PSI-B-24 - Assessment of the combined use of antibacterial substances on the in vitro model in the development of veterinary drugs

The wide use of antibacterial drugs in the agricultural and veterinary industries as growth stimulants and antimicrobial therapies has led to increased resistance of pathogens and opportunistic pathogens to many chemotherapy drugs. The purpose of our study is to assess the additive effect of these compounds to enhance the inhibitory action of antibiotics. Antibacterial drugs of various chemical groups, extracts from medicinal plants with microbicide and anti-quorum effects, inorganic copper and zinc salts, as well as probiotic strains of the genus Bacillus of veterinary purpose, were used to achieve the goal. The main methodical approach to assessing the additive effect of complex compounds in the work was the method of diffusion into agar, combined with the method of serial dilution. The selection of antibacterial drugs was carried out using the disk diffusion method. S. enteritidis, S. typhimurium, and P. aeruginosa were used as the test organisms in studies. The main criterion for the selection of antibacterial drugs was the resistance of probiotic strains and the moderate sensitivity of the test organisms in relation to their action. Cefixime was experimentally selected for the study against S. enteritidis and S. typhimurium and Fosfomycin against P. aeruginosa. Of all the studied phytobiotics, the most promising for further study was the oak bark extract. Against P. aeruginosa, the most significant chemical compound is CuSO₄ at a concentration of 40 mg/ml, which does not affect the growth of probiotic strains. The pronounced additive effect of the combined compound based on cefixime, oak bark, and B. subtilis 534 was observed against S. enteritidis and S. typhimurium by 23% and 25%, respectively. The combined use of fosfomycin, B. subtilis 534, CuSO₄, and the oak bark extract increases P. aeruginosa growth suppression by 19 % compared to the control of the growth suppression of this antibiotic.