Evaluation of different detector types in measurement of ATP bioluminescence compared to colony counting method for measuring bacterial burden of hospital surfaces

Impact of Plastic-Wrap Properties and Cleaning Intervals on the Disinfection of Elevator Buttons

Fomite transmission is a possible route by which different pathogens spread within facilities. In hospital settings, elevator buttons are widely observed to be covered with various types of plastic wraps; however, limited information is available concerning the impact of different plastic materials on cleaning. Our study aimed to identify which plastic material is suitable for the coverage of elevator buttons and the optimal intervals for their cleaning. We tested six plastic covers, including polyethylene (PE), polymethylpentene (PMP), polyvinyl chloride (PVD), and polyvinylidene chloride (PVDC) plastic wraps; a thermoplastic polyurethane (TPU) keyboard cover; and a polyethylene terephthalate-ethylene vinyl acetate (PET-EVA) laminating film, which are plastic films. The bioburden on the elevator buttons at different time intervals was measured using an adenosine triphosphate (ATP) bioluminescence assay. Our results show that wraps made of PVDC had superior durability compared with those of PMP, PVC, and PVDC, in addition to the lowest detectable ATP levels among the six tested materials. Regarding different button locations, the highest ATP values were found in door-close buttons followed by door-open, and first-floor buttons after one- and three-hour intervals (p = 0.024 and p < 0.001, respectively). After routine disinfection, the ATP levels of buttons rapidly increased after touching and became more prominent after three hours (p < 0.05). Our results indicate that PVDC plastic wraps have adequate durability and the lowest residual bioburden when applied as covers for elevator buttons. Door-close and -open buttons were the most frequently touched sites, requiring more accurate and precise disinfection; therefore, cleaning intervals of no longer than three hours may be warranted.

The correlation between ATP measurement and microbial contamination of inanimate surfaces

Background

The objective of this study was to determine the correlation between adenosine triphosphate (ATP) measurements and microbial contamination using a standardized method. Secondarily, analyzing reproducibility of ATP measurements and aerobic colony counts (ACC’s) on the same surface.

Methods

ATP measurements and ACC’s were conducted on 10 pre-defined fomites in a hospital and nursing home setting. Per fomite two ATP measurements and two agar plate measurements were conducted, each measurement was conducted on a 25 cm² surface. Both measurements were compared and analyzed for correlation.

Results

In total 200 paired measurements were conducted, 200 ATP measurements and 200 ACC’s. The mean of all ATP measurements tested on the same surface was calculated, as was for all 200 ACC’s. There was a strong correlation between the mean of two ATP measurements on two different sites on the same fomite (R = 0.800, p < 0.001) as well as between two ACC measurements on the same fomite (R = 0.667, p < 0.001). A much weaker correlation was found between RLU values and ACC’s (R = 0.244, p < 0.001).

Conclusions

Reproducibility of ATP measurements and ACC’s on the same fomite was good. However, the correlation between RLU values and ACC’s on hospital surfaces was much lower. This may be explained by the wide variety of biological material that is measured with ATP, of which the bacterial load is only one of many components. ATP measurement can be used to give a quantifiable outcome for the rating of cleanliness in health care facilities, however the results cannot be translated into the level of microbial contamination.

Antibacterial Activities of Phytofabricated ZnO and CuO NPs by Mentha pulegium Leaf/Flower Mixture Extract against Antibiotic Resistant Bacteria

Purpose: In this study, leaf/flower aqueous extract of medicinal plant species Mentha pulegium was used to synthesize ZnO and CuO nanoparticles (NPs) as a cost-effective, one-step, and eco-friendly method. Methods: Physicochemical properties of both metal oxide NPs (MONPs) were determined by UV-Vis spectroscopy, X-ray diffraction (XRD), Fourier-transform infrared (FTIR) spectroscopy, scanning electron microscope (SEM) and energy dispersive X-ray (EDX) techniques. Results: Phytofabricated ZnONPs and CuNPs illustrated 65.02±7.55 and 26.92±4.7 nm with antibacterial activities against antibiotic-resistant Escherichia coli and Staphylococcus aureus. Higher antibacterial activities were observed for CuONPs compared with ZnONPs. Conclusion: Large surface area and more reactivity resulted from smaller size as well as higher production of reactive oxygen species (ROS) were considered to antibacterial efficiency of CuONPs against antibiotic-resistant E. coli and S. aureus.

Real-time monitoring of extracellular ATP in bacterial cultures using thermostable luciferase

Adenosine triphosphate (ATP) is one of the most important indicators of cell viability. Extracellular ATP (eATP) is commonly detected in cultures of both eukaryotic and prokaryotic cells but is not the focus of current scientific research. Although ATP release has traditionally been considered to mainly occur as a consequence of cell destruction, current evidence indicates that ATP leakage also occurs during the growth phase of diverse bacterial species and may play an important role in bacterial physiology. ATP can be conveniently measured with high sensitivity in luciferase-based bioluminescence assays. However, wild-type luciferases suffer from low stability, which limit their use. Here we demonstrate that an engineered, thermostable luciferase is suitable for real-time monitoring of ATP release by bacteria, both in broth culture and on agar surfaces. Different bacterial species show distinct patterns of eATP accumulation and decline. Real-time monitoring of eATP allows for the estimation of viable cell number by relating luminescence onset time to initial cell concentration. Furthermore, the method is able to rapidly detect the effect of antibiotics on bacterial cultures as Ampicillin sensitive strains challenged with beta lactam antibiotics showed strongly increased accumulation of eATP even in the absence of growth, as determined by optical density. Patterns of eATP determined by real-time luminescence measurement could be used to infer the minimal inhibitory concentration of Ampicillin. Compared to conventional antibiotic susceptibility testing, the method presented here is faster and more sensitive, which is essential for better treatment outcomes and reducing the risk of inducing antibiotic resistance. Real-time eATP bioluminescence assays are suitable for different cell types, either prokaryotic or eukaryotic, thus, permitting their application in diverse fields of research. It can be used for example in the study of the role of eATP in physiology and pathophysiology, for monitoring microbial contamination or for antimicrobial susceptibility testing in clinical diagnostics.