The mechanisms of action are not always completely known and continue to be investigated. A range of different factors needs to be considered as part of the process of selection including the mode of action, efficacy, compatibility, cost and with reference to current health and safety standards.
A disinfectant must have a wide spectrum of activity. This refers to the ability of the disinfectant to kill micro-organisms of varying types and in different physiological states.
Is there a requirement for the disinfectant to be sporicidal? This requirement influences the type of disinfectant purchased. Sporicidial disinfectants tend to have greater health and safety considerations and some, particularly chlorine-based disinfectants, are aggressive to certain types of surfaces and will cause discolouration and abrasion.
The disinfectants must meet the requirements of the validation standards to measure bactericidal, fungicidal and, if appropriate, sporicidal and virucidal activity.
The disinfectant must be rapid in action with an ideal contact time of less than 15 min. The contact time is the time taken for the disinfectant to bind to the micro-organism, traverse the cell wall and membrane and to reach its specific target site. The longer the contact time, then the longer the surface or article needs to be left, prior to reuse.
Some disinfectants require certain temperature and pH ranges to function correctly. One type of disinfectant, for example, may not be effective in a coldroom due to the lower temperature. The reason for this is that the validation standards for disinfectants measure the bactericidal activity at 20°C and therefore the disinfectant may not be as effective at higher or lower temperatures.
Prior to the use of disinfectants it is essential that as much dirt and soil is removed as possible. This requires the application of a detergent. Some disinfectants are not compatible with certain detergents. In such instances, detergent residues could neutralise the active ingredient in the disinfectant. Any disinfectant purchased should be compatible with the detergent used.
Different disinfectants are not compatible with all types of surfaces. The disinfectants must not damage the material to which they are applied (although it is recognised that repeated applications over several years may cause some corrosion). For more aggressive disinfectants, a wipe down using water or a less aggressive disinfectant such as an alcohol is sometimes necessary to remove the residues. In addition to some disinfectants having a corrosive effect, others may be absorbed by fabrics, rubber etc, which lessens their bactericidal properties.
The cost of the disinfectant is also a factor to consider, especially if it is to be used over a large surface area.
Health & Safety
The presentation of the disinfectant is an important choice, whether as a pre-diluted preparation in a trigger spray or as a ready-to-use concentrate or an impregnated wipe.
The disinfectants must be safe to use, in terms of health and safety standards. Here, the main concern is with operator welfare. A related concern is the impact upon the environment.