Mechanism of Resistance Development in E. coli against TCAT, a Trimethoprim-Based Photoswitchable Antibiotic

Abstract

During the last decades, a continuous rise of multi-drug resistant pathogens has threatened antibiotic efficacy. To tackle this key challenge, novel antimicrobial therapies are needed with increased specificity for the site of infection. Photopharmacology could enable such specificity by allowing for the control of antibiotic activity with light, as exemplified by trans/cis-tetra-ortho-chloroazobenzene-trimethoprim (TCAT) conjugates. Resistance development against the on (irradiated, TCATa) and off (thermally adapted, TCATd) states of TCAT were compared to that of trimethoprim (TMP) in Escherichia coli mutant strain CS1562. Genomics and transcriptomics were used to explore the acquired resistance. Although TCAT shows TMP-like dihydrofolate reductase (DHFR) inhibition in vitro, transcriptome analyses show different responses in acquired resistance. Resistance against TCATa (on) relies on the production of exopolysaccharides and overexpression of TolC. While resistance against TCATd (off) follows a slightly different gene expression profile, both indicate hampering the entrance of the molecule into the cell. Conversely, resistance against TMP is based on alterations in cell metabolism towards a more persister-like phenotype, as well as alteration of expression levels of enzymes involved in the folate biosynthesis. This study provides a deeper understanding of the development of new therapeutic strategies and the consequences on resistance development against photopharmacological drugs.

Hypothesis-Driven, Structure-Based Design in Photopharmacology: The Case of eDHFR Inhibitors

“… 41 Furthermore, they indicate that the observed differences in antibacterial activities might arise from other coexisting mechanisms (e.g., different accumulation in bacteria), as recently suggested by our follow-up study of resistance development against the best candidate. 42 Furthermore, a cheminformatics analysis of key physicochemical parameters revealed that these TMP derivatives have molecular weights and calculated log P s outside of the drug-like ranges ( SI , Section S5.3). Overall, despite being responsive to visible light, these previously designed compounds still offer major room for improvement and are an attractive starting point for structure-based design in photopharmacology.…”

Photoresponsive Small Molecule Inhibitors for the Remote Control of Enzyme Activity

“…In 2021, the same group studied the mechanism of resistance development in E. coli against the photoswitchable DHFR inhibitor 39. [44] While in vitro studies showed that 39 exhibits DHFR inhibitory activity analogous to that of the parent compound, transcriptome analysis indicated that the acquired resistance for the photochromic and classical DHFR inhibitors occurred via different mechanisms. In a follow-up study, Kobauri et al [43b] reported the IC 50 values for the photoswitchable DHFR inhibitors 37-39 (Figure 8).…”

“…An 8‐fold difference in antibacterial activity was observed against E. coli , in which MIC 50 values of >80 μM and 10 μM were obtained for 39‐ E and the photo‐enriched 39‐ Z form, respectively. In 2021, the same group studied the mechanism of resistance development in E. coli against the photoswitchable DHFR inhibitor 39 [44] . While in vitro studies showed that 39 exhibits DHFR inhibitory activity analogous to that of the parent compound, transcriptome analysis indicated that the acquired resistance for the photochromic and classical DHFR inhibitors occurred via different mechanisms.…”

Antibiotic resistance in Escherichia coli from Animals, Food and Humans

“…This resistance mechanism is used by bacteria resistant to trimethoprim and sulfonamides. The mechanism is based on a decrease in bacterial sensitivity and a decrease in the affinity of the enzymes dihydropteroate synthetase and dihydropteroate reductase (Lauxen et al 2021). Alteration of cell membrane permeability is a bacterial mechanism of resistance, which often occurs in gram-negative bacteria to certain water-soluble AB.…”