Revealing the dual role of gallic acid in modulating ampicillin sensitivity of Pseudomonas aeruginosa biofilms

Abstract

Aim: To understand the effects of gallic acid (GA) on ampicillin (Amp) sensitive or resistant strain of Pseudomonas sp. and also in modulating the corresponding biofilms.

Methodology: The cell viability was determined by broth dilution, dry weight and CFU assays. Biofilm formation was measured by crystal violet assay while oxygen consumption rate was measured to verify the metabolic status of the cells. The membrane damage and drug efflux/accumulation were studied by fluorimetric assays.

Results: GA transformed the Amp resistant cells, both planktonic and biofilms, into highly sensitive one by inducing membrane damage and enhancing accumulation of drug, whereas the Amp sensitive cells gained resistance against Amp.

Conclusion: Use of GA as an antimicrobial compound should be analyzed more critically depending on the drug dosages, drug sensitivity as well as types of bacterial strains being studied.

Keywords: ampicillin; bacterial biofilm; drug efflux and drug accumulation; drug resistance; gallic acid; membrane potential; oxygen consumption assay.