Belay, M. | bioRxiv Science

bioRxiv2020

Cellular and Cytokine Responses in the Granulomas of Asymptomatic Cattle naturally infected with Mycobacterium bovis in Ethiopia

Cellular (CD3+ T cell and CD68+ macrophages), cytokines (IFN-{gamma}+ and TNF-+) and effector molecule (iNOS+) responses were evaluated in the lymph nodes and tissue of cattle naturally infected with Mycobacterium bovis. Detailed post mortem and immunonohistochemical examinations of lesions were performed on 16 cows positive for single intradermal cervical comparative tuberculin test (SICCTT) and identified from dairy farms located around the Addis Ababa City. The severity of the gross lesion was significantly higher (p=0.003) in M. bovis culture positive (n=12) cows than in culture negative (n=4). Immunohistochemical techniques showed that the mean percentage labelling of CD3+ T cells decreased as the stage of granuloma increased from stage I to stage IV in culture positive cows (p<0.001). On the other hand, the proportional fraction of CD68+ macrophages and the concentrations of IFN-{gamma}+, TNF-+ and iNOS+ increased significantly from stage I to stage IV (p< 0.001) in culture positive cows. At the early stage of the granuloma, the culture negative cows showed significantly higher mean proportions of CD68+ macrophages (p=0.03) as well as the concentrations of iNOS+ (p=0.007) compared to culture positive cows. Similarly, at advanced granuloma stages, culture negative cows demonstrated significantly higher mean proportions of CD3+ T cells (p< 0.001) compared to culture positive cows. Thus, the present study demonstrated that following natural infection of cows with M. bovis, as the stage of granuloma increases from stage I to stage IV, the proportion of CD3+ cells decreases while the immunolabeling fraction of CD68+ macrophages, IFN-{gamma}+, TNF- and iNOS+ increases.

immunology↗

bioRxiv2019

Prevalence of pulmonary tuberculosis among patients presenting with cough of any duration in Addis Ababa, Ethiopia

BackgroundThe current practice in Ethiopia to diagnose tuberculosis is screening patients with cough for at least two weeks. A health facility based study was conducted to estimate the prevalence of smear and culture positive pulmonary TB among patients presenting with cough [≥]2 weeks and <2 weeks in Addis Ababa, Ethiopia.\n\nMethodsA cross-sectional study design was used to recruit patients with cough of any duration from four selected health centers in Addis Ababa, between August and December 2016. Sputum samples were collected from patients reporting productive cough of any duration and screened for Pulmonary Tuberculosis (PTB) using smear microscopy and culture methods. Mycobacterium tuberculosis isolates obtained from culture positive samples were characterized using RD9 deletion typing.\n\nResultsMajority (39.7%) of the 725 study participants was in the age range of 20-30 years, and 5.0% were smear positive using smear microscopy. The prevalence of smear positive PTB among patients presented with cough duration of [≥]2 weeks was significantly higher compared to those patients presented with cough duration of <2 weeks (10.9% versus 0.7%; {chi}2=38.98; p=0.001). Using culture method, a total of 86 (11.9%) participants were positive for mycobacteria, and the prevalence (14.6%) of PTB among patients presented with cough duration of [≥]2 weeks was not significantly higher compared to prevalence (9.9%) in those patients presented with cough duration of <2 weeks ({chi}2=3.63; p=0.057). Molecular characterization of 86 culture positive mycobacterial isolates showed that 41 were infected with Mtb; 19(46.3%) from those who had cough duration of <2 weeks and 22(53.7%) from those who had cough duration of [≥]2 weeks.\n\nConclusionScreening of PTB using smear microscopy alone and cough duration of at least two weeks would negatively affect early diagnosis and treatment initiation in a considerable number of PTB patients who reports cough duration of <2 weeks with the potential of contributing to the spread of TB. Therefore, screening of patients with cough of any duration using both smear microscopy and culture methods is likely to contribute to the success of any effort towards the control of TB.

epidemiology↗