Effect of meropenem and fluconazole combination therapy on polymicrobial biofilms (Pseudomonas aeruginosa and candida albicans): an in vitro study

Polymicrobial biofilms, consisting of Pseudomonas aeruginosa and Candida albicans, pose a significant challenge in the field of microbiology due to their antimicrobial resistance. This study aims to investigate the potential effects of combined therapy involving meropenem and fluconazole on polymicrobial biofilms formed by these two species. Employing a true experimental laboratory design with a post-test-only control group, 32 stored clinical isolates, including meropenem-susceptible Pseudomonas aeruginosa and fluconazole-susceptible Candida albicans, were randomly selected. Polymicrobial biofilms of Pseudomonas aeruginosa and Candida albicans were established using a microtiter plate biofilm assay. After 24-hour exposure to meropenem, fluconazole, or a combination of meropenem and fluconazole, the biofilms formed were stained with 0.1% crystal violet. Optical density (OD) measurements were obtained using a spectrophotometer (ELISA reader). Data analysis using parametric ANOVA revealed significant differences (p < 0.05) in the statistical test results. Subsequent Post Hoc Test Least Significant Difference (LSD) analysis demonstrated no significant differences (p > 0.05) in the group treated with monotherapy of meropenem and fluconazole, while a significant difference (p < 0.05) was observed in the group treated with the combination therapy. The decline in optical density observed in this study could be attributed to a reduction in the extracellular matrix of the biofilm, a decline in the number of viable microbial cells, which subsequently reduces the production of the biofilm matrix, or a combination of both factors.