Hand Washing Testing Methods for Food Safety

by Meritech, on September 16,2020

Food safety and handwashing go hand in hand. Good hand hygiene is paramount to prevent the spread of pathogens at your facility and ensure consumer safety, but how can you make sure that your facility’s chosen handwashing method is actually working? 

There are several handwashing testing methodologies that can be used to validate the efficacy of your facility’s hand hygiene protocols. However, each method has its limitations and should be fully evaluated before a system of ongoing hygiene validation is written into an SOP or GMP system.  

ATP testing for hand hygiene validation

The ATP test for handwashing is a process of quickly measuring actively growing microorganisms through detection of Adenosine triphosphate, or ATP. ATP is an organic compound that provides energy to drive many processes in living cells and organisms, such as muscle contraction and chemical synthesis. ATP serves as a great marker for the prevalence of protein-like material on the surface of the skin (or other organic surface) —some of which could be dangerous and pathogenic.

ATPTestingIn ATP testing, microorganisms on the surface of the hands combine with a certain enzyme to produce light which can then be measured using a device called a Luminometer. The amount of light that is “read” by the device is expressed in Relative Light Units (RLU’s). The more microorganisms that exist on the surface of the skin, the more light that is generated and thus, the higher the RLU reading will be. High ATP levels indicate that more organic material—some of which may possibly be harmful -- are present. 

At Meritech, we recommend ATP testing for hand hygiene testing because it:

  • Provides real time results so you can forget the time and hassle required of incubation or microbiological reading in a certified lab. 
  • Involves fewer variables compared to other test methods, increasing reliability and accuracy.
  • Far less expensive and requires fewer materials. 
  • The incidence of outliers (data that cannot be explained) is much lower.

We’ve put together an entire guide to help you understand and begin ATP testing for handwashing at your facility: 

Download the ATP Testing Guide

ASTM E1174 or "Glove Juice Test" Methodology

Meritech has conducted 30+ efficacy studies in a 3rd party, FDA-certified lab utilizing the ASTM (American Society of Testing and Measures) method for hand hygiene testing that is mandated by the FDA in the Guidelines for Healthcare Hand Hygiene TFM. The ASTM E1174 methodology is the only standard in the United States for validating hand hygiene effectiveness. 

ASTM E1174 uses the “Glove Juice Test Methodology” which is administered in a controlled environment that minimizes the variables that affect skin hygiene testing. During a hand hygiene validation process using an ASTM E1174 or Glove Juice Method, sterile gloves are put on the subject after their hands have been exposed to high levels of pathogens. A solution is then added to the gloves for sampling that tells us the concentration of pathogens on the subject’s hands. The hands are then washed using the chosen hand hygiene methodology and the test is performed again to determine pathogen reduction. You can see an example of this sampling procedure in the video below: 

 

Unfortunately, while this is one of the most common and best test methodologies for handwashing validation, it cannot be performed with any level of accuracy in a “field” environment such as in a food processing facility because not all environmental factors can be controlled as they are in a lab. This is why we recommend the ATP testing methodology described above for handwashing validation within facilities. 

Finger press / Agar plate testing for hand hygiene efficacy

Microbiologist holding a Petri dish with bacteria, horizontalAgar plating involves taking a fingerprint from a test subject and measuring the number of colony forming units (CFUs) present on the sample.  While it may sound simple, this method is the least accurate and least effective for measuring handwashing efficacy for several reasons. First, it is difficult to neutralize an antimicrobial agent that has been applied to the fingers, which often results in a “false positive” reading – the plate appears to be cleaner than it actually is on the surface of the skin because antimicrobials in the soap continue to kill organisms after being plated. 

Second, it is very difficult to “read” a plate (i.e., count the CFUs) and extrapolate some sort of result as there is no way to compare pre-wash CFU levels to post-wash levels. Without a comparison, there is no way to determine the CFU reduction of a hand hygiene event provided  as there will always be organisms growing on the plate and there is no way to distinguish between harmful vs. natural organisms with the fingertip method. 

Swabs & test media for handwashing method validation 

Swabs and test media can be used in a hand hygiene validation protocol, but these methods are not suitable for regular validation. Test swabs that are designed to measure levels of CFUs on hard surfaces should not be used to verify that those particular pathogens (e.g., listeria, salmonella, other) are also not present on employees hands, shoes, garments. This test is also timely and requires incubation and identification of the microbes in a lab setting.

 

Each of the testing methods above can be used to validate the efficacy of the handwashing method used at your facility. At Meritech we have conducted several efficacy studies on our CleanTech® Automated Handwashing Stations through 3rd party labs to ensure more than 99.9% of pathogen removal with each 12 second hand wash. For more information, download our efficacy studies or contact our team

Topics:Hand Hygiene Resources

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