Inhibition of the system quorum sensing LuxI/LuxR-type by combining of antibiotics

Currently, most infectious diseases are caused by biofilm forming bacteria, and this process is controlled by the Quorum sensing (QS), which greatly complicates the work of antibacterial drugs. In this regard, this work aimed to evaluate the combined effect of antibiotics from different groups on the QS system. The wild strain of C. subtsugae ATCC 31532 was used as the object of research. As the studied substances, four different groups of antibiotics were used: amikacin, meropenem, doxycycline and azithromycin. The anti-QS activity of each of these compounds was determined by recording: 1) the optical density of biomass at 450 ± 5 nm (OD450), and 2) the amount of violacein pigment after its ethanol extraction at 600 ± 5 nm (OD600). During the study, we found that all the antibiotics, when used separately, showed a pronounced antibacterial and QS-inhibiting effect of the model test microorganism. The results of studies conducted in a cross-matrix of antibiotic concentrations showed a pronounced antagonistic effect of azithromycin and meropenem, amikacin and azithromycin, azithromycin and doxycycline, meropenem and doxycycline, and amikacin and doxycycline. The only combination of antibiotics that showed a superadditive effect was a combination of meropenem and amikacin.