Studies on Arcobacter species, their isolation and pathogenicity
Etonsi, Majde Ali
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Arcobacter species, a genus previously classified as ‘aerotolerant campylobacters’, have gained consideration as emerging food and water-borne pathogens. Studies increasingly suggest that they are of significance to veterinary public health and agriculture, but their pathogenicity mechanisms and ability to cause disease in animals and humans are not well understood. This project has revealed that only two of eleven Scottish surface water sources were contaminated with Arcobacter (18 %), and this was the first isolation of Arcobacter spp. from surface waters in Scotland. The two Arcobacter water isolates (SW-DL2 and SW-OL2) were shown to be closely related to species of Arcobacter butzleri. The extracellular proteins (ECP) of all strains were positive for gelatinase activity (50-310 units) and caused haemolysis of sheep and chicken erythrocytes. The A. butzleri reference strain D2686 showed poor haemolysis of human erythrocytes. The cadF genes of A. butzleri D2686 and SW-OL2 were cloned and sequenced, and showed high levels of sequence identity with a gene that encodes fibronectin-binding protein in Campylobacter jejuni. All Arcobacter strains in this study showed the ability to adhere to INT-407 cells in vitro and mutagenizing the cadF genes of A. butzleri D2686 and SW-OL2 resulted in a significant reduction in adherence (P >0.01 and P >0.001 respectively). Five putative virulence genes (cadF, ciaB, flaA, flaB and pldA) have been detected in each of the Arcobacter strains studied. cadF mRNA was also shown to be expressed in all strains with higher levels in A. cryaerophilus and SW-OL2 than the other strains. RT-PCR analysis also revealed that expression of the cadF gene was upregulated in all strains on infection of tissue culture cells with significant differences in levels of expression observed.