Air sampling and ATP bioluminescence for quantitative detection of airborne microbes

Exposure to bioaerosol contamination has detrimental effects on human health. Recent advances in ATP bioluminescence provide more opportunities for the quantitative detection of bioaerosols. Since almost all active organisms can produce ATP, the amount of airborne microbes can be easily measured by detecting ATP-driven bioluminescence. The accurate evaluation of microorganisms mainly relies on following the four key steps: sampling and enrichment of airborne microbes, lysis for ATP extraction, enzymatic reaction, and measurement of luminescence intensity. To enhance the effectiveness of ATP bioluminescence, each step requires innovative strategies and continuous improvement. In this review, we summarized the recent advances in the quantitative detection of airborne microbes based on ATP bioluminescence, which focuses on the advanced strategies for improving sampling devices combined with ATP bioluminescence. Meanwhile, the optimized and innovative strategies for the remaining three key steps of the ATP bioluminescence assay are highlighted. The aim is to reawaken the prosperity of ATP bioluminescence and promote its wider utilization for efficient, real-time, and accurate detection of airborne microbes.

A novel phagomagnetic separation-ATP bioluminescence (PhMS-BL) for rapid and sensitive detection of viable Vibrio parahaemolyticus in aquatic product

Detection of viable Vibrio parahaemolyticus (V. parahaemolyticus) is a major challenge due to its significant risk to food safety and human health. Herein, we developed a phagomagnetic separation-ATP bioluminescence (PhMS-BL) assay based on phage VPHZ6 for rapid and sensitive detection of viable V. parahaemolyticus. Phage as a recognition element was coupled to magnetic beads to capture and enrich V. parahaemolyticus, shortening detection time and improving method sensitivity. The intracellular ATP released by chemical lysis using CTAB was quantified using firefly fluorescein-adenosine triphosphate bioluminescence system to detect viable bacteria. So, PhMS-BL method was able to detect V. parahaemolyticus in a linear range of 2.3 × 102 to 1.3 × 107 CFU mL-1, with a detection limit of 78 CFU mL-1 within 15 min. It is successfully applied to detect V. parahaemolyticus in spiked lake water, lobster tail meat, and clam meat. The developed detection strategy can rapidly and sensitively detect viable V. parahaemolyticus in food matrixes.

Evaluation of ATP bioluminescence for rapid determination of cleanliness of livestock trailers after a commercial wash

Pathogens such as porcine epidemic diarrhea virus (PEDV), porcine reproductive and respiratory syndrome (PRRSV), and E. coli are known to spread by contaminated vehicles and equipment. Pork producers have adopted trailer wash policies where each trailer is washed, disinfected, and dried before it can return to a farm. Cleanliness of livestock trailers after washing is determined by visual inspection rather than any objective method. Adenosine triphosphate (ATP) bioluminescence is used in many industries to provide real-time feedback on surface cleanliness through the detection of ATP from organic sources. That same technology may provide trailer wash facilities a way of objectively characterizing a livestock trailer's suitability to return to a farm after washing. Two ATP luminometers (3M Clean-Trace and Neogen AccuPoint) were used to estimate the correlation between ATP bioluminescence readings and aerobic bacterial plate counts (APCs) from sampled surfaces and to determine locations within a livestock trailer that can accurately estimate surface cleanliness. Five locations in livestock trailers were evaluated. Those locations included the nose access door (NAD), back door flush gate, rear side access door (RSAD), belly flush gate (BFG), and belly side access door (BSAD). There was a positive log-log association between the two luminometers (r = 0.59, P < 0.01). Every log unit increase in one unit, resulted in a 0.42 log increase (P < 0.01) in the other unit. ATP can come from bacteria, yeasts, molds, and manure. There was a poor association (r ≥ 0.10, P ≥ 0.02) between APCs and the ATP luminometers. Still, an increase in relative light units (RLUs) resulted in a corresponding increase in colony-forming units. The greatest area of surface contamination measured by APC was the NAD. RLUs were also greater in the NAD compared to the RSAD, the BFG, and the BSAD (P ≤ 0.01). Because APCs and luminometer RLUs provided similar outcomes, statistical process control charts were developed to determine control limits for RLUs. This provides real-time feedback to trailer wash workers in determining cleanliness outcomes for livestock trailers. These data suggest that ATP bioluminescence can be a reliable method to monitor cleaning effectiveness in livestock trailers. Bioluminescence is a monitoring tool that should be used in conjunction with microbial methods to monitor procedures for cleaning and disinfection.

Hygiene management practices and adenosine triphosphate luminometry of feeding equipment in preweaning calves on dairy farms in Quebec, Canada

