Efficacy of Violet-Blue (405 nm) LED Lamps for Disinfection of High-Environmental-Contact Surfaces in Healthcare Facilities: Leading to the Inactivation of Microorganisms and Reduction of MRSA Contamination

Effective disinfection procedures in healthcare facilities are essential to prevent transmission. Chemical disinfectants, hydrogen peroxide vapour (HPV) systems and ultraviolet (UV) light are commonly used methods. An emerging method, violet-blue light at 405 nm, has shown promise for surface disinfection. Its antimicrobial properties are based on producing reactive oxygen species (ROS) that lead to the inactivation of pathogens. Studies have shown significant efficacy in reducing bacterial levels on surfaces and in the air, reducing nosocomial infections. The aim of this study was to evaluate the antimicrobial effectiveness of violet-blue (405 nm) LED lamps on high-contact surfaces in a hospital infection-control laboratory. High-contact surfaces were sampled before and after 7 days of exposure to violet-blue light. In addition, the effect of violet-blue light on MRSA-contaminated surfaces was investigated. Exposure to violet-blue light significantly reduced the number of bacteria, yeasts and moulds on the sampled surfaces. The incubator handle showed a low microbial load and no growth after irradiation. The worktable and sink showed an inconsistent reduction due to shaded areas. In the second experiment, violet-blue light significantly reduced the microbial load of MRSA on surfaces, with a greater reduction on steel surfaces than on plastic surfaces. Violet-blue light at 405 nm has proven to be an effective tool for pathogen inactivation in healthcare settings Violet-blue light shows promise as an additional and integrated tool to reduce microbial contamination in hospital environments but must be used in combination with standard cleaning practices and infection control protocols. Further research is needed to optimise the violet-blue, 405 nm disinfection method.

Disinfecting Slush Machines by an Innovative Near Ultraviolet Light Emitting Diode (UV LED) Technological System

Background

Microbial contamination of food and beverages is a topic of great interest. The most innovative technologies take advantage from UV light. This study aimed to evaluate a possible configuration of a nUV LED device at a wavelength of 405 nm installed on slush machines in order to reduce the microbial contamination.

Study Design and Methods

Study Design and Methods. The study was conducted in the Department of Molecular and Developmental Medicine, University of Siena, Italy. A nUV LED device with 408 nm wavelength was installed and used on the slush machines. The inner walls of the machine tanks were fouled with contaminated slush, to evaluate the effectiveness of nUV radiation in reducing microbial contamination over time.

Results

Experiment results on the slush machine showed a statistically significant logarithmic microbial reduction, in relation with the distance from the nUV LED light source. It has also been shown that the reduction of microbes is possible with a proper management of some parameters: the exposure time, the power and wavelength of the light source, the distance and the obstacles between the light source and the target to be irradiated.

Conclusion

To reduce the incidence of foodborne diseases it is necessary to take all necessary precautionary measures, and the use of nUV technology has proved to be a crucial element in achieving this goal.

Effectiveness of near-UVA in SARS-CoV-2 inactivation

This experimental study aimed to determine the activity of a near-UVA (405 nm) LED ceiling system against the SARS-CoV-2 virus. The ceiling system comprised 17 near-UVA LED lights with a radiant power of 1.1 W/each centred at 405 nm wavelength. A 96-multiwell plate, fixed to a wooden base, was inoculated with suspensions of VERO E6 cell cultures infected with SARS-CoV-2 virus and irradiated at a distance of 40 cm with a dose of 20.2 J/cm² for 120 min. The collected suspensions were transferred to VERO cell culture plates and incubated for 3 days. The maximum measurable log reduction obtained, starting from a concentration of 10^7.2 TCID50/mL, was 3.0 log₁₀ and indicated inhibition of SARS-CoV-2 replication by the near-UVA LED ceiling system. Near-UVA light at a 405-nm wavelength is emerging as a potential alternative treatment for localised infections and environmental decontamination because it is far less harmful to living organisms' cells than UV-C irradiation.

Safer school with near-UV technology: novel applications for environmental hygiene

Systems capable of disinfecting air and surfaces could reduce the risk of infectious diseases transmission. Aim: to evaluate the effectiveness of near-UV LED ceiling lamps, with a wavelength of 405 nm, in improving environmental hygiene. Between November and December 2020, we conducted an experimental study having a pre-post design in a kindergarten room in Siena where 4 ceiling lamps with 405 nm LED technology were installed. Twice per day, sampling was performed before (T0) and after treatment with near-UV (T1). We used between 8 and 12 pairs of contact plates to sample at various random spots each day. Air samplings were also performed. The plates were incubated at 22 and 36 °C. Significance was set at 95% (p < 0.05). The mean level of Colony Forming Unit (CFU) at T(0) was 249 (95% CI 193.1 - 305.0) at 36 °C and 535.2 (374.3 - 696.1) at 22 °C. The reduction was significant at T(1): by 65% at 36 °C and, 72% at 22 °C. Also, for air contamination: 95.3% (98.4-92.3). A dose threshold of about 5 J/cm² was identified to have an 80% CFU abatement and remains nearly constant. The advantage of being able to use this technology in the presence of people is very important in the context of controlling environmental contamination.

