Synergistic antibiofilm efficacy of a gallotannin 1,2,6-tri-O-galloyl-β-D-glucopyranose from Terminalia chebula fruit in combination with gentamicin and trimethoprim against multidrug resistant uropathogenic Escherichia coli biofilms

In recent years the emergence of multiple drug resistance microbes has become a global public health problem. The aim of the present investigation was to evaluate possible antibiofilm efficacy of a gallotannin 1,2,6-tri-O-galloyl-β-D-glucopyranose from Terminalia chebula fruits alone and in combination with gentamicin and trimethoprim against preformed biofilms of multidrug-resistant (MDR) uropathogenic E . coli isolates using microbroth dilution, checkerboard titration and kill kinetics methods. Test gallotannin showed > 50% antibiofilm efficacy after 24 h when administered alone whereas gentamicin and trimethoprim failed to do so. But in combination, test gallotannin/gentamicin and test gallotannin/trimethoprim showed 71.24±6.75% and 93.4±8.46% antibiofilm activity respectively. On the basis of FICI values, test gallotannin/gentamicin showed synergistic interactions against 71.42% and test gallotannin/trimethoprim against 85.71% biofilm forming test bacterial isolates. Kill-kinetics study confirmed their synergistic interactions. Thus, gentamicin and trimethoprim in combination with test gallotannin may have potential for treatment of urinary tract infections caused by biofilm forming MDR uropathogenic E . coli .