The objective of this study was to describe the cleaning practices currently used for preweaning calves on dairy farms in Quebec, Canada. In addition, contamination of feeding equipment for preweaning calves was described using ATP (expressed as relative light units, RLU), visual assessment, and bacteriological analysis. A questionnaire was administered on 50 commercial dairy farms in Quebec, Canada, regarding the self-reported cleaning protocol used for feeding equipment of preweaning calves. During the visit, a visual score was given to the feeding equipment available at the farm. Afterward, ATP luminometry measurements were obtained using Hygiene UltraSnap and MicroSnap swabs (Hygiene, Camarillo, CA), and the liquid rinsing technique for buckets, nipples, bottles, esophageal tube feeders (ET), the tube of automatic milk feeders (AMF), water samples, and milk replacer. An additional direct swabbing technique was performed on buckets and nipples. The fluid retrieved from the liquid rinsing technique was also used to determine the total bacterial count (TBC) and total coliform count. Based on the bacteriological analysis, optimal RLU cutoff values to determine contamination were obtained. The median (interquartile range) luminometer measurements using the UltraSnap and direct technique for buckets and nipples were 2,082 (348-7,410) and 3,462 (462-7,518) RLU, respectively; and, using the liquid technique for bottles, ET, AMF, water, and milk replacer were 43 (4-974), 15 (4-121), 301 (137-1,323), 190 (71-358), and 94 (38-218) RLU, respectively. Overall, for all equipment and both techniques used, higher RLU values were seen in UltraSnap samples compared with MicroSnap samples. Additionally, for buckets and nipples, higher RLU values were obtained for the direct swabbing method compared with the liquid sampling method for both swabs used. No differences in the level of contamination were seen between the different feeding equipment used within a farm. Overall, a higher correlation with bacteriological results was noticed for ATP luminometry compared with the visual score, with a high correlation for nipples and bottles using the UltraSnap and liquid technique. Based on the classification of "contaminated" (TBC ≥100,000 cfu/mL) or "not contaminated" (TBC <100,000 cfu/mL), optimal ATP luminometer cutoff values for buckets, nipples, bottles, AMF, water, and milk replacer were 798, 388, 469, 282, 1,432, and 93 RLU, respectively. No clear association was found between ATP measurements and the self-reported cleaning protocol. This study gave new insights into the current cleaning procedures and contamination of feeding equipment for preweaning calves on dairy farms in Quebec. In addition, ATP luminometry cutoff values could help benchmark farms regarding cleaning practices and provide customized advice, improving the overall hygiene management, and thus the health, of preweaning calves on dairy farms.

A novel strategy for bioaerosol rapid detection based on broad-spectrum high-efficiency magnetic enrichment and separation combined with ATP bioluminescence

Bioaerosol detection technology represented by laser-induced fluorescence (LIF) cannot effectively detect bioaerosols in the presence of interferents such as plant-derived smoke, industrial waste gas, pollen and pollen debris which can produce strong non-biological fluorescence interference. To overcome this drawback, in this study, a novel method based on broad-spectrum high-efficiency magnetic enrichment and separation combined with adenosine triphosphate (ATP) bioluminescence was proposed for Escherichia coli (E. coli) bioaerosols rapid detection. First, E. coli bioaerosols mixed with interferents were collected. Core-shell Fe3O4@Polydopamine@Polyethyleneimine magnetic particles were used as bioaerosol enrichment materials to enrich E. coli bioaerosol sampling solutions. Subsequently, an ATP bioluminescence assay was performed to determine the concentration of E. coli. A linear relationship was observed between ATP bioluminescence intensity after enrichment and the E. coli bioaerosol concentration in the range of 870-49,098 particles per liter; the bioluminescence intensity measured after enrichment was significantly higher than that before enrichment, and this enrichment method provide a 6-fold better sensitivity in bioaerosol detection. More importantly, this method efficiently enriched and detected bioaerosols in plant-derived smoke. This method can effectively improve the sensitivity of ATP bioluminescence detection, and possesses the advantages of convenient operation and strong anti-interference ability. It also provides a foundation for the effective detection of bioaerosols mixed with interfering substances, and a reference for evaluating the sensitivity and anti-interference of LIF-based instruments.

Comprehensive insights into advances in ambient bioaerosols sampling, analysis and factors influencing bioaerosols composition

While the study of bioaerosols has a long history, it has garnered heightened interest in the past few years, focusing on both culture-dependent and independent sampling and analysis approaches. Observations have been made regarding the seasonal fluctuations in microbial communities and their connection to particular ambient atmospheric factors. The study of airborne microbial communities is important in public health and atmospheric processes. Nevertheless, the establishment of standardized protocols for evaluating airborne microbial communities and utilizing microbial taxonomy as a means to identify distinct bioaerosols sources and seasonal patterns remains relatively unexplored. This article discusses the challenges and limitations of ambient bioaerosols sampling and analysis, including the lack of standardized methods and the heterogeneity of sources. Future prospects in the field of bioaerosols, including the use of high-throughput sequencing technologies, omics studies, spectroscopy and fluorescence-based monitoring to provide comprehensive incite on metabolic capacity, and activity are also presented. Furthermore, the review highlights the factors that affect bioaerosols composition, including seasonality, atmospheric conditions, and pollution levels. Overall, this review provides a valuable resource for researchers, policymakers, and stakeholders interested in understanding and managing bioaerosols in various environments.

