Phylogeny and molecular typing of Mycoplasma agalactiae and Mycoplasma bovis by multilocus sequencing

Mycoplasma agalactiae and Mycoplasma bovis are important pathogens producing similar pathologies in small ruminants and cattle, respectively. They share many phenotypic and genotypic traits and comparison of their 16S rDNA sequences lacks sufficient resolution for phylogenetic analysis. The aim of this study was to develop a multilocus sequence typing (MLST) scheme to analyse the phylogenetic relationships between M. agalactiae and M. bovis and to assess its use for unequivocal strain characterisation and molecular typing. An MLST based on fusA, gyrB, lepA and rpoB was applied to a sample of strains from both species, some of which could not be classified by serology or PCR. A robust phylogenetic tree was inferred, where the two species were clearly resolved. The use of this tool for the molecular typing of M. agalactiae strains was further evaluated on 19 presumably unrelated isolates, resulting in the discrimination of 14 sequence types (ST). The discriminatory power was increased (17 ST) by including an alternative target located in a more variable region. The diversity of M. agalactiae in Turkey (9 strains) and Israel (15 strains) was also assessed. Five closely related ST were evidenced in Turkey and 6 in Israel, with one ST common to both countries. Each country showed a predominant type that persisted over years. The MLST scheme developed here constitutes a universal tool for unequivocal strain characterisation and global, long-term screening of dissemination of M. agalactiae and M. bovis, whereas addition of more variable, non-housekeeping gene targets allows precise epidemiological investigations.