ANTIMICROBIAL EVALUATION OF ZIRCONIUM DIOXIDE NANOPARTICLES ASSOCIATED WITH SILVER AGAINST METHICILLIN-RESISTANT Staphylococcus aureus

Methicillin-resistant Staphylococcus aureus (MRSA) is a Gram-positive coccus commonly found in our common microbiota as in tissues and of great importance in the medical aspect, since these microorganisms are responsible for a variety of infections ranging from superficial to high degree of severity. This species is able to form biofilms associated with materials widely used in hospital and dental environments, such as catheters. In addition, several isolates have shown increasing resistance to antibiotics. Zirconium dioxide (ZrO2) is a material with interesting properties, such as corrosion and mechanical resistance, and is a possible option in coating materials in order to inhibit the proliferation of pathogenic bacteria. In this context, the objective of this study was to evaluate the antimicrobial action of ZrO2 nanoparticles associated with different concentrations of silver (Ag) (silver 1% (ZAg1) and 10% (ZAg10)) against MRSA-induced biofilms. MRSA strain (ATCC 43300) was cultured in a Mueller Hinton broth at the concentration of 107 bacteria / ml. Four concentrations (2; 1; 0.5; 0.25 mg / ml) of nanoparticles were tested on bacterial growth kinetics at 0, 2, 4 and 6 hours intervals. The capacity of biofilm formation through the Congo red agar medium was determined. Subsequently, the violet crystal assay was performed, aiming to quantify the bacterial biomass produced against the nanoparticles and scanning electron microscopy. The growth kinetics assay demonstrated potent action of ZAg1 nanoparticles against MRSA over a 6 hours period at the concentration of 2 mg / ml, inhibiting 100% thereof. Zag10 nanoparticles showed better inhibition of growth than ZrO2. The capacity of biofilm formation through Congo red agar medium was confirmed by the change in color of the peal, from transparent to black. In the violet crystal assay, ZAg1 nanoparticles induced 80% inhibition of biofilms, ZrO2 nanoparticles inhibited 40% and ZAg10 showed 60% inhibition. The images obtained by Scanning Electron Microscopy showed deformity of the colonies and perforations in the cell membrane, confirming the potent action of the nanoparticles. Our results show antimicrobial action of Zirconium nanoparticles, mainly associated with low concentrations of silver, such as ZAg1. Therefore, our results suggest that this material is a potential candidate for its use as a coating of hospital, dental and catheter materials, reducing and preventing contaminations caused by methicillin-resistant Staphylococcus aureus.