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Oxygen status of lung granulomas in Mycobacterium tuberculosis ‐infected mice
Author(s) -
Aly S,
Wagner K,
Keller C,
Malm S,
Malzan A,
Brandau S,
Bange FC,
Ehlers S
Publication year - 2006
Publication title -
the journal of pathology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.964
H-Index - 184
eISSN - 1096-9896
pISSN - 0022-3417
DOI - 10.1002/path.2055
Subject(s) - mycobacterium tuberculosis , tuberculosis , granuloma , lung , pathology , pulmonary pathology , biology , hypoxia (environmental) , pathological , immunology , microbiology and biotechnology , medicine , oxygen , chemistry , organic chemistry
It is often assumed that Mycobacterium tuberculosis (Mtb) ‐induced granulomatous lesions, particularly those undergoing central caseation, are anoxic, and that the survival of Mtb in these lesions requires the integrity of its non‐oxidative respiratory pathways. Using the hypoxia marker pimonidazole, we now provide immunohistochemical evidence that in the most frequently used animal model system of inbred mice Mtb ‐induced granulomas, even after more than one year of aerogenic infection, are not severely hypoxic. In contrast, chronic aerosol infection with M. avium strain TMC724 was associated with hypoxia surrounding necrotizing granuloma centres. Direct measurements of oxygen tension with a flexible microelectrode in mouse lungs chronically infected with Mtb disclosed a wide range of oxygen partial pressures in different parts of the lungs which, however, rarely approached the anoxic conditions consistently found in necrotizing tumours. We further show that an Mtb mutant, defective in nitrate reductase (narG) necessary for survival under anaerobic conditions in vitro , can persist in the lungs of chronically infected mice to a similar extent as wild‐type Mtb . These findings have important implications for the use of the mouse model of Mtb infection in developing eradication chemotherapy and for evaluating putative mechanisms of chronic persistence and latency of Mtb . Copyright © 2006 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

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