Being a Clean Freak, I'm passionate about building the
science behind cleaning and disinfection.
The infection prevention guidelines we follow are built around
science-based evidence so I certainly agree that the more we study,
investigate, hypothesize, pontificate the more we will learn and improve upon
our current practices. However, we need
to understand the limitations of some of the methods we use to build the
science.
The use of ATP meters is certainly gaining popularity and
don't get me wrong, I think there is a place for their use, but in designing
studies to help further the science behind cleaning and disinfection we MUST
understand the limitations of some of the methods we are using. In October of last year, we posted a blog on
ATP (ATP – a microbiologist’s square peg) the impetus of which was based on the
realization that Environmental Service Managers and Infection Preventionists
believed that ATP can be used to compare cleaning and disinfection efficacy
between different disinfectants.
don't get me wrong, I think there is a place for their use, but in designing
studies to help further the science behind cleaning and disinfection we MUST
understand the limitations of some of the methods we are using. In October of last year, we posted a blog on
ATP (ATP – a microbiologist’s square peg) the impetus of which was based on the
realization that Environmental Service Managers and Infection Preventionists
believed that ATP can be used to compare cleaning and disinfection efficacy
between different disinfectants.
Truth is ATP CANNOT be used to compare the cleaning and
disinfection efficacy between different disinfectant chemistries. If you talk to suppliers of ATP meters - they
agree. This is not the intended use and
such use could lead you down a slippery slope of unintended consequences. Since October of last year our research team
has worked with several of the leading companies who supply ATP meters and at
the CHICA-Canada conference held at the beginning of this month presented our
findings with a research poster "Evaluating market leading ATP meters for the reliability of their test results as measurement tools for surface cleanness in Healthcare applications".
The following summarizes the findings:
disinfection efficacy between different disinfectant chemistries. If you talk to suppliers of ATP meters - they
agree. This is not the intended use and
such use could lead you down a slippery slope of unintended consequences. Since October of last year our research team
has worked with several of the leading companies who supply ATP meters and at
the CHICA-Canada conference held at the beginning of this month presented our
findings with a research poster "Evaluating market leading ATP meters for the reliability of their test results as measurement tools for surface cleanness in Healthcare applications".
The following summarizes the findings:
ATP can be used as an indicator to determine cleanliness
of a surface, however there are a number of limitations with its use:
of a surface, however there are a number of limitations with its use:
1. The measurement of ATP is not standardized:
1. Each ATP meter
has different detection limits therefore a statistical analysis must be done to ensure that consistent results can
be achieved.
has different detection limits therefore a statistical analysis must be done to ensure that consistent results can
be achieved.
2. No ATP meter
is the same.
is the same.
3. Each ATP meter
has its own minimum detection limit – if the contamination of a surface is below a certain level the ATP meter may
not be able to detect it. This means that a surface
can have significant contamination and have an ATP reading of zero!
has its own minimum detection limit – if the contamination of a surface is below a certain level the ATP meter may
not be able to detect it. This means that a surface
can have significant contamination and have an ATP reading of zero!
2. Chemical interference from residual cleaners and
disinfectants has an effect on the ATP readings:
disinfectants has an effect on the ATP readings:
1. Disinfectant
and cleaning chemistries can either quench – causing false low readings as seen with bleach or enhance – causing
false high readings as seen with quats and anionic
surfactants (detergents).
and cleaning chemistries can either quench – causing false low readings as seen with bleach or enhance – causing
false high readings as seen with quats and anionic
surfactants (detergents).
2. There are two
possible explanations for quenching:
possible explanations for quenching:
a. The disinfectant ingredients are breaking the ATP
molecules and thus they are no longer active/detectible;
molecules and thus they are no longer active/detectible;
b. The disinfectant ingredients enter into the enzymatic
reaction from the swab and interfere with the enzymatic pathways for
luminescence production.
reaction from the swab and interfere with the enzymatic pathways for
luminescence production.
3. The level of
quenching (providing false low readings) with sodium hypochlorite (bleach) increases as the concentration of bleach
increases.
quenching (providing false low readings) with sodium hypochlorite (bleach) increases as the concentration of bleach
increases.
4. These chemical
interferences can give misleading results that can have significant implications on interpretation of data.
interferences can give misleading results that can have significant implications on interpretation of data.
3. There is conflicting evidence to support a correlation
between RLUs and the bacteria left on a surface (the amount of bacteria is
determined by Colony Forming Units or CFUs):
between RLUs and the bacteria left on a surface (the amount of bacteria is
determined by Colony Forming Units or CFUs):
1. Some studies
show a correlation between RLUs and CFUs, other studies show a loose correlation while other studies have not
examined the correlation between the two.
show a correlation between RLUs and CFUs, other studies show a loose correlation while other studies have not
examined the correlation between the two.
I completely stand behind the fact that ATP can be used
to assess the effectiveness of a cleaning program but if used for quality
control measures the results should be cautiously interpreted and at least
periodically checked with plate counting methods. As illustrated in our study, depending on the
sensitivity of the ATP meter, even high levels of contamination on the surface
may not be detected. This can lead to a
false confidence in the cleaning program.
Most importantly, ATP CANNOT AND SHOULD NOT be used to compare cleaning or disinfection
effectiveness between difference chemistries.
Different chemistries have distinctive quenching or enhancing effects on
ATP readings making meaningful and accurate evaluations between cleaning/disinfectant
chemistries unreliable as the RLU
readings do not account for such differences.
to assess the effectiveness of a cleaning program but if used for quality
control measures the results should be cautiously interpreted and at least
periodically checked with plate counting methods. As illustrated in our study, depending on the
sensitivity of the ATP meter, even high levels of contamination on the surface
may not be detected. This can lead to a
false confidence in the cleaning program.
Most importantly, ATP CANNOT AND SHOULD NOT be used to compare cleaning or disinfection
effectiveness between difference chemistries.
Different chemistries have distinctive quenching or enhancing effects on
ATP readings making meaningful and accurate evaluations between cleaning/disinfectant
chemistries unreliable as the RLU
readings do not account for such differences.
If you're looking to change cleaning and disinfecting
products and are looking at the use of ATP to determine which product works
better I hope you'll think twice!
products and are looking at the use of ATP to determine which product works
better I hope you'll think twice!
Bugging Off!
Nicole
