Effect of Tannic and Gallic Acids Alone or in Combination with Carbenicillin or Tetracycline on Chromobacterium violaceum CV026 Growth, Motility, and Biofilm Formation

Chromobacterium violaceum is an opportunistic pathogen which causes infections that are difficult to treat. The goal of this research was to evaluate the effect of selected tannins (tannic acid (TA) and gallic acid (GA)) on bacterial growth, motility, antibiotic (carbenicillin, tetracycline) susceptibility, and biofilm formation. Both tannins, particularly TA, impaired bacterial growth levels and swimming motilities at sub-MIC concentrations. In combination with tannins, antibiotics showed increased minimum inhibitory concentration (MIC) values, suggesting that tannins interfered with antibacterial activity. Sub-MIC concentrations of tetracycline or TA alone enhanced biofilm formation of C. violaceum; however, in combination, these compounds inhibited biofilm formation. In contrast, carbenicillin at sub-MIC was effective in inhibiting C. violaceum biofilm formation; however, in combination with lower concentrations of TA or GA, biofilms were enhanced. These results provide insights into the effects of tannins on C. violaceum growth and their varying interaction with antibiotics used to target C. violaceum infections.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author