Prevalence, Species Characterization and Factors Associated With Non Tuberculous Mycobacteria among Tuberculosis Retreatment Patients Submitting Samples to the National Tuberculosis Reference Laboratory, Kenya

Abstract

The frequency of pulmonary disease from non-tuberculous mycobacterium (NTM) is reportedly on the rise in Europe, North America, Asia and Southern Africa. In sub-Saharan Africa, information on the extent of the burden of pulmonary disease from NTM is lacking due to limitations in tools for mycobacterial species identification. Failure to characterize acid fast bacilli (AFB) positive NTM lung infections has led to their misclassification and to inappropriate treatment for pulmonary tuberculosis in developing countries. Kenya is ranked among top African countries with high Tuberculosis (TB) cases associated with high Human Immunodeficiency Virus/ Acquired Immunodeficiency Syndrome (HIV/AIDS) burden. Arguably the emergence of NTM as opportunistic infections in the HIV/AIDS patients would complicate TB management given that their treatment is not directly analogous to that of TB. This cross sectional study therefore, characterized and identified the correlates of NTM among TB retreatment patients whose samples are sent to the National Tuberculosis Reference Laboratory (NTRL). The TB retreatment patients of BACTEC™ MGIT™ (Mycobacteria Growth Indicator Tube) culture positive samples were consented and enrolled into the study. The patients‟ health records and case investigation forms were used to gather information associated with NTM infection. All subjects were assigned a subject identification number (SID). All paper research records were kept in a locked filing cabinet located in a restricted-access xiii room at the research center in the NTRL, Nairobi. All data was entered into Microsoft Excel (USA) which was associated with SID in password protected files. Descriptive statistics (frequency and proportions) were used to summarize data and presented using tables. The overall NTM prevalence was determined for the entire patient’s population. Bivariate and multivariate analyses were used to determine factors associated with NTM infection using Poisson regression at the significance level of p ≤0.05. All statistical analyses were performed using STATA v 13 (StataCorp LP, Texas, and USA). The median (IQR) age of the 210 TB retreatment patients‟ enrolled was 35 (28 - 75) years. Slightly over fifty percent (53.8%) of the patients were females, 33.8% were aged between 25 to 34 years, and 18% were smokers, while 22% were HIV positive. About 37% had respiratory symptoms while 36.2% had animal contact. Seventy-five of 210 (35.7%) of the TB retreatment patients were infected with NTM. The Mycobacterium intracellulare (62.7%) was the most frequent NTM observed. Others included; 16% M. absessus, 8% M. fortuitum, 5.3% M. sacrofuloceum, 4% M. kansasii, 1.3% M. interjectum, 1.3% M. gordonae and 1.3% M. xenopi. Female gender OR 1.8 (95% CI 1.1 to 3.1), residence of Eastern region OR 2.2 (95%CI 1.1 to 4.6) and Nairobi region OR 2.3 (95%CI 1.1 to 5.1), those who had respiratory symptoms OR 1.5(95% CI 1.01 to 2.5) and animal contact OR 1.7 (95%CI 1.1 to 2.7) as well as those who kept livestock OR 1.6 (95%CI 1.06 to 2.6) were likely to be infected with NTM. Infection due to NTM among TB retreatment cases is high in xiv Kenya and missed diagnosis jeopardizes proper management. Involvement of NTM during management of clinical pulmonary TB is important in planning for prevention and treatment of TB in Kenya especially among patients in pastoral community.