Environmental decontamination of a hospital isolation room using high-intensity narrow-spectrum light

Controlling hospital-acquired infection: focus on the role of the environment and new technologies for decontamination

There is increasing interest in the role of cleaning for managing hospital-acquired infections (HAI). Pathogens such as vancomycin-resistant enterococci (VRE), methicillin-resistant Staphylococcus aureus (MRSA), multiresistant Gram-negative bacilli, norovirus, and Clostridium difficile persist in the health care environment for days. Both detergent- and disinfectant-based cleaning can help control these pathogens, although difficulties with measuring cleanliness have compromised the quality of published evidence. Traditional cleaning methods are notoriously inefficient for decontamination, and new approaches have been proposed, including disinfectants, steam, automated dispersal systems, and antimicrobial surfaces. These methods are difficult to evaluate for cost-effectiveness because environmental data are not usually modeled against patient outcome. Recent studies have reported the value of physically removing soil using detergent, compared with more expensive (and toxic) disinfectants. Simple cleaning methods should be evaluated against nonmanual disinfection using standardized sampling and surveillance. Given worldwide concern over escalating antimicrobial resistance, it is clear that more studies on health care decontamination are required. Cleaning schedules should be adapted to reflect clinical risk, location, type of site, and hand touch frequency and should be evaluated for cost versus benefit for both routine and outbreak situations. Forthcoming evidence on the role of antimicrobial surfaces could supplement infection prevention strategies for health care environments, including those targeting multidrug-resistant pathogens.

Inactivation of Streptomyces phage ɸC31 by 405 nm light: Requirement for exogenous photosensitizers?

Exposure to narrowband violet-blue light around 405 nm wavelength can induce lethal oxidative damage to bacteria and fungi, however effects on viruses are unknown. As photosensitive porphyrin molecules are involved in the microbicidal inactivation mechanism, and since porphyrins are absent in viruses, then any damaging effects of 405 nm light on viruses might appear unlikely. This study used the bacteriophage ɸC31, as a surrogate for non-enveloped double-stranded DNA viruses, to establish whether 405 nm light can induce virucidal effects. Exposure of ɸC31 suspended in minimal media, nutrient-rich media, and porphyrin solution, demonstrated differing sensitivity of the phage. Significant reductions in phage titer occurred when exposed in nutrient-rich media, with ~3-, 5- and 7-log₁₀ reductions achieved after exposure to doses of 0.3, 0.5 and 1.4 kJ/cm², respectively. When suspended in minimal media a 0.3-log₁₀ reduction (P = 0.012) occurred after exposure to 306 J/cm²: much lower than the 2.7- and > 2.5-log₁₀ reductions achieved with the same dose in nutrient-rich, and porphyrin-supplemented media, suggesting inactivation is accelerated by the photo-activation of light-sensitive components in the media. This study provides the first evidence of the interaction of narrowband 405 nm light with viruses, and demonstrates that viral susceptibility to 405 nm light can be significantly enhanced by involvement of exogenous photosensitive components. The reduced susceptibility of viruses in minimal media, compared with that of other microorganisms, provides further evidence that the antimicrobial action of 405 nm light is predominantly due to the photo-excitation of endogenous photosensitive molecules such as porphyrins within susceptible microorganisms.

Efficacy of three light technologies for reducing microbial populations in liquid suspensions

The aim of the current study was to evaluate the effectiveness of three nonthermal light technologies (NUV-Vis, continuous UV, and HILP) on their ability to inactivate Escherichia coli K12 and Listeria innocua.  E. coli K12 was selected as a representative microorganism for the enterohaemorrhagic foodborne pathogen E. coli O157:H7 and L. innocua as a surrogate microorganism for the common foodborne pathogen Listeria monocytogenes, respectively. The liquid matrix used for the disinfection experiments was a liquid matrix (MRD solution). The results of the present study show that the HILP treatment inactivated both E. coli and L. innocua more rapidly and effectively than either continuous UV-C or NUV-vis treatment. With HILP at 2.5 cm from the lamp, E. coli and L. innocua populations were reduced by 3.07 and 3.77 log10 CFU/mL, respectively, after a 5 sec treatment time, and were shown to be below the limit of detection (<0.22 log10 CFU/mL) following 30 sec exposure to HILP (106.2 J/cm(2)). These studies demonstrate the bactericidal efficacy of alternative nonthermal light technologies and their potential as decontamination strategies in the food industry.

