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Joseph Cherian,
Inhee Choi,
Amit Nayyar,
Ujjini H Manjunatha,
Tathagata Mukherjee,
Yong Sok Lee,
Helena I Boshoff,
Ramandeep Singh,
Young Hwan Ha,
Michael Goodwin,
Suresh B Lakshminarayana,
Pornwaratt Niyomrattanakit,
Jan Jiricek, Sindhu Ravindran,
Thomas Dick,
Thomas H Keller,
Veronique Dartois,
Clifton E Barry
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ABSTRACT: The (S)-2-nitro-6-(4-(trifluoromethoxy)benzyloxy)-6,7-dihydro-5H-imidazo[2,1-b][1,3]oxazine named PA-824 (1) has demonstrated antitubercular activity in vitro and in animal models and is currently in clinical trials. We synthesized derivatives at three positions of the 4-(trifluoromethoxy)benzylamino tail, and these were tested for whole-cell activity against both replicating and nonreplicating Mycobacterium tuberculosis (Mtb). In addition, we determined their kinetic parameters as substrates of the deazaflavin-dependent nitroreductase (Ddn) from Mtb that reductively activates these pro-drugs. These studies yielded multiple compounds with 40 nM aerobic whole cell activity and 1.6 μM anaerobic whole cell activity: 10-fold improvements over both characteristics from the parent molecule. Some of these compounds exhibited enhanced solubility with acceptable stability to microsomal and in vivo metabolism. Analysis of the conformational preferences of these analogues using quantum chemistry suggests a preference for a pseudoequatorial orientation of the linker and lipophilic tail.
Journal of Medicinal Chemistry 08/2011; 54(16):5639-59. · 4.80 Impact Factor
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Kevin Pethe,
Patricia C Sequeira,
Sanjay Agarwalla,
Kyu Rhee,
Kelli Kuhen,
Wai Yee Phong,
Viral Patel,
David Beer,
John R Walker,
Jeyaraj Duraiswamy, [......],
Anne Goh,
Suresh B Lakshminarayana,
Carolyn Shoen,
Michael Cynamon,
Barry Kreiswirth,
Veronique Dartois,
Eric C Peters,
Richard Glynne,
Sydney Brenner,
Thomas Dick
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ABSTRACT: Candidate antibacterials are usually identified on the basis of their in vitro activity. However, the apparent inhibitory activity of new leads can be misleading because most culture media do not reproduce an environment relevant to infection in vivo. In this study, while screening for novel anti-tuberculars, we uncovered how carbon metabolism can affect antimicrobial activity. Novel pyrimidine-imidazoles (PIs) were identified in a whole-cell screen against Mycobacterium tuberculosis. Lead optimization generated in vitro potent derivatives with desirable pharmacokinetic properties, yet without in vivo efficacy. Mechanism of action studies linked the PI activity to glycerol metabolism, which is not relevant for M. tuberculosis during infection. PIs induced self-poisoning of M. tuberculosis by promoting the accumulation of glycerol phosphate and rapid ATP depletion. This study underlines the importance of understanding central bacterial metabolism in vivo and of developing predictive in vitro culture conditions as a prerequisite for the rational discovery of new antibiotics.
Nature Communications 08/2010; 1:57. · 7.40 Impact Factor
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ABSTRACT: Sixty-eight ancestral Mycobacterium tuberculosis isolates were previously identified by using the tuberculosis-specific deletion 1 (TbD1) PCR and mycobacterial interspersed-repetitive-unit-variable-number tandem repeat (MIRU-VNTR) typing (Y. J. Sun, R. Bellamy, A. S. G. Lee, S. T. Ng, S. Ravindran, S.-Y. Wong, C. Locht, P. Supply, and N. I. Paton, J. Clin. Microbiol. 42:1986-1993, 2004). These TbD1(+) ancestral isolates were further characterized and typed in this study by IS6110 restriction fragment length polymorphism (RFLP) typing, VNTR typing using exact tandem repeats (VNTR-ETR), and spoligotyping of the direct-repeat region. To our knowledge, this is the first characterization of this genogroup by multiple genetic markers based on a fairly large sample size. In this genogroup, all spoligotypes were characterized by the absence of spacers 29 to 32 and 34. In addition, VNTR-ETR typing could add further resolution to the clustered isolates identified by MIRU-VNTR, and the combination of MIRU-VNTR and VNTR-ETR, called MIRU-ETR, showed the highest discriminatory power for these strains compared to IS6110 RFLP typing and spoligotyping alone. However, MIRU-ETR appeared to still cluster some probably epidemiologically unrelated strains, as judged by IS6110 RFLP divergence. Therefore, a typing strategy based on stepwise combination of MIRU-ETR and IS6110 RFLP is proposed to achieve maximal discrimination for unrelated TbD1(+) strains. This typing strategy may be useful in areas where TbD1(+) ancestral strains are prevalent.
Journal of Clinical Microbiology 12/2004; 42(11):5058-64. · 4.15 Impact Factor
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ABSTRACT: Strain typing using variable-number tandem repeats of mycobacterial interspersed repetitive units (MIRU-VNTR) is a powerful tool for studying the epidemiology and genetic relationships of Mycobacterium tuberculosis isolates. For this study, isolates from 291 patients in Singapore were genotyped by this method. One hundred sixty-six distinct MIRU-VNTR patterns were detected. One hundred sixty-two strains were grouped into 1 of 35 different MIRU-VNTR clusters and 131 isolates were unique. In this sample collection, 9 of the 12 MIRU-VNTR loci were moderately or highly discriminative according to their allelic diversities. The Hunter-Gaston discriminatory index was 0.975, indicating the high power of discrimination of MIRU-VNTR typing. By direct comparisons with previously typed MIRU-VNTR patterns and by genetic relationship analyses, we could identify and clearly define four epidemic groups of M. tuberculosis in our sample, corresponding to the W/Beijing, East-Africa-Indian, Haarlem, and Delhi genotype families. Furthermore, MIRU-VNTR typing was able to clearly distinguish ancestral and modern M. tuberculosis strains as defined by TbD1 genomic deletion analysis. These results indicate that MIRU-VNTR typing can be a useful first-line tool for studying the genetic diversity of M. tuberculosis isolates in a large urban setting such as Singapore.
Journal of Clinical Microbiology 06/2004; 42(5):1986-93. · 4.15 Impact Factor
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ABSTRACT: Prolonged cough occurs in a large proportion of the 2 million pilgrims who participate in the annual Hajj in Saudi Arabia. In a prospective seroepidemiological study to determine the incidence of pertussis among 358 adult pilgrims, 5 (1.4%) were found to have acquired pertussis (defined as prolonged cough and a >4-fold increase in the level of immunoglobulin G to whole-cell pertussis antigen). Of the 40 pilgrims who had no pre-Hajj immunity to pertussis, 3 (7.5%) acquired pertussis. Administration of acellular pertussis vaccine to pilgrims before the Hajj should be considered to address this problem.
Clinical Infectious Diseases 11/2003; 37(9):1270-2. · 9.15 Impact Factor
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ABSTRACT: After an outbreak of meningococcal disease caused by Neisseria meningitidis W135, associated with the Hajj pilgrimage in 2001, 15% of returning vaccinated pilgrims carried a single W135 clone, and 55% were still carriers 6 months later. Transmission to 8% of their unvaccinated household contacts occurred within the first few weeks, but no late transmission took place. Public health interventions are needed to protect household contacts.
Emerging infectious diseases 02/2003; 9(1):123-6. · 6.17 Impact Factor
