Disinfectants cetrimide

Selective media for pseudomonads. These media depend on the relative resistance of pseudomonads to the quaternary ammonium disinfectant cetrimide. In some recipes the antibiotic nalidixic acid (Chapter 5) is added, to which pseudomonads are also resistant. 

As is apparent from the above information, there is no ideal disinfectant, antiseptic or preservative. All chemical agents have their limitations either in terms of their antimicrobial activity, resistance to organic matter, stability, incompatibility, irritancy, toxicity or corrosivity. To overcome the limitations of an individual agent, formulations consisting of combinations of agents are available. For example, ethanol has been combined with chlorhexidine and iodine to produce more active preparations. The combination of chlorhexidine and cetrimide is also considered to improve activity. QACs and phenols have been combined with glutaraldehyde so that the same effect can be achieved with lower, less irritant concentrations of glutaraldehyde. Some... 

Microbial degradation of biocides has been described by Hugo [72] who points out that soil organisms are able to break down substances such as phenols added as fumigants. He also reviewed the utilization by bacteria of aromatic compounds (including the preservatives cresol, phenol, benzoic acid and esters of 4-hydroxybenzoic acid). Several types of preservatives and disinfectants, such as the QACs (e.g. cetrimide, cetylpyridinium chloride, benzalkonium chloride), chlorhexidine and phenylethanol can also be inactivated. Significantly, this only occurs at concentrations well below inhibitory or in-use concentrations [33] and thus cannot be responsible for insusceptibility. A further comment about chlorhexidine is given below. 

Cetrimide is also used as a cleanser and disinfectant for hard contact lenses, although it should not be used on soft lenses as an ingredient of cetrimide emulsifying wax, and in o/w creams (e.g. cetrimide cream). 

Unfortunately, viable count procedures carry the proviso that one colony develops from one cell or one colony-forming unit (CFU). Such techniques are, therefore, not ideal for disinfectants (e.g. Q ACs such as cetrimide) that promote clumping in bacter-... 

Cetrimide is mainly used in cutaneous preparations, especially in creams in which it is used as active substance (disinfectant) and emulsifier. 

Quaternary ammonium salts are formed by direct reaction of a tertiary amine with an alkyl halide. For example, trimethylamine can be reacted with cetyl bromide to produce the disinfectant agent cetrimide (Fig. 3.25). 

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