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Title: Studies on Actinobacillus equuli
Author: Kim, Bong Hwan
ISNI:       0000 0001 3599 2415
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 1976
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The morphological, cultural and biochemical characteristics of 138 strains of Actinpbacillus equuli from various sources have been investigated and evaluated in order to provide useful criteria for the identification of this taxonomically disputed species of microorganism. The antigenic structure of all these strains was investigated by agglutination and agglutinin-absorption tests and 98.6 per cent, of them can be arranged into 28 groups on the basis of their heat-stable antigens (O antigens). The heat-labile antigens associated with extracellular slime have been demonstrated and found to be relatively common to organisms of different O groups. Although agglutination tests offer a means of classifying this serologically heterogeneous group of organisms, the autoagglutinability of rough strains and inagglutinability due to its viscous nature have often been found to interfere with such tests. Thus the feasibility of applying other serological procedures to overcome the difficulties has been sought and a passive haemagglutination test and an immunodiffusion precipitin test for serogroupiny of A. equuli were developed. The conditions for the passive haemagglutination test have been investigated and are discussed in some detail with special reference to the soluble antigens of A. equuli. Heat extracts of the organisms were used in the immunodiffusion precipitin test to group A. equuli strains into 28 O-groups. The immunodiffusion precipitin test appeared to be the test of choice for the serogrouping of isolates of A. equuli because of its specificity and its simplicity and rapidity in performance. Moreover, the immunodiffusion precipitin test has a great advantage over the other serological methods in showing a clear proof of an antigenic relationship between 0 groups. The work has shown that serological classification of the organism is fairly well correlated with certain biochemical characters of the organism and the majority of the strains can be arranged into two main divisions. The term biotype is applied for the differentiation of these divisions of A« equuli. Of the 138 strains studied, 84 were of Type I, 42 were of Type II and the remaining 12 were intermediate in type. Type I strains gave a positive reaction with mannitol, whilst their reaction with salicin and cellobiose were negative. All the strains comprising Type I were aesculin-negative and, with the exception of one, non-haemolytic. These strains fell into O groups 1-22 inclusive. On the other hand, Type II strains were mannitol negative, whilst the majority of the strains fermented salicin and cellobiose and hydrolysed aesculin, and all haemolysed sheep erythrocytes. The Type II strains were made up of 0 groups 24 - 28 inclusive. An antigenic relationship between A. equuli, A. suis and A. lignieresi has been demonstrated. Comparative biochemical and serological studies of these 3 species of Actinobacillus have shown that A. suis is closely related to Type II of A. equuli and that A. suis differs sufficiently from both A. lignieresi and Type I of A. equuli to warrant its separation as a different species within the genus. Further work is required to characterise haemolytic actinobacilli from horses and pigs, but the results obtained in the work appear to suggest the not infrequent occurrence in the upper respiratory tract of normal horses of organisms resembling A. suis and the association of such organisms with disease in this host species on occasions.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available