Synergistic treatment of linoleic acid and cefazolin on Staphylococcus aureus biofilm-related catheter infections

Abstract

Staphylococcus aureus is a human pathogen that causes severe infections through biofilm formation. S. aureus biofilm is particularly susceptible to catheters in patients undergoing peritoneal dialysis. Although antibiotics are used to treat catheter infections, high-concentration treatments adversely affect human host immune systems and change the physicochemical properties of the catheters. To improve therapeutic outcomes without side effects, we combined antibiotics and natural products. In this study, we propose a combination of linoleic acid (LA) and cefazolin (CFZ) to treat S. aureus infections synergistically and apply it to catheter environments and in vivo systems. LA is a polyunsaturated fatty acid derived from natural products, and CFZ is a major antibiotic used to treat S. aureus catheter-related infections. The optimum synergistic condition was determined using silicon pad-forming biofilm similar to catheter materials. S. aureus biofilms were considerably inhibited in vitro and in vivo owing to the improved antibacterial effects. Furthermore, the combination negatively regulated the chemokine levels in the peritoneum, kidney, and liver extracted from mouse models. Moreover, it did not affect the cytotoxicity of human omentum mesothelial cells and the functions of the kidney and liver. Therefore, the combination of LA and CFZ could be a potential synergistic therapy for S. aureus catheter infections.IMPORTANCECatheter contamination is commonly caused by Staphylococcus aureus biofilm formation, primarily in peritoneal dialysis patients. Although antibiotics are used to treat catheter infections, high concentrations of antibiotics impair the immune system of the human host and alter the physicochemical properties of catheters. Therefore, it is crucial to improve therapeutic outcomes while minimizing the side effects of antibiotics. Combined treatments with natural products can be solutions to alleviate these problems. Our study offers a new synergistic combination (linoleic acid and cefazolin) for the control of catheter infections caused by S. aureus biofilms, especially in peritoneal dialysis.

Keywords: Staphylococcus aureus; catheter biofilm; cefazolin; linoleic acid; synergistic combination.

Fig 1

Bacterial growth and biofilm formation against S. aureus at various linoleic acid (LA) and cefazolin (CFZ) concentrations in a 96-well plate. (A) Bacterial growth and (B) biofilm formation by LA treatment (0–1,000 µM). (C) Bacterial growth and (D) biofilm formation by CFZ treatment (0–5.5 µM). (**) P < 0.005 compared with the control.

Fig 2

S. aureus biofilm formation and eradication by LA and CFZ combinations in a 96-well plate. (A) Image of crystal violet-stained biofilm cells. (B) Biofilm formation at different combinations of LA (0–50 µM) and CFZ (0–0.4 µM). (C) Biofilm eradication at different combinations of LA (0–50 µM) and CFZ (0–110 µM). (*) P < 0.05 and (**) P < 0.005 compared with the control.

Fig 3

S. aureus biofilm formation by LA and CFZ combinations on silicon pads. (A) Silicon pads used in this study. (B) S. aureus biofilm formation at different combinations of LA (0–50 µM) and CFZ (0.2–0.4 µM) under static conditions. (C) Biofilm formation by the optimal combination of LA (25 µM) and CFZ (0.4 µM) under continuous conditions. (**) P < 0.005 compared with the control.

Fig 4

Bioavailability of LA (25 µM) on human mesothelial cells obtained by the primary cell culture from the omentum. (A) Lactate dehydrogenase (LDH) and (B) MTS cell proliferation using colorimetric methods. (C) Creatinine and (D) blood urea nitrogen (BUN) levels to monitor the renal function. (E) Aspartate transaminase (AST) and alanine transaminase (ALT) levels to monitor the liver function.

Fig 5

Mouse models for testing S. aureus infections by the optimal combination of LA (25 µM) and CFZ (0.4 µM). (A) Schematic diagram of the methodology. (B) Biofilm formation on silicon pads obtained from mice. (C) Chemokine and (D) cytokine levels extracted from mice organs. (*) P < 0.05 and (**) P < 0.005 compared with the control.