Design, synthesis, and In vitro antituberculosis activity of 2(5H)-Furanone derivatives

A series of 2(5H)-furanone-based compounds were synthesized from commercially available mucohalic acids. From the first-generation compounds, three showed inhibitory activity (10 µg/mL) of at least 35% against Mycobacterium smegmatis mc(2) 155 growth (Bioscreen C system). In screening the active first-generation compounds for growth inhibition against Mycobacterium tuberculosis H37Rv, the most active compound was identified with a minimum inhibitory concentration (MIC99 ) of 8.07 µg/mL (15.8 µM) using BACTEC 460 system. No cross-resistance was observed with some current first-line anti-TB drugs, since it similarly inhibited the growth of multidrug resistant (MDR) clinical isolates. The compound showed a good selectivity for mycobacteria since it did not inhibit the growth of selected Gram-positive and Gram-negative bacteria. It also showed synergistic activity with rifampicin (RIF) and additive activity with isoniazid (INH) and ethambutol (EMB). Additional time-kill studies showed that the compound is bacteriostatic to mycobacteria, but cytotoxic to the Chinese Hamster Ovarian (CHO) cell line. From a second generation library, two compounds showed improved anti-TB activity against M. tuberculosis H37Rv and decreased CHO cell cytotoxicity. The compounds exhibited MIC values of 2.62 µg/mL (5.6 µM) and 3.07 µg/mL (5.6 µM) respectively. The improved cytotoxicity against CHO cell line of the two compounds ranged from IC50  = 38.24 µg/mL to IC50  = 45.58 µg/mL when compared to the most active first-generation compound (IC50  = 1.82 µg/mL). The two second generation leads with selectivity indices (SI) of 14.64 and 14.85 respectively, warrant further development as anti-TB drug candidates. © 2016 IUBMB Life, 68(8):612-620, 2016.

Rapid deletion-based subtyping system for the Manila family of Mycobacterium tuberculosis

The Manila family of Mycobacterium tuberculosis is a group of clonal isolates seen throughout the Pacific Basin. Commonly used rapid molecular typing methods often leave large groups of Manila family isolates clustered together. Here we describe a simple deletion-based PCR method that improves the discrimination for Manila family isolates, with or without the use of mycobacterial interspersed repetitive-unit-variable-number tandem-repeat (MIRU-VNTR) classification, and that is both rapid and affordable. Twenty-eight Manila family isolates, classified by spoligotyping, were collected from around the Pacific Basin from 1995 to 2003 and were tested for known genomic deletions. Nine of 15 regions of difference tested were identified as potentially discriminatory, with 18 distinct patterns; of these 9, 5 were selected for optimal discrimination using 61 Manila family isolates collected from California in 2009. For this geographically limited sample, the single large cluster was reduced to 14 distinct patterns. When the isolates were tested by spoligotyping and MIRU-VNTR, the addition of deletion analysis increased the number of distinct patterns from 43 to 56. In summary, the two study groups, which together form a single group of 89 isolates by spoligotyping, were segregated into 17 subgroups by our deletion-based subtyping system.

Determinants of multidrug-resistant tuberculosis clusters, California, USA, 2004-2007

Laboratory and epidemiologic evidence suggests that pathogen-specific factors may affect multidrug-resistant (MDR) tuberculosis (TB) transmission and pathogenesis. To identify demographic and clinical characteristics of MDR TB case clustering and to estimate the effect of specific isoniazid resistance-conferring mutations and strain lineage on genotypic clustering, we conducted a population-based cohort study of all MDR TB cases reported in California from January 1, 2004, through December 31, 2007. Of 8,899 incident culture-positive cases for which drug susceptibility information was available, 141 (2%) were MDR. Of 123 (87%) strains with genotype data, 25 (20%) were aggregated in 8 clusters; 113 (92%) of all MDR TB cases and 21 (84%) of clustered MDR TB cases occurred among foreign-born patients. In multivariate analysis, the katG S315T mutation (odds ratio 11.2, 95% confidence interval 2.2-Yen; p = 0.004), but not strain lineage, was independently associated with case clustering.