AbstractThe antibacterial effect of 19 new commercially manufactured disinfectant substances on aSalmonella typhimuriumstrain was studied. The substances tested represent 9 quaternary ammonium salts (QAT) and 11 combinated QAT with other ingredients. The antimicrobial efficacy was characterized by influencing the growth and reproduction of bacterial cells expressed either by MIC and ED50values (ED50 values represent concentration of substance in μ/ml which cause inhibition of growth by 50%), as well as by the inhibition of incorporation rate of [14C] adenine and [14C] leucine. The disinfectants are divided into three groups according to their efficacy. The first group comprises substances with strong inhibitory effect (MIC 0.04–0.19 μ/ml) such as Neoquat S, Antibacteric P, Divoquat forte, Sokrena and Diesin forte (sole from the group belonging to multicomponent substances). QAT except Antibacteric P interfere with energy metabolism (R values ∼1). The second group represents substances with good antibacterial efficacy (MIC values up 1.56 μg/ml), and the third group substances with MIC values up 12.5 μg/ml. Cutasept G was found ineffective also in the concentration 100 μg/ml. The method of inhibition of [14C] precursors is suitable as one from possible criterion in evaluation of antibacterial efficacy of various synthetic su