Genotyping of Mycobacterium avium subsp. avium isolates from naturally infected lofts of domestic pigeons by IS901 RFLP

Abstract

ObjectivesAvian tuberculosis is one of the most important infections affecting most species of birds. Several mycobacterial species have been identified causing avian tuberculosis, but the organisms confirmed most frequently are Mycobacterium avium and Mycobacterium genavense. All species of birds can be infected with M. avium. M. avium cannot only infect all species of birds, but can also infect some domesticated mammals to cause the disease, usually with localized lesions. Disseminated tuberculosis caused by M. avium has also been reported in rabbits and swine. In immune-competent humans, M. avium complex)MAC(isolates produce localized soft tissue infections, including chronic pulmonary infections in the elderly and cervical lymphadenitis in children, but rarely any disseminated disease. In HIV infected and AIDS patients, or in other immuno-compromised persons, MAC isolates frequently cause severe systemic infections.The most crucial aspect of control and eradication of the disease is identification of infection sources and transmission routes. The use of serotyping for epidemiological studies of virulent M. avium subsp. avium isolates in birds is limited by the prevalence of only three serotypes and untypable auto-agglutinating isolates. Molecular techniques, such as restriction fragment length polymorphism and pulse field gel electrophoresis, have been shown to be much more discriminatory and therefore suitable for use in the epidemiological study of M. avium complex infections. Materials and methodsEighty suspected pigeons with avian tuberculosis based on their clinical signs were subjected to the study. Forty M. avium subsp. avium isolates out of a total of 51 identified isolates were subjected to the test. Results and discussionClinical signs, necropsy findings, ZN staining and molecular identification confirmed that the pigeons were infected with M. avium subsp. avium. IS901-RFLP using PvuII was successfully conducted on 40 isolates and produced 7 patterns. The majority of isolates (60%) were RFLP type PI.1 and in comparison this type was the most similar type to the standard strain; however, all the patterns obtained in this study were different from the standard strain (M. avium subsp. avium D4 strain, ATCC number 35713). This is probably due to these isolates belonging to this region. In addition, no common pattern between this study and the only other similar study in Iran was found, and it indicates that the sources of their infection are not same. In conclusionIt is suggested that more DNA fingerprinting tests for non-tuberculous Mycobacteria, particularly M. avium complex isolated from infected birds and humans, be conducted to find the source of their infections.