Graphical abstract

Wind of change: Better air for microbial environmental control

Background

The COVID19 epidemic highlighted the importance of air in the transmission of pathogens. Air disinfection is one of the key points to reduce the risk of transmission both in the health sector and in public, civil and industrial environments. All bacteria and viruses tested to date can be inactivated by UV-C rays. Laboratory tested UV-C systems are increasingly popular and proposed as effective technologies for air purification; few studies have evaluated their performance in populated indoor environments. The aim of this investigation was to evaluate the effectiveness of a UV-C disinfection system for air in a real working context.

Methods

This experimental study was conducted between December 2020 and February 2021 in an office of the Department of Molecular and Developmental Medicine of the University of Siena, Italy. A pre-final version air purifier (Cleaning Air T12), capable of treating 210 m³/h of air, was first tested for its ability to filter particulates and reduce microbial air contamination in the absence of people. Subsequently, the experiments were conducted in the presence of 3-5 subjects who worked for several hours in an office. During the tests, microbiological samples of air were collected in real time, switching the system on and off periodically. Air samples were collected and incubated on Petri dishes at 36 °C and 22 °C. Statistical analysis was performed with Stata 16 software assuming a significance level of 95%. An interpolating model was identified to describe the dynamics of contamination reduction when the device operates.

Results

Preliminary tests showed a significant 62.5% reduction in Colony-Forming Units (CFUs) with 36 °C incubation. Reductions in the particulate component were also observed. In the main test, comparison of CFU data, between the device-on phase (90 min) and the subsequent device-off phase (60 min), showed statistically significant increase (p = 0.001) of environmental contamination passing from a mean of 86.6 (65.8-107.4) to 171.1 (143.9-198.3) CFU/m³, that is a rise of about 100%. The interpolating model exhibited a good fit of CFU reduction trend with the device on.

Conclusions

The system, which mainly uses UV-C lamps for disinfection, was able to significantly reduce environmental and human contamination in real time. Experimental tests have shown that as soon as the device is switched off, after at least half an hour of operation, the healthiness of the air decreases drastically within 10 minutes, bringing the airborne microbial contamination (induced by the presence of operators in the environment) to levels even higher than 150% of the last value with the device on. Re-engineering strategies for system improvement were also discussed.

Efficacy of violet-blue light to inactive microbial growth

The increase in health care-associated infections and antibiotic resistance has led to a growing interest in the search for innovative technologies to solve these problems. In recent years, the interest of the scientific community has focused on violet-blue light at 405 nm (VBL405). This study aimed to assess the VBL405 efficiency in reducing microbial growth on surfaces and air. This descriptive study run between July and October 2020. Petri dishes were contaminated with P. aeruginosa, E. coli, S. aureus, S. typhimurium, K. pneumoniae and were placed at 2 and 3 m from a LED light source having a wavelength peak at 405 nm and an irradiance respectively of 967 and 497 µW/cm². Simultaneously, the air in the room was sampled for 5 days with two air samplers (SAS) before and after the exposition to the VBL405 source. The highest microbial reduction was reached 2 m directly under the light source: S. typhimurium (2.93 log₁₀), K. pneumoniae (2.30 log₁₀), S. aureus (3.98 log₁₀), E. coli (3.83 log₁₀), P. aeruginosa (3.86 log₁₀). At a distance of 3 m from the light source, the greatest reduction was observed for S. aureus (3.49 log₁₀), and P. aeruginosa (3.80 log₁₀). An average percent microbial reduction of about 70% was found in the sampled air after 12 h of exposure to VBL405. VBL405 has proven to contrast microbial growth on the plates. Implementing this technology in the environment to provide continuous disinfection and to control microbial presence, even in the presence of people, may be an innovative solution.

Is it really possible to leave sars-cov-2 outside the door?

Background

In this historical period, it has become very important to live in healthy environments. By using everyday objects, cross-contamination is possible because of prolonged microbial persistence on surfaces. UV-C irradiation is an environmentally friendly method to disinfect objects as no harmful chemicals or heat are involved. This study aims to determine the virucidal activity, against SARS-CoV-2, of UV-C irradiation occurring in a designed UV device, ‘Purity Capsule'.

Methods

An experimental study was performed in September 2020. The ‘Purity capsule’ has an 11 W lamp (3.5W UV-C) positioned in the centre of the device. The lamp has a dome covered with a reflective, protective coating. Three metal carriers were placed at the maximum distance from the UV-C lamp in three different positions and tested at 30 and 60 seconds 3 times. The carriers were inoculated with 100 µL of SARS-CoV-2 viral suspension with a concentration of 106.5 TCID50 /mL. After treatment, laboratory procedures were used to transfer the treated virus from carriers to multiwell plates. The samples were compared with positive controls (not exposed to UV-C light) after incubation, at 37 °C in 5% COÕ · in a humidified atmosphere, for 3 days. The residual viral activity was tested by assessing the 50% infectious dose per tissue culture (TCID50%).

