Isolation, Molecular Identification and Genomic Pattern of Mycobacterium Bovis Isolates Collected from Tuberculin-positive Cattle in Infected Farms of Shiraz, Iran

Background Mycobacterium bovis is the main cause of tuberculosis in cattle. The most commonly used method to identify bovis-infected cattle is tuberculin test.  Objective The present study aimed to investigate the population structure of Mycobacterium bovis in infected cattle farms of Shiraz City in Iran. Methods In this descriptive cross-sectional study, 50 pathological samples from tuberculin-positive cattle that were collected from two abattoirs were cultured on glycerinated and pyruvated Lowenstein-Jensen media. Genomic material from culture-positive slopes was extracted and used in polymerase chain reaction (PCR)-16S rRNA, PCR-IS6110, and PCR--regions of difference (RD) typing. All the M. bovis isolates were then digested by PvuII restriction enzyme and genotyped by polymorphic guanine/cytosine-rich repetitive sequences (PGRS)-restriction fragment length polymorphism (RFLP) technique. Findings In bacterial culture, 13 (26%) of samples had living mycobacteria where PCR test results revealed their identity as Mycobacterium bovis. Genotype profiling by RFLP-PGRS method displayed two patterns with 10 isolates shared a single profile identical to that of M. bovis bacillus calmette-guerin (BCG) strain (1173 P2) and three isolated with a different genotype. Conclusion Higher prevalence of BCG-like M. bovis (as a typical characteristic of Iranian M. bovis population) in cattle farms of Shiraz City was expected. This may indicate the local evolution of new M. bovis strains in the region or the infiltration of such strains through cattle farming activities.