Relationship between ATP Bioluminescence Measurements and Microbial Assessments in Studies Conducted in Food Establishments: A Systematic Literature Review and Meta-Analysis

ABSTRACT

Adherence to proper environmental cleaning practices is critical in food establishments. To validate cleanliness, cleaning practices should be routinely monitored, preferably by a rapid, reliable, and cost-effective method. The aim of this study was to determine whether a correlation exists between ATP bioluminescence measurements and selected microbial assessments in studies conducted in food establishments. A systematic literature review and meta-analysis was conducted using the principles of preferred reporting items for systematic reviews and meta-analyses. Twelve online databases and search engines were selected for the review. Peer-reviewed articles published in English between January 2000 and July 2020 were included in the search. From a total of 19 eligible studies, 3 that included Pearson correlation coefficients (r) between ATP bioluminescence measurements and microbial assessments were used for the meta-analysis calculations. Only the fixed-effect model produced a strong correlation because one value dominated the estimates: r = 0.9339 (0.9278, 0.9399). In contrast, both the random effects model, 0.2978 (0.24, 0.3471), and the mixed effects model, r = 0.3162 (-0.0387, 0.6711), indicated a weak relationship between ATP bioluminescence and microbial assessments, with no evidence of a strong correlation. The meta-analysis results indicated no sufficient evidence of a strong correlation between ATP bioluminescence measurements and microbial assessments when applied within food establishments. This lack of evidence for a strong correlation between the results of these two monitoring tools suggests that food establishments cannot depend on only one method. Yet, with immediate feedback and quantification of organic soiling, ATP bioluminescence could be an effective monitoring tool to use in food establishments.

HIGHLIGHTS

Antibacterial Activity Evaluation of ZnO, CuO, and TiO2 Nanoparticles in Solution and Thin Films

This chapter introduces unique methodology of antibacterial activity evaluation of nanoparticles in both solution and thin films. Nanoparticles of ZnO, TiO₂, and CuO are synthesized via the sol-gel method. Antibacterial tests are carried out against Gram-positive Staphylococcus aureus and Gram-negative Escherichia coli bacteria using disk diffusion and bioluminescence. To perform antibacterial tests on thin films and to overcome bacterial strains recuperation on the supports, a new method of bacterial detaching from the slides is developed based on French standard NF EN 14561.

Essential Oils as Alternative Biocides for the Preservation of Waterlogged Archaeological Wood

Waterlogged archaeological wood is exposed to a high risk of biological degradation during the post-excavation phases of storage and restoration. For this reason, often biocides must be used to preserve wooden remains. In the present work three essential oils (cinnamon, wild thyme, and common thyme) were tested as possible alternative biocides to use in the preservation of waterlogged archaeological wood. The oils were first tested in vitro to establish the minimum inhibitory concentration (MIC) and to evaluate the biocidal activity on selected fungal strains. Then, the established MIC was applied on waterlogged archaeological wood samples and during an actual restoration treatment. The effectiveness of the oils was evaluated through cultural analyses, ATP quantification, and next-generation sequencing. The results showed that the oils caused a significant decrease in the vitality of fungal mycelia grown in vitro and of the microbiota present in treated wood and storage water. Furthermore, an influence on the composition of the bacterial communities of treated wood samples was observed. Although further tests are needed to evaluate interferences with the materials used during restoration procedures, essential oils could be considered as a possible alternative to the currently used biocide.

Elimination of Extracellular Adenosine Triphosphate for the Rapid Prediction of Quantitative Plate Counts in 24 h Time-Kill Studies against Carbapenem-Resistant Gram-Negative Bacteria

Traditional in vitro time-kill studies (TKSs) require viable plating, which is tedious and time-consuming. We used ATP bioluminescence, with the removal of extracellular ATP (EC-ATP), as a surrogate for viable plating in TKSs against carbapenem-resistant Gram-negative bacteria (CR-GNB). Twenty-four-hour TKSs were conducted using eight clinical CR-GNB (two Escherichia coli, two Klebsiella spp., two Acinetobacter baumannii, two Pseudomonas aeruginosa) with multiple single and two-antibiotic combinations. ATP bioluminescence and viable counts were determined at each timepoint (0, 2, 4, 8, 24 h), with and without apyrase treatment. Correlation between ATP bioluminescence and viable counts was determined for apyrase-treated and non-apyrase-treated samples. Receiver operator characteristic curves were plotted to determine the optimal luminescence threshold to discriminate between inhibitory/non-inhibitory and bactericidal/non-bactericidal combinations, compared to viable counts. After treatment of bacteria with 2 U/mL apyrase for 15 min at 37 °C, correlation to viable counts was significantly higher compared to untreated samples (p < 0.01). Predictive accuracies of ATP bioluminescence were also significantly higher for apyrase-treated samples in distinguishing inhibitory (p < 0.01) and bactericidal (p = 0.03) combinations against CR-GNB compared to untreated samples, when all species were collectively analyzed. We found that ATP bioluminescence can potentially replace viable plating in TKS. Our assay also has applications in in vitro and in vivo infection models.

Implications of Adenylate Metabolism in Hygiene Assessment: A Review

The assessment of a hygienic state or cleanliness of contact surfaces has significant implications for food and medical industries seeking to monitor sanitation and exert improved control over a host of operations affecting human health. Methods used to make such assessments commonly involve visual inspections, standard microbial plating practices, and the application of ATP-based assays. Visual methods for inspection of hygienic states are inherently subjective and limited in efficacy by the accuracy of human senses, the degree of task-specific work experience, and various sources of human bias. Standard microbial swabbing and plating techniques are limited in that they require hours or even days of incubation to generate results, with such steps as enrichment and colony outgrowth resulting in delays that are often incompatible with manufacturing or usage schedules. Rapid in conduct and considered more objective in operation than visual or tactile inspection techniques, swabbing surfaces using ATP-based assessments are relied on as routine, even standard, methods of hygienic assessment alone or in complement with microbial and visual inspection methods. Still, current ATP methods remain indirect methods of total hygiene assessment and have limitations that must be understood and considered if such methods are to be applied judiciously, especially under increasingly strict demands for the verification of hygiene state. Here, we present current methods of ATP-based bioluminescence assays and describe the limitations of such methods when applied to general food manufacturing or health care facilities.

