Effect of non β-lactams on stable variants of inhibitor resistant TEM β-lactamase in uropathogenic E. coli : Implication for alternative therapy

β-lactamase inhibitor resistance(BLIR) among the uropathogenic E.coli (UPEC) minimizes treatment options. This study aims to identify inhibitor-resistant TEM (IRT) β-lactamase that impart BLIR phenotype and explore non-β-lactams as alterative therapeutics. 30 BLIR UPEC isolates was detected by Kirby-Bauer disk diffusion technique using β-lactam-β-lactamase inhibitor combination. Conjugal transfer of BLIR was successful from 17 isolates. PCR and sequencing of the TEM β-lactamases from the transconjugants indicated 14 TEM-84 (IRT) and 3 novel IRT variants (pUE184TEM, pUE203TEM, pUE210TEM). 3D models of the latter were predicted and validated. Molecular docking of selected non-β-lactams (morin, catechin, naringenin triacetate) with the variants using Autodock4.2 showed comparable docking scores with significant hydrogen bond and hydrophobic interactions. Molecular dynamics simulation study confirmed stability of the non-β-lactams inside the catalytic pocket of the enzymes. Moreover all three non-β-lactams were found to inhibit the purified TEM β-lactamase variants in vitro. Microbroth dilution method indicated naringenin triacetate; 64μg/ml in combination with ceftazidime; 30μg/ml to be most effective against the BLIR transconjugants. BLIR were primarily attributed to the production of IRT β-lactamases. Administration of the non-β-lactams with ceftazidime demonstrated an alternative therapeutic strategy against the IRT β-lactamase producers. This study indicates high risk of transmission of IRT β-lactamases and suggests β-lactam-non-β-lactam combination therapy to combat BLIR. This article is protected by copyright. All rights reserved.