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Background: The spread of pathogens via the airborne route is often underestimated, and little is known about the extent to which airborne microbial contamination levels vary throughout the day and night in hospital facilities., Aims: To evaluate airborne contamination levels within intensive care unit (ICU) isolation rooms over 10-24-h periods in order to improve understanding of the variability of environmental aerial bioburden, and the extent to which ward activities may contribute., Methods: Environmental air monitoring was conducted within occupied and vacant inpatient isolation rooms. A sieve impactor sampler was used to collect 500-L air samples every 15 min over 10-h (08:00-18:00 h) and 24-h (08:00-08:00 h) periods. Samples were collected, room activity was logged, and bacterial contamination levels were recorded as colony-forming units (cfu)/m 3 air., Findings: A high degree of variability in levels of airborne contamination was observed across all scenarios in the studied isolation rooms. Air bioburden increased as room occupancy increased, with air contamination levels highest in rooms occupied for the longest time during the study (10 days) (mean 104.4 cfu/m 3 , range 12-510 cfu/m 3 ). Counts were lowest in unoccupied rooms (mean 20 cfu/m 3 ) and during the night., Conclusion: Peaks in airborne contamination were directly associated with an increase in activity levels. This study provides the first clear evidence of the extent of variability in microbial airborne levels over 24-h periods in ICU isolation rooms, and found direct correlation between microbial load and ward activity., (Copyright © 2019 The Healthcare Infection Society. Published by Elsevier Ltd. All rights reserved.)

Background: Previous work has shown that a ceiling-mounted, 405 nm high-intensity narrow-spectrum light environmental decontamination system (HINS-light EDS) reduces bacterial contamination of environmental surfaces in a burns unit by between 27% and 75%. Examination of the efficacy of the light over extended exposure times and its probable mode of action was performed., Aim: To ascertain the correlation between bacterial kill achieved on sampled surface sites around the burns unit and both irradiance levels of the 405 nm light, and exposure time., Methods: Seventy samples were taken using contact agar plates from surfaces within an occupied side-room in the burns unit before, during, and after a seven-day use of the HINS-light EDS. This was repeated in three separate studies. Statistical analysis determined whether there was significant decrease in environmental contamination during prolonged periods of HINS-light treatment, and whether there was an association between irradiance and bacterial kill., Findings: A decrease of between 22% and 86% in the mean number of surface bacteria was shown during the use of the HINS-light EDS. When the light ceased to be used, increases of between 78% and 309% occurred. There was no correlation between bacterial kill and irradiance levels at each sampling site but strong correlation between bacterial kill and exposure time., Conclusion: Prolonged exposure to the HINS-light EDS causes a cumulative decontamination of the surfaces within a burns unit. The importance of exposure time and possible airborne effect over irradiance levels is emphasized., (Copyright © 2017 The Healthcare Infection Society. Published by Elsevier Ltd. All rights reserved.)

Background: Although the germicidal properties of ultraviolet (UV) light have long been known, it is only comparatively recently that the antimicrobial properties of visible violet-blue 405 nm light have been discovered and used for environmental disinfection and infection control applications., Aim: To review the antimicrobial properties of 405 nm light and to describe its application as an environmental decontamination technology with particular reference to disinfection of the hospital environment., Methods: Extensive literature searches for relevant scientific papers and reports., Findings: A large body of scientific evidence is now available that provides underpinning knowledge of the 405 nm light-induced photodynamic inactivation process involved in the destruction of a wide range of prokaryotic and eukaryotic microbial species, including resistant forms such as bacterial and fungal spores. For practical application, a high-intensity narrow-spectrum light environmental disinfection system (HINS-light EDS) has been developed and tested in hospital isolation rooms. The trial results have demonstrated that this 405 nm light system can provide continuous disinfection of air and exposed surfaces in occupied areas of the hospital, thereby substantially enhancing standard cleaning and infection control procedures., Conclusion: Violet-blue light, particularly 405 nm light, has significant antimicrobial properties against a wide range of bacterial and fungal pathogens and, although germicidal efficacy is lower than UV light, this limitation is offset by its facility for safe, continuous use in occupied environments. Promising results on disinfection efficacy have been obtained in hospital trials but the full impact of this technology on reduction of healthcare-associated infection has yet to be determined., (Copyright © 2014 The Healthcare Infection Society. Published by Elsevier Ltd. All rights reserved.)

