Staphylococci biocide sensitivity

As already pointed out, staphylococci and streptococci are generally more sensitive to biocides than are Gram-negative bacteria examples are provided in Table 13.3. On the... 

The ebr gene is identical to the qacC/qacD gene family [221], Sasatsu and his colleagues [230, 231] demonstrated that the nucleotide sequence of an amplified DNA fragment of the ebr gene from sensitive and resistant cells of S. aureus was identical and thus concluded that antiseptic-resistant cells result from an increase in copy number of a gene whose usual function is to remove toxic substances from normal sensitive cells of staphylococci (and also of enterococci). It is not always possible to demonstrate low-level resistance to cationic biocides in S. aureus [232-236] this could be due to the instability of plasmids in these clinical isolates. 

As already pointed out, staphylococci and streptococci are generally more sensitive to biocides than Gram-negative bacteria examples are provided in Table 18.4. On the other hand, mycobacteria and especially bacterial spores are much more resistant. A major reason for this variation in response is associated with the chemical composition and structure of the outer cell layers such that there is restricted uptake of a biocide. In consequence of this cellular impermeability, a reduced concentration of the antimicrobial compound is available at the target site(s) so that the cell may escape severe injury. Another, less frequently observed, mechanism is the presence of constitutive, biocidedegrading enzymes. 

The cell wall of staphylococci is composed essentially of peptidoglycan and teichoic acids. Substances of high molecular weight can traverse the wall, a ready explanation for the sensitivity of these organisms to most biocides. However, the plasticity of the bacterial cell envelope is well known and the... 

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