Cleaning and decontamination of the healthcare environment

Evidence is accumulating for the role of cleaning in controlling hospital infections. Hospital pathogens such as meticillin-resistant Staphylococcus aureus (MRSA), vancomycin-resistant enterococci (VRE), norovirus, multi-resistant Gram-negative bacilli and Clostridium difficile persist in the healthcare environment for considerable lengths of time. Cleaning with both detergent and disinfectant-based regimens help control these pathogens in both routine and outbreak situations. The most important transmission risk comes from organisms on frequently handled items because hand contact with a contaminated site could deliver a pathogen to a patient. Cleaning practices should be tailored to clinical risk, near-patient areas and hand-touch-sites and scientifically evaluated for all surfaces and equipment in today’s hospitals.

A randomized controlled trial of enhanced cleaning to reduce contamination of healthcare worker gowns and gloves with multidrug-resistant bacteria

OBJECTIVE. To determine whether enhanced daily cleaning would reduce contamination of healthcare worker (HCW) gowns and gloves with methicillin-resistant Staphylococcus aureus (MRSA) or multidrug-resistant Acinetobacter baumannii (MDRAB). DESIGN. A cluster-randomized controlled trial. SETTING. Four intensive care units (ICUs) in an urban tertiary care hospital. PARTICIPANTs. ICU rooms occupied by patients colonized with MRSA or MDRAB. INTERVENTION. Extra enhanced daily cleaning of ICU room surfaces frequently touched by HCWs. RESULTS. A total of 4,444 cultures were collected from 132 rooms over 10 months. Using fluorescent dot markers at 2,199 surfaces, we found that 26% of surfaces in control rooms were cleaned and that 100% of surfaces in experimental rooms were cleaned (P < .001). The mean proportion of contaminated HCW gowns and gloves following routine care provision and before leaving the rooms of patients with MDRAB was 16% among control rooms and 12% among experimental rooms (relative risk, 0.77 [95% confidence interval, 0.28-2.11]; P = .23). For MRSA, the mean proportions were 22% and 19%, respectively (relative risk, 0.89 [95% confidence interval, 0.50-1.53]; P = .16). DISCUSSION. Intense enhanced daily cleaning of ICU rooms occupied by patients colonized with MRSA or MDRAB was associated with a nonsignificant reduction in contamination of HCW gowns and gloves after routine patient care activities. Further research is needed to determine whether intense environmental cleaning will lead to significant reductions and fewer infections.

Relationship between nasal colonization and ventilator-associated pneumonia and the role of the environment in transmission of Staphylococcus aureus in intensive care units

BACKGROUND

This study assessed the relationship between nasal colonization and ventilator-associated pneumonia (VAP) by Staphylococcus aureus, as well the role of the environment in the transmission of this organism.

METHODS

We performed a cohort study of patients with VAP caused by methicillin-resistant S aureus (MRSA) or methicillin-sensitive S aureus during 2 years in an adult intensive care unit (ICU). All patients had nasal swab specimens obtained at admission and during the ICU stay. Clinical samples also were collected for analysis, as were samples from the hands of health care professionals and the environment, and were typed using pulsed-field gel electrophoresis.

RESULTS

S aureus VAP represented 12.5% of the cases, and statistical analysis identified colonization as a risk factor for the development of this infection. MRSA was isolated from the environment and hands, indicating the existence of a secondary reservoir. Molecular typing revealed a polyclonal profile; however, clone J was the most frequent (45.5%) among isolates of MRSA tested, with a greater profile of resistance than the other isolates. There was strong evidence suggesting transmission of MRSA to patients from the environment.

CONCLUSION

Nasal colonization for S aureus is a risk factor for development of VAP.

Can biowarfare agents be defeated with light?