Development of a highly sensitive microplate luminometer using ATP bioluminescence

Analytical techniques using ATP bioluminescence, which has a high quantum yield and substrate specificity, are widely used in various assays, such as luciferase reporter assays, in the biological sciences. Although most microplate luminometers can be used to measure ATP luminescence with 96-well or 384-well microplates, their ATP detection limits are typically several tens of amol, which is not sufficient for evaluating cell activities and variability within small samples, such as those containing only a few cells. To analyze cell activities at low ATP concentrations, a more sensitive microplate luminometer is required. Therefore, in this study, we developed an automated highly sensitive microplate luminometer that could perform reagent dispensing and bioluminescence measurement with a 96-well microplate within 10 min. ATP bioluminescence was detected by pressing a photomultiplier tube (PMT) against a microplate surface to seal the measured well with the light-receiving surface of the PMT. This enabled a high light collection efficiency and low luminescence crosstalk, defined as the intensity of stray light from an adjacent well. As a result, the ATP detection limit was 0.97 amol, and the luminescence crosstalk was 4.4 × 10^-6 . Both values were one order of magnitude better than that of a typical microplate luminometer. In addition, the same gradient linearity of luminescence intensity against the ATP concentration was confirmed for both high and low ATP concentrations, and the dynamic range of our microplate luminometer was 10⁶ . Overall, our findings demonstrated that our novel microplate luminometer may have wide application in biological sciences research.

In situ lysis droplet supply to efficiently extract ATP from dust particles for near-real-time bioaerosol monitoring

Simultaneous improvement in detection speed and reliability is critical for bioaerosol monitoring. Recent rapid detection strategies exhibit difficulties with misinterpretation due to signal interference from co-existing nonbiological particles, whereas biomolecular and bioluminescent approaches require long process times (>several tens of minutes) to generate readable values despite their better detection reliability. To overcome these shortcomings, we designed a system to achieve rapid reliable field detection of bioaerosols (>10⁴ relative luminescence units [RLU] per cubic meter of air) in <3 min processing time (equivalent to 24 L sampling air volume) by employing a lysis droplet supply for efficient extraction of adenosine triphosphate (ATP) from particulate matter (PM) and a photomultiplier tube detector for signal amplification of ATP bioluminescence. We also suggested the use of the ratio of RLU (m^-3) to total PM (μg m^-3), or specific bioluminescence (RLU μg^-1), as a measure of the biofraction of PM (i.e., potential biohazards). A correlation between RLU and colony forming unit was also obtained from simultaneous aerosol sampling using an agar-inserted sampler.

Use of ATP bioluminescence to survey the spread of aerosol and splatter during dental treatments

Aerosol and splatter produced during dental treatments (ultrasonic scaling and professional mechanical tooth cleaning) are potential sources of infection. Contamination patterns on the mask, goggles, chest and gowned right arm of operators, and on the goggles of patients before and after dental treatments were investigated using ATP bioluminescence analysis. Contamination on every surface tested increased significantly after dental treatment. Maximum contamination was found on the goggles of patients. Aerosol and splatter produced during dental treatments therefore have the potential to spread infection to operators and patients. ATP bioluminescence is a useful tool for monitoring surface contamination.

Effectiveness of a combination denture-cleaning method versus a mechanical method: comparison of denture cleanliness, patient satisfaction, and oral health-related quality of life

PURPOSE

Effective denture plaque control is necessary in elderly individuals to prevent oral and systemic diseases. However, comparative studies of denture cleaning methods are limited, especially those investigating patient satisfaction. The present study aimed to evaluate effectiveness of a mechanical denture cleaning method versus a combination of mechanical and chemical methods in terms of denture cleanliness, patient satisfaction, and oral health-related quality of life (OHRQoL).

METHODS

Thirty edentulous participants were allocated to one of two groups: mechanical or combination method. The mechanical method group was instructed to brush dentures after each meal for 2min using tap water and a denture brush, and to soak them in saline solution while sleeping. The combination method group was instructed to brush dentures the same way, but to soak them in denture cleansers while sleeping. Both groups cleaned their dentures according to the respective method for 3 weeks. Denture cleanliness, patient satisfaction, and OHRQoL were examined.

RESULTS

There were significant differences in adenosine triphosphate bioluminescence (p=0.00003), staining (p=0.003), and Candida albicans (C. albicans) abundance in upper complete dentures (p=0.002) between methods. There were no significant differences in oral mucosa C. albicans abundance, participant satisfaction, ease of cleaning, comfort, esthetics, or Oral Health Impact Profile for edentulous patients (Japanese version) scores between methods.

CONCLUSIONS

A combination of mechanical and chemical denture cleaning methods was more effective at cleaning dentures than the mechanical method alone. Even if denture cleaning improves denture hygiene, it may not increase patient satisfaction or OHRQoL.

Residual contamination and bioburden after reprocessing of single-use endoscopic ultrasound needles: An ex vivo study

BACKGROUND AND AIM

Endoscopic ultrasound (EUS) aspiration needles are single-use devices. However, in many centers, because of cost-constraints, these devices are reused multiple times. We studied microbiological contamination and bioburden on reprocessed needles to evaluate whether these devices can be successfully sterilized.

