Trevor Glasbey

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

Abstract 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 ( P = 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 1.0 mg L –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 log 10 RLU 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 0.002 mg L –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.

A new dry-surface biofilm model: An essential tool for efficacy testing of hospital surface decontamination procedures.

UNLABELLED The environment has been shown to be a source of pathogens causing infections in hospitalised patients. Incorporation of pathogens into biofilms, contaminating dry hospital surfaces, prolongs their survival and renders them tolerant to normal hospital cleaning and disinfection procedures. Currently there is no standard method for testing efficacy of detergents and disinfectants against biofilm formed on dry surfaces. AIM The aim of this study was to develop a reproducible method of producing Staphylococcus aureus biofilm with properties similar to those of biofilm obtained from dry hospital clinical surfaces, for use in efficacy testing of decontamination products. The properties (composition, architecture) of model biofilm and biofilm obtained from clinical dry surfaces within an intensive care unit were compared. METHODS The CDC Biofilm Reactor was adapted to create a dry surface biofilm model. S. aureus ATCC 25923 was grown on polycarbonate coupons. Alternating cycles of dehydration and hydration in tryptone soy broth (TSB) were performed over 12 days. Number of biofilm bacteria attached to individual coupons was determined by plate culture and the coefficient of variation (CV%) calculated. The DNA, glycoconjugates and protein content of the biofilm were determined by analysing biofilm stained with SYTO 60, Alexa-488-labelled Aleuria aurantia lectin and SyproOrange respectively using Image J and Imaris software. Biofilm architecture was analysed using live/dead staining and confocal microscopy (CM) and scanning electron microscopy (SEM). Model biofilm was compared to naturally formed biofilm containing S. aureus on dry clinical surfaces. RESULTS The CDC Biofilm reactor reproducibly formed a multi-layered, biofilm containing about 10(7) CFU/coupon embedded in thick extracellular polymeric substances. Within run CV was 9.5% and the between run CV was 10.1%. Protein was the principal component of both the in vitro model biofilm and the biofilms found on clinical surfaces. Continued dehydration and ageing of the model biofilm for 30 days increased the % of protein, marginally decreased gylcoconjugate % but reduced extracellular DNA by 2/3. The surface of both model and clinical biofilms was rough reflecting the heterogeneous nature of biofilm formation. The average maximum thickness was 30.74±2.1 μm for the in vitro biofilm model and between 24 and 47 μm for the clinical biofilms examined. CONCLUSION The laboratory developed biofilm was similar to clinical biofilms in architecture and composition. We propose that this method is suitable for evaluating the efficacy of surface cleaners and disinfectants in removing biofilm formed on dry clinical surfaces as both within run and between run variation was low, and the required equipment is easy to use, cheap and readily available.

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).

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.

Reliability testing for portable adenosine triphosphate bioluminometers.

Bloomberg School of Public Health, Baltimore, Maryland; 2. Division of Infectious Diseases, Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland; and Healthcare Epidemiology and Infection Control, Johns Hopkins Health System, Baltimore, Maryland; 3. Department of Pathology, Johns Hopkins Medical Institutions, Baltimore, Maryland. Address correspondence to Alain Labrique, PhD, MHS, MS, 615 North Wolfe Street E5543, Baltimore, MD 21205 (alabriqu@jhsph.edu). Received September 30, 2012; accepted December 28, 2012; electronically published April 9, 2013. Infect Control Hosp Epidemiol 2013;34(5):536-538

A new sampling algorithm demonstrates that ultrasound equipment cleanliness can be improved

Background: Australia has established guidelines on cleaning for reusable ultrasound probes and accompanying equipment. This is a preliminary study investigating cleanliness standards of patient‐ready ultrasound equipment in 5 separate health care facilities within a major city. Methods: The cleanliness was assessed using rapid adenosine triphosphate (ATP) testing used with a sampling algorithm which mitigates variability normally associated with ATP testing. Each surface was initially sampled in duplicate for relative light units (RLUs) and checked for compliance with literature recommended levels of cleanliness (<100 RLUs). Triplicate sampling was undertaken where necessary. A cleaning intervention step (CIS) followed using a disposable detergent wipe, and the surface was retested for ATP. Results: There were 253 surfaces tested from the 5 health care facilities with 26% (66/253) demonstrating either equivocal or apparent lack of cleanliness. The CIS was conducted on 148 surfaces and demonstrated that for >91% (135/148) of surfaces, the cleaning standards could be improved significantly (P > .001). For 6% (9/148) of devices and surfaces, the CIS needed to be repeated at least once to achieve the intended level of cleanliness (<25 RLUs). Conclusions: This study indicates that ATP testing is an effective, real‐time, quality assurance tool for cleanliness monitoring of ultrasound probes and associated equipment.

The importance of stakeholder consultation for infection control guidelines

First, is the recommendation of the use of anionic detergents in the chapter on prions and related diseases (Chapter 31). In the original there were only two references to anionic detergents for cleaning. However, an investigation of the revised chapter on prions repeatedly and widely indicates the use of anionic detergents for pre-cleaning of potentially contaminated instruments. The recommendations are unreferenced and contradict the literature, which is confused at best about anionic detergents as a mandated step. We cannot determine where the original reference arose.

Flawed recommendations on surface hygiene within the existing Interim Influenza Pandemic National Infection Control Guidelines

Abstract The Interim Infection Control Guidelines for Pandemic Influenza in Healthcare and Community Settings, published by the Australian Commonwealth Government in 2006, have been reviewed and found to contain recommendations that, if they were made by a private organisation, would be potentially illegal under the Therapeutic Goods Act 1989, and also raise some concern in relation to occupational health and safety. The guidelines also fail to recommend the use of disinfecting products with specific claims relating to influenza virus that have been approved by the Therapeutic Goods Agency.