Sunday, April 5, 2009

Disinfecting Against Microorganisms

The chemicals most widely used in disinfectant formulations attack microorganisms in both broad and specific ways. For example, the extremely low or high pH levels of many of these products may present an inherently hostile environment to certain organisms, while the active ingredients make a targeted attack on a specific cell structure.
In other words, different disinfectant formulations work differently against various organisms. Furthermore, not all organisms have the same susceptible cell structures. There are real differences in susceptibility between a vegetative bacterium and a spore former.
Disinfectants should be selected on the basis of performance against common environmental contaminants and more than one product must be included in the disinfectant program in order to achieve broad-spectrum performance. The program should include routine disinfectants, sporicides, and residue reducing agents.
Routine disinfectants are those that contain phenolic or quaternary ammonium chloride compounds as active ingredients. These products are widely used and well characterized in terms of performance against common bacteria, fungi, and viruses. The advantages of using these products are that they are safe for everyday use on common cleanroom substrates and they are safe and relatively low in toxicity for the user. They are also effective at handling soil loads that would inactivate other products, particularly oxidizing chemistries such as bleach and peracetic acid blends. Routine disinfectants are not effective against spore-forming organisms such as Bacillus subtilis and many provide minimally effective performance against resistant molds such as Aspergillus niger.
To control inherently challenging organisms such as spore-formers and molds, sporicides must be used as part of a long-term strategy. These chemistries include bleach, peracetic acid/hydrogen peroxide blends, and chlorine dioxide. The advantage of these chemistries is that they will eliminate all microbial life forms, including the most resistant forms, if applied correctly. This makes them well-suited for applications during a catastrophic failure or when bringing a facility back on line after a preventative maintenance shutdown. Sporicides can also be used for more frequent applications as a preventative measure, or more frequently as part of a short-term strategy to address environmental monitoring failures until a root cause has been identified and a corrective action implemented.

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