objective. To determine the bactericidal effect on surfaces of ceiling- and wall-mounted UV C (UVC) light (wavelength, 254 nm) in isolation units, compared with standard hospital environmental cleaning and chemical disinfection during final disinfection after patients are treated for infections.
design. Microbial samples were obtained from surfaces in isolation units (patient room, anteroom, and bathroom) before and after irradiation with UVC, chloramine disinfection, and standard hospital environmental cleaning. Samples were tested using standard contact plates.
setting. Four identical, negative air-pressure isolation units (patient room, anteroom, and bathroom) with a defined number of ceiling- and wall-mounted UVC light units. The UVC distribution was monitored in one isolation unit after irradiation for approximately 40 minutes, corresponding to doses ranging from 160 J/m2 in a shadowed area to 19,230 J/m2 at the mostly highly exposed site (which is high enough to inactivate most bacterial organisms, including spores).
results. UVC disinfection significantly reduced the number of bacteria on surfaces directly or indirectly exposed to UVC to a very low number, as did 5% chloramine disinfection alone (P <.001 for both). Completely shadowed areas in the isolation unit (eg, the bed rail, lockers, and mattresses) still required disinfection by chemicals. conclusion. Disinfection with UVC light may significantly reduce environmental bacterial contamination and thereby protect the next patient housed in an isolation room. UVC disinfection may not be used alone but is a good addition to chemical disinfection.
Infect Control Hosp Epidemiol 2006; 27:729-734
To control the spread of pathogens in hospital environments, good hygienic routines are required to clean and disinfect surfaces contaminated with biological materials.1-7 Chemicals such as chlorine and 5% chloramine have traditionally been used in Norway to disinfect surfaces during final room disinfection.8 However, chemical disinfection is both time- and labor-consuming, and it might be harmful for staff and the environment.8 The search for more environmentally friendly and healthier methods has therefore been under way for many years.
UV C light (UVC; wavelength, 200-280 nm) has a germicidal effect on microorganisms in water, on surfaces, and in air, and it is used for disinfection both inside and outside hospitals.9-19 UVC is lethal to bacteria, bacterial spores, viruses, mold, mold spores, yeast, and algae, but the doses needed to inactivate them vary.20 UVC is absorbed by organic materials, and its ability to penetrate is low. Therefore, cleaning of visibly soiled surfaces is necessary before UVC disinfection. Also, chemical disinfection agents such as chlorine or chloramines may have reduced effect in the presence of organic materials. As a separate procedure, soil and visible organic materials are always removed immediately when they are detected by the staff during “spot cleaning” and disinfection.8 When the final disinfection is done, all visible organic materials and soil have been removed first. Chloramine disinfection of surfaces in rooms is always followed by standard hospital environmental cleaning, to remove the chemical agent.8
In the present study, we tested the bactericidal effect of UVC from ceiling- and wall-mounted units in negative air- pressure isolation units for patients with airborne infections. The main aim was to see whether UVC could be used for final surface disinfection in patient rooms.
METHODS
Four identical negative air-pressure isolation units for patients with infectious diseases were studied with respect to the effect of final disinfection after a patient has been discharged. The isolation rooms were used for patients with, for example, methicillin-resistant Staphylococcus aureus (MRSA) infection, tuberculosis of the lung, and other airborne infections. Standard hospital environmental cleaning with non-antibacterial soap and water was done daily during each patient’s hospitalization. Mop heads were changed between each procedure. Used mop heads and water containers were decontaminated at 85°C after each cleaning and placed in the patient decontamination room. The equipment was not used in other patient rooms. Soil and visible organic materials were removed immediately by the ward staff when they were detected, by spot cleaning and disinfection.8 Final disinfection (after the patient was discharged) was done with the water container and chloramine prediluted to 5%, for 1 hour, using a cloth on walls and equipment and the mop on the floor. This was followed by standard hospital environmental cleaning to remove the chloramine.8 Each unit consisted of an anteroom, a patient room, and a bathroom/decontamination room, as shown in Figure 1. Negative air pressure (approximately -45 Pa) was provided with inward airflow and an air change rate in the patient room of 5-6 air changes per hour. All exhaust air from the rooms was disinfected with filtration and UVC exposure.
All rooms were supplied with stainless steel UVC units for the exposure of walls, floors, and equipment: the ceiling-mounted Z-300 unit (fan capacity, 170 m3/h; UVC lamps, 10 x 30 W Osram HNS OFR; power supply, 230 V single-phase AC; power consumption, 391 W; current, 1.7 A; dimensions, 1205 x 505 x 100 mm; weight, approximately 30 kg) and wall-mounted Z-30 unit (no fan; UVC lamps, 1 x 30 W Osram HNS OFR; power supply, 230 V single-phase AC; power consumption, 30 W; current, 0.15 A; dimensions, 1180 x 150 x 79 mm; weight, approximately 7 kg) (Figure 1) (Klean ASA System).19 The system has been tested and approved by Norwegian technical authority (NEMCO). The patient room had 9 wall-mounted and 2 ceiling-mounted UVC units, the anteroom had 5 wall-mounted units and 1 ceiling-mounted unit, and the bathroom had 3 wall-