Electrostatic finite element modelling software and an ac equivalent circuit model have been used to investigate an impediometric microelectrode array biosensor for the detection of bacteria. The electrostatic model showed the capacitance of the biosensor to decrease with increasing numbers of bacteria trapped on the sensor's surface in a suspension of relatively high dielectric permittivity. Optimization of the model suggests that reducing the spatial wavelength of the biosensor's electrodes either through a decrease in electrode width or gap will improve the sensor's sensitivity. In addition, the model confirmed that the permittivity of the external medium had a significant effect on detection efficiency. Increased sensitivity in suspensions of lower relative dielectric permittivity was observed. The equivalent circuit model (ECM) was used to analyze the effect of high levels of immobilized bacteria at fixed signal frequencies (100 Hz and 1 MHz). It has been shown that the ECM discussed in this paper is able to successfully model the experimental data for the actual sensor in the low frequency ranges, allowing prediction of the sensor response and analysis of its performance. Overall, the modelling results obtained in the present paper are in general agreement with those from other published data and can be used in the development and optimization of impediometric biosensors for rapid and reliable detection of pathogenic bacteria. [ABSTRACT FROM AUTHOR]

Aims: To apply scanning electron microscopy, image analysis and a fluorescent viability stain to assess lethal and sublethal injury in food-borne bacteria exposed to pulsed-plasma gas discharges (PPGD). Methods and Results: The fluorescent redox probe 5-cyano-2,3-ditolyl tetrazolium chloride (CTC) was used for enumerating actively respiring cells of Campylobacter jejuni, Escherichia coli, Listeria monocytogenes, Staphylococcus aureus and Salmonella enterica serovar Typhimurium that were suspended in sterile water at 4°C and exposed to separate PPGD and heat treatments. While there was good agreement between use of respiratory staining (RS) and direct-selective agar plate counting (PC) for enumerating untreated bacteria, there were c. 1 and 3 log-unit differences in surviving cell numbers per millilitre for test organisms subjected to PPGD and heat treatments respectively, when enumerated by these different viability indicators. PPGD-treated bacteria were markedly altered at the cellular level when examined by scanning electron microscopy. Conclusions: Use of this RS method revealed that substantial subpopulations of test bacteria rendered incapable of forming colonies by separate PPGD and heat treatments may remain metabolically active. Significance and Impact of the Study: Use of this RS method offers interesting perspectives on assessing established and novel microbial inactivation methods, and may also provide a better understanding of mechanisms involved in microbial inactivation induced by high-intensity PPGD treatments. [ABSTRACT FROM AUTHOR]

s. yaqub, j.g. anderson, s.j. macgregor and n.j. rowan. 2004. To apply scanning electron microscopy, image analysis and a fluorescent viability stain to assess lethal and sublethal in food-borne bacteria exposed to high-intensity pulsed electric fields (PEF). A rapid cellular staining method using the fluorescent redox probes 5-cyano-2,3-ditolyl tetrazolium chloride (CTC) and 4′,6-diamidino-2-phylindole was used for enumerating actively respiring cells of Listeria mononcytogenes, Bacillus cereus and Escherichia coli. This respiratory staining (RS) approach provided good agreement with the conventional plate count agar method for enumerating untreated and high-intensity PEF-treated bacteria suspended in 0.1% (w/v) peptone water. However, test organisms subjected to similar levels of lethality by heating at 56°C resulted in ca 3-log-unit difference in surviving cell numbers ml−1 when enumerated by these different viability indicators. PEF-treated bacteria were markedly altered at the cellular level when examined by scanning electron microscopy. While PEF-treatment did not produce sublethally injured cells ( P < 0.05), substantial subpopulations of test bacteria rendered incapable of forming colonies by heating may remain metabolically active. The fluorescent staining method offers interesting perspectives on assessing established and novel microbial inactivation methods. Use of this approach may also provide a better understanding of the mechanisms involved in microbial inactivation induced by PEF. [ABSTRACT FROM AUTHOR]