Antibiofilm and antibacterial activity of diclofenac against clinical enterococcal isolates

Background: Antimicrobial drug resistance is an emerging threat worldwide. Replacing antibiotics with non-antibiotic compounds has been suggested as a way to counteract the magnitude of this problem. We aimed to assess the effect of the non-steroidal anti-inflammatory drug, diclofenac, on the growth of clinical enterococcal isolates, their resistance to the fluoroquinolone antibiotic, ciprofloxacin, and their biofilm forming ability. Methods: We retrieved fifty enterococcal isolates from 36 urine and 14 purulent discharge specimens and determined diclofenac's antimicrobial activity and its effect on their biofilm formation. The effect of exposure of enterococci to diclofenac on the expression levels of the efflux pump genes (efrA and efrB) and the adherence-related genes (asa1, efaA) was also studied. Results: We observed that diclofenac inhibited the growth of enterococcal isolates and induced a statistically significant reduction in the expression of efrA and efrB. However, it failed to reduce either ciprofloxacin resistance rates or its minimal inhibitory concentration. Both ciprofloxacin and diclofenac showed a significant inhibitory effect on enterococcal biofilm formation. Furthermore, diclofenac induced a statistically significant reduction of the expression of asa1 and efaA. Conclusions: The antibacterial activity and the anti-biofilm forming ability of diclofenac demonstrated in this study may provide a promising preventive and therapeutic alternative for medical and dental prosthesis-associated enterococcal infections.