NSAIDs as a Drug Repurposing Strategy for Biofilm Control

Abstract

Persistent infections, usually associated with biofilm-producing bacteria, are challenging for both medical and scientific communities. The potential interest in drug repurposing for biofilm control is growing due to both disinvestment in antibiotic R&D and reduced efficacy of the available panel of antibiotics. In the present study, the antibacterial and antibiofilm activities of four non-steroidal anti-inflammatory drugs (NSAIDs), piroxicam (PXC), diclofenac sodium (DCF), acetylsalicylic acid (ASA) and naproxen sodium (NPX) were evaluated against Escherichia coli and Staphylococcus aureus. The minimum inhibitory/bactericidal concentrations (MICs and MBCs) and the dose-response curves from exposure to the selected NSAIDs were determined. MICs were found for PXC (800 μg/mL) and ASA (1750 μg/mL) against E. coli, and for DCF (2000 μg/mL) and ASA (2000 μg/mL) against S. aureus. No MBCs were found (>2000 μg/mL). The potential of NSAIDs to eradicate preformed biofilms was characterized in terms of biofilm mass, metabolic activity and cell culturability. Additionally, the NSAIDs were tested in combination with kanamycin (KAN) and tetracycline (TET). ASA, DCF and PXC promoted significant reductions in metabolic activity and culturability. However, only PXC promoted biofilm mass removal. Additive interactions were obtained for most of the combinations between NSAIDs and KAN or TET. In general, NSAIDs appear to be a promising strategy to control biofilms as they demonstrated to be more effective than conventional antibiotics.

Keywords: Escherichia coli; NSAIDs; Staphylococcus aureus; antibiotic resistance; biofilm eradication; drug repurposing.

Figure 1

Dose–response curves. The y-axis reports the log CFU/mL of E. coli planktonic cells, while the x-axis reports the period of 6 h of exposure to the NSAIDs: (a) PXC (piroxicam) at three different concentrations (1/2× MIC, MIC and a concentration above the MIC), grown in broth culture medium with lactose and treated with DMSO; (b) ASA (acetylsalicylic acid) at three different concentrations (1/2× MIC, MIC and a concentration above the MIC), treated with DMSO. Cells without NSAIDs and cells with DMSO were used as negative controls. Mean values ± SD are presented.

Figure 2

Dose–response curves. The y-axis reports the log CFU/mL of S. aureus planktonic cells, while the x-axis reports the period of 6 h of exposure to the NSAIDs: (a) DCF (diclofenac sodium) at three different concentrations (1/2× MIC, MIC and a concentration above the MIC), untreated with DMSO; (b) ASA (acetylsalicylic acid) at three different concentrations (1/2× MIC, MIC and a concentration above the MIC) treated with DMSO. Cells without NSAIDs and cells with DMSO were used as negative controls. Mean values ± SD are represented.

Figure 3

Effects of PXC (piroxicam), DCF (diclofenac sodium), ASA (acetylsalicylic acid), at three different concentrations (MIC, 5× MIC and 10× MIC) and KAN (kanamycin) and TET (tetracycline) at MIC (in this case, 5× MIC and 10× MIC were not tested) against E. coli and S. aureus after 24 h of exposure in terms of: (a,b) biomass removal (%) and (c,d) biofilm inactivation. ▲/∆ represents 0% biofilm removal. Mean values ± SD of three independent experiments are illustrated.

Figure 4

Effect of PXC (piroxicam), DCF (diclofenac sodium), ASA (acetylsalicylic acid), at three different concentrations (MIC, 5× MIC and 10× MIC) and KAN (kanamycin) and TET (tetracycline) at MIC (in this case, 5× MIC and 10× MIC were not tested) in the biofilm culturable cells—log CFU/cm² reduction. (a) E. coli and (b) S. aureus, after 24 h exposure. Mean values ± SD of three independent experiments are illustrated.