Prevalence of and risk factors for resistance to second-line drugs in people with multidrug-resistant tuberculosis in eight countries: a prospective cohort study.

BACKGROUND: The prevalence of extensively drug-resistant (XDR) tuberculosis is increasing due to the expanded use of second-line drugs in people with multidrug-resistant (MDR) disease. We prospectively assessed resistance to second-line antituberculosis drugs in eight countries. METHODS: From Jan 1, 2005, to Dec 31, 2008, we enrolled consecutive adults with locally confirmed pulmonary MDR tuberculosis at the start of second-line treatment in Estonia, Latvia, Peru, Philippines, Russia, South Africa, South Korea, and Thailand. Drug-susceptibility testing for study purposes was done centrally at the Centers for Disease Control and Prevention for 11 first-line and second-line drugs. We compared the results with clinical and epidemiological data to identify risk factors for resistance to second-line drugs and XDR tuberculosis. FINDINGS: Among 1278 patients, 43·7% showed resistance to at least one second-line drug, 20·0% to at least one second-line injectable drug, and 12·9% to at least one fluoroquinolone. 6·7% of patients had XDR tuberculosis (range across study sites 0·8-15·2%). Previous treatment with second-line drugs was consistently the strongest risk factor for resistance to these drugs, which increased the risk of XDR tuberculosis by more than four times. Fluoroquinolone resistance and XDR tuberculosis were more frequent in women than in men. Unemployment, alcohol abuse, and smoking were associated with resistance to second-line injectable drugs across countries. Other risk factors differed between drugs and countries. INTERPRETATION: Previous treatment with second-line drugs is a strong, consistent risk factor for resistance to these drugs, including XDR tuberculosis. Representative drug-susceptibility results could guide in-country policies for laboratory capacity and diagnostic strategies. FUNDING: US Agency for International Development, Centers for Disease Control and Prevention, National Institutes of Health/National Institute of Allergy and Infectious Diseases, and Korean Ministry of Health and Welfare.

Inhibition of Mycobacterium tuberculosis strains H37Rv and MDR MS-115 by a new set of C5 modified pyrimidine nucleosides.

Two sets of pyrimidine nucleoside derivatives bearing extended alkyloxymethyl or alkyltriazolidomethyl substituents at position 5 of the nucleobase were synthesized and evaluated as potential antituberculosis agents. The impact of modifications at 3'- and 5'-positions of the carbohydrate moiety on the antimycobacterial activity and cytotoxicity was studied. The highest effect was shown for 5-dodecyloxymethyl-2'-deoxyuridine, 5-decyltriazolidomethyl-2'-deoxyuridine, and 5-dodecyltriazolidomethyl-2'-deoxycytidine. They effectively inhibited the growth of two Mycobacterium tuberculosis strains in vitro, laboratory H37Rv (MIC99=20, 10, and 20µg/mL, respectively) and clinical MDR MS-115 resistant to five top antituberculosis drugs (МIC99=50, 10, and 10µg/mL, respectively).

The synthesis and antituberculosis activity of 5'-nor carbocyclic uracil derivatives.

A series of new carbocyclic uracil derivatives were synthesized and evaluated as potential antituberculosis agents. Racemic 1-[4'-hydroxy-2'-cyclopenten-1'-yl]-5-tetradecynyluracil completely inhibited the growth of Mycobacterium tuberculosis H37Rv in vitro at a concentration of 10 µg/ml. Individual (+) and (-) isomers of the above uracil derivative were isolated and showed the same level of activity against two strains of Mycobacterium tuberculosis: laboratory sensitive (H37Rv) and clinical resistant to five top antituberculosis drugs (MS-115).

Antigen-Specific IFN-γ Responses Correlate with the Activity of M. tuberculosis Infection but Are Not Associated with the Severity of Tuberculosis Disease.

IFN-γ is a key cytokine in antituberculosis (TB) defense. However, how the levels of its secretion affect M. tuberculosis (Mtb) infection is not clear. We have analyzed associations between IFN-γ responses measured in QuantiFERON®-TB Gold In-tube (QFT) assay, TB disease severity, and Mtb infection activity. TB severity was evaluated based on the results of radiological, microbiological, and clinical examinations. Antigen-driven IFN-γ secretion did not correlate with TB severity. Mitogen-induced IFN-γ secretion correlated inversely with the form of pulmonary pathology and the area of affected pulmonary tissue; the levels of spontaneous IFN-γ secretion correlated with patients' age (r = 0.395, p = 0.001). Mtb infection activity was evaluated based on radiological data of lung tissue infiltration, destruction, dissemination or calcification, and condensation. The rate of positive QFT results and the levels of antigen-driven IFN-γ secretion increased in a row: patients with residual TB lesions < patients with low TB activity < patients with high TB activity. Thus, antigen-driven IFN-γ secretion and QFT results did not associate with TB severity but associated with the infection activity. The results suggest that quantitative parameters of IFN-γ secretion play a minor role in determining the course of TB disease but mirror the activity of the infectious process.

5-Arylaminouracil Derivatives: New Inhibitors of Mycobacterium tuberculosis.

Three series of 5-arylaminouracil derivatives, including 5-(phenylamino)uracils, 1-(4'-hydroxy-2'-cyclopenten-1'-yl)-5-(phenylamino)uracils, and 1,3-di-(4'-hydroxy-2'-cyclopenten-1'-yl)-5-(phenylamino)uracils, were synthesized and screened for potential antimicrobial activity. Most of compounds had a negative effect on the growth of the Mycobacterium tuberculosis H37Rv strain, with 100% inhibition observed at concentrations between 5 and 40 µg/mL. Of those, 1-(4'-hydroxy-2'-cyclopenten-1'-yl)-3-(4‴-hydroxy-2‴-cyclopenten-1‴-yl)-5-(4″-butyloxyphenylamino)uracil proved to be the most active among tested compounds against the M. tuberculosis multidrug-resistant strain MS-115 (MIC90 5 µg/mL). In addition, the thymidylate kinase of M. tuberculosis was evaluated as a possible enzymatic target.

Novel pyridazino[4,3-b]indoles with dual inhibitory activity against Mycobacterium tuberculosis and monoamine oxidase.

Tuberculosis is one of the most common infectious diseases known to man. About 37% of the world's population (about 1.86 billion people) are infected with Mycobacterium tuberculosis. According to the World Health Organization, every year approximately 8 million people develop active tuberculosis and almost 2 million of those die from the disease. The incidence of multidrug-resistant tuberculosis (MDR-TB) is increasing. The present drug regimen for treating tuberculosis has been in existence for 30 years. New drugs that will shorten total treatment duration, improve the treatment of MDR-TB, and address latent tuberculosis are the most urgent need of tuberculosis control programs. A new series of synthetic 3-amino-4-arylpyridazino[4,3-b]indoles (pyridazinoindoles) were identified as inhibitors of Mycobacterium tuberculosis. The design, synthesis, and antimycobacterial activity of these compounds are described. While the most active compounds are still not comparable to the front-line drugs rifampicin and isoniazid, they do show promise. Most of the pyridazinoindoles with appreciable antituberculosis activity also inhibit monoamine oxidase, suggestive of a novel inhibitory effect on mycobacterial redox reactions.