Investigation of the effects of quercetin and hyperthermia applications on colistin-resistant Acinetobacter baumannii and Staphylococcus epidermidis

Aim: The aim was to investigate the effects of quercetin and hyperthermia application, alone and in combination, on the growth and biofilm inhibition and morphological structures of colistin-resistant A. baumannii and S. epidermidis. Material and Method: Experiments were performed at 37°C, 42°C, and 45°C. Quercetin was tested in the range of 512-1 μg/ml. Eight colistin-resistant A. baumannii and eight S. epidermidis isolates, whose biofilm production was determined by the Congo red agar method, were included in the study. Growth inhibition level was tested by broth microdilution, and biofilm inhibition level was tested by crystal violet method. The effect of two hour hyperthermia was observed in an in vitro treatment model experiment. Inhibition levels were determined by spectrophotometric measurement. Morphological effects were evaluated by TEM analysis. In the statistical analysis of the results, p≤0.05 was considered significant. Results: The combination of hyperthermia and quercetin MIC values decreased. Significant differences were observed between the growth inhibition levels of both bacteria at 512, 256, and 128 μg/ml quercetin concentrations. Hyperthermia alone significantly slowed growth for both bacteria. No significant difference was observed between the biofilm inhibition levels. Hyperthermia alone had a significant effect on biofilm inhibition for S. epidermidis. When the bacteria were compared with each other, no significant difference was observed in terms of biofilm inhibition. S. epidermidis was more sensitive to hyperthermia than colistin-resistant A. baumannii in terms of growth. In the in vitro treatment model experiment, a significant difference was observed only in biofilm inhibition of colistin-resistant A. baumannii at a concentration of 64 μg/ml quercetin. TEM results showed that the combination of quercetin and hyperthermia affected cell morphology. No S. epidermidis cells were found at 45°C+quercetin, probably due to inhibition of growth.Conclusion: The combination of quercetin and hyperthermia had a significant effect on growth and morphological changes. The study found that hyperthermia had an adjuvant effect when used with quercetin.