Cell wall biocide resistance

Resistance to antimicrobial agents is of concern as it is well known that bacterial resistance to antibiotics can develop. Many bacteria already derive some nonspecific resistance to biocides through morphological features such as thek cell wall. Bacterial populations present as part of a biofilm have achieved additional resistance owkig to the more complex and thicker nature of the biofilm. A system contaminated with a biofilm population can requke several orders of magnitude more chlorine to achieve control than unassociated bacteria of the same species. A second type of resistance is attributed to chemical deactivation of the biocide. This deactivation resistance to the strong oxidising biocides probably will not occur (27). 

Intrinsic (natural, innate) resistance. In one form of intrinsic resistance, the fungal cell wall (see Chapter 2) is considered to present a barrier to exclude or, more likely, to reduce the penetration by biocide molecules. The evidence to date is sketchy but the available information tentatively links cell wall glucan, wall thickness and consequent relative porosity to the sensitivity of Saccharomyces cerevisiae to chlorhexidine. 

Impermeability (Mycobacteria) Chlorhexidine QACs Organomercurials Glutaraldehyde Waxy cell wall prevents adequate biocide entry Reason for high resistance of some strains of M.chelonael... 

Many years ago, it was proposed [105] that resistance of mycobacteria to QACs was related to the lipid content of the cell wall thus, M. phlei (with low total lipid) was more sensitive than M. tuberculosis, which possessed a higher total cell lipid content. It was also pointed out [105] that the resistance of various species of mycobacteria was related to the content of waxy material in the wall. As noted above, the mycobacterial cell wall is highly hydrophobic with a mycoylarabinogalactanpeptidoglycan skeleton. Hydrophilic type biocides are generally unable to penetrate the cell wall in sufficiently high concentration to produce a lethal effect. However, low concentrations... 

---