Mechanisms of bacterial resistance to biocides

Mechanisms of bacterial resistance to biocides can conveniently be considered as being of two types: (i) intrinsic, a natural property of an organism; (ii) acquired, resulting from genetic changes in a bacterial cell and arising either by mutation or by the acquisition of plasmids or transposons. Intrinsic resistance is demonstrated by bacterial spores, mycobacteria and Gram-negative organisms and is also shown by physiological (phenotypic) adaption as exemplified by cells growing as biofilms. Acquired resistance to biocides has been found with methicillin-resistant Staphylococcus aureus (MRSA) strains, but is most widely seen as bacterial resistance to mercury compounds and other metallic salts.