Restriction fragment length polymorphism pattern of Mycobacterium isolates from rodents in infected cattle farms

Mycobacterium tuberculosis, the etiologic agent of tuberculosis, causes large-scale morbidity and mortality, particularly in developing countries. In recent years, there has been a significant increase in the drug-resistant ability of M. tuberculosis, triggering a major public health crisis. A detailed analysis of the evolution of the mycobacterial genome helps to better understand the genotype-phenotype relationship in this bacterium. Different strain typing methods have already revealed the worldwide diversity of mycobacterial isolates. Therefore, DNA-fingerprinting tools have been developed to improve tuberculosis case detection and control. Molecular typing techniques allow to detect and follow the spread of individual strains of the M. tuberculosis complex (MTC), complementing conventional epidemiological methods. Among these techniques, restriction fragment length polymorphism (RFLP) has been considered the standard method for genotyping of MTC. The aim of this work was to isolate M. tuberculosis from rodents in cattle farms contaminated with MTC located in the city of Booin-Zahra, Iran.

A total of 100 samples were collected from the rodents in the contaminated farms and analyzed for the presence of Mycobacterium by growing the samples on Lowenstein-Jensen medium. All isolates were further identified by RFLP and DNA hybridization studies.

As much as five samples showed the presence of Mycobacterium and these were subjected to PCR-16SrRNA, PCR-IS6110, and RD Typing (RD1, RD4, RD9, and RD12) methods. Further differentiation was performed with PvuII digestion (RFLP) and DNA hybridization using the polymorphic guanine/cytosine-rich repetitive sequences (PGRS) probe. The PGRS probe results classified two of the isolates as belonging to one cluster, whereas the remaining isolates were classified as belonging to different clusters. An analysis of the obtained genetic pattern and a comparison of these patterns with the genetic pattern of other infected farms allowed us to record the similarities and difference. The results indicated the transmission of Mycobacterium from infected rodents to the cows located in the same farm.

These results highlight the possible danger of transmission of Mycobacterium among animals.