Effect of subinhibitory concentrations of biocides on formation of adaptive resistance of clinical isolates of Klebsiella pneumoniae

The purpose of the research is to study the effect of subinhibitory concentrations of biocides on the formation of adaptive resistance of clinical isolates of K. pneumoniae. The study analyzes the effect of chlorhexidine, benzalkonium chloride, povidone iodine, ethanol, glycolic acid, polyhexamethylene guanidine on the formation of adaptive resistance of clinical isolates of Kl. pneumoniae (n=9), isolated in 2021 from patients undergoing treatment in various departments of the oncological hospital in Minsk. Determination of the sensitivity of bacteria to biocides was carried out with the serial dilutions method in a dense nutrient medium and with the serial microdilutions method in a liquid nutrient medium, using a twofold dilution of each antimicrobial substance. Throughout the course of the research, it was found that subcultivation of clinical isolates of K. pneumoniae on media with subinhibitory concentrations of chlorhexidine and benzalkonium chloride led to 60 and 40 times increase in bacterial resistance to them, respectively. It was shown that variability which does not affect the bacterial genome makes the maximum contribution to the development of resistance of K. pneumoniae clinical isolates to chlorhexidine, and both phenotypic and mutational variability to benzalkonium chloride. Povidone iodine, ethanol and glycolic acid did not cause the development of adaptive resistance of microorganisms. The results obtained indicate that the irrational and uncontrolled use of antiseptic and disinfectants containing chlorhexidine and benzalkonium chloride as active substances can lead to the development of adaptive resistance of microorganisms and thereby reduce the effectiveness of preventive and therapeutic measures.