Table 5.

Intrinsic resistance mechanisms in bacteria to antiseptics and disinfectants

Type of resistanceExample(s)Mechanism of resistance
Impermeability
 Gram-negative bacteriaQACs, triclosan, diaminesBarrier presented by outer membrane may prevent uptake of antiseptic or disinfectant; glycocalyx may also be involved
 MycobacteriaChlorhexidine, QACsWaxy cell wall prevents adequate biocide entry
GlutaraldehydeReason for high resistance of some strains of M. chelonae(?)
 Bacterial sporesChlorhexidine, QACs, phenolicsSpore coat(s) and cortex present a barrier to entry of antiseptics and disinfectants
 Gram-positive bacteriaChlorhexidineGlycocalyx/mucoexopolysaccaride may be associated with reduced diffusion of antiseptic
Inactivation (chromosomally mediated)ChlorohexidineBreakdown of chlorhexidine molecule may be responsible for resistance