Abstract
Colonization by Helicobacter species is commonly noted in many mammals. These infections often remain unrecognized, but can cause severe health complications or more subtle host immune perturbations. The aim of this study was to isolate and characterize putative novel Helicobacter spp. from Bengal tigers in Thailand. Morphological investigation (Gram-staining and electron microscopy) and genetic studies (16SrRNA, 23SrRNA, flagellin, urease and prophage gene analyses, RAPD DNA fingerprinting and restriction fragment polymorphisms) as well as Western blotting were used to characterize the isolated Helicobacters. Electron microscopy revealed spiral-shaped bacteria, which varied in length (2.5–6 µm) and contained up to four monopolar sheathed flagella. The 16SrRNA, 23SrRNA, sequencing and protein expression analyses identified novel H. acinonychis isolates closely related to H. pylori. These Asian isolates are genetically very similar to H. acinonychis strains of other big cats (cheetahs, lions, lion-tiger hybrid and other tigers) from North America and Europe, which is remarkable in the context of the great genetic diversity among worldwide H. pylori strains. We also found by immunoblotting that the Bengal tiger isolates express UreaseA/B, flagellin, BabA adhesin, neutrophil-activating protein NapA, HtrA protease, γ-glutamyl-transpeptidase GGT, Slt lytic transglycosylase and two DNA transfer relaxase orthologs that were known from H. pylori, but not the cag pathogenicity island, nor CagA, VacA, SabA, DupA or OipA proteins. These results give fresh insights into H. acinonychis genetics and the expression of potential pathogenicity-associated factors and their possible pathophysiological relevance in related gastric infections.
Highlights
The genus Helicobacter comprises a heterogeneous group of Gram-negative bacteria that colonise different mammalian hosts, including domestic and wild animals, non-human primates and humans [1,2]
The stomachs of mammalian carnivores are often naturally infected by non-pylori Helicobacter species, including H. felis, H. bizzozeronii and H. salomonis, which are very different from H. pylori [1,2,38], and interestingly, the stomachs of large felines, can be infected with H. acinonychis, which is closely related to H. pylori [31,33,44,48,49,50,51,52,61,63]
Compared to H. pylori we know very little about H. acinonychis, with most of our knowledge about
Summary
The genus Helicobacter comprises a heterogeneous group of Gram-negative bacteria that colonise different mammalian hosts, including domestic and wild animals, non-human primates and humans [1,2]. Helicobacter pylori’s hallmark enzyme is a potent multi-subunit urease complex, which is fundamental for neutralizing the acidic pH in the stomach [5]. Other bacterial factors such as the blood-group antigen binding protein BabA [6], sialic acid-binding adhesin SabA [7], outer inflammatory protein OipA [8], neutrophil activating protein NapA [9,10,11], lytic transglycosylase Slt [12], duodenal ulcer promoter protein A (DupA) [13,14,15] and c-glutamyl transpeptidase (GGT) [16] contribute significantly to successful H. pylori pathogenesis. The cagA gene, located in the cag pathogenicity island (cagPAI), is a marker of a type IV secretion system, a molecular syringe-like structure (composed of VirB1 to VirB11, VirD4 and several other Cag proteins) through which CagA can be delivered into host target cells [25]
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