Biological warfare and bioterrorism is an unpleasant fact of 21st century life. Highly infectious and profoundly virulent diseases may be caused in combat personnel or in civilian populations by the appropriate dissemination of viruses, bacteria, spores, fungi, or toxins. Dissemination may be airborne, waterborne, or by contamination of food or surfaces. Countermeasures may be directed toward destroying or neutralizing the agents outside the body before infection has taken place, by destroying the agents once they have entered the body before the disease has fully developed, or by immunizing susceptible populations against the effects. A range of light-based technologies may have a role to play in biodefense countermeasures. Germicidal UV (UVC) is exceptionally active in destroying a wide range of viruses and microbial cells, and recent data suggests that UVC has high selectivity over host mammalian cells and tissues. Two UVA mediated approaches may also have roles to play; one where UVA is combined with titanium dioxide nanoparticles in a process called photocatalysis, and a second where UVA is combined with psoralens (PUVA) to produce "killed but metabolically active" microbial cells that may be particularly suitable for vaccines. Many microbial cells are surprisingly sensitive to blue light alone, and blue light can effectively destroy bacteria, fungi, and Bacillus spores and can treat wound infections. The combination of photosensitizing dyes such as porphyrins or phenothiaziniums and red light is called photodynamic therapy (PDT) or photoinactivation, and this approach cannot only kill bacteria, spores, and fungi, but also inactivate viruses and toxins. Many reports have highlighted the ability of PDT to treat infections and stimulate the host immune system. Finally pulsed (femtosecond) high power lasers have been used to inactivate pathogens with some degree of selectivity. We have pointed to some of the ways light-based technology may be used to defeat biological warfare in the future.

Light based anti-infectives: ultraviolet C irradiation, photodynamic therapy, blue light, and beyond

Owing to the worldwide increase in antibiotic resistance, researchers are investigating alternative anti-infective strategies to which it is supposed microorganisms will be unable to develop resistance. Prominent among these strategies, is a group of approaches which rely on light to deliver the killing blow. As is well known, ultraviolet light, particularly UVC (200-280 nm), is germicidal, but it has not been much developed as an anti-infective approach until recently, when it was realized that the possible adverse effects to host tissue were relatively minor compared to its high activity in killing pathogens. Photodynamic therapy is the combination of non-toxic photosensitizing dyes with harmless visible light that together produce abundant destructive reactive oxygen species (ROS). Certain cationic dyes or photosensitizers have good specificity for binding to microbial cells while sparing host mammalian cells and can be used for treating many localized infections, both superficial and even deep-seated by using fiber optic delivered light. Many microbial cells are highly sensitive to killing by blue light (400-470 nm) due to accumulation of naturally occurring photosensitizers such as porphyrins and flavins. Near infrared light has also been shown to have antimicrobial effects against certain species. Clinical applications of these technologies include skin, dental, wound, stomach, nasal, toenail and other infections which are amenable to effective light delivery.

Continuous decontamination of an intensive care isolation room during patient occupancy using 405 nm light technology

Environmental contamination within intensive care units (ICU) is recognised as a source of patient infection, and improved cleaning and disinfection methods are continually being sought. Visible light of 405 nm has been shown to have bactericidal properties, and this communication reports on the use of a ceiling-mounted 405 nm light system for continuous environmental disinfection of contact surfaces and air in an occupied ICU isolation room. Levels of bacterial contamination on a range of contact surfaces around the room were assessed before, during and after use of the system. For each study, the lighting units were operated continuously during daylight hours. Results demonstrate that the spatial distribution of bacterial contamination was reduced almost uniformly across all sampled contact surfaces during use of the 405 nm light system. Pooled data showed that significant reductions in overall bacterial contamination around the room were achieved, with bacterial counts reduced by up to 67% ( p=0.0001) over and above that achieved with standard cleaning and infection control procedures alone. Use of 405 nm light significantly reduced environmental contamination across almost all sampled contact surfaces within the ICU isolation room. This has particular benefit in ICU where equipment and other ‘hand-touch’ sites make routine cleaning difficult, thus helping maintain a cleaner environment, and contributing to reducing cross-infection from environmental sources.

Roles of sunlight and natural ventilation for controlling infection: historical and current perspectives

BACKGROUND

Infections caught in buildings are a major global cause of sickness and mortality. Understanding how infections spread is pivotal to public health yet current knowledge of indoor transmission remains poor.

AIM

To review the roles of natural ventilation and sunlight for controlling infection within healthcare environments.

METHODS

Comprehensive literature search was performed, using electronic and library databases to retrieve English language papers combining infection; risk; pathogen; and mention of ventilation; fresh air; and sunlight. Foreign language articles with English translation were included, with no limit imposed on publication date.

