The Truth about Disinfectant Contact Time in Foodservice
The role of environmental disinfection in the food service industry is important in maintaining a low bioburden and helping prevent the role of fomites as a vector for foodborne illness. Recent studies have shown that environmental contamination plays an important role in the transmission of Methicillin resistant Staphylococcus aureus(MRSA), Carbapenem Resistant Enterobacteriaceae (CRE), Clostridium difficileand Norovirus. For effective disinfection of non-food contact environmental surfaces, users turn to Environmental Protection Agency (EPA) registered disinfectants.
Product labels for EPA regulated disinfectants contain fundamental information for the user, such as key safety warnings and directions for use. The end user must refer to this information to select personal protective equipment, if necessary, first aid in the event of an accident, and surface disinfection contact times. While certain principle information is required, it can be difficult for the end-user to decipher the specific language used on one product versus another. Micro-organisms differ in their innate sensitivity to disinfectants, thus it is common to see varying contact times for different micro-organisms within the same use directions. Individual product labels are not all the same. Even products from the same manufacturer may carry different language and instructions for use. It should not be a surprise that these issues can lead to confusion and a lack of compliance.
Upon review of the commonly used disinfectants currently available, we can see a number of different iterations of contact time directions for use:
- “Repeated use of the product may be required to ensure that the surface remains visibly wet”
- “Allow surface to remain wet for x minute(s)”
- “Treated surface must remain wet for x minutes”
- “Treated surface must remain wet for appropriate contact time listed on this label”
Most manufacturers suggest that the end user maintain wetness for the duration of the contact time. That appears to make sense, but there are flaws with this approach. First, there is the practicality of observing wetness, especially if the contact time is long (i.e. 10 minutes) – no user has time to watch disinfected surfaces dry. Next, there is the subjectivity of wetness; is it thoroughly wet or partially wet? Wetness is truly subjective and therefore open to interpretation, which may impact how the product is used. Finally, consider the environmental conditions. Temperature, humidity and air flow all play a role in how long a disinfectant (or any liquid) will remain wet on a surface.
For the truth, one needs to turn to the manner in which efficacy of disinfectants for hard non-porous surfaces are assessed by the EPA. In this example, we review the method used for evaluating disinfectant sprays and wipes; the AOAC Germicidal Spray Test. Succinctly, test micro-organisms are dried upon a glass surface prior to being treated by the disinfectant in a standardized manner with environmental controls. Following the desired contact time, the glass surfaces are placed in growth medium to inactivate the active ingredient and determine if the test micro-organism(s) have been eradicated. The contact time is determined based on testing by the manufacturer, but must be no more than ten minutes in accordance with the EPA regulations. During the contact time, the liquid delivered on the glass surface by the wipe is exposed to the air, simulating a typical environment. As such, the glass surfaces will exhibit varying levels of wetness according to the test conditions. Surfaces are not assessed for wetness and the EPA does not require test surfaces to remain wetduring the test method.
So if the disinfectant time is not the wet time, what is it?
Users should wipe down the surface and allow the treated area to remain undisturbedfor the given contact time. Regardless of whether the surface is wet, dry or somewhere in between, the efficacy is assured to be in line with the EPA registration.
Proper disinfecting is essential in all operations to help keep guests and employees disease-free. To request more information about how Sani Professional® products can help improve your cleaning, sanitizing, disinfecting, and hand hygiene protocols please contact us.
Article contributed by James Clayton, Director of Laboratory Sciences & Services, PDI, Inc. (Sani Professional is a division of PDI, Inc.)