The evolution of Quaternary Ammonium Compounds

To achieve satisfactory disinfection of healthcare facilities, and to ensure pathogens are eliminated, an efficacious disinfectant is required. An ideal disinfectant should have a high inactivating capacity for a wide range of bacteria, fungi, and viruses (referred to as spectrum of activity).¹ The reduction in bacterial population is tied to the appropriateness of the disinfectant; the concentration of the agent; the method of application; and its contact time (the time that the disinfectant must remain in contact with the surface in order to reach and react with any microorganisms present). Here a balance must be drawn between a long contact time, necessary for absolute kill, and the time allotted between patient sessions. Other factors also need to be accounted for, including toxicity levels, residue formation, and personnel safety.

The essential factor is, however, the efficacy of the disinfectant against the types of microorganisms that present the most significant potential patient risk. There is an array of different disinfectants available. The two groups of disinfectants that have a wide spectrum of activity and are less affected by organic soiling are quaternary ammonium compounds and amphoteric agents. Quaternary ammonium compounds have the added advantage of lower residue formation.

Quaternary ammonium compounds are surfactants composed of positively charged polyatomic ions.² A longstanding example is benzalkonium chloride. Later generations of QACs achieve synergies through the incorporation of other chemicals designed to enhance their efficacy. This class of disinfectant has a broad-spectrum antimicrobial activity.³ The antimicrobial action of quaternary ammonium compounds involves perturbation of cytoplasm and the lipid bilayers that form the bacterial cell membrane.⁴