BACKGROUND AND OBJECTIVESAntimicrobial resistance and biofilm formation are becoming one of the most important public health. Therefore, the prevention of theirs formation has been a serious challenge. The present study focuses on understanding the new strategy to inhibit biofilm formation and explores the potential role of
Echium italicum -derived carbon dots (CDs) as biofilm inhibitor compound.MATERIALS AND METHODSThe minimal inhibitory concentration (MIC) of CDs was determined by broth microdilution method. The antibacterial activity of CDs in combination with clindamycin and ciprofloxacin was evaluated using the checkerboard method. By microtitre plate method, the anti-biofilm effect of CDs alone and in combination with clindamycin and ciprofloxacin was also evaluated. Then the toxicity of each of the agents was investigated on L۹۲۹ fibroblast cells. Finally, the effects of CDs on the expression of pslA, pelA and ppyR genes in P. aeruginosa and icaA, icaC, icaD and bap genes in S. aureus, which are related to biofilm formation were determined using RT-q PCR.RESULTS AND DISCUSSIONThe synthesized CDs had an emission maximum of ۴۵۵ nm and the average diameter of the CDs was estimated to be ۳.۴ ± ۰.۵ nm. CDs showed the lowest inhibitory concentration (MIC) between ۱۲۵-۵۰۰ μg/ml against clindamycin-resistant
S. aureus isolates and between ۰.۵-۱mg/ml against ciprofloxacin-resistant P. aeruginosa isolates. CDs at MIC and sub-MIC concentrations significantly prevented biofilm formation in P. aeruginosa (P<۰.۰۴۷۷, P<۰.۰۲۸۰) and
S. aureus (P<۰.۰۰۸۲, P<۰.۰۰۵۵). Also, the combination of CDs with ciprofloxacin and clindamycin significantly reduced growth (P<۰.۰۰۰۱) and inhibited biofilm formation in clindamycin-resistant
S. aureus and ciprofloxacin-resistant P. aeruginosa isolates (P<۰.۰۰۵۳, P<۰.۰۱(. In addition, the ability of the antibiotics clindamycin and ciprofloxacin decreased by approximately ۹۸% within ۷۲ hours. The toxicity of the antibiotics also decreased in combination with CDs. The expression of pslA, pelA and ppyR genes in P. aeruginosa and icaA, icaC, icaD and bap genes in
S. aureus decreased significantly after exposure to CDs (P<۰.۰۰۲۳, P<۰.۰۰۴۵).CONCLUSIONThis study revealed a promising new method for the treatment of chronic infections. In addition, by minimizing the dose of antibiotics, the toxic effects of dose-dependent antibiotics and the antimicrobial activity can be improved.