Morphometric Analysis of Enteric Lesions in C3H/HeN Mice Inoculated with \u3ci\u3eSerpulina hyodysenteriae\u3c/i\u3e Serotypes 2 and 4 with or without Oral Streptomycin Pretreatment

Abstract

The segmental distribution and sequential progression and the role of the indigenous bacterial flora in the development of enteric lesions associated with Serpulina hyodysenteriae infection in laboratory mice have not been defined. We examined the distribution and sequential morphometric changes in the large intestine of mice orally inoculated with S. hyodysenteriae serotypes 2 and 4. To determine the role of colonization resistance conferred by the indigenous bacterial flora, 40 female C3H/HeN mice were administered water alone or water containing 5 mg/mL streptomycin sulfate ad libitum for seven days prior to orogastric inoculation either with S. hyodysenteriae or sterile trypticase soy broth (TSB). Clinical signs were monitored daily and three mice per group were necropsied on postinoculation days (PID) 7 and 14 for pathological assessment of the cecum, proximal colon, transverse colon, and descending colon, and bacteriological culture of the cecum for S. hyodysenteriae. Weekly pooled fecal samples were collected from each group for determination of total numbers of anaerobe bacteria. Gross examination revealed soft fecal pellets on PID 7 and 14 and catarrhal typhlitis on PID 14, irrespective of streptomycin pretreatment. The recovery rates of S. hyodysenteriae from the ceca of serotype 2- and serotype 4-inoculated mice was 100 and 91.7%, respectively. Statistically significant differences in morphometric changes between TSB- and S. hyodysenteriae- inoculated mice were present on PID 7 and 14 and were restricted to the cecum. Although oral administration of streptomycin for seven days prior to S. hyodysenteriae inoculation resulted in a significant reduction in the numbers of fecal anaerobes, it did not affect the colonization, distribution, severity, or progression of cecal lesions. La distribution segmentaire, la progression sequentielle et le role de la flore bacterienne indigene dans le developpement des lesions enteriques associees \u27a une infection par Serpulina hyodysenteriae chez des souris de laboratoire ne sont toujours pas connus. Nous avons etudie la distribution et les changements morphometriques sequentiels du gros intestin de souris inoculees oralement avec S. hyodysenteriae serotypes 2 et 4. Afin d\u27evaluer le role de la flore bacterienne indigene dans la resistance a la colonisation, 40 souris femelles C3H/HeN ont requ de l\u27eau uniquement ou de l\u27eau contenant 5 mg/mL de streptomycine ad libidum pendant sept jours avant d\u27etre inoculees par voie orogastrique avec S. hyodysenteriae ou un bouillon sterile. Les signes cliniques ont ete notes a chaque jour et trois souris de chacun des groupes ont ete necropsiees aux jours 7 et 14 post-inoculation (PI) pour examen du caecum, du colon proximal, du c\u27lon transverse et du colon descendant et pour culture bacterienne du caecum. Des pools de feces ont ete obtenus a chaque semaine pour determiner le nombre total de bacteries anaerobies. L\u27examen macroscopique a revele la presence de feces molles aux jours 7 et 14 PI et d\u27une typhlite catarrhale au jour 14 PI, que les animaux aient requ ou non de la streptomycine. S. hyodysenteriae serotype 2 et serotype 4 a etet reisole\u27 respectivement de 100 et 91,7 % des caeca des souris inoculees. Des differences statistiquement significatives de changements morphometriques ont ete observees aux jours 7 et 14 PI entre les souris inoculees avec un bouillon sterile et celles ayant recu S. hyodysenteriae et ce, uniquement dans le caecum. Bien que l\u27administration orale de streptomycine ait reduit de facon significative le nombre d\u27anaerobes fecaux, elle n\u27a pas affecte la colonisation, la distribution, la severite ou la progression des lesions. (Traduit par Dre Christiane Girard