A suggested sampling algorithm for use with ATP testing in cleanliness measurement

Introduction: Rapid Adenosine Triphosphate (ATP) testing is becoming a commonly used method to measure cleanliness on reusable medical devices and healthcare environmental surfaces. Unfortunately, ATP testing devices suffer from inherent variability from a number of sources including imprecision in ATP measurement. Method: This paper proposes a new sampling algorithm which reduces the impact of inherent variability and thus improves decision making when using ATP testing. Conclusion: This algorithm can be applied across a variety of applications to provide more reliable data on measurable cleanliness standards for both medical devices and environmental surfaces. Formal trials using the new ATP sampling algorithm are required

Failure analysis in the identification of synergies between cleaning monitoring methods

Background The 4 monitoring methods used to manage the quality assurance of cleaning outcomes within health care settings are visual inspection, microbial recovery, fluorescent marker assessment, and rapid ATP bioluminometry. These methods each generate different types of information, presenting a challenge to the successful integration of monitoring results. A systematic approach to safety and quality control can be used to interrogate the known qualities of cleaning monitoring methods and provide a prospective management tool for infection control professionals. We investigated the use of failure mode and effects analysis (FMEA) for measuring failure risk arising through each cleaning monitoring method. Methods FMEA uses existing data in a structured risk assessment tool that identifies weaknesses in products or processes. Our FMEA approach used the literature and a small experienced team to construct a series of analyses to investigate the cleaning monitoring methods in a way that minimized identified failure risks. Results FMEA applied to each of the cleaning monitoring methods revealed failure modes for each. The combined use of cleaning monitoring methods in sequence is preferable to their use in isolation. Conclusions When these 4 cleaning monitoring methods are used in combination in a logical sequence, the failure modes noted for any 1 can be complemented by the strengths of the alternatives, thereby circumventing the risk of failure of any individual cleaning monitoring method

Sampling plans for use of rapid adenosine triphosphate (ATP) monitoring must overcome variability or suffer statistical invalidity

To the Editor—We write with respect to the article by Visrodia et al. on using a commercial rapid adenosine triphosphate (ATP) device for validation of cleaning of flexible gastroendoscopes. The importance of timeliness in quality assurance testing in this device area is critical owing to the time pressures on the use of the gastroendoscopes by clinical staff involved in patient care. The work is a useful additional contribution to this growing field of use for ATP devices.2 Nonetheless, we highlight concerns with 2 aspects of the method adopted within the work by Visrodia et al

Reliability testing for portable adenosine triphosphate bioluminometers

Measurement of adenosine triphosphate (ATP) using portable bioluminometers has been adapted from the food manufacturing sector, and it has been suggested that it could be used as an indicator of surface soiling or cleanliness in hospital settings.1 Some healthcare authorities are considering the use of portable ATP bioluminometers as a tool for standard setting for surface cleanliness to improve cleaning standards.2 Central to this approach is the use of a commonly accepted level of detected ATP—expressed as relative light units (RLUs)—that may be used as a surrogate for underlying soiling, including the presence of pathogenic microorganisms.3 It has been demonstrated that improvements can be made to cleaning processes with fluorescent markers through a simpler approach that provides a qualitative efficiency measurement of the cleaning process.4 Measurement of surface hygiene using ATP bioluminometers is thought to provide a more quantitative surrogate of surface cleanliness.5 A proposed ATP/RLU standard for acceptable cleanliness has been revised from 500 RLUs, originally suggested by Griffith et al,1 to 250 RLUs by Lewis et al6 and most recently to 100 RLUs by Mulvey et al.7 However, a close examination of the references reveals that different brands of ATP bioluminometers were used to establish the data in each reference—a substantial problem given that each unit reads on a different relative scale.8 Even with a single branded unit variable results are observed without a clear explanation.9 There also is debate over the validity of using ATP measurement as an analogue for surface soils and the presence of pathogenic microorganisms.10 Our aim was to validate the reliability of measurement of 3 commonly available brands of portable ATP bioluminometers. Two of the brands selected (Hygiena and 3M) feature prominently in the published literature, and the third brand (Kikkoman) provided a different approach to luciferase presentation (a powder rather than a preprepared liquid)

The comparative performance of three brands of portable ATP-bioluminometer intended for use in hospital infection control

