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Antimicrobial Agents and Chemotherapy, November 2009, p. 4789-4793, Vol. 53, No. 11
0066-4804/09/$08.00+0 doi:10.1128/AAC.01658-08
Copyright © 2009, American Society for Microbiology. All Rights Reserved.

Departments of Infectious Diseases and Research,1 Clinical Microbiology,3 Anatomic Pathology, Lahey Clinic Medical Center, Burlington, Massachusetts,4 Department of Clinical Microbiology, Mayo Clinic, Rochester, Minnesota2
Received 17 December 2008/ Returned for modification 26 February 2009/ Accepted 24 June 2009
The sulfonamides were the first drugs with antituberculous effects. Their use was abandoned and basically forgotten with the advent of streptomycin and isoniazid combination treatment. There is a widespread belief, apparently based on testing a single isolate on questionable media, that Mycobacterium tuberculosis is resistant to trimethoprim-sulfamethoxazole (TMP-SMX). We saw a complex immunocompromised patient with tuberculosis who was initially treated with TMP-SMX without antituberculous drugs and defervesced on this treatment. An isolate of M. tuberculosis from this patient was found to be sensitive to TMP-SMX. We examined how frequently M. tuberculosis is sensitive to TMP-SMX. Isolates were tested for susceptibility to TMP-SMX on supplemented Middlebrook 7H10 plates. We found that 43 of 44 (98%) isolates of M. tuberculosis were susceptible to the combination of
1 µg/ml of TMP and 19 µg/ml of SMX (
1/19 µg/ml). Thus, the vast majority of our M. tuberculosis isolates were susceptible to TMP-SMX at an MIC similar to that for Mycobacterium kansasii, Mycobacterium marinum, and sensitive rapidly growing mycobacteria, organisms successfully treated with TMP-SMX as part of the treatment regimen. It is possible that TMP-SMX may be useful in treating patients with multiple-drug-resistant and extended drug-resistant tuberculosis. We feel that a clinical trial looking at the effectiveness of TMP-SMX as an antituberculous drug is worthwhile.
Published ahead of print on 29 June 2009.
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