Thirty-seven local isolates of Actinobacillus suis-like organisms from diseased and clinically normal horses and 1 Ilama were compared with reference strains of A suis, A lignieresii, A equuli, A capsulatus, A hominis, A (Pasteurella) ureae, and equine A suis-like organisms (ASLO) previously described in literature. Comparison was by 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 Ilama 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. We conclude that the 4 strains were hemolytic 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 Ilama isolate had similar profiles. The groupings of cultures resulting from the different testing methods had little relation to each other and to the anatomic source of the strains except the strains comprising API-CH biotype III, which originated in the equine respiratory tract, and the A lignieressi cluster.

Thirty-seven local isolates of Actinobacillus suis-like organisms from diseased and clinically normal horses and 1 Ilama were compared with reference strains of A suis, A lignieresii, A equuli, A capsulatus, A hominis, A (Pasteurella) ureae, and equine A suis-like organisms (ASLO) previously described in literature. Comparison was by 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 Ilama 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. We conclude that the 4 strains were hemolytic 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 Ilama isolate had similar profiles. The groupings of cultures resulting from the different testing methods had little relation to each other and to the anatomic source of the strains except the strains comprising API-CH biotype III, which originated in the equine respiratory tract, and the A lignieressi cluster.

Whole-cell lysates and proteinase K-extracted lipopolysaccharide (LPS) of 19 strains of the group eugonic fermenter-4 (EF-4) were analyzed by electrophoresis and protein immunoblotting. These strains were isolated from dog- and cat-bite abscesses in human beings, ferret and human gastric lesions, and cat-lung infections. These strains represent 2 biovar groupings; EF-4a biovars ferment glucose and possess arginine dihydrolase activity, whereas EF-4b biovars do not. Electrophoresis of whole-cell lysates could distinguish between these biovars groups. Electrophoresis of LPS extracts revealed that all strains of EF-4 possess smooth chemotypes. Two strains of EF-4a reacted weakly in protein immunoblots and revealed distinct LPS profiles. These studies suggests that subgroups of EF-4 biovars may exist.