Objective: Microbiological and virulence characterization of 2 moderately hemolytic Brachyspira strains. Materials and methods: Clinical isolates were obtained from diarrheic (3603F2) and healthy (G79) pigs. Phenotypic characterization included assessment of hemolytic activity on blood agar and biochemical profiling. Genotyping was performed by sequencing the nicotinamide adenine dinucleotide oxidase (nox) gene, whole genome sequencing, and comparison to relevant Brachyspira. Pig inoculation included 4 treatment groups in 2 challenge experiments: negative control (sterile broth media; n = 12), positive control (Brachyspira hampsonii genomovar 2 strain 30446; n = 18), and 3603F2 (n = 12) or G79 (n = 12). Fecal scoring and rectal swabbing for culture were performed daily. Animals were euthanized following onset of mucohemorrhagic diarrhea or between 21 and 28 days post inoculation (dpi). Gross and microscopic pathology were assessed. Terminal colon samples were used to characterize postinfection mucosal ion secretion. Results: Both strains were moderately hemolytic. Whole genome and nox sequencing identified 3603F2 as Brachyspira murdochii and G79 as a novel strain. Both challenge trials revealed intestinal colonization, but no mucohemorrhagic diarrhea. Sporadic watery diarrhea was induced by 3603F2 associated with a pattern of microscopic lesions similar to pigs with swine dysentery (positive controls). No diarrhea was observed in G79 inoculated pigs, but microscopic lesions were more severe than in controls. Both strains induced greater colonic anion secretory potential than negative controls 21 dpi. Implications: Allegedly avirulent Brachyspira species most closely related to B murdochii can be associated with subclinical colitis and may be a concern for growfinish pigs.
|Translated title of the contribution||Subclinical colitis associated with moderately hemolytic Brachyspira strains|
|Number of pages||14|
|Journal||Journal of Swine Health and Production|
|State||Published - 2019|
Bibliographical noteFunding Information:
College of Veterinary Medicine (WCVM) Research Trust. Summer student stipends were provided by the WCVM Interprovincial Undergraduate Student Research program and an Undergraduate research award by the Natural Sciences and Engineering Research Council of Canada.
Funding for this project was generously provided by the Alberta Livestock and Meat Agency Ltd (project No. 2013R054R) and the Agriculture Development Fund (project No. 20130138), the University of Saskatchewan Innovation Enterprise, and the Western dysenterylike colonic lesions or mucohemorrhagic diarrhea in trial pigs. Brachyspira resembling nonpathogenic species induced microscopic lesions in a similar pattern to, but milder than, B hampsonii and B hyodysenteriae. Changes to the mucosal ion transport capacity following inoculation with allegedly nonpathogenic Brachyspira suggest a subclinical form of colitis.
- Subclinical diarrhea
- Swine dysentery