Cell membrane permeability and mitochondrial dysfunction-inducing activities in cell-free supernatants from Serpulina hyodysenteriae serotypes 1 and 2

Weakly haemolytic variants of Brachyspira hyodysenteriae newly emerged in Europe belong to a distinct subclade with unique genetic properties

Brachyspira (B.) hyodysenteriae is widespread globally, and can cause mucohaemorrhagic colitis (swine dysentery, SD) with severe economic impact in infected herds. Typical strains of B. hyodysenteriae are strongly haemolytic on blood agar, and the haemolytic activity is believed to contribute to virulence in vivo. However, recently there have been reports of atypical weakly haemolytic isolates of B. hyodysenteriae (whBh). In this study, 34 European whBh and 82 strongly haemolytic isolates were subjected to comparative genomic analysis. A phylogenetic tree constructed using core single nucleotide polymorphisms showed that the whBh formed a distinct sub-clade. All eight genes previously associated with haemolysis in B. hyodysenteriae were present in the whBh. No consistent patterns of amino acid substitutions for all whBh were found in these genes. In contrast, a genome region containing six coding sequences (CDSs) had consistent nucleotide sequence differences between strongly and whBh isolates. Two CDSs were predicted to encode ABC transporter proteins, and a TolC family protein, which may have a role in the export of haemolysins from B. hyodysenteriae. Another difference in this region was the presence of three CDSs in whBh that are pseudogenes in strongly haemolytic isolates. One of the intact CDSs from whBh encoded a predicted PadR-like transcriptional repressor that may play a role in repression of haemolysis functions. In summary, a sub-clade of whBh isolates has emerged in Europe, and several genomic differences, that potentially explain the weakly haemolytic phenotype, were identified. These markers may provide targets for discriminatory molecular tests needed in SD surveillance.

Minimal prophylactic concentration of dietary zinc compounds in a mouse model of swine dysentery

Dietary supplementation with 6000 mg of Zn2+/kg of feed has been shown to modify the clinicopathologic expression ofBrachyspira hyodysenteriaeinfection in a laboratory mouse model of swine dysentery. However, this concentration impaired the body weight gain of the mice. The purpose of the present study was to determine a minimal prophylactic concentration of feed-grade zinc compounds that would not affect the growth of mice challenge-exposed withB. hyodysenteriae. A total of 440, 6- to 8-week-old, C3H/HeN mice were allocated randomly to groups and fed either a defined diet or a defined diet containing either 1000, 2000 or 4000 mg/kg ZnO, ZnSO4or zinc-methionine for 7 days before intra- gastric inoculation withB. hyodysenteriae. From days 7 to 35 after inoculation, mice in each group were necropsied at weekly intervals for determination of body weight, presence ofB. hyodysenteriaein the cecum, and histological assessment of cecal lesions. Only ZnO fed at 2000 mg/kg had a prophylactic effect againstB. hyodysenteriaeinfection without affecting the body weight gain of the mice. The prophylactic effect of Zn2+against infection withB. hyodysenteriaewas also affected by the relative concentration of Fe2+and Zn2+/Fe2+ratio of the diet.

Comparative pathology of bacterial enteric diseases of swine

Enteric bacterial infections are among the most common and economically significant diseases affecting swine production worldwide. Clinical signs of these infections include diarrhea, reduced growth rate, weight loss, and death of preweaned, weanling, grower-finisher, young and adult age breeding animals. The most common etiological agents include Escherichia coli, Clostridium perfringens, Lawsonia intracellularis, Salmonella enterica, and Brachyspira (Serpulina) spp. With the exception of Brachyspira (Serpulina) hyodysenteriae, the cause of swine dysentery, and Lawsonia intracellularis, the cause of proliferative enteropathy, the pathological changes seen with these agents closely resemble the diseases occurring in human beings. Histological changes in the intestines of swine with enteric bacterial infections include bacterial colonization without significant damage (e.g., certain enterotoxigenic E. coli and C. perfringens type A), attaching and effacing lesions with enteropathogenic E. coli and Brachyspira pilosicoli, the cause of colonic spirochetosis, inflammation with S. enterica, and necrotizing and hemorrhagic lesions with certain C. perfringens. Extraintestinal spread of bacteria and/or toxins occurs with some serotypes of E. coli and most serotypes of S. enterica. Enteric bacterial diseases of swine have been used as models to study the pathogenesis of similar diseases of human beings. Several of these pathogens are also important causes of food-borne disease in humans.

Outer membrane-associated serine protease of intestinal spirochetes

Pathogenic intestinal spirochetes cause damage to the intestinal mucosa of humans and animals by an unknown mechanism. The purpose of this study was to assess the pathogenic intestinal spirochetes Serpulina hyodysenteriae, Serpulina pilosicoli, and Brachyspira aalborgi and the non-pathogenic commensal intestinal spirochetes Serpulina innocens and Treponema succinifaciens for protease activity. A partially heat stable, subtilisin-like, serine protease was identified in the outer membrane of all spirochetes and thus may be essential for survival in the intestinal environment. The outer membrane protease may indirectly contribute to intestinal damage caused by pathogenic spirochetes during association with the mucosal surface of the host.