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Understanding mechanisms of cavitation in tuberculosis (TB) is the missing link that could advance the field towards better control of the infection. Descriptions of human TB suggest that postprimary TB begins as lipid pneumonia of foamy macrophages that undergoes caseating necrosis and fragmentation to produce cavities. This study aimed to investigate the various mycobacterial antigens accumulating in foamy macrophages and their relation to tissue destruction and necrosis. Pulmonary tissues from mice with slowly progressive TB were studied for histopathology, acid-fast bacilli (AFB) and presence of mycobacterial antigens. Digital quantification using Aperio ImageScope was done. Until week 12 postinfection, mice were healthy, and lesions were small with scarce AFB and mycobacterial antigens. Colony-forming units (CFUs) increased exponentially. At week 16-33, mice were sick, macrophages attained foamy appearance with an increase in antigens (P < .05), 1.5 log increase in CFUs and an approximately onefold increase in AFB. At week 37-41, mice started dying with a shift in morphology towards necrosis. A >20-fold increase in mycobacterial antigens was observed with only less than one log increase in CFUs and sevenfold increase in AFB. Secreted antigens were significantly (P < .05) higher compared to cell-wall antigens throughout infection. Focal areas of necrosis were associated with an approximately 40-fold increase in antigen MPT46, functionally active thioredoxin, and a significant increase in all secreted antigens. In conclusion, mycobacterial antigens accumulate in the foamy macrophages in TB lesions during slowly progressive murine pulmonary TB. Secreted antigens and MPT46 correlated with necrosis, thereby implying that they might trigger the formation of cavities., (© 2020 The Authors. Scandinavian Journal of Immunology published by John Wiley & Sons Ltd on behalf of The Scandinavian Foundation for Immunology.)

Objective: To demonstrate the application of TB management time as an alternative parameter to estimate the size of the tuberculosis infectious pool in West Gojjam Zone of Amhara Region, Ethiopia., Methods: In this study, we used the TB management time, i.e. the number of days from start of cough until start of treatment, to determine the infectious period. Patients with sputum smear-positive and smear-negative pulmonary TB, retreatment and an estimated number of undetected cases were included. The infectious pool was then estimated as the annual number of infectious person days in a defined population., Results: The TB management time of presently undiagnosed TB cases and sputum smear-positive patients contributed significantly to the infectious pool with 151,840 and 128,750 infectious person days per year, respectively. The total infectious pool including sputum smear-negative TB cases and retreatment patients in the study area was estimated at 325,410 person days or 15,447 person days per 100,000 population during the study year., Conclusion: Recording TB management time may be used to estimate the infectious pool of TB and to monitor programme performance in the community., (© 2014 The Authors. Tropical Medicine & International Health Published by John Wiley & Sons Ltd.)