FINDINGS

In the past, hospitals were designed with south-facing glazing, cross-ventilation and high ceilings because fresh air and sunlight were thought to reduce infection risk. Historical and recent studies suggest that natural ventilation offers protection from transmission of airborne pathogens. Particle size, dispersal characteristics and transmission risk require more work to justify infection control practices concerning airborne pathogens. Sunlight boosts resistance to infection, with older studies suggesting potential roles for surface decontamination.

CONCLUSIONS

Current knowledge of indoor transmission of pathogens is inadequate, partly due to lack of agreed definitions for particle types and mechanisms of spread. There is recent evidence to support historical data on the effects of natural ventilation but virtually none for sunlight. Modern practice of designing healthcare buildings for comfort favours pathogen persistence. As the number of effective antimicrobial agents declines, further work is required to clarify absolute risks from airborne pathogens along with any potential benefits from additional fresh air and sunlight.

Lethal effects of high-intensity violet 405-nm light on Saccharomyces cerevisiae, Candida albicans, and on dormant and germinating spores of Aspergillus niger

This study assessed the effects of high-intensity violet light on selected yeast and mould fungi. Cell suspensions of Saccharomyces cerevisiae, Candida albicans, and dormant and germinating spores (conidia) of the mould Aspergillus niger were exposed to high-intensity narrow band violet light with peak output at 405 nm generated from a light-emitting diode (LED) array. All three fungal species were inactivated by the 405-nm light without a requirement for addition of exogenous photosensitiser chemicals. Of the fungal species tested, S. cerevisiae was most sensitive and dormant conidia of A. niger were most resistant to 405-nm light exposure. Five-log10 colony forming units per millilitre (CFU ml(-1)) reductions of the tested species required exposure doses of 288 J cm(-2) for S. cerevisiae, 576 J cm(-2) for C. albicans, and a much higher value of 2.3 kJ cm(-2) for dormant conidia of A. niger. During germination, A. niger conidia became more sensitive to 405-nm light exposure and sensitivity increased as germination progressed over an 8 h test period. Light exposure under aerobic and anaerobic conditions, together with results obtained using ascorbic acid as a scavenger of reactive oxygen species, revealed that 405-nm light inactivation in fungi involved an oxygen-dependent mechanism, as previously described in bacteria. The inactivation results achieved with yeast cells and fungal spores together with operational advantages associated with the use of a visible (nonultraviolet (UV)) light source highlight the potential of 405-nm light for fungal decontamination applications.

Self-disinfecting surfaces: review of current methodologies and future prospects

Methods to improve disinfection of environmental surfaces in hospital rooms include improving cleaning/disinfection by environmental service workers through education and feedback on cleaning effectiveness (eg, use of fluorescent dyes), "no-touch" methods (eg, UV-C light), and self-disinfecting surfaces. Self-disinfecting surfaces can be created by impregnating or coating surfaces with heavy metals (eg, silver or copper), germicides (eg, triclosan), or miscellaneous methods (eg, light-activated antimicrobials). These methods are under active investigation but to date have not been assessed for their ability to reduce health care-associated infections.

Photoinactivation of bacteria attached to glass and acrylic surfaces by 405 nm light: potential application for biofilm decontamination

Attachment of bacteria to surfaces and subsequent biofilm formation remains a major cause of cross-contamination capable of inducing both food-related illness and nosocomial infections. Resistance to many current disinfection technologies means facilitating their removal is often difficult. The aim of this study was to investigate the efficacy of 405 nm light for inactivation of bacterial attached as biofilms to glass and acrylic. Escherichia coli biofilms (10(3)-10(8) CFU mL(-1)) were generated on glass and acrylic surfaces and exposed for increasing times to 405 nm light (5-60 min) at ca 140 mW cm(-2). Successful inactivation of biofilms has been demonstrated, with results highlighting complete/near-complete inactivation (up to 5 log10 reduction on acrylic and 7 log10 on glass). Results also highlight that inactivation of bacterial biofilms could be achieved whether the biofilm was on the upper "directly exposed" surface or "indirectly exposed" underside surface. Statistically significant inactivation was also shown with a range of other microorganisms associated with biofilm formation (Staphylococcus aureus, Pseudomonas aeruginosa and Listeria monocytogenes). Results from this study have demonstrated significant inactivation of bacteria ranging from monolayers to densely populated biofilms using 405 nm light, highlighting that with further development this technology may have potential applications for biofilm decontamination in food and clinical settings.

