Rapid Cytolysis of Mycobacterium tuberculosis by Faropenem, an Orally Bioavailable β-Lactam Antibiotic

Abstract

Recent clinical studies indicate that meropenem, a ␤-lactam antibiotic, is a promising candidate for therapy of drug-resistant tuberculosis. However, meropenem is chemically unstable, requires frequent intravenous injection, and must be combined with a ␤-lactamase inhibitor (clavulanate) for optimal activity. Here, we report that faropenem, a stable and orally bioavailable ␤-lactam, efficiently kills Mycobacterium tuberculosis even in the absence of clavulanate. The target enzymes, L,D-transpeptidases, were inactivated 6-to 22-fold more efficiently by faropenem than by meropenem. Using a real-time assay based on quantitative time-lapse microscopy and microfluidics, we demonstrate the superiority of faropenem to the frontline antituberculosis drug isoniazid in its ability to induce the rapid cytolysis of single cells. Faropenem also showed superior activity against a cryptic subpopulation of nongrowing but metabolically active cells, which may correspond to the viable but nonculturable forms believed to be responsible for relapses following prolonged chemotherapy. These results identify faropenem to be a potential candidate for alternative therapy of drug-resistant tuberculosis.

Binding and processing of β‐lactam antibiotics by the transpeptidase LdtMt2 from Mycobacterium tuberculosis

“…) and subsequently captured in the crystal structure of Ldt Mt2 (Figs and ). The same fragment was observed from the recent investigation of the homolog Ldt Mt1 suggesting a general mechanism of faropenem action. We show here that the formation of this small adduct derived from faropenem is dependent on a functional enzyme active site, since the H336A mutant displayed a decrease in the faropenem‐driven acylation reaction by several orders of magnitude.…”

New agents for the treatment of drug-resistant Mycobacterium tuberculosis

“…The penem ring system is slightly less strained and consequently has improved chemical stability, and has been modified to a prodrug ester (faropenem medoxomil) that allows for oral administration, both desirable advantages for treating MDR-TB [77, 78]. Already approved for treatment of respiratory infections in humans, faropenem has displayed promising bactericidal activity in both active and non-growing, metabolically active Mtb cells [79], which is comparable to that seen with meropenem. Such results combined with renewed efforts to design a new generation of Mtb-targeted β-lactams, especially in conjunction with recent advances in β-lactamase inhibitor design, hold promise for clinical development as MDR-TB therapies.…”

Targeting Phenotypically TolerantMycobacterium tuberculosis

“…A number of other molecules have been reported to target nonreplicating mycobacteria by disrupting steps of peptidoglycan biosynthesis, including: L,D-transpeptidases by faropenem ( compound 33 ) (38, 201); UDP-galactopyranose mutase ( compound 34 ) (202); phospho-N-acetylmuramoyl-pentapeptidetransferase (MurX) by CPZEN-45 ( compound 35 ) (203); and the capuramycin analogue UT-01320 ( compound 36 ) (204). CPZEN-45 may additionally target decaprenyl-phosphate-GlcNAc-1-transferase (WecA, encoded by rv1302 ), which has a role in synthesizing teichoic acid in Bacillus subtilis and mycoylarabinogalactan in mycobacteria (205).…”