METHODS

We studied 10 EUS needles each of 19 G, 22 G, and 25 G in size, and five 22-G ProCore needles. After initial use, each needle was reprocessed by a standardized protocol. We used standard microbiological cultures, as well as ATP bioluminescence technique to quantify bioburden as relative light units (RLU). We defined significant soil contamination by RLU values >200. We also used extractant fluid to disrupt cell membranes in an attempt to enhance ATP detection.

RESULTS

We found culture positivity in 3/34 (8.8%), and detectable bioburden on the exposed surface of 33/35 (94.3%), and inside lumen of 29 (82.9%) reprocessed FNA needles. Significant bioburden was found in three (8.6%) and two (5.7%) needles on the surface and lumen, respectively. We found that use of extractant fluid enhanced detection of bioburden. Larger (19 G) needles had higher surface contamination (P = 0.016), but there was no relation of luminal contamination with needle diameter (P = 0.138). Sheath design and presence of side bevel did not influence extent of contamination. There was significant correlation between the surface and intraluminal bioburden (P < 0.001).

CONCLUSIONS

There is significant bioburden in reprocessed EUS needles; standard microbiological cultures have low sensitivity for detection of needle contamination. We have provided objective evidence for the futility of reprocessing attempts, and practice of EUS needle reuse should be discontinued.

Assessment of terminal cleaning in pediatric isolation rooms: Options for low-resource settings

BACKGROUND

Few studies have evaluated terminal cleaning in low-resource settings.

METHODS

Adequacy of pediatric isolation room terminal cleaning was evaluated using quantitative bacterial surface cultures, ATP bioluminescence assays, and fluorescent high-touch surface markers at Tygerberg Children's Hospital in South Africa (August 1, 2014-October 31, 2015). Cleaning adequacy was assessed by comparing pre- and postcleaning measurements. Influence of verbal feedback was determined by comparing cleaners' first and subsequent cleaning episodes. Cleaning methods were compared for cost, time, and feasibility.

RESULTS

Adequacy of terminal cleaning was evaluated in 25 isolation rooms after hospitalization for pulmonary tuberculosis (n = 13), respiratory (n = 5) and enteric viruses (n = 5), pertussis (n = 1), and methicillin-resistant Staphylococcus aureus (n = 1). Mean aerobic colony counts and mean ATP relative light units declined between pre- and postcleaning evaluations (39 ± 41 to 15 ± 30 [P < .001] and 72 ± 40 to 23 ± 11 [P < .001]). Fluorescent marker removal was initially poor, but improved significantly at subsequent cleaning episodes (17 out of 78 [22%] to 121 out of 198 [61%]; P < .001); mean aerobic colony counts and ATP values also declined significantly following feedback. Cost, time, and resources required for ATP and surface cultures far exceeded that required for fluorescent markers.

CONCLUSIONS

Adequacy of isolation room cleaning improved following feedback to cleaning staff. Fluorescent markers are an inexpensive option for cleaning evaluation and training in low-resource settings.

Continuous and real-time bioaerosol monitoring by combined aerosol-to-hydrosol sampling and ATP bioluminescence assay

We present a methodology for continuous and real-time bioaerosol monitoring wherein an aerosol-to-hydrosol sampler is integrated with a bioluminescence detector. Laboratory test was conducted by supplying an air flow with entrained test bacteria (Staphylococcus epidermidis) to the inlet of the sampler. High voltage was applied between the discharge electrode and the ground electrode of the sampler to generate air ions by corona discharge. The bacterial aerosols were charged by the air ions and sampled in a flowing liquid containing both a cell lysis buffer and adenosine triphosphate (ATP) bioluminescence reagents. While the liquid was delivered to the bioluminescence detector, sampled bacteria were dissolved by the cell lysis buffer and ATP was extracted. The ATP was reacted with the ATP bioluminescence reagents, causing light to be emitted. When the concentration of bacteria in the aerosols was varied, the ATP bioluminescence signal in relative light units (RLUs) closely tracked the concentration in particles per unit air volume (# cm^-3), as measured by an aerosol particle sizer. The total response time required for aerosol sampling and ATP bioluminescence detection increased from 30 s to 2 min for decreasing liquid sampling flow rate from 800 to 200 μLPM, respectively. However, lower concentration of S. epidermidis aerosols was able to be detected with lower liquid sampling flow rate (1 RLU corresponded to 6.5 # cm^-3 of S. epidermidis aerosols at 200 μLPM and 25.5 # cm^-3 at 800 μLPM). After obtaining all data sets of concentration of S. epidermidis aerosols and concentration of S. epidermidis particles collected in the flowing liquid, it was found that with our bioluminescence detector, 1 RLU corresponded to 1.8 × 10⁵ (±0.2 × 10⁵) # mL^-1 of S. epidermidis in liquid. After the lab-test with S. epidermidis, our bioaerosol monitoring device was located in the lobby of a building. Air sampling was conducted continuously for 90 min (air flow rate of 8 LPM, liquid flow rate of 200 μLPM) and the ATP bioluminescence signal of indoor bioaerosols was displayed with time. Air sampling was also carried out using the 6th stage of Andersen impactor in which a nutrient agar plate was used for the impaction plate. The sample was cultured at 37 °C for five days for colony counting. As a result, it was found that the variation of the bioluminescence signal closely followed the variation of indoor bioaerosol concentration in colony forming unit (CFU) and 1 RLU corresponded to 1.66 CFU m^-3 of indoor bioaerosols. Our method can be used as a trigger in biological air contamination alarm systems.