Results

Tests performed at 30 seconds of UV-C irradiation show an average viral reduction of 4.0 Log10 (99.99%). All three tests performed at 60 seconds reached the maximum measurable log10 viral reduction: 5.0 Log10 (99.999%).

Conclusions

The study assessed the effectiveness of the device in significantly reducing the viral load on all carriers regardless exposure time and distance from the UV-C light source, with no impact on the level of environmental pollution.

Key messages

• UV-C light has the property of inactivating viral growth; its physical approach is considered a good compromise between cost and effectiveness.

• The device was effective in disinfecting all small everyday objects tested.

Stylish UV-C lamp for disinfecting household objects

Background

Considering the current pandemic situation, the growing problem of antibiotic resistance and the increase in healthcare costs, attention to daily disinfection is becoming increasingly important. This study aimed to evaluate the bactericidal efficacy of a modern and stylish UV-C device designed for the home environment.

Methods

The experimental study was conducted between July-August 2020 on four bacterial strains: Staphylococcus aureus, Salmonella typhymurium, Klebsiella pneumoniae and Escherichia coli. The UV-C device consist of a protective dome with a reflective coating, a UV-C lamp (placed in the device base) and three reflective holders. Different positions and exposure times were tested using two different carriers holder for the bacterial inoculum (plastic and stainless steel) to estimate the germicidal efficency related to UV-C lamp exposure, with direct and reflected (from the dome coating) light.

Results

The experiment showed that the higher bacterial inactivation effect (3.5 to 7 log10) was achieved for all four strains at 3 minutes, but even at 1 minute, there is a marked reduction in the bacterial load with the only exception of Klebsiella pneumoniae. After 45 and 30 seconds, steel carriers contaminated by Escherichia coli and Staphylococcus aureus on the opposite side of the UV-C source showed significant reductions in the range between 99 and 99,9%.

Conclusions

The device has proven to be effective for the disinfection of various everyday objects placed into the lamp and introduces beauty to the household environment.

Key messages

• In this study, UV-C device proved to be a valuable tool for disinfecting household items and enhancing safety for everyday health.

• UV-C device proved to be a valuable tool for disinfecting household items and enhancing safety for everyday health.

A novel technology for disinfecting surfaces infested with Candida auris: the UVC chip

Background

The fungal pathogen Candida Auris is increasingly associated with multidrug-resistant infections that are highly expensive for the Health Care System. The spreading of this pathogen can occur, among others, through contact with infected surfaces or medical instruments. This study evaluated the efficacy of a novel UVC chip, novel alternative to UVC LEDs and lamps, in inactivating Candida auris strain.

Methods

This experimental study was carried out between July and September 2020 at the University of Siena. Candida auris (ATCC 12372) at two known concentrations (1.5X107 and 1.5x106 CFU/ml) at a fixed distance (7,5 cm) from the chip (5.1mW radiant power) was tested, in triplicates, with three exposure times (5, 10 and 15 minutes). Potato Dextrose Agar (PDA) plates without the plate lid and containing Candida auris were exposed to UVC light. Subsequently, the plates were incubated at 36 °C for 48 h. Log reduction between treated and positive control (not exposed to UVC light) samples was calculated.

Results

At 15 minutes, we had the highest inactivation result, mean 4.43 log10, starting from a 1.5x106 CFU/mL concentration. At a higher concentration, 1.5X107 CFU/mL, the reduction had a mean of 3.51 log10.

Conclusions

The results of the experiments showed a significant microbial reduction in relation to the exposure time. The highest level of reduction was reached after 15 minutes of exposure. UVC chip had a relevant biocidal effect on Candida auris and may represent a valuable tool in the prevention of infections caused by this pathogen, which is becoming increasingly prevalent and persistent globally.

Key messages

• The use of UVC Chip decreases surface contamination.

• New technology against healthcare-associated infections.

Don’t be scared to touch! Effectiveness of a new disinfection technology based on Ag ions & Zeolite

Background

Disinfection of contact surfaces has become common practice since the two-year Covid-19 pandemic. The transmission of microbial agents has long been the focus of public health and hygiene awareness campaigns. Indeed, the development of new disinfection technologies and approaches is attracting considerable interest in the scientific community. Mixed plastic powders with antimicrobial properties and silver ions that compromise the metabolism of microorganisms could reduce the contamination of the contact surfaces. We aimed to evaluate an inorganic antimicrobial agent (IAA) based on Ag ions and zeolite mixed in a resin.

Methods

This experimental study was carried out at the University of Siena, Italy. Different objects were produced in two versions: i) with an IAA mixed in plastic resin; ii) with a standard plastic mixture. To the eye, the two versions were indistinguishable and were randomly contaminated with the hands of several operators. After the hand contamination, T0, we sampled the objects using RODAC plates at T1 (1h) and T2 (6h), incubating at 36 °C for 48 hours. Comparisons of the biocidal effect were made at T1 and T2. Statistical analysis was carried out with Stata.

Results

The mean level of contamination of the objects made with standard plastic were, respectively 50 CFU (SD 36.5) at T1 and 20 CFU (SD 13.6) at T2. In comparison, the objects made with IAA resin showed a mean level of contamination of 10 CFU (SD 5.9) at T1 and 6 CFU (SD3.6) at T2. The objects made with IAA resin have shown a mean percentage reduction of contamination of 79.5% at T1 and 78.3% at T2.

Conclusions

IAA resin reduced contamination on objects that came into contact with hands. Antimicrobial plastic blends, are a valuable aid in counteracting the spread of infection related to contact with surfaces and fomites. The public health system could support and raise awareness for using these innovative materials for everyday applications and in healthcare facilities.

Key messages

• Inorganic antimicrobial agent based on Ag ions and Zeolite mixed in a resin are efficient in reducing the contamination on different items in a real-life context.

• Public health system have to support and sensitize to production with inorganic materials with proven antimicrobial properties.

Air purifiers, comparison between real and declared surface for use: fake it or make it?

Introduction

Air pollution has been recognized as one of the major risk factors for the global burden of disease. In modern society, most exposure occurs indoors, and air quality may be improved with air purifiers utilizing various cleaning techniques. This analysis aims to evaluate whether recommended room surface in which to use these devices as declared by producers is actually in line with their real effective area of activity.

Methods

A review of devices for the purification of the air was carried out between January-April 2022. Four different types of air purifiers were considered based on the adopted technologies: I) HEPA filters and UV lamps; II) only with HEPA filters; III) only UV lamps and IV) those using other technologies. For each group, based on the CADR (Clean Air Delivery Rate) provided by the producers, the optimal real surface area of the room to use the device was calculated, referring to the standard EN779:2012. This value was compared with the recommended area of the room declared by the producers. Descriptive statistics and Wilcoxon matched pair test used for comparisons. The significance level was set at p &lt; 0.05.

Results

The analysis was carried out on 252 devices; I) 52 had HEPA filters + UV lamps, with a recommended mean room area of 40 m2 (IQR 49.75), II) 142 devices had only HEPA filters with 52.5 m2 (IQR 46.75), III) 27 devices only UV lamps, 40 m2 (IQR 105), IV) 31 devices with other technologies, 54 m2 (IQR 84.2). As required by EN779:2012, the effective area of activity was calculated using CADR x 0.075: the medians of the 4 groups were I) 12 m2 (IQR 16.5), II) 15.83 m2 (IQR 26.4), III) 4.5 m2 (IQR 22.5), IV) 7.5 m2 (IQR 21.53), respectively. Comparing declared and calculated CADR values, all the groups showed significant differences (p &lt; 0.05).

Conclusions

Results show that recommended surfaces derived from CADR declared by producers largely overestimate the real volume of the room that devices can purify, whatever the technology used.

Key messages

• There’s no correspondence between recommended area of room to be sanitized indicated by producers of air purifiers and area that they are actually able to sanitize, which is significantly lower.

• It is necessary to be aware of the difference between data indicated by producers and real data, in order to purchase a device that actually corresponds to dimensional needs of the environment itself.

Safer school with near-UVA technology: novel applications for Environmental Hygiene

Background

Schools are crowded places where outbreaks can occur. Systems capable of disinfecting air and surfaces could reduce the risk of transmission of infectious diseases.

Aim

to evaluate the effectiveness of a near-UVA (nUVA) LED ceiling lamp in improving environmental hygiene.

Methods

This cross-sectional study was conducted for 2 weeks between November and December 2020 in a kindergarten in Siena, Italy. Four ceiling lamps with LED wavelength of 405 nm were mounted on the room ceiling. The distance of the lamps from the floor was 2.70 m and 2.0 m from the desks. We preliminary selected 12 points in different sites of the room by measuring their irradiance values. We randomly sampled between 8 and 12 pairs of Petri Dishes (PD) daily during the study, incubated at 22 and 36C°, at different irradiation times: 8, 12 or 36 hours. Paired controls were used before using the lamps (at time T0), which were automatically switched ON overnight and compared with treatment (at time T1). Air sampling was also performed at T0 and T1. Statistical analysis was performed with Stata 14. Significance was set at 95% (p &lt; 0.05).

Results

520 PDs were used in the study: 130 PDs at T0 matched at T1 incubated at 36 °C and as many at 22 °C. The mean level of contamination at T0 was respectively 249 CFU (95 % CI 193.1 - 305.0) at 36 °C and 535.2 CFU (374.3 - 696.1) at 22 °C. The reduction was significant (p &lt; 0.05) at T1: we had 87.4 CFU (56.3 - 118.6), equal to 65%, at 36C° and 149.6 CFU (83.7 - 215.4), equal to 72%, at 22C°. Different values were recorded stratifying for dose (irradiance per exposition time). A significant mean percentage reduction of air contamination was 95.3% (98.4 - 92.3).

Conclusions

The system was able to improve the environmental hygiene of the kindergarten. The advantage of using this technology in the presence of people is very important in the context of controlling environmental contamination.

Key messages

• Near-UVA are efficient in reducing the contamination level significantly in a real-life context, on the surfaces and of the air.

• Crowded places favour germ outbreaks. Hygiene control is essential to reduce the risk of transmission of infectious diseases.

Can a UV-C box help cinema industry by hygienizing video-cameras?

Background

UV-C has proven to be an effective microbiocide method for disinfecting objects in domestic and work environments. Aim of this study was to test the biocidal efficiency of an UVC box on a real video-camera.

Methods

In February 2021, a descriptive study on a parallelepiped-shaped UVC box, produced by Cartoni S.p.a., was conducted at the University of Siena. The box has 10 UV-C lamps (254 nm at 0.9 Watt/each) and all six mirrored reflective walls. It was specifically engineered for disinfecting equipments for film makers. A real professional camera was used to assess the level of disinfection. Contamination was obtained inoculating 1.5x107CFU/mL of S. Aureus ATCC 43300 on five 20 cm2 plastic carriers positioned in five different spots (referred as spots A, B, C, D, E), both directly (spot A), and indirectly (by reflected light, spots B, C, D, E) exposed to a UV-C light source. After a cycle of 3 minutes' exposition to UV-C: all carriers were transferred on empty Petri dishes; 10 mL D/E medium was added, transferred into a 50 ml Falcon and spun for 40 minutes at 4500 rpm; the supernatant was then removed and 100 µl of it was incubated into a Petri dish (with a generic growth medium) at 36 °C for 48 h. The experiment was run in triplicate. The mean logarithmic reduction and its 95% confidence interval were calculated from the replicates data and compared with positive controls (1.5x107CFU/mL).

Results

Mean logarithmic reduction compared to positive control was in spot A: 6.33 log10(C.I. 5.90-6.75), spot B: 4.74 log10(C.I. 4.11-5.33), spot C: 4.83 log10(C.I. 4.75-4.91), spot D: 4.89 log10(C.I. 4.12-5.65), spot E: 5.00 log10(C.I. 4.79-5.21).

Conclusions

These experiments showed that after 3 minutes of UV-C exposure there is a significant reduction in the bacterial load, 4 to 6 log10 (99.99% to 99.9999% reduction), on the carriers. The results also highlight the ability of the UV-C box to disinfect all infected spots, including those irradiated by reflected light.

Key messages

UV-C Box devices are effective in decreasing bacterial contamination on shared work tools in cinema industries, regardless of the direct or indirect exposition to the UV-C source. UV-C box's speed in hygienizing shared work tools can help cinema industry professionals to work in a safer and cleaner environment.

An emerging innovative UV disinfection technology: virucide activity on SARS-CoV-2

Background

Surface sanitation is one of the key points to reduce the risk of transmission both in healthcare and other public spaces. UV-C is already used in hospital and laboratory's disinfection procedure furthermore some recent studies show effectiveness on SARS-CoV-2. UV-C may be generated by Lamps and Light Emitting Diode, but novel sources are emerging. The aim of the study was to test a device having UV chips for inactivating SARS-CoV2.

Methods

The descriptive study was conducted in the period between June and July 2019, in laboratories of the University of Siena and of the scientific park of Toscana life sciences. The device, shaped in a rectangular box, contained six UV chips (10 mW each, with a peak at 264nm nm ranging from 260 to 350 nm) placed in the bottom. Central and short side long positions were tested expecting different dose levels. Each experiment was conducted in triplicate, with and without the device lid, at 3, 6 and 10 minutes. All repetitions were tested for SARS-CoV-2 having a virus suspension of 10^7.2.

Results

The zones with the higher value of irradiance (max 187.9 µW/cm2) were near the corners of the box, while the lowest (min 61.9 µW/cm2) near one of the long sides. The light distribution was almost symmetrical. The tests revealed a viral charge reduction from an initial concentration of virus suspension of 10^7.2 TCID50/mL, of more than 99.9% after 3 minutes of UV exposure; at 6 minutes, the minimum Log10 attenuation value was over 5 Log10(99,999%); the maximum detectable attenuation value of Log10 = 5.7 was measured at 10 minutes.

Conclusions

This device is the first one which introduces this novel UV chip source, similarly it is the first time it was tested against the SARS-CoV-2. Objects that need to be disinfected may benefit of such devices according a proper exposition time for homogeneous disinfections of the surfaces.

Key messages

Implementation of cleaning and disinfection devices has been shown to reduce Sars-cov-2 infection incidence. In the hospital sanitation field, but also in public places and homes, using viable alternatives as UV-C can contribute to the reduction of pandemic spread.

Efficacy of nearuv-a to inactive microbial growth

Background

Microbes are less able to develop resistance towards antimicrobial blue light (aBL), at 405nm, towards disinfectants/antibiotics. In addition, Near UV-A light (nUV) is less harmful to host cell compared to UV-C irradiation. This study aimed to assess the efficiency aBL in reducing microbial growth on surfaces.

Methods

This cross-sectional study, run between July-October 2020. Petri dishes were contaminated with P. Aeruginosa, E. Coli, S. Aureus, S. Typhimurium, K. Pneumoniae at a concentration of 1.5x104 CFU/mL and were placed at 2 and 3m of distances from the light source having an irradiance of 967,39 and 497,33 µW/cm2 for 12 hours. The air confined the room was sampled for two weeks with two air samplers (SAS), before and after the exposition to the nUV light source to estimate the reduction of the environmental microbial contamination. The analysis was conducted using Stata software. Final results were expressed as logarithmic reduction mean with 95% confidence interval.

Results

The highest microbial reduction was reached 2m directly under the light. Significant (p &lt; 0.05) log-reduction were achieved for S. Typhimurium, 2.93 (IC 2.44-3.40), K.Pneumoniae, 2.30 (IC 2.14-2.46), S.Aureus, 3.98 (IC 3.78-4.12), E.Coli, 3.83 (IC 3.17-4.50), P. Aeruginosa, 3.86 (IC 3.22-4.48). At 3m of distance from the light source, it was observed a significant logarithmic reduction for S. Aureus, 3.49 (IC 3.34-3.65), and P. Aeruginosa, 3.80 (IC 3.11-4.47). In the air tests, we observed a mean percentage microbial reduction of about 70% after 12 h of exposure to nUV light.

Conclusions

nUV has proven to contrast microbial growth on the plates. It is possible to implement this technology in the environment for controlling microbial presence in “ad hoc” scenario but also in common areas. Mitigating the energy, it is possible to use this technology in presence of persons.

Key messages

In this experimental study, nearUV-A has proven to be efficient to reduce the microbial growth and to disinfect air and surface. NearUV light (nUV) can be use as an innovative technology for decreasing bacterial contamination, also in presence of people.

There is no planet B: masks UVC disinfection to rise to the environmental challenge during COVID-19

Background

Since the outbreak of Sars-CoV-2 public health measures have been adopted globally, most notably the use of face masks has become essential and often mandatory. As a result, about 3.4 billion single-use face masks are estimated to be discarded daily worldwide. Due to waste mismanagement, the COVID-19 pandemic is severely impacting the environment, the ecosystem and therefore human health. We aimed to assess if UV-C light is an efficient tool for proper mask disinfection, to guarantee their safe reuse and reduce their waste.

Methods

In October 2020 we conducted a cross sectional study on KN95 masks. Various operators wore the masks during their shift in the laboratory for 8, 16 and 24h. Contact plates were used to measure microbial contamination on both surfaces of the masks at time T(0). Then, masks were placed into a UV-C box (volume of 0.012 m3, 40 UVC LED at 270nm at 3mW) for a treatment of 3 minutes. We repeated the sampling at time T(1). We incubated all plates at 36 °C and read them after 48h. We performed descriptive and inferential (Wilcoxon matched pair test) analysis with Stata. Significance level was set at p < 0.05.

Results

We always observed greater contamination on internal surfaces than external ones. At T(0) the medians of CFU on samples of internal surface were 212.7 (CI 95% 0-480.2) at 8h, 311.7 (0-683.1) at 16h and 404.7 (0-736.1) at 24h; at T(1), CFU reduced (p < 0.05) and were respectively 3.2 (0-6.2), 2 (0-5.9) and 50.6 (0-164.7). At T(0) the medians of CFU on external surface were 23.7 (0-48.4), 53.2 (0-143) and 24.3 (0-71.8); at T(1) they respectively reduced (p < 0.05) to 8.7 (0-25.2), 18.2 (0-70), 2.3 (0-6.1).

Conclusions

Results showed that UV-C is effective in mask disinfection although an uncomplete abatement of the microbial load. It could be due to the limited UV-C dose or to its difficulty to penetrate among the meshes of the mask. Further investigation is needed to find a sustainable solution for mask use.

Key messages

UV-C seems a valid disinfection tool for used KN95 masks.

The development of strategies for proper disinfection of masks should be carried out to guarantee reusability and reduce waste production.

Wind of change: better air for microbial environmental control

Background

COVID19 outbreak highlighted air disinfection's importance. All bacteria and viruses tested to date (including various coronaviruses) respond to UV-C disinfection. This study aims to assess the effectiveness of an UVC disinfection system for air in a real working context.

Methods

This descriptive study was carried out in November 2020 in an office of the Department of Molecular and Developmental Medicine at the University of Siena. The disinfecting air system, Cleaning Air T12, produced by Italia Iso Group, has 12 lamps of 6.9 Watt of UVC/each, two inlet grills in its bottom and 2 outlet grills in the superior part. The volume of air that the system treat is of 210m3/h. The experiments were run over several days during the activities of 3-5 subjects working for several hours. Real time microbial air samplings were run during the tests switching the system ON and OFF. To verify microbial time variation, initial samplings (phase 1) had the system OFF, then ON (phase 2) and finally OFF again (phase 3). Petri dishes were incubated at 36 and 22 C°. Statistical analysis was executed with Stata 16. Significance level was set at p &lt; 0.05.

Results

The longest test highlighted that during phase 2, after 8 minutes from the end of phase 1, the system acted significantly (p = 0.001) on the reduction of environmental contamination up to a mean of 70 (95% C.I. 64 - 77) CFU/500 liters (about 70% at 22 °C) and 50% at 36 °C. In phase 3 the mean values became 171 (144 - 198) CFU/500 liters at 22C° and 259 (228-291) at 36 °C.

Conclusions

The system was able to significantly reduce the environmental contamination in real time. The experimental tests show how, as soon as the device is turned OFF after at least half an hour of operation, air healthiness drops dramatically within 10 minutes, bringing the levels of microbial contamination (induced by the presence of the operators in the room) to levels even higher than 150%.

Key messages

In order to convey a correct and truthful message about the disinfection capabilities of an air purification system, testing the device under real operating would be necessary. Testing the device under real operating conditions, with and without the presence of people in controlled environments, would be necessary before the final product is placed on the market.

Rapid detection of Legionella spp in water samples by ScanVIT method: comparison of acid vs heat treatment

BACKGROUND

A rapid detection of Legionella bacteria in water samples is crucial to minimize the risk of acquiring infections, especially in health care facilities. Different detection methods and different decontamination procedures have been reported to affect the recovery of Legionella spp. Our goal was to test the recovery of Legionella pneumophila and Legionella non-pneumophila species using a kit based on non-specific and species-specific probes to treat water samples after two different decontamination procedures.

METHODS

The study was conducted with samples collected in the teaching hospital "Le Scotte" of Siena (Italy). Waters samples were analyzed by: i) ScanVIT method after treatment with acids; ii) ScanVIT method after heating; and iii) cultural standard method after heating. The results of the decontamination procedures and the detection methods were evaluated by comparing the number of Legionella-positive and -negative samples, and the recovery rates (CFU l-1) obtained by ScanVIT and the standard method.

RESULTS

We find that ScanVIT method is highly sensitive with both decontamination treatments, yielding a higher recovery of L. pneumophila compared to the standard method. Conversely, ScanVIT associated with the acid-treatment yielded the highest recovery of L. non-pneumophila.

CONCLUSIONS

The acid-treatment combined to the ScanVIT method increases the recovery of L. non-pneumophila in water samples compared to both ScanVIT associated with heat-treatment and standard culture method. Thus, this method may represent the best choice to detect L. non-pneumophila in water samples and reduce the risk of infection due to underestimation of Legionella loads.

Tuning a UV-C device to challenge new threats in the sanitization setting of healthcare facilities

Background

Environmental hospital hygiene plays a role in healthcare-associated infections emergency caused by resistant multi-drug organisms. The implementation of new and effective disinfection procedures is now more than ever important to prevent the cross-transmission of pathogens in the hospital facilities. In combination with common chemicals biocides, UV technology is a realistic option for environmental disinfection. In this study, we evaluate a UV device for its effectiveness on an emerging pathogen.

Methods

A laboratory cross section experiment was performed between August and October 2019. Two different strains of Candida auris (CBS 10913 and CBS 12372) were tested on 20 cm2 stainless steel carriers inoculated with 10 µl of bacterial culture at a concentration of 1x105 CFU/mL. The inoculum was spread until dry in aseptic condition. Carriers were placed parallel to the UV device, having 4 UV-C lamps that emit 325 W, at a fixed distance of 2.44 m. Biocidal tests were carried out in triple at three different light exposure times (5, 10 and 20 minutes). After treatment, laboratories procedures were used to detach and transfer the remaining microorganisms from the carriers to plates and compared them to controls after incubation at 37 °C for 48 h.

Results

A significant inactivation of C. auris already occurred at 5 minutes, reaching 3-4 log10 reduction at 20 minutes of UV-C exposure. No substantial differences were identified by analyzing the results between the two strains.

Conclusions

The chosen distance of 2.44 m from the target allows to ideally sanitize an entire hospital room. However, to avoid the limit of shaded areas due to the presence of non-movable objects, a couple of positions are recommended, so that shorter distances can reduce the exposure time or increase the average irradiance level of exposed surfaces.

Key messages

In sanitation of hospital environments, the use of viable alternatives as UV-C can contribute to the reduction of infections caused by multidrug-resistant microorganisms. Accurate testing of different space-time irradiation configurations allows to achieve important results related to the biocidal effects of UV devices.

A simulation model of microbe overlapping for the correct estimation of UV-C device log-reduction

Background

Candida auris is an emerging pathogen responsible for several outbreaks within healthcare facilities. It can be found on hospital surfaces and patient care devices. UV- C sanitisation may constitute an effective adjunct to routine room cleaning to prevent the spreading of this yeast. Previous findings with this technology suggest to investigate different sources of variability in the study of the biocidal effect of UV devices on C. auris. In this study we develop a computer simulation of surface distribution of microorganisms on a stainless steel carrier, to optimize UV-device experiments.

Methods

Based on the literature about C. auris studies and its estimated average size (about 5 μm diameter), several Matlab simulations have been performed to include as many microorganisms as possible to be ideally placed on a 20 cm2 stainless steel support, avoiding cell overlapping. This was done in order to maximize the effectiveness of UV exposure.

Results

Two initial simulations were performed to evaluate a random arrangement of a very large number of microorganisms (8x107 CFU) on the steel support, widely overlapped. In this case, due to the poor UV-C penetrability, we would not exceed two log10 reduction. By randomly distributing 1x106 CFU, the probability of overlapping was about 1.3%, but even a partial overlap limits the log10 reduction. By randomly distributing 1x105 CFU, the overlaps were at least 10 times less likely.

Conclusions

The simulation results allowed us to evaluate the most appropriate microorganism distribution model able to optimize the biocidal effects of UV-C devices. The overlapping of microorganisms reduces UV-C penetrability. Our simulated study is consistent with literature results where we observed a lower log-reduction by increasing the concentration of microorganisms and therefore the probability of overlapping. The resulting model would simulate any log-reduction scenario, at any distance and any concentration, with and without overlapping.

Key messages

The complete or partial microorganism overlapping plays a relevant role in the outcome of UV-C biocidal experiments. To identify the exponential CFU reduction curve and estimate accurately the inactivation rate constant, simulated experiments should be performed to assess the real effectiveness of UV devices.

Papanicolaou staining of exfoliated vaginal epithelial cells facilitates the prediction of ovulation in the giant panda

The giant panda is seasonally monoestrus, experiencing a single estrous with spontaneous ovulation in the spring. Therefore, accurate monitoring of the estrous cycle to pinpoint the time of ovulation is critical for the success of timed mating or artificial insemination. Analysis of exfoliated vaginal epithelial cells is a simple technique that rapidly yields information about the estrous status of a panda. Vaginal swabs were obtained during five estrous cycles of two nulliparous females. Cells were stained with the trichrome Papanicolaou and classified as basophils, intermediates or superficials. The color of stained cells, basophilic, acidophilic or keratinized, was recorded as a characteristic independent of the three standard cell types. The day urinary conjugates of estrogen fell from peak levels was considered the day of ovulation. A chromic shift occurred 8-9 days before ovulation when the majority of exfoliated vaginal cells changed from basophilic (blue) to acidophilic (pink) without accompanying nuclear or cytoplasmic changes. A second chromic shift was consistently observed 2 days prior to ovulation when keratinized (orange) cells replaced acidophils as the majority of vaginal cells. Monochrome staining of vaginal cells is sufficient to quantify superficial cells, which is a useful adjunct to behavioral and endocrinological data in determining estrous in the giant panda. However, the timing and duration of superficial cell elevations are substantially different between and within individual females, which limits the accuracy of timing ovulation for artificial insemination. The predictive value of vaginal cytology was greatly enhanced with the trichrome stain and evaluation of cell color.

Expression of developmentally regulated crypt cell antigens in human and rat intestinal tumors

The expression of 5 antigens specific for adult intestinal crypt cells and defined by monoclonal antibodies prepared to surface membrane components of the human colon tumor cell line CaCo-2 was studied during fetal and postnatal development of Sprague-Dawley rat small and large intestines. In the small intestine, all epithelial cells were stained during fetal life; antigen distribution became restricted to the crypt and lower villus cells in suckling animals and to the crypt cells after weaning. In the colon, these antigens could be detected only during a short period of development, comprising the last 3-4 days of fetal life and the first 8-10 days after birth. Expression of the antigens defined by this group of antibodies was investigated in rat intestinal tumors induced by 1,2-dimethylhydrazine (CAS: 540-73-8) and in normal and diseased human colons. In rats, these antigens were detected in all poorly and moderately differentiated adenocarcinomas of the small and large intestines. In most specimens, antigen distribution was not uniform; intensely stained areas were surrounded by completely negative tumor regions. Antigen expression was less intense in well-differentiated tumors, and about half of the tumors were negative for antigen expression. A similar pattern of expression of these antigens was observed in all human colonic adenocarcinomas examined; all samples of normal colon, benign polyps, and inflammatory bowel diseases examined were negative. These results suggest that this group of monoclonal antibodies recognizes oncofetal rat antigens expressed in chemically induced rat intestinal tumors and human colonic adenocarcinomas.