Epidemiological and microbiological characterization of pulmonary tuberculosis in Kano State, Nigeria: insights from acid fast bacilli smear microscopy and socio-demographic determinants

Abstract

Tuberculosis (TB) remains a significant public health challenge in Nigeria, with Kano State representing one of the highest burdened regions due to its dense population, urban-rural dynamics, and limited diagnostic access. This study aimed to characterize the epidemiological and microbiological profile of smear-positive pulmonary TB (PTB) in Kano, including prevalence patterns, socio-demographic determinants, and the burden of drug resistance. A cross-sectional study was conducted across 19 strategically selected Directly Observed Therapy Short course (DOTS) clinics in Kano State from January 2018 to December 2019. A total of 401 smear-positive PTB patients were enrolled using proportionate stratified sampling. Data on demographics, clinical history, Human immunodeficiency virus (HIV) status, and behavioral factors were collected through structured questionnaires. Sputum samples were analyzed using Ziehl-Neelsen (ZN) AFB smear microscopy, with laboratory procedures carried out at Aminu Kano Teaching Hospital. Descriptive and inferential statistical analyses were performed to explore associations between TB positivity and socio-demographic variables. Among the 401 patients, 46.1% tested AFB smear-positive. High bacillary load (2+/3+) was observed in 19.7% of cases, indicating high infectiousness. TB positivity was highest among males (71.6%), individuals aged 25–34 years (35.4%), and those with low educational attainment or income. Urban Local Government Areas (LGAs), particularly Nasarawa and Kano Municipal Council (KMC), accounted for over 60% of smear-positive cases. HIV co-infection was more prevalent in smear-negative and scanty cases but declined with increasing bacillary load, suggesting an inverse relationship between bacillary burden and HIV status. This study demonstrates a high burden of smear-positive TB in Kano State, with notable clustering in urban LGAs and among socioeconomically disadvantaged groups. Males and young adults bore a disproportionate burden, while HIV co-infection correlated with lower smear grades. These findings highlight the need for targeted interventions focusing on early detection, urban transmission control, and integrated TB/HIV services.