In a pharmaceutical cleanroom, airborne Gram-positive bacteria are a significant problem, as they can contaminate any and all surfaces within the manufacturing area. Gram-negative bacteria, which are typically introduced by human operators within the cleanroom, are also an issue, and they tend to be more difficult to eradicate. A further layer of complexity is added by the propensity of Gram-positive bacteria to form spores, which are notoriously difficult to eradicate using disinfectants.
The choice of disinfectant depends on the nature of the microbial contamination that is present or possible within the manufacturing area. On the whole, the use of quaternary ammonium disinfectants (quats) suffice in common practice. These quats bind to the outer surface of Gram-positive bacteria, which typically bear a negative charge, and this binding disturbs the cell membrane and kills the bacteria. The surface of a Gram-negative bacterium is less negatively charged, so quats alone are not as effective. The reduced efficacy can be counteracted by adding, for example, guanidine or glucoprotamin components to the quats; this combination will also assist in the removal of yeasts and moulds.
Severe contamination, especially if spores are present, will require more extreme disinfectants to be applied, but these have drawbacks. Peracetic acid is often used, which works by oxidising bacterial membrane proteins and phospholipids, and disturbs components inside the cell such as the ribosome. However, it is very non-specific, acidic and corrosive, and causes damage to the surfaces to which it is applied. It is therefore not suitable for routine disinfection.
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