Mycobacterium Tuberculosis Infection Among Homeless Individuals in Addis Ababa, Ethiopia: Disease Burden, Drug Resistance Patterns and Molecular Epidemiology
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Date
2024-05
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Addis Ababa University
Abstract
In high tuberculosis (TB) burden countries like Ethiopia, rapid screening and prompt treatment initiation among vulnerable groups, such as the homeless, are essential for TB control efforts. During the last three decades, Ethiopia has experienced a rise in homelessness, which is attributed to internal conflicts and economic stress. In spite of the fact that TB disproportionately affects homeless individuals, the majority of research conducted on it in Ethiopia has not adequately addressed the disease burden on this vulnerable group. This study aimed to determine the disease burden, molecular epidemiology, and drug resistance patterns of Mycobacterium tuberculosis (M. tuberculosis) among homeless individuals in Addis Ababa, Ethiopia. A cross-sectional study was conducted in Addis Ababa between February 2019 and December 2020. Homeless individuals underwent pulmonary tuberculosis (PTB) clinical screening according to WHO guidelines. Suspected cases provided sputum samples for acid-fast bacillus (AFB), Xpert MTB/RIF assay, TB culture, and drug sensitivity test (DST). The M. tuberculosis isolates were typed using Polymerase-Chain-Reaction (PCR) based Region of Difference-9 (RD9), spoligotyping, and 24-loci M. tuberculosis Interspersed Repetitive Unit-Variable Number Tandem Repeat (MIRU-VNTR) typing. DST was performed using the BD Bactec Mycobacterial Growth Indicator Tube (MGIT) 960. Data analyses were performed using SPSS software version 26 and the M. tuberculosis complex (MTBC) online database. Out of 5,600 homeless individuals enrolled in the study and clinically screened for PTB symptoms, 641 suspected cases were identified. Thus, the clinical prevalence of PTB was 1054 per 100,000 homeless individuals. Being homeless for more than 5 years, a body mass index (BMI) < 18.5, smoking cigarettes, living in a group of more than 5 persons,
close contact with chronic coughers, imprisonment, and HIV infections were significantly associated with the prevalence of PTB in the homeless (P < 0.05). Out of 59 isolates, 58 were confirmed as M. tuberculosis by the RD9 PCR test. Genotyping revealed three MTBC lineages and eight sub-lineages, with Euro-American lineage predominating. Furthermore, Spoligo International Types (SIT), SIT53, SIT37, and SIT149 were highly prevalent strains detected in this study. Ethiopia_3, Delhi/CAS and Ethiopia_2 were determined to be the most prevalent sub-lineages in the study population. Strain clustering rates were 77.6% using spoligotyping, 39.7% using 24-loci MIRU-VNTR typing, and 10.3% using a combination approach. Living in a group was significantly associated with strain clustering (P < 0.05). Three homeless individuals with PTB harbored mixed M. tuberculosis strains. DST revealed 6.8% (4/59) of isolates resistant to at least one first-line anti-TB drug. Overall, the prevalence of PTB in homeless individuals was higher than that in the general population of Addis Ababa. Therefore, governmental and non-governmental organizations working on TB prevention and control must consider homeless settings as hotspots for TB control. Regular PTB screening, directly observed treatment short course (DOTS) centers, and mobile clinics must be established to control TB among homeless individuals and its spread to the general population.
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Tuberculosis, Pulmonary Tuberculosis, M. Tuberculosis, Homeless Individuals, Drug Sensitivity, Genetic Diversity, Genotyping, Addis Ababa