MOLECULAR CHARACTERISATION OF MYCOBACTERIUM TUBERCULOSIS COMPLEX AND RISK FACTORS AMONG PATIENTS ATTENDING A NATIONAL TUBERCULOSIS CENTRE IN ZARIA, NIGERIA

Abstract

Tuberculosis is one of the most widespread infectious diseases and a leading cause of death among adults worldwide. Globally, Nigeria ranks fourth among high tuberculosis countries and first in Africa with an incidence of 300/100,000. Mycobacterium tuberculosis is the most common species causing human tuberculosis but other members of the Mycobacterium tuberculosis complex (MTC) are increasingly recognized as a cause of human infections. However, there is paucity of information on species of MTC causing tuberculosis in Nigeria. This study was aimed at characterizing MTC species from sputum of tuberculosis patients and identifying risk factors for infection. The study was conducted in the National Tuberculosis and Leprosy Training Centre, Zaria, Nigeria from April 2010 to June 2010. Case control study design involving consecutive selection of 102 smear-positive tuberculosis patients as cases and simple random selection of 102 smear-negative patients as controls was conducted. A structured interviewer administered questionnaire was used to collect demographics, document HIV status, clinical information and risk factors for tuberculosis such as previous contact with tuberculosis patients and cattle, and consumption of unpasteurized milk from 204 respondents. Species of MTC were identified using a multiplex Polymerase Chain Reaction (PCR) method based on genomic regions of difference (RD1, RD4, RD9 and RD12) and insertion sequence 61 10 targeting for I 23bp and 245bp fragments. Data was analyzed using descriptive statistics, Chi square test and logistic regression at 5% level of significance. The mean age of the cases and controls were 36.2 ±9.0 and 35.8 ±9.7 years respectively. Majority, 70.6% of cases and 70.6% of controls were males. Fifty eight percent of cases and 66 % of controls had at least secondary school education. Seventy seven percent of the cases and 81% of the controls reported receiving BCG immunization. Twenty one percent of the cases and 20% of the controls were HIV positive. All sputa from the smear positive respondents were positive for MTC. Ninety one (89.2%) of the sputa were identified as M tuberculosis while 11 (10.8%) were M africanum. Fifty percent and 17% of cases and controls respectively had history of contact with TB patients. Many of the cases (59.8%) and 53.9% of controls thought tuberculosis was air borne. Sixty four percent of the cases and 28% of the controls have lived in close contact with cattle. There was no statistical difference in knowledge of transmission of tuberculosis between cases and controls. Those who usually consume unpasteurized milk (AOR: 8.33, 95%CI=4.28-16.2), have had close contact with cattle (AOR: 4.42, 95%C1=2.45-7.98), and had previous contact with tuberculosis patients (AOR: 5.0, 95%CI= 2.61-9.57) were more likely to have tuberculosis. Mycobacterium tuberculosis remains the major cause of human tuberculosis in Nigeria however, Mycobacterium a_fricanum plays a significant role in the aetiology of tuberculosis. Previous contact with patients with tuberculosis, cattle or pets poses risk for infectious tuberculosis. Specific health messages tailored towards these risk factors are needed. Further studies to elucidate the transmission of tuberculosis between pets and humans are recommended.