Invasive Species Compendium

Detailed coverage of invasive species threatening livelihoods and the environment worldwide

Abstract

Actinobacillus suis-like organism and evidence of hemolytic strains of Actinobacillus lignieresii in horses.

Abstract

Thirty-seven local isolates of Actinobacillus suis-like organisms from diseased and clinically normal horses and 1 llama were compared with reference strains of A. suis, A. lignieresii, A. equuli, A. capsulatus, A. hominis, A. (Pasteurella) ureae, and equine A. suis-like organism (ASLO) previously described in literature based on cultural characteristics, carbohydrate fermentation, enzyme profiles, and whole-cell protein polyacrylamide gel electrophoresis. Carbohydrate fermentation, determined by API-CH gallery, divided 36 equine ASLO isolates into 6 API-CH biotypes. The llama isolate was an additional distinct biotype. The biochemical comparisons between A. suis and ASLO did not reveal remarkable and consistent differences. Enzyme analysis revealed 5 API-ZYM biotypes, one of which included the same strains as one of the API-CH biotypes and consisted in both instances of 4 esculin- negative ASLO cultures and the reference strain of A. lignieresii. It was concluded that the 4 strains were haemolytic variants of A. lignieresii. Protein electrophoresis disclosed 15 banding patterns, 10 of which represented equine ASLO strains. The reference strains of A. suis shared the pattern predominant among equine ASLO. Four of the remaining reference strains of Actinobacillus species each had a unique profile, whereas the type strain of A. capsulatus and the llama isolate had similar profiles. The groupings of cultures resulting from the different testing methods had little relation to each other or to the anatomical source of the strains except the strains comprising API-CH biotype III, which originated in the equine respiratory tract, and the A. lignieresii cluster.