Effect of efflux pump inhibitors on the susceptibility of Mycobacterium tuberculosis to isoniazid

Abstract

Background:Mycobacterium can develop drug resistance (DR) by mutation of its existing gene. However, the existence of DR without mutation shows the need to look for an alternative mechanism such as the role of efflux pumps. In this study, we examined the effect of efflux pump inhibitors on isoniazid (INH) susceptibility in clinical isolates of Mycobacterium tuberculosis (Mtb).Materials and Methods:Resazurin microtiter assay was used to examine the effect of efflux pump inhibitors on minimum inhibitory concentration (MIC) levels of INH in eighteen Mtb clinical isolates.Results:The observed reduction in INH-MIC was 2–16-fold in INH-resistant isolates with katG and inhA gene mutations, 2–8-fold in INH-resistant isolates without mutation and 2–4-fold in INH-sensitive isolates. The MIC reduction by verapamil (VER) was observed in 83% isolates, by carbonyl cyanide m-chlorophenylhydrazone (CCCP) 61% isolates, by chloropromazine (CPZ) 61% isolates, by reserpine (RES) in 61% isolates and by 2,4-dinitro phenol (DNP) in 55% isolates.Interpretation and Conclusions:The results obtained in this study confirm that MIC of INH decreased in the presence of efflux pump inhibitors (VER, CCCP, CPZ, DNP, RES) in clinical isolates of Mtb and that the inhibition of efflux pumps by the efflux pump inhibitors can enhance the clinical effect of a drug. The results showed that these efflux pump inhibitors are active against both drug susceptible and drug resistant isolates, indicating that the effect of efflux pump inhibitors is not dependent on the mutational profile of the isolate. We observed in this study that VER was the most effective efflux pump inhibitor.

Propranolol, chlorpromazine and diclofenac restore susceptibility of extensively drug-resistant (XDR)-Acinetobacter baumannii to fluoroquinolones

“…In this study, CPZ combinations with CIP or LEV have markedly reduced the MIC of resistance isolates. Our result agreed with studies previously carried out against Mycobacterium spp [78,79]. It has been found that CPZ had a significant bactericidal effect [6,75] in addition to the efflux pump inhibitor action when tested for their effect on antibiotic resistance [79,80].…”

Genome-Wide Transcriptional Responses of Mycobacterium to Antibiotics

“…Antibiotic adjuvants or potentiators are compounds that enhance antibiotic activity by inactivating resistance mechanism (Wright, 2016). As a proof of concept, it was shown that the MIC of isoniazid decreased in the presence of various categories of efflux pump inhibitors in clinical isolates of M. tuberculosis (Jaiswal et al, 2017). Efflux pump inhibitors should thus be considered to improve current TB therapy (Pule et al, 2016).…”

Developing Synergistic Drug Combinations To Restore Antibiotic Sensitivity in Drug-Resistant Mycobacterium tuberculosis

“…We investigated the utility of potentiating combinations, anchored by SPT, to circumvent drug resistance and potentially restore (partial) susceptibility where genetically drug-resistant mutants preexist for one of the partner compounds. We applied combination screens utilizing (i) chlorpromazine (CPZ), a phenothiazine whose complex and unresolved mechanism of action involving disruption of the mycobacterial electron transport chain ( 23 ) has been implicated in efflux pump inhibition ( 24 ), and (ii) fusidic acid (FA), a translational inhibitor with demonstrated (albeit moderate) activity in vitro ( 25 , 26 ). FA was selected owing to its potential for repositioning as anti-TB agent and because it possesses a unique mechanism of action, specifically, inhibition of bacterial protein synthesis by binding to elongation factor G (EF-G) ( 27 ).…”