Zoonotic tuberculosis caused by Mycobacterium bovis, Central province, Iran

Abstract

Abbreviations: TB, tuberculosis; M. Bovis, mycobacterium bovis; M. tuberculosis, mycobacterium tuberculosis; MTBC, mycobacterium tuberculosis complex; HIV, human immunodeficiency virus IntroductionTuberculosis still remains a global health problem. Most cases of disease are reported as Mycobacterium tuberculosis complex, while identification of Mycobacterium bovis as a member of this complex could be valuable in term of public health control measures. Although most cases of human tuberculosis are due to M. tuberculosis a proportion, called zoonotic TB, is caused by M. bovis as almost 3% of tuberculosis cases in the world are attributed to M. bovis.1 Human to human transmission of zoonotic TB is a rarely reported event 2,3 and bovids (eg. Cattle) are the main hosts for M. bovis therefore, contact with infected animals or infectious animal products are blamed most in zoonotic TB cases.2,4 Prevalence of bovine tuberculosis is exacerbated by the presence of multiple additional risk factors such as high prevalence of human immunodeficiency virus (HIV) infections. However, HIV/AIDS facilitates transmission of any form of TB, some studies showed a significantly increased proportion of Mycobacterium bovis infections among HIV-co-infected TB patients compared with HIV-negative TB patients. 5 According to the World Health Organization report, the prevalence of tuberculosis in Iran in 2013 was estimated 33 cases per 100000 people. 6 On the other hand, Iran is among the seven Asian States with an existing bovine TB control scheme operating at national scale with a very homogenous of bovine M. bovis. This appears in concordance with few previously reported observations 7 that cases of zoonotic TB in Iranian population is lower compared to its neighboring countries.8 Different approaches to differentiate M. bovis from M. tuberculosis complex are done but the PCR-RFLP using OxyR gene is highly sensitive and inexpensive method. The aim of this research is improving our epidemiological understand of M. bovis infection in human subjects in Iran. We performed a cross-sectional molecular epidemiology study on pulmonary tuberculosis patients admitted to a general hospital in central province of Iran to investigate zoonotic tuberculosis. During the study period forty two MTBC (Mycobacterium tuberculosis complex) isolates were identified by phenotypic tests, PCR-RFLP OxyR gene and genotypic methods including PCR-RFLP. Using IS6110-PCR, PCR-RFLP for OxyR gene plus RFLP (with PGRS and DR markers) genotyping strategies, the present research represents an epidemiological investigation into zoonotic TB in Central Province, Iran. Materials and methodsStudy population: 41 Sputum specimens and one gastric lavage were collected during the period of March 2009 to September 2010 from all smear-positive TB patients (e.g. 38 Iranians and 4 Afghans) admitted to the public hospitals across the Markazi province, central Iran (Figure 1). In this study, five standard strains of mycobacterium including three strains of Mycobacterium tuberculosis (C, DT,...