Homogeneity of Mycoplasma agalactiae vaccine strains isolated from Taliqan, Lorestan, and Shiraz in Iran

Iran continues to hold one of the most currently active world foci of agalaxy in ruminants. The three local strains of Taliqan, Lorestan, and Shiraz have been used for many years in preparation of the only commercially available killed vaccine against agalaxy in the Iranian market. This study was conducted to determine the genetic link between these strains.

All three strains of Taleghan, Lorestan, and Shiraz were cultivated freshly on PPLO agar media. The genetic material was extracted by boiling method. In order to investigate the genomic relations between these strains, a Multi-Locus Variable Number Tandem Repeat Analysis (MLVA) strategy concentrating on 4 VNTR loci of 5, 9, 17, and 19 was employed. The nucleotide sequences of all PCR products were determined, as well.

Nucleotide sequence analysis showed an identical MLVA pattern by all the three strains. When compared to the Mycoplasma agalactiae PG2 laboratory strain, the only VNTR19 locus was different between Iranians and the PG2 strain, with respect to a 3bps addition at this locus in Iranian strain.

The identical genetic pattern of the three Iranian strains is likely an indication of the activity of one or more indigenous ancestral clone in the geography of Iran that has been appeared and evolved throughout its livestock history and became homogeneous and predominant due to the absence of efficient disease control policies. The similarity between three Iranian and the PG2 strains might be due to homoplasy or human intervention through animal husbandry activities such as livestock importation. Applying standard genotyping methods to a larger number of local isolates help to better assess this observation