Genetic evolution of Mycoplasma capricolum subsp. capripneumoniae strains and molecular epidemiology of contagious caprine pleuropneumonia by sequencing of locus H2.

Contagious caprine pleuropneumonia (CCPP) is a major threat to goat farming in developing countries. Its exact distribution is not well known, despite the fact that new diagnostic tools such as PCR and competitive ELISA are now available. The authors developed a study of the molecular epidemiology of the disease, based on the amplification of a 2400 bp long fragment containing two duplicated gene coding for a putative membrane protein. The sequence of this fragment, obtained on 19 Mycoplasma capricolum subsp. capripneumoniae (Mccp) strains from various geographical locations, gave 11 polymorphic positions. The three mutations found on gene H2prim were silent and did not appear to induce any amino acid modifications in the putative translated protein. The second gene may be a pseudogene not translated in vivo, as it bore a deletion of the ATG codon found in the other members of the "Mycoplasma mycoides cluster" and as the six mutations evidenced in the Mccp strains would induce modifications in the translated amino acids. In addition, an Mccp strain isolated in the United Arab Emirates showed a deletion of the whole pseudogene, a further indication that this gene is not compulsory for mycoplasma growth. Four lineages were defined, based on the nucleotide sequence. These correlated relatively well with the geographical origin of the strains: North, Central or East Africa. The strain of Turkish origin had a sequence similar to that found in North African strains, while strains isolated in Oman had sequences similar to those of North or East African strains. The latter is possibly due to the regular import of goats of various origins. Similar molecular epidemiology tools have been developed by sequencing the two operons of the 16S rRNA gene or by AFLP. All these various techniques give complementary results. One (16S rRNA) offers the likelihood of a finer identification of strains circulating in a region, another (H2) of determining the geographical origin of the strains. These tools can make a very useful contribution to understanding the epidemiology of CCPP.