Sitagliptin attenuates urease-associated phenotypes and potentiates meropenem in multidrug-resistant Gram-negative clinical isolates: a preliminary repurposing study.

BACKGROUND

Urease contributes to urinary tract pathogenesis and catheter encrustation, whereas metallo-β-lactamases contribute to carbapenem resistance.

OBJECTIVES

We investigated whether the dipeptidyl peptidase-4 inhibitor sitagliptin attenuates urease-associated phenotypes and potentiates meropenem against selected multidrug-resistant Gram-negative clinical isolates.

METHODS

Urease-associated activity was assessed in whole-cell suspensions and crude lysates of Proteus mirabilis. Alkalinization, crystal formation in artificial urine, and catheter-associated total biomass were also examined. Meropenem potentiation was evaluated by combined-disk and chequerboard assays, and meropenem-hydrolyzing activity was measured. Relative transcript abundance was assessed by quantitative reverse-transcription PCR, and docking was used to generate structural hypotheses. Vero-cell metabolic activity was evaluated by the MTT assay.

RESULTS

Sitagliptin (2000 µg/mL; one-eighth of its MIC) inhibited urease-associated assay signal by 53.2%-55.2% in whole-cell suspensions and crude lysates, reduced the urease-driven pH increase from 9.21 to 7.34 after 24 h, and reduced crystal-violet-stained catheter-associated biomass by 83.6%. It reduced the apparent meropenem hydrolysis signal in periplasmic extracts by 33%-55% and reduced meropenem MICs by 16- to 64-fold in combination assays, with FICI values of 0.1406-0.1875. In the Vero-cell assay, viability at 2000 µg/mL was 94.4%, and a 50% reduction in viability was not observed within the tested range. Sitagliptin exposure was associated with reduced relative transcript abundance of ureR, ureC, blaNDM, blaIMP, and blaVIM. Docking generated binding poses near catalytic metal centres.

CONCLUSIONS

In the tested preparations and isolate panel, sitagliptin attenuated urease-associated phenotypes, reduced apparent meropenem-hydrolyzing activity and potentiated meropenem, supporting its further investigation as a potential anti-virulence and antibiotic-adjuvant candidate.