Effect of sub-minimum inhibitory concentrations of ceftriaxone on the Pseudomonas aeruginosa adhesion to human oral mucosal epithelial cells and biofilm formation to polystyrene in vitro

Abstract

The adhesion of Pseudomonas aeruginosa to human oral mucosal epithelial cells (OMECs) and the formation of biofilms on artificial materials are crucial in bacterial oral infections. The role of sub-inhibitory concentrations of ceftriaxone on the P. aeruginosa adhesion to human OMECs and biofilm formation onto polystyrene is not clear. The study aims to explore the role of sub-inhibitory ceftriaxone concentrations in P. aeruginosa adhesion to human OMECs and biofilm formation to polystyrene. Nineteen isolates of P. aeruginosa were obtained from infected wounds. Minimum inhibitory concentrations (MICs) of ceftriaxone against 19 isolates of P. aeruginosa (Pa1-Pa19) and biofilm formation were determined for all isolates. Epithelial cells were isolated from the mucous layer of the healthy volunteers' mouths. The effect of pre-treating Pa2, Pa6, and Pa10 (the highest biofilm-forming isolates) with sub-minimum inhibitory concentrations (sub-MICs) of ceftriaxone (0.5xMIC, 0.25xMIC, 0.125xMIC, and 0.06xMIC) on biofilm formation on polystyrene and adhesion to human (OMECs) was evaluated. The ceftriaxone MICs against all P. aeruginosa isolates were variable (311.6 ± 437.3 µg/ml, they ranged from 15.62 to 2000 µg/ml). All isolates form variable biofilm amounts (0.35±0.1 OD570nm). All used sub-MICs of ceftriaxone reduced biofilm formation and adhesion to human (OMECs) by Pa2, Pa6, and Pa10 significantly (P<0.05) as compared to control (biofilm formation and adhesion of Pa2, Pa6, and Pa10 without antibiotic stress). The effect of sub-MICs on biofilm formation to polystyrene and adhesion to humans (OMECs) was highly variable according to P. aeruginosa isolate and concentration of sub-MIC. The study showed that ceftriaxone sub-MICs decrease P. aeruginosa biofilm formation to polystyrene and adhesion to human OMECs in isolates isolates-dependent manner and not a concentration-dependent manner.