Mycoplasma capricolum subsp. capripneumoniae, the cause of contagious caprine pleuropneumonia, comprises two distinct biochemical groups

Mycoplasma capricolum subsp. capripneumoniae, the cause of the World Organisation of Animal Health- listed contagious caprine pleuropneumonia, is a member of the Mycoplasma mycoides cluster which comprises five pathogenic mycoplasmas of ruminants. These mycoplasmas are closely related immunologically and genetically which can lead to difficulties for differential diagnosis. The patterns of substrate metabolism of strains of M. c. capripneumoniae, gathered from diverse geographic regions, were studied by measurement of oxygen uptake rates. The strains fell into two major biochemical groups: one which only oxidised organic acids and glycerol and the other which could additionally metabolise sugars. Furthermore when DNA-DNA hybridisation tests were carried out these two groups of strains could be separated by their degree of DNA homology, the mean hybridisation value between members of the two groups was 86% well above the value of 70% normally used to indicate separate species. DNA-DNA hybridisation was also carried out between M. c. capripneumoniae strains and other members of the M. mycoides cluster. These experiments used labelled DNA from two representative subsp. capripneumoniae strains; these were 7/1a (organic acid-oxidising) and 4/2 LC (glucose-oxidising). The results showed a particularly close relationship of the glucose-oxidising strain to M leachii strains.