Elucidating the Antimycobacterial Mechanism of Action of Ciprofloxacin Using Metabolomics

Abstract

In the interest of developing more effective and safer anti-tuberculosis drugs, we used a GCxGC-TOF-MS metabolomics research approach to investigate and compare the metabolic profiles of Mtb in the presence and absence of ciprofloxacin. The metabolites that best describe the differences between the compared groups were identified as markers characterizing the changes induced by ciprofloxacin. Malic acid was ranked as the most significantly altered metabolite marker induced by ciprofloxacin, indicative of an inhibition of the tricarboxylic acid (TCA) and glyoxylate cycle of Mtb. The altered fatty acid, myo-inositol, and triacylglycerol metabolism seen in this group supports previous observations of ciprofloxacin action on the Mtb cell wall. Furthermore, the altered pentose phosphate intermediates, glycerol metabolism markers, glucose accumulation, as well as the reduction in the glucogenic amino acids specifically, indicate a flux toward DNA (as well as cell wall) repair, also supporting previous findings of DNA damage caused by ciprofloxacin. This study further provides insights useful for designing network whole-system strategies for the identification of possible modes of action of various drugs and possibly adaptations by Mtb resulting in resistance.

Keywords: GCxGC-TOFMS; Mycobacterium tuberculosis; ciprofloxacin; fluoroquinolones; tuberculosis; untargeted metabolomics.

Figure 1

Distribution of the coefficients of variation values for technical repeatability.

Figure 2

PCA scores plot obtained from GCxGC-TOFMS whole metabolome analysis of Mtb samples in the presence and absence of ciprofloxacin. The variances accounted for are indicated in parentheses.

Figure 3

Venn diagram illustrating the multi-statistical approach for selecting the metabolites that best describe the variation detected in the metabolome of Mtb cultured with and without ciprofloxacin.

Figure 4

Metabolomic pathway map of Mtb treated with ciprofloxacin. The metabolite markers best describing the variation in the metabolome compared to those of untreated Mtb are represented in bold text with up or down arrows indicating elevated or reduced concentrations, respectively.