Biocides insusceptibility

Several factors are known to influence biocidal activity these include the period of contact, biocide concentration, pH, temperature, the presence of oigartic matter and the nature and condition of the microorgartisms being treated. Bacterial resistance to antibiotics is a well-established phenomenon and has been widely studied for luar years. By contrast, the mechanisms of insusceptibility to non-antibiotic chemical agents are less well understood. 

Three words (resistance, insusceptibility, tolerance) and their corresponding adjectives find widespread use, often interchangeably, to signify the lack of effect of an antimicrobial agent on a microbial cell. Tolerance is usually used to denote lack of lysis in some penicillin-treated streptococci. Resistance in terms of insusceptibility to biocides is often used to denote an in-... 

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. 

Intrinsic resistance to biocides as a consequence of bacterial degradative activities is thus not a major mechanism of insusceptibility. There are, of course, examples of plasmid-mediated enzymes that confer resistance to inorganic (and sometimes organic) mercurials and these will be discussed later... 

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See also in sourсe #XX -- [ ]

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