Monitoring of bacterial contamination of dental unit water lines using adenosine triphosphate bioluminescence

Bacterial contamination of dental unit waterlines (DUWLs) was evaluated using ATP bioluminescence analysis and a conventional culture method. Water samples (N=44) from DUWLs were investigated for heterotrophic bacteria by culture on R2A agar, which gave counts ranging from 1.4×10³ to 2.7×10⁵ cfu/mL. The ATP bioluminescence results for DUWL samples ranged from 6 to 1189 relative light units and could be obtained within 1min; these correlated well with the culture results (r=0.727-0.855). We conclude that the results of the ATP bioluminescence assay accurately reflect the results of conventional culture-based testing. This method is potentially useful for rapid and simple monitoring of DUWL bacterial contamination.

Quantifying implant-associated biofilms: Comparison of microscopic, microbiologic and biochemical methods

Biofilm-associated infections pose severe problems in modern implant medicine. Screening for new implant materials with antibacterial properties requires reliable quantification of colonizing bacteria. There are many different methods to quantify biofilms on solid surfaces in vitro, employing different (bio-)chemical/microbiological reference parameters. It is therefore difficult to compare studies with different quantification techniques. Here, we have evaluated commonly used microscopic, microbiologic and biochemical methods to quantify bacterial biofilms, in order to clarify their comparability and applicability. Two bacterial species frequently involved in biofilm-associated infections, Staphylococcus aureus and Aggregatibacter actinomycetemcomitans, were used as model organisms; their initial adhesion and biofilm formation on titanium and on antibacterial copper were analyzed using the following methods: LIVE/DEAD fluorescence staining and confocal laser-scanning microscopy, ultrasonic or a newly developed enzymatic detachment followed by standard plate counting (CFU method), a resazurin-based assay, the BacTiter-Glo™ assay and crystal violet staining. The methods differed greatly in complexity, reliability and the applicability to initial adhesion and biofilm formation. To screen biofilm formation on a multitude of surfaces, the resazurin-based and the BacTiterGlo™ assay are well suited. LIVE/DEAD staining and confocal laser-scanning microscopy can be applied for a more detailed analysis of both, initial adhesion and biofilm formation. When using the CFU method for screening purposes, the introduced enzymatic detachment procedure is to be favored over ultrasonic detachment. There is not one single method, which is suitable for all purposes. The appropriate biofilm quantification method has to be chosen on the basis of the specific scientific question.

ATP bioluminescence method: tool for rapid screening of organic and microbial contaminants on deteriorated mural paintings

The extent of the microbial contamination of the seventeenth-century wall paintings in the nave of the old Church of the Holy Ascension (Veliki Krčimir, Serbia) was evaluated via newly implemented ATP bioluminescence method, and traditional cultivation-based method, utilising commercially available dip slides. To assess the validity of ATP, as a biomarker for rapid detection of mural surface contamination, obtained zones of cleanliness values, in range from 1.0 to 5.3, were compared to documented total microbial counts, ranging between seven and 247 CFU/cm². Small coefficients of determination, 0.0106-0.0385, suggest poor correlation between microbial counts and surface ATP levels; however, zones of cleanliness values are of great help in determining the high points of contamination, aka 'hotspots', which should be given special attention during sampling and investigation using other methods. In addition, various aspects of the possible implementation of the ATP bioluminescence method in an integrated system of wall painting conservation are discussed.

Manual cleaning of hospital mattresses: an observational study comparing high- and low-resource settings

BACKGROUND

Hospital-associated infections (HAIs) are more frequently encountered in low- than in high-resource settings. There is a need to identify and implement feasible and sustainable approaches to strengthen HAI prevention in low-resource settings.

AIM

To evaluate the biological contamination of routinely cleaned mattresses in both high- and low-resource settings.

METHODS

In this two-stage observational study, routine manual bed cleaning was evaluated at two university hospitals using adenosine triphosphate (ATP). Standardized training of cleaning personnel was achieved in both high- and low-resource settings. Qualitative analysis of the cleaning process was performed to identify predictors of cleaning outcome in low-resource settings.

FINDINGS

Mattresses in low-resource settings were highly contaminated prior to cleaning. Cleaning significantly reduced biological contamination of mattresses in low-resource settings (P < 0.0001). After training, the contamination observed after cleaning in both the high- and low-resource settings seemed comparable. Cleaning with appropriate type of cleaning materials reduced the contamination of mattresses adequately. Predictors for mattresses that remained contaminated in a low-resource setting included: type of product used, type of ward, training, and the level of contamination prior to cleaning.

CONCLUSION

In low-resource settings mattresses were highly contaminated as noted by ATP levels. Routine manual cleaning by trained staff can be as effective in a low-resource setting as in a high-resource setting. We recommend a multi-modal cleaning strategy that consists of training of domestic services staff, availability of adequate time to clean beds between patients, and application of the correct type of cleaning products.

Applying ATP bioluminescence to design and evaluate a successful new intensive care unit cleaning programme

This was a two-phase prospective intervention study in the cardiology intensive care unit (CICU) and medical intensive care unit (MICU) and of a public 1800-bed medical centre in Taiwan. In phase I, cleaning efficacy was monitored by ATP bioluminescence after daily morning cleaning, and only 43.9% of 221 tested surfaces passed. The baseline data were used to define an intervention consisting of a new cleaning protocol as well as a new education/training programme. In phase II, following the intervention, 88.1% of 270 surfaces were found to be clean. The combined infection rate in the CICU and MICU showed a statistically significant decrease of 49.7%.

