Evaluation of Antibacterial Activity of Three Quaternary Ammonium Disinfectants on Different Germs Isolated from the Hospital Environment

Background: The microbiological risk of the hospital environment, including inert surfaces, medical devices, and equipment, represents a real problem.

Objective: This study is aimed at demonstrating and assessing the antibacterial activity of three synthetic disinfectants classified as quaternary ammoniums on different bacterial strains (Gram-negative and Gram-positive like , , , , , and ) isolated from the hospital environment. The reference strains included ATCC 25922, ATCC 29213, and ATCC 27853 used as negative control strains.

Method: Three quaternary ammonium disinfectants were tested: DDN9® (0.5%) which contains didecylmethylpolyoxyethylammonium propionate as an active substance, spray (0.4%) containing quaternary ammonium compounds, and Phagosurf ND® (0.4%) with didecyldimethylammonium chloride. Their effect was evaluated using the disk diffusion technique and the broth dilution methods, allowing the Minimum Inhibitory Concentration (MIC) and then the Minimum Bactericidal Concentration (MBC).

Result: Only the growth of Gram-positive bacteria and some strains of Gram-negative bacteria were inhibited by the three synthetic disinfectants. NDD9® demonstrated an antibacterial effect only against the Gram-positive strains ( and ATCC 29213) with a MIC of 0.25 mg/ml. The disinfectant spray showed effect against all four strains including (9), , ATCC 25922, and ATCC 27853 with an inhibitory concentration of 4 mg/ml, while the growth of ATCC 29213 was inhibited at 2 mg/ml. The third disinfectant, Phagosurf ND®, inhibited only the growth of ATCC 29213 at a MIC of 4 mg/ml.

Conclusion: This study is the first here in Morocco to evaluate the bacterial activity of products intended for the control of the healthcare environment. The results obtained on the three disinfectants tested reveal an ineffectiveness against some isolated strains from the hospital environment.