Background: Portable adenosine triphosphate (ATP)-bioluminometers have been used in the food industry to monitor the effectiveness of surface cleaning but their intended use in hospital infection control suggests a need for instrument validation to confirm effective technology transfer. Methods: The performance of three readily available brands of portable bioluminometer was compared in terms of their ability to generate relative light units (RLU) from a range of standard ATP solutions. Quality control of standards was carried out using high pressure liquid chromatography (HPLC). Results: There was no significant difference (Ρ=0.05) in the ability of different meters to effectively measure hygiene change on a log scale in a central measurement range of 0.001 to 1.0mgL-1 ATP. Outside this range meter performance deteriorated, with the possibility of individual and comparative measurement error. No out-of-range warning system existed for any of the meters. While different brands generated widely different log10RLU values for fixed quantities of ATP in this range, curve similarities suggested standardisation possibilities to enable comparison of results. Testing at a higher level of resolution in the 0.0001 to 0.002mgL-1 ATP range proximate to a proposed 100 RLU cleaning benchmark also revealed poor repeatability as a potential for measurement error. Conclusions: Portable ATP-bioluminometers, when used to indicate surface cleaning effectiveness, demonstrate reliable performance when measuring over a very wide range of ATP concentrations. Monitoring hygiene in terms of an absolute threshold value such as a cleaning benchmark may, however, be invalid as a concept when using existing portable ATP-bioluminometer technology

The perennial problem of variability in adenosine triphosphate (ATP) tests for hygiene monitoring within healthcare settings

Objective. To investigate the reliability of commercial ATP bioluminometers and to document precision and variability measurements using known and quantitated standard materials. Methods. Four commercially branded ATP bioluminometers and their consumables were subjected to a series of controlled studies with quantitated materials in multiple repetitions of dilution series. The individual dilutions were applied directly to ATP swabs. To assess precision and reproducibility, each dilution step was tested in triplicate or quadruplicate and the RLU reading from each test point was recorded. Results across the multiple dilution series were normalized using the coefficient of variation. Results. The results for pure ATP and bacterial ATP from suspensions of Staphylococcus epidermidis and Pseudomonas aeruginosa are presented graphically. The data indicate that precision and reproducibility are poor across all brands tested. Standard deviation was as high as 50% of the mean for all brands, and in the field users are not provided any indication of this level of imprecision. Conclusions. The variability of commercial ATP bioluminometers and their consumables is unacceptably high with the current technical configuration. The advantage of speed of response is undermined by instrument imprecision expressed in the numerical scale of relative light units (RLU)

Reply to Roady

[No abstract available

An assessment of effectiveness of cleaning critical surfaces in elementary schools

Inadequate cleaning and maintenance practices in schools, compounded by the effects of emerging infectious disease agents, can put students' health at increased risk. Adenosine triphosphate (ATP) is a useful tool for establishing pre- and post-cleaning residual surface contamination on high contact surfaces. Fluorescent markers (FM) are also used frequently in the cleaning industry as a means to determine whether or not a surface has been "touched" as an indication of thoroughness of cleaning. This paper provides parallel pre- and post-cleaning data of FM pass (FM removed) and FM fail (FM still present after cleaning) tests on surfaces, as compared to % reduction in ATP values from 34 schools (17 control and 17 study schools) over a one year school period. Based on these preliminary results, using a FM may not necessarily relate to a reduction in ATP residual on the surface, and thus may serve as an efficiency measure of cleanliness without indicating cleaning effectiveness

Response to Russotto et al

Letter to the editor

Staphylococcus aureus dry-surface biofilms are more resistant to heat treatment than traditional hydrated biofilms

Background: The importance of biofilms to clinical practice is being increasingly realized. Biofilm tolerance to antibiotics is well described but limited work has been conducted on the efficacy of heat disinfection and sterilization against biofilms. Aim: To test the susceptibility of planktonic, hydrated biofilm and dry-surface biofilm forms of Staphylococcus aureus, to dry-heat and wet-heat treatments. Methods: S. aureus was grown as both hydrated biofilm and dry-surface biofilm in the CDC biofilm generator. Biofilm was subjected to a range of temperatures in a hot-air oven (dry heat), water bath or autoclave (wet heat). Findings: Dry-surface biofilms remained culture positive even when treated with the harshest dry-heat condition of 100 C for 60 min. Following autoclaving samples were culture negative but 62-74% of bacteria in dry-surface biofilms remained alive as demonstrated by live/dead staining and confocal microscopy. Dry-surface biofilms subjected to autoclaving at 121̊C for up to 30 min recovered and released planktonic cells. Recovery did not occur following autoclaving for longer or at 134̊C, at least during the time-period tested. Hydrated biofilm recovered following dry-heat treatment up to 100̊C for 10 min but failed to recover following autoclaving despite the presence of 43-60% live cells as demonstrated by live/dead staining. Conclusion: S. aureus dry-surface biofilms are less susceptible to killing by dry heat and steam autoclaving than hydrated biofilms, which are less susceptible to heat treatment than planktonic suspensions