Mechanical vs. manual cleaning of hospital beds: a prospective intervention study

BACKGROUND

Cleaning regimens for hospital beds were evaluated in the context of a rising prevalence of highly resistant micro-organisms and increasing financial pressure on healthcare systems. Dutch hospitals have to choose between standardized, mechanical bed-washers advised in national guidance and manual cleaning.

AIM

To evaluate the quality of mechanical and manual bed-cleaning regimens.

METHODS

The multi-faceted analysis of bed-cleaning regimens consisted of three steps. In Step 1, the training of the domestic service team was evaluated. In Step 2, the cleaning quality of manual and mechanical regimens was assessed. Soiled beds, obtained at random, from different departments were evaluated using microbiological analysis (N = 40) and ATP (N = 20). ATP and microbiological contamination were measured in five predetermined locations on all beds. In Step 3, manual cleaning was introduced over a two-month pilot study at the surgical short-stay unit, and beds from other departments were processed according to the 'gold standard' mechanical cleaning. ATP levels were evaluated in three locations on 300 beds after cleaning.

FINDINGS

Training was found to improve the quality of cleaning significantly. Mechanical cleaning resulted in significantly lower ATP levels than manual cleaning.

CONCLUSIONS

Mechanical cleaning shows less variation and results in consistently lower ATP levels than manual cleaning.

Assessment of hospital daily cleaning practices using ATP bioluminescence in a developing country

Visual assessment of surfaces may not be enough to document the level of cleanliness in the hospital setting. It is necessary to introduce quantitative methods to document the results of this practice.

OBJECTIVE

To evaluate the efficacy of hospital terminal cleaning procedures, using an adenosine triphosphate (ATP) bioluminescence method in a teaching hospital.

METHOD

During 2008 we conducted an evaluation using ATP bioluminescence LIGHTNING MVP™ (Arquimed) of external and internal housekeeping service. After conducting an initial evaluation we implemented education of cleaning practices and finally we did a post intervention evaluation. Using chi-square method we compared prior versus after cleaning, quality of cleaning performed by external versus internal personnel, single versus double terminal cleaning procedures and prior versus after intervention. A finding of three RLU or less was considered a clean surface.

RESULTS

We performed 198 evaluations in 33 patient units and nine OR. Internal personnel accomplished 25.37% of clean surfaces before and 80% after the education intervention (p=0.01). In contrast, external personnel obtained 68.8% before and 73.33% after intervention (p=0.3).

CONCLUSIONS

This study suggests that visual assessment is not enough to ensure quality of the process and it is necessary to document the level of cleanliness by quantitative methods.

Evaluating and operationalizing an environmental auditing program: a pilot study

BACKGROUND

Environmental auditing is an important tool to ensure consistent and effective cleaning. Our pilot study compared an alcohol-based fluorescent marking product and an adenosine-5'-triphosphate bioluminescence product for use in an environmental auditing program to determine which product was more practical and acceptable to users.

METHODS

Both products were tested on 15 preselected high touch objects in randomly selected patient rooms, following regular daily cleaning. A room was considered a "pass" if ≥80% of surfaces were adequately cleaned as defined by manufacturers' guidelines. A qualitative survey assessed user preference and operational considerations.

RESULTS

Using fluorescent marking, 9 of 37 patient rooms evaluated (24%) were considered a "pass" after daily cleaning. Using adenosine-5'-triphosphate bioluminescence, 21 of 37 patient rooms passed (57%). There was great variability in results between different high touch objects. Eighty percent of users preferred the alcohol-based fluorescent marking product because it provided an effective visual aid to coach staff on proper cleaning techniques and allowed simple and consistent application.

CONCLUSIONS

Environmental auditing using translucent, alcohol-based fluorescent marking best met the requirements of our organization. Our results reinforce the importance of involving a multidisciplinary team in evaluating and operationalizing an environmental auditing program.

Variation in detection limits between bacterial growth phases and precision of an ATP bioluminescence system

To determine the detection limits of the SystemSure Plus, Escherichia coli and Staphylococcus aureus growth curve samples were taken in lag (1 h), log (6 h), stationary (12 h) and death phases (E. coli 144 h, Staph. aureus 72 h). At each time point, the log10 CFU ml(-1) was determined for the dilution where the SystemSure read 0 relative light units (RLU). Average detection limits were E. coli: lag 6·27, log 5·88, stationary 7·45 and death 6·88; Staph. aureus: lag 4·37, log 5·15, stationary 7·88 and death 7·57. Between-run precision was determined with positive control; within-run precision with positive control, lag and log growth for each bacteria. Within-run precision mean RLU (CV): positive control 274 (12%), E. coli lag 1 (63%), log 2173 RLU (19%), Staph. aureus lag 2 (58%) and log 5535 (18%). Between-run precision was 232 (16%). The precision is adequate with most values within the 95% confidence interval. The detection limit varied by 3·51 log10 for Staph. aureus and 1·47 log10 for E. coli. The lowest detection limits were during E. coli log and Staph. aureus lag phases; the highest was during stationary phase. These results suggest that organism identification and growth phase both impact ATP RLU readings.

