In Vitro Activity of a Novel Antimycobacterial Compound, N -Octanesulfonylacetamide, and Its Effects on Lipid and Mycolic Acid Synthesis

Abstract

␤-Sulfonyl carboxamides have been proposed to serve as transition-state analogues of the ␤-ketoacyl synthase reaction involved in fatty acid elongation. We tested the efficacy of N-octanesulfonylacetamide (OSA) as an inhibitor of fatty acid and mycolic acid biosynthesis in mycobacteria. Using the BACTEC radiometric growth system, we observed that OSA inhibits the growth of several species of slow-growing mycobacteria, including Mycobacterium tuberculosis (H37Rv and clinical isolates), the Mycobacterium avium complex (MAC), Mycobacterium bovis BCG, Mycobacterium kansasii, and others. Nearly all species and strains tested, including isoniazid and multidrug resistant isolates of M. tuberculosis, were susceptible to OSA, with MICs ranging from 6.25 to 12.5 g/ml. Only three clinical isolates of M. tuberculosis (CSU93, OT2724, and 401296), MAC, and Mycobacterium paratuberculosis required an OSA MIC higher than 25.0 g/ml. Rapid-growing mycobacterial species, such as Mycobacterium smegmatis, Mycobacterium fortuitum, and others, were not susceptible at concentrations of up to 100 g/ml. A 2-dimensional thin-layer chromatography system showed that OSA treatment resulted in a significant decrease in all species of mycolic acids present in BCG. In contrast, mycolic acids in M. smegmatis were relatively unaffected following exposure to OSA. Other lipids, including polar and nonpolar extractable classes, were unchanged following exposure to OSA in both BCG and M. smegmatis. Transmission electron microscopy of OSA-treated BCG cells revealed a disruption in cell wall synthesis and incomplete septum formation. Our results indicate that OSA inhibits the growth of several species of mycobacteria, including both isoniazid-resistant and multidrug resistant strains of M. tuberculosis. This inhibition may be the result of OSA-mediated effects on mycolic acid synthesis in slow-growing mycobacteria or inhibition via an undescribed mechanism. Our results indicate that OSA may serve as a promising lead compound for future antituberculous drug development.

Growth, Congo Red Agar Colony Morphotypes and Antibiotic Susceptibility Testing of Mycobacterium avium subspecies paratuberculosis

“…The novel compound DSA demonstrated consistent activity against all strains tested and was more active than the closely related n-octanesulfonylacetamide. 50 Our study illustrates the significant strain variability in MAP. This variability is reflected in growth rate, nutritional requirements, colonial morphology, and staining characteristics, as well as within strain changes during subculture in vitro.…”

Novel Saccharomyces cerevisiae Screen Identifies WR99210 Analogues That Inhibit Mycobacterium tuberculosis Dihydrofolate Reductase

“…One might have chosen to screen these drugs in Mycobacterium smegmatis, taking advantage of its rapid growth (the growth rate is about equal to that of S. cerevisiae) and ease of genetic manipulation relative to those for M. tuberculosis (11). However, drug screening in M. smegmatis has not always been an accurate predictor of activity (28,29) or the mechanism of action (1,22) in M. tuberculosis. In addition, S. cerevisiae has several advantages that we have exploited to develop similar systems for the screening of inhibitors of the DHFR enzymes from P. falciparum, C. parvum, and P. carinii DHFRs (2,19,36,43).…”

New drugs and vaccines for drug-resistantMycobacterium tuberculosisinfections

“…Analysis of lipid biosynthesis after exposure to OSA revealed a marked inhibition of mycolic acid biosynthesis in Mycobacterium bovis BCG with no alteration in the panoply of other complex lipids generated by the bacterium; mycolic acid biosynthesis in the relatively insensitive M. smegmatis was unaffected [87]. Electron microscopy of treated sensitive bacteria revealed dysfunction in cell wall biosynthesis and incomplete septation [87]. The overproduction in OSA-treated M. bovis BCG of the β-subunit of F 1 F 0 ATP synthase encoded by atpF [88] suggested the involvement of ATP synthase, either directly or indirectly.…”

“…Surprisingly, the activity profile of these compounds was particularly species dependent, they exhibit no significant activity against bacteria other than M. tuberculosis and closely related strains, including nonpathogenic mycobacteria [86]. One of these, N-octanesulphonylacetamide (OSA), was tested further against several pathogenic and drug-resistant mycobacteria, including MDR-TB, strains [87]. Analysis of lipid biosynthesis after exposure to OSA revealed a marked inhibition of mycolic acid biosynthesis in Mycobacterium bovis BCG with no alteration in the panoply of other complex lipids generated by the bacterium; mycolic acid biosynthesis in the relatively insensitive M. smegmatis was unaffected [87].…”

“…One of these, N-octanesulphonylacetamide (OSA), was tested further against several pathogenic and drug-resistant mycobacteria, including MDR-TB, strains [87]. Analysis of lipid biosynthesis after exposure to OSA revealed a marked inhibition of mycolic acid biosynthesis in Mycobacterium bovis BCG with no alteration in the panoply of other complex lipids generated by the bacterium; mycolic acid biosynthesis in the relatively insensitive M. smegmatis was unaffected [87]. Electron microscopy of treated sensitive bacteria revealed dysfunction in cell wall biosynthesis and incomplete septation [87].…”