Gizem Kaleli Can1 Pinar Yurdakul-Mesutoğlu1 Ferda Ozguzar1 Elvan Hortaç-Istar2 Gözde Kabay1 H. Cenk Mirza2 Ahmet Basustaoglu2 Julide Sedef Göçmen1 Mehmet Mutlu1

1, TOBB ETU, Ankara, , Turkey
2, Baskent University, Ankara, , Turkey

Candida spp are considered as one of the common microorganisms of health care associated infections, mostly through biofilm associated infections. Biofilms are well known for forming on implanted medical devices such as catheters, pacemakers, prosthetic joints etc. Candida biofilms are resistant to many antifungals clinically used, making these infections a significant challenge. Higher doses of antifungals with removal of the colonized device are generally the only options to cure these infections. One of successful approaches to prevent biofilm formation is surface modification by plasma polymerization, coating only surface of device. In this study, biofilm formation on plasma polymerized microplate surfaces were investigated.

Thirty biofilm positive Candida spp isolated from blood as well as two ATCC control strains (C. albicans ATCC 10231 and C. parapsilosis) were included in this study. Biofilm formation was determined as described by quantitative plaque assay method. Suspensions of Candida spp isolated from blood cultures were inoculated in triplicates onto microplate wells. Individual strains isolated from patients as well as negative and positive controls were incubated for 48 hours. Biofilm production on plasma modified and non-modified surfaces were evaluated both at 48 hours and two weeks after. Evaluation was done using crystal violet (CV) binding assay. After staining with CV, the optical density (OD) of each well stained with CV was measured at 570 nm against the OD of negative controls (at 48 hours and at two weeks).

Surface modification of microplates with plasma polymerization technique was achieved by low pressure plasma system. In this particular study, acrylic acid (AA), 2–hydroxyethyl methacrylate (HEMA) and diethyl phosphite (DP) were assessed for their biofilm inhibition efficacy.

On non-coated control surfaces 100% biofilm formation by Candida spp was observed. When plasma-modified microplate surfaces were evaluated at different plasma powers (30, 60 and 90W), the most significant inhibition of biofilms was observed on DP coated microplate wells at 90W, for all Candida spp tested. For HEMA and AA coated microplates at 90W, biofilm formation was observed for only one Candida isolate. When all three monomers (AA, HEMA and DP) were investigated at 60W and 30W, DP and AA were the most effective monomers, respectively. When readings were re- evaluated after two weeks, only DP seemed to be stable at 90W whereas AA and HEMA in particular seemed to have lost their anti-biofilm effects.

Regardless of the monomers and plasma parameters used, biofilm formation was inhibited for all plasma modified microplate wells (p<0,000). Of all the monomers included, the most significant anti-biofilm effect was shown for DP at 90W. In this study, in-vitro results indicated a potential for reducing biofilm associated Candida infections on selected plasma modified surfaces.