The effect of new disinfectant substances on the metabolism of Enterobacter cloacae.

The antimicrobial mechanism of 16 new commercially manufactured disinfectant substances on an Enterobacter cloacae strain was studied. The substances tested represent 11 quaternary ammonium salts (QAS) and five combinated QAS with other ingredients. The antimicrobial efficacy was characterized by influencing the growth of bacterial cells expressed by MIC and ED50 values as well as by the inhibition of the incorporation rate of [14C] adenine and [14C] leucine. The disinfectants are divided into three groups according to their efficacy. The first group comprised substances with strong inhibitory effect (MIC 0.006-0.048 mg l(-1)) such as triquart, topax 91, benzalkonium chloride, neoquat S, ID 213, and antibacteric P. The second group represented substances with good antibacterial efficacy (MIC 0.048-0.15 mg l(-1)), and the third group were substances with MIC values up to 0.195-0.39 mg l(-1). Cetrimide had low activity (MIC 3.12-6.25 mg l(-1)). The effect of substances studied on the biosynthetic processes expressed by R values (IC50 Ade:IC50 Leu) showed that these values were < 1 except ADL 007. Much lower IC50 Ade and IC50 Leu values of the disinfectant substances studied suggested interference of these substances with nucleic acid synthesis and proteins synthesis which was expressed by inhibition of both precursors. All substances except cetrimide caused an inhibition of the endogenous respiration. The highest inhibition was caused by benzalkonium chloride. This affected the respiration significantly in the presence of intermediators of the Krebs' cycle (glycerol, aspartate). The tested substance suppressed the growth of E. cloacae probably through interference with energy-yielding and energy-requiring processes of the cells.