SIGNIFICANCE AND IMPACT OF THE STUDY

Surface hygiene is a critical component of food safety and infection control; increasingly, ATP detection by bioluminescence is used to evaluate surface hygiene and effective cleaning. This is the first study to show that the number of living and potentially infectious bacteria remaining when the device reads zero varies between the different bacterial life cycle phases: lag, log, stationary and death. ATP device users need to be aware of this information to use the devices appropriately.

Use of ATP bioluminescence for assessing the cleanliness of hospital surfaces: a review of the published literature (1990-2012)

Hospital cleanliness tends to be considered by patients and the public as an important indicator of the general quality of healthcare. Tests for detecting the presence of adenosine triphosphate (ATP) as a proxy of microbial contamination are increasing in popularity, and several studies have been conducted on this topic in the last few decades. The aim of the present study was to review the published literature on this topic and summarize and discuss the available results. The review focused on relevant English-language articles that were identified through searches of two databases [PubMed and Scopus (1990-2012)] by using the keywords "ATP", "bioluminescence", "hospital", and "surfaces". Twelve articles were included and analyzed. ATP measurements showed a wide variation, with values ranging from 0 to >500,000 relative light units (RLU)/s before cleaning and from 3 to 500,000RLU/s after cleaning. ATP benchmarks used by authors ranged from 100 to 500RLU/s. The percentage of surfaces exceeding the chosen cut-off limit showed a failure rate varying from 21.2% to 93.1% before cleaning and from 5.3% to 96.5% after cleaning. Although the use of ATP bioluminescence can be considered a quick and objective method for assessing hospital cleanliness, it appears to be still poorly standardized at both the national and international level.

Real-time monitoring of bioaerosols via cell-lysis by air ion and ATP bioluminescence detection

In this study, we introduce a methodology for disrupting cell membranes with air ions coupled with ATP bioluminescence detection for real-time monitoring of bioaerosol concentrations. A carbon fiber ionizer was used to extract ATP from bacterial cells for generating ATP bioluminescence. Our methodology was tested using Staphylococcus epidermidis and Escherichia coli, which were aerosolized with an atomizer, and then indoor bioaerosols were also used for testing the methodology. Bioaerosol concentrations were estimated without culturing which requires several days for colony formation. Correlation equations were obtained for results acquired using our methodology (Relative Luminescent Unit (RLU)/m(3)) and a culture-based (Colony Forming Unit (CFU)/m(3)) method; CFU/m(3)=1.8 × measured RLU/m(3) for S. epidermidis and E. coli, and CFU/m(3)=1.1 × measured RLU/m(3) for indoor bioaerosols under the experimental conditions. Our methodology is an affordable solution for rapidly monitoring bioaerosols due to rapid detection time (cell-lysis time: 3 min; bioluminescence detection time: <1 min) and easy operation.

Diagnostic assessment of different environmental cleaning monitoring methods

In a simultaneous assessment of 250 environmental surfaces after terminal cleaning using aerobic cultures as a gold standard, both fluorescent marker and an adenosine triphosphate bioluminescence assay system demonstrated better diagnosticity compared with subjective visual inspection. These results support the use of these environmental monitoring systems in the health care setting.

Use of a Rapid Microbial ATP Bioluminescence Assay to Detect Contamination on Beef and Pork Carcasses †

A new microbial ATP bioluminescence assay was shown to be an accurate and rapid method to determine the levels of generic bacterial contamination on beef (n = 400 and pork (n = 320) carcasses sampled in commercial processing plants. Based on in vitro fecal dilution studies, the rapid microbial ATP (R-mATP) assay is as accurate as the standard plate count method for estimating bacteria in bovine or porcine fecal samples. The correlations (r) between the R-mATP assay and the standard aerobic plate count for beef and pork carcasses sampled in commercial processing were 0.91 and 0.93, respectively. A segmented-model statistical approach to determine the lower limits of assay sensitivity was developed. By using this model to analyze the in-plant data, the R-mATP test responded in a linear fashion to levels of microbial contamination of > log₁₀ 2.0 aerobic CFU/cm² on beef carcasses and of > log₁₀ 3.2 aerobic CFU/cm² for pork carcasses. The R-mATP assay requires approximately 5 min to complete, including sampling. Given the rapidity and accuracy of the assay, processors interested in monitoring critical control points in the slaughter process could potentially use the R-mATP assay to monitor microbiological prevention and intervention procedures for minimizing carcass contamination.

Microbial ATP Bioluminescence as a Means to Detect Contamination on Artificially Contaminated Beef Carcass Tissue †

The use of microbial ATP bioluminescence was evaluated as a means to rapidly detect gross microbial contamination from feces on bovine-carcass surface tissue (BCT). Microbial ATP was selectively distinguished from nonmicrobial ATP by the assay procedure used. Regression analyses of microbial ATP and viable count scatterplots showed lean and adipose BCT artificially contaminated with bovine feces had the same regression line parameters (P < 0.05), and therefore, the microbial ATP responses were similar for both tissue types. Correlation coefficients (r) of these regression lines were >0.90 for both tissue types. Results indicated that swab samples can be held at 5°C for up to 6 h without compromising microbial ATP bioluminescence assay results. The microbial ATP bioluminescence assay shows potential for use as a means to rapidly detect fecal contamination on red meat carcasses and to gauge decontamination effectiveness and hence could monitor critical control points in a processing-plant HACCP plan.