The chemotherapeutic drug methotrexate selects for antibiotic resistance

Abstract

Background Understanding drivers of antibiotic resistance evolution is fundamental for designing optimal treatment strategies and interventions to reduce the spread of antibiotic resistance. Various cytotoxic drugs used in cancer chemotherapy have antibacterial properties, but how bacterial populations are affected by these selective pressures is unknown. Here we test the hypothesis that the widely used cytotoxic drug methotrexate affects the evolution and selection of antibiotic resistance. Methods First, we determined methotrexate susceptibility (IC 90 ) and selective abilities in a collection of Escherichia coli and Klebsiella pneumoniae strains with and without pre-existing trimethoprim resistance determinants. We constructed fluorescently labelled pairs of E. coli MG1655 differing only in trimethoprim resistance determinants and determined the minimum selective concentrations of methotrexate using flow-cytometry. We further used an experimental evolution approach to investigate the effects of methotrexate on de novo trimethoprim resistance evolution. Findings We show that methotrexate can select for acquired trimethoprim resistance determinants located on the chromosome or a plasmid. Additionally, methotrexate co-selects for genetically linked resistance determinants when present together with trimethoprim resistance on a multi-drug resistance plasmid. These selective effects occur at concentrations 40- to >320-fold below the methotrexate minimal inhibitory concentration. Interpretation Our results strongly suggest a selective role of methotrexate for virtually any antibiotic resistance determinant when present together with trimethoprim resistance on a multi-drug resistance plasmid. The presented results may have significant implications for patient groups strongly depending on effective antibiotic treatment. Funding PJJ was supported by and the Northern Norway Regional Health Authority (SFP1292–16/HNF1586–21) and JPI-EC-AMR (Project 271,176/H10). DIA was supported by the (grant 2017–01,527). The publication charges for this article have been funded by a grant from the publication fund of UiT The Arctic University of Norway.

The anticancer chemotherapy drug 5-Fluorouracil has positive interaction with antibiotics and can select for antibiotic resistance inStaphylococcus aureus

“…Importantly, growth was affected at 5-FU concentrations that were below the MIC for the drug. Similar findings were recently published for the cancer chemotherapy drug methotrexate, which also acts through inhibiting the folate synthesis pathway (43). It is now appreciated that the sub-MIC selective window is important in the evolution of drug resistance, with concentrations of drug far below the MIC capable of selecting for the evolution of resistance over time (44).…”

“…We observed this phenomenon here with S. aureus with the evolution of much greater tolerance to 5-FU after exposure to sub-inhibitory concentrations for ∼200 generations. Similar studies where increased tolerance to a non-antibiotic drug has evolved during experimental evolution have found corresponding evolution of cross-resistance to clinically used antimicrobials, such as trimethoprim in the case of methotrexate (43) or quinolones, ciprofloxacin and tetracycline in the case of disinfectants (45). We did not detect evidence for this for 5-FU, however the method used – disc diffusion – is not particularly sensitive and further analyses using dose response curves are required to confirm these results.…”

Arylazopyrazole-Based Photoswitchable Inhibitors Selective for Escherichia coli Dihydrofolate Reductase

“…These results are consistent with those of previous studies showing that MTX did not inhibit bacterial growth because of the tolC -dependent multidrug resistance mechanism of E. coli. , Therefore, for the effective application of azoPyQ s as photopharmacological antibacterial agents, an additional design strategy to circumvent the bacterial multidrug resistance mechanism should be developed.…”

Common themes in antimicrobial and anticancer drug resistance

“…Mitomycin C has been shown to be a potent inducer of the bacterial SOS response, being used to select resistant E. coli clones with resistance mediated by mdfA efflux pump overexpression (Wei et al, 2001) increases the transcription of genes necessary to horizontal transfer the SXT element that encodes resistance to multiple antibiotics in Vibrio cholerae (Beaber et al, 2004). Methotrexate, a dihydrofolate reductase inhibitor, acts by blocking dihydrofolic acid synthesis similarly to trimethoprim antibiotic and thus, co-selects bacterial cells carrying the trimethoprim resistance gene on the same plasmid (Guethmundsdottir et al, 2021). Non-lethal doses of cisplatin resulted in a 3-7-fold increase in mutation frequency, leading to resistance to rifampicin and ciprofloxacin and the administration of antioxidants (ascorbic acid) decreased genotoxicity by 41% and bacterial mutation rates by 65% (Lofmark et al, 2006;Chistyakov et al, 2018).…”