Chris Derry

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.

Engaging communities of practice for risk communication in the Hawkesbury Water Recycling Scheme

Sustainable conceptions of urban water management include the recycling of treated effluent and urban stormwater as valued resources. The future acceptability and confidence in these initiatives depends upon pluralist approaches for communicating and managing associated risks. The case study described here focuses on risk communication and management associated with the Hawkesbury Water Recycling Scheme near Sydney, Australia. Action research strategies with communities of practice have contributed to the co-construction of effective risk management strategies. These strategies are both informed by differentiated perspectives and practices, and supported by a network of coordinated information. The focus on communities of practice is discussed in relation to pragmatic approaches to action research and systemic inquiry, along with the implications for the role of universities in engaging with the complex issues of sustainability.

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.

Regrowth of enterococci indicator in an open recycled-water impoundment.

The purpose of the research was to assess the potential for enterococci faecal-indicator to regrow in recycled water while under environmentally-open storage. Regrowth would result in false-positive indicator results with possible downgrading, rejection or over-chlorination of recycled water. The research setting was the main 93-megalitre storage impoundment of the Hawkesbury Water Recycling Scheme in Sydneys North West, receiving tertiary treated (chlorinated) effluent from the Richmond sewage treatment plant. The water is used to irrigate horticultural food crops, pasture for dairy cattle, sheep, deer and horses, and for the maintenance of lawns and sports fields. Highly significant positive relationships were noted in multivariate analysis between indicator counts and the growth factors atmospheric temperature and UV254 unfiltered as proxy for total organic carbon (p=0.001 and 0.003 respectively). Nitrate and phosphate did not show significant relationships suggesting that these nutrients may not be growth-limiting at levels found in recycled water. Rainfall and wild duck presence did not appear to have an impact on enterococcal growth in the study. The overall predictive power of the regression model was shown to be highly significant (p=0.001). These findings will assist in recycled water monitoring and the revision of guidelines, with potential for the reduction of the chlorination by-product burden on the environment. A formula derived for the relationship between the indicator and atmospheric temperature could be used in food-production and climate-change modelling.

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 pilot study into locating the bad bugs in a busy intensive care unit

BACKGROUND The persistence of multidrug-resistant organisms (MDROs) within an intensive care unit (ICU) possibly contained within dry surface biofilms, remains a perplexing confounder and is a threat to patient safety. Identification of residential locations of MDRO within the ICU is an intervention for which new scientific approaches may assist in finding potential MDRO reservoirs. METHOD This study investigated a new approach to sampling using a more aggressive environmental swabbing technique of high-touch objects (HTOs) and surfaces, aided by 2 commercially available adenosine triphosphate (ATP) bioluminometers. RESULTS A total of 13 individual MDRO locations identified in this pilot study. The use of ATP bioluminometers was significantly associated with the identification of 12 of the 13 individual MDRO locations. The MDRO recovery and readings from the 2 ATP bioluminometers were not significantly correlated with distinct cutoffs for each ATP device, and there was no correlation between the 2 ATP devices. CONCLUSION The specific MDRO locations were not limited to the immediate patient surroundings or to any specific HTO or type of surface. The use of ATP testing helped rapidly identify the soiled locations for MDRO sampling. The greatest density of positive MDRO locations was around and within the clinical staff work station.

Considerations in establishing a health risk management system for effluent irrigation in modern agriculture

Treated sewage effluent is a valuable and reliable agricultural irrigation resource in areas of low or unpredictable rainfall. Its importance is likely to grow under the influence of global climate change. The use of this resource is not, however, without health risk which is difficult to estimate using data from standard microbial and physicochemical monitoring alone. A health risk management system enables risk reduction through hazard identification, risk characterisation and analysis, strategy development and implementation, intervention assessment and risk communication. In this process data from both risk assessment and routine technological monitoring are integrated to yield synergies. In addition to meaningful information is a need for intersectoral collaboration in making the right decisions. This can be achieved through the establishment of a multidisciplinary risk management team with members drawn from communities of practice. Examples from the University of Western Sydney (UWS) experience are...

Examples of coping strategies with agrometeorological risks and uncertainties for Integrated Pest Management

Some risks in the agricultural sector are unavoidable while others can be managed. Agrometeorological risks in the farming sector include the temporal and spatial variability of rainfall, temperature, evaporation and, in climate change scenarios, atmospheric carbon dioxide levels. While such factors may impact directly on plant growth and development they can also exert an important indirect effect by influencing the life cycles of plant diseases and pests. In addition they may have a profound influence on attempts to control such pests, as is seen when an unexpected rainfall event causes dilution or early hydrolysis of a surface pesticide, or when hail damage opens the way for mould, bacterial or insect attack. Integrated pest management (IPM) must take into account such risks if crop damage is to be minimized. The implications of agrometeorological risk studies in countries such as Australia offer not only local perspectives on IPM but also provide information for improved crop profitability, natural resource usage and agricultural sustainability in other countries, where a critical relationship between crop success, regional food security and human survival may exist.

Wastewater treatment by a modular, domestic-scale reedbed system for safe horticultural irrigation.

The aim of the study was to assess the sequential treatment performance of a commercial, domestic-scale modular reedbed system intended to provide safe horticultural irrigation water. Previously only mechanical treatment systems involving forced aeration with subsequent disinfection, usually by tablet-chlorination, had been accredited in Australia. The modular design of the hybrid, subsurface-flow reedbed system offered 5 control points where monitoring and management of the treatment train could be carried out. Ten chemical parameters (chemical and biochemical oxygen demand, total organic carbon, total Kjeldahl nitrogen, ammonia nitrogen, nitrite nitrogen, nitrate nitrogen, total nitrogen, dissolved oxygen percentage saturation and suspended solids) and 4 microbial parameters (total coliform, Escherichia coli, enterococci and Clostridium perfringens) reached satisfactory levels as a result of the treatment process. Health requirements for safe horticultural irrigation were met by the outlet of the second reedbed, providing a high level of treatment-backup capacity in terms of the remaining 2 reedbeds. This suggested that chlorination was a redundant backup precaution in treating irrigation water to the acceptable regional guideline level for all horticultural uses, including the spray irrigation of salad crops eaten raw.