Mechanism and resistance for antimycobacterial activity of a fluoroquinophenoxazine compound

BioRxiv : the Preprint Server for Biology
Yuk-Ching Tse-DinhFenfei Leng

Abstract

We have previously reported the inhibition of bacterial topoisomerase I activity by a fluoroquinophenoxazine compound (FP-11g) with a 6-bipiperidinyl lipophilic side chain that exhibited promising antituberculosis activity (MIC = 2.5 µM against Mycobacterium tuberculosis, SI = 9.8). Here, we found that the compound is bactericidal towards Mycobacterium smegmatis, resulting in greater than 5 Log10 reduction in colony-forming units [cfu]/mL following a 10 h incubation at 1.25 µM (4X MIC) concentration. Growth inhibition (MIC = 50 µM) and reduction in cfu could also be observed against a clinical isolate of Mycobacterium abscessus. Stepwise isolation of resistant mutants of M. smegmatis was conducted to explore the mechanism of resistance. Mutations in the resistant isolates were identified by direct comparison of whole-genome sequencing data from mutant and wild-type isolates. These include mutations in genes likely to affect the entry and retention of the compound. FP-11g inhibits Mtb topoisomerase I and Mtb gyrase with IC50 of 0.24 and 31.5 µM, respectively. Biophysical analysis showed that FP-11g binds DNA as an intercalator but the IC50 for inhibition of Mtb topoisomerase I activity is >10 fold lower than the compound concent...Continue Reading

Related Concepts

DNA
DNA Topoisomerases, Type I
DNA-Binding Proteins
Genes
Intercalating Agents
Ligation
Mycobacterium tuberculosis
Isolation Aspects
Mycobacterium smegmatis
Antimycobacterial agent

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