimura two-parameter distance estimation method. Bootstrap values of >75%, generated from 500 replicates, are shown at the nodes. The scale bar represents substitutions per site. The tree is rooted to C. jejuni strain NCTC 11168. The A. halophilus strain LA31B concatenated sequence was extracted from the draft A. halophilus genome. The group 1 A. cryaerophilus sequence types include ST-209, ST-220, ST-221, ST-231, ST-232, and ST-270. Figure adopted from reference 103 .
Distinguishing features of Arcobacter butzleri, Campylobacter jejuni, and Helicobacter pylori
Number of publications cited in Biological Abstracts describing Arcobacter, Campylobacter, and Helicobacter
Initial descriptions of Arcobacter species
Chronological listing of human cases of Arcobacter
Recovery of Arcobacter spp. from exotic animals
Distribution of Arcobacter in shellfish and fish
Distribution of Arcobacter in healthy live birds, poultry carcasses, and meat
Distribution of Arcobacter in feces of healthy dairy and beef cattle, raw beef, and raw milk
Distribution of Arcobacter in live hogs and pork meat