Biofilm Growth of Pseudomonas Aeruginosa Tgc04 Exposed to Metformin and Variations in Cod Content

Abstract

Purpose: This work aimed to evaluate the biofilm formation of Pseudomonas aeruginosa TGC04 exposed to 100 and 200 µg/mL of metformin, varying the Chemical Oxygen Demand (COD) and flow regime.   Theoretical framework: Metformin is an oral antidiabetic agent with antimicrobial properties, excreted in an active and unmetabolized form. Like some non-antibiotic drugs, subinhibitory concentrations of metformin may contribute to the expression of microbial resistance in wild-type strains.   Methods: After the Minimum Inhibitory Concentration (MIC) of metformin was known, nine microcosms were filled with 500 mL of synthetic wastewater with Chemical Oxygen Demand (COD) at 10,000 and 1,000 mg/L in the presence of MIC and sub-MIC of metformin. Two incubation conditions were tested, with and without aeration (4 L/min). Biofilms were quantified after 2 and 24 hours at 25ºC by the crystal violet test.   Results and conclusion: It was observed reductions and increases in biofilm growth around 13 and 64%, respectively. The greatest biofilm growth occurred in cells exposed to 200 µg/mL of metformin. Both the flow regime and COD concentration were important for the development of the biofilm, whose cells were mostly weakly to moderately adhered.   Research implications: This work showed that wild strain P. aeruginosa colonize biofilms in the presence of non-antibiotic drug with antimicrobial activity.   Originality/value: The study provides evidence that in polluted aquatic systems with turbulent regimes, the inhibitory concentration of metformin promoted the least disturbances to the biofilm.