Sporicidal effects of high-intensity 405 nm visible light on endospore-forming bacteria

Resistance of bacterial endospores to treatments, including biocides, heat and radiation is a persistent problem. This study investigates the susceptibility of Bacillus and Clostridium endospores to 405 nm visible light, wavelengths which have been shown to induce inactivation of vegetative bacterial cells. Suspensions of B. cereus endospores were exposed to high-intensity 405 nm light generated from a light-emitting diode array and results demonstrate the induction of a sporicidal effect. Up to a 4-log(10) CFU mL(-1) reduction in spore population was achieved after exposure to a dose of 1.73 kJ cm(-2). Similar inactivation kinetics were demonstrated with B. subtilis, B. megaterium and C. difficile endospores. The doses required for inactivation of endospores were significantly higher than those required for inactivation of B. cereus and C. difficile vegetative cells, where ca 4-log(10) CFU mL(-1) reductions were achieved after exposure to doses of 108 and 48 J cm(-2), respectively. The significant increase in dose required for inactivation of endospores compared with vegetative cells is unsurprising due to the notorious resilience of these microbial structures. However, the demonstration that visible light of 405 nm can induce a bactericidal effect against endospores is significant, and could have potential for incorporation into decontamination methods for the removal of bacterial contamination including endospores.

Priorities in the prevention and control of multidrug-resistant Enterobacteriaceae in hospitals

BACKGROUND

Multidrug-resistant Enterobacteriaceae (MDE) are a major public health threat due to international spread and few options for treatment. Furthermore, unlike meticillin-resistant Staphylococcus aureus (MRSA), MDE encompass several genera and multiple resistance mechanisms, including extended-spectrum beta-lactamases and carbapenemases, which complicate detection in the routine diagnostic laboratory. Current measures to contain spread in many hospitals are somewhat ad hoc as there are no formal national or international guidelines.

AIM

We sought to establish what should be the priorities for the prevention and control of MDE and what is feasible for implementation. We also identify areas for further research.

METHODS

We reviewed the published literature and other sources e.g. national agencies, for measures and interventions used to control MDE.

FINDINGS

Certain categories of at risk patients should be screened, especially in critical care areas, using appropriate laboratory methods. Standard and contact precautions are essential and hand hygiene compliance requires continued emphasis and high compliance levels. As MDE may persist on environmental surfaces for weeks, environmental decontamination could also be an effective control intervention. There are limited options for decolonisation with inadequate studies to date and antibiotic stewardship within and outside the hospital remains important.

CONCLUSION

As there is a clear deficit in the evidence base to infor guidance on prevention and control, research in key areas, such as rapid detection, is urgently required.

Blue light for infectious diseases: Propionibacterium acnes, Helicobacter pylori, and beyond?

Blue light, particularly in the wavelength range of 405-470 nm, has attracted increasing attention due to its intrinsic antimicrobial effect without the addition of exogenous photosensitizers. In addition, it is commonly accepted that blue light is much less detrimental to mammalian cells than ultraviolet irradiation, which is another light-based antimicrobial approach being investigated. In this review, we discussed the blue light sensing systems in microbial cells, antimicrobial efficacy of blue light, the mechanism of antimicrobial effect of blue light, the effects of blue light on mammalian cells, and the effects of blue light on wound healing. It has been reported that blue light can regulate multi-cellular behavior involving cell-to-cell communication via blue light receptors in bacteria, and inhibit biofilm formation and subsequently potentiate light inactivation. At higher radiant exposures, blue light exhibits a broad-spectrum antimicrobial effect against both Gram-positive and Gram-negative bacteria. Blue light therapy is a clinically accepted approach for Propionibacterium acnes infections. Clinical trials have also been conducted to investigate the use of blue light for Helicobacter pylori stomach infections and have shown promising results. Studies on blue light inactivation of important wound pathogenic bacteria, including Staphylococcus aureus and Pseudomonas aeruginosa have also been reported. The mechanism of blue light inactivation of P. acnes, H. pylori, and some oral bacteria is proved to be the photo-excitation of intracellular porphyrins and the subsequent production of cytotoxic reactive oxygen species. Although it may be the case that the mechanism of blue light inactivation of wound pathogens (e.g., S. aureus, P. aeruginosa) is the same as that of P. acnes, this hypothesis has not been rigorously tested. Limited and discordant results have been reported regarding the effects of blue light on mammalian cells and wound healing. Under certain wavelengths and radiant exposures, blue light may cause cell dysfunction by the photo-excitation of blue light sensitizing chromophores, including flavins and cytochromes, within mitochondria or/and peroxisomes. Further studies should be performed to optimize the optical parameters (e.g., wavelength, radiant exposure) to ensure effective and safe blue light therapies for infectious disease. In addition, studies are also needed to verify the lack of development of microbial resistance to blue light.

Clinical studies of the High-Intensity Narrow-Spectrum light Environmental Decontamination System (HINS-light EDS), for continuous disinfection in the burn unit inpatient and outpatient settings

Infections are the leading cause of morbidity and mortality in burn patients and prevention of contamination from exogenous sources including the hospital environment is becoming increasingly emphasised. The High-Intensity Narrow-Spectrum light Environmental Decontamination System (HINS-light EDS) is bactericidal yet safe for humans, allowing continuous disinfection of the environment surrounding burn patients. Environmental samples were collected from inpatient isolation rooms and the outpatient clinic in the burn unit, and comparisons were then made between the bacterial contamination levels observed with and without use of the HINS-light EDS. Over 1000 samples were taken. Inpatient studies, with sampling carried out at 0800 h, demonstrated a significant reduction in the average number of bacterial colonies following HINS-light EDS use of between 27% and 75%, (p<0.05). There was more variation when samples were taken at times of increased activity in the room. Outpatient studies during clinics demonstrated a 61% efficacy in the reduction of bacterial contamination on surfaces throughout the room during the course of a clinic (p=0.02). The results demonstrate that use of the HINS-light EDS allows efficacious bacterial reductions over and above that achieved by standard cleaning and infection control measures in both inpatient and outpatient settings in the burn unit.

Assessing the efficacy of photocatalytic oxidation on bacterial contamination in a clinical setting – a randomised controlled trial

Airborne contamination has been shown to be a significant source of wound contamination in orthopaedic surgery. This is the first reported study looking at the efficacy of ActivTek 300, a portable UV/TiO2-based air purifier unit to reduce airborne contamination in a clinical setting. In this randomised study the investigator was blinded as to whether the unit had been on or off for the previous seven days.

Air contamination was measured weekly using a validated technique in ward treatment rooms using a Mini Air Sampler (MAS-100) and agar plates, over a period of 12 weeks. The agar plates were then incubated for 24 hours and the results were expressed as number of colony forming units per plate (cfu). The biomedical scientist who manually counted the number of cfus was blinded as to whether the unit was on or off. Measurements were duplicated to improve the accuracy of the study, and in addition to this an identical experiment was set up in a second treatment room on a separate randomisation schedule. Analysis of the data demonstrated median colony count was significantly lower with the unit on (Median = 43 interquartile range (IQR) 30 to 83) than when it was off (median = 95 IQR 44 to 143) ( p < 0.01). This represents a 55% mean reduction in the colony count. This study suggests that the portable UV/TiO2-based air purifier unit is efficacious in reducing airborne contamination in the clinical environment and may have a promising role in reducing overall infection rates in surgical patients.

Effect of 405-nm high-intensity narrow-spectrum light on fibroblast-populated collagen lattices: an in vitro model of wound healing

High-intensity narrow-spectrum (HINS) 405-nm light is a novel technology developed to address the significant problem of health-care associated infection. Its potential for wound-decontamination applications is assessed on mammalian cells and bacteria. The fibroblast-populated collagen lattice (FPCL) is used as an in vitro model of wound healing, and the effect of HINS light on contraction is examined. Effects on cell proliferation, morphological changes, and α-smooth muscle actin (α-SMA) expression are investigated. Bactericidal effects are assessed using the bacterium Staphylococcus epidermidis. Low doses of HINS light were found to have no significant inhibitory effects on FPCL contraction, cell proliferation, or α-SMA expression. Doses of up to 18 Jcm(-2) had no significant inhibitory effects on FPCL cell numbers, and this dose was shown to cause almost complete inactivation of bacteria. These results show that HINS light has potential for disinfection applications without adversely influencing wound healing.