Diversity among isolates of Actinobacillus equuli and related organisms as revealed by ribotyping.
OBJECTIVE
The objective of this work was to examine the diversity within Australian isolates of Actinobacillus equuli and related organisms by the genotypic method of ribotyping.


METHODS
Ribotyping, performed using the enzyme HaeIII, was used to examine the diversity in 12 field isolates of A equuli (five being capable of fermenting L-arabinose), one field isolate of Pasteurella caballi and two unclassifiable field isolates. Isolates were obtained from Australian horses, except for three isolates of A equuli (one L-arabinose positive and two L-arabinose negative) which were obtained from horses and a pig in Africa. In addition, the type strains for A equuli and P caballi and a reference strain for Bisgaard Taxon 9 were included in the study.


RESULTS
The ribotype patterns were analysed by computerised cluster analysis, yielding five clusters (A to E). All five of the L-arabinose positive A equuli were assigned to cluster A, with all the other seven A equuli isolates (all L-arabinose negative) and the type strain being assigned to cluster B. One of the two unclassified isolates formed cluster C along with the reference strain for Bisgaard Taxon 9. The remaining unclassified isolate formed cluster D. Cluster E consisted of the field isolate and reference strain of P caballi.


CONCLUSIONS
The results of this study indicate that A equuli is a diverse species, with L-arabinose positive isolates of A equuli being quite distinct from typical L-arabinose negative isolates. Ribotyping appears to be a useful tool in confirming the identity of A equuli-like organisms from horses.
Department of Primary Industries, Animal Research Institute, Yeerongpilly Queensland.
P J
PJ
Blackall
J P
JP
Christensen
M
M
Bisgaard
D000188:Actinobacillus / Q000145:classification* / Q000235:genetics; D000189:Actinobacillus Infections / Q000382:microbiology / Q000662:veterinary*; D000818:Animals; D001315:Australia; D016000:Cluster Analysis; D004269:DNA, Bacterial / Q000032:analysis; D015252:Deoxyribonucleases, Type II Site-Specific; D014644:Genetic Variation; D006734:Horse Diseases / Q000382:microbiology*; D006736:Horses; D015183:Restriction Mapping; D013552:Swine; D013553:Swine Diseases / Q000382:microbiology
D004269:DNA, Bacterial; D015252:Deoxyribonucleases, Type II Site-Specific; C024403:GGCC-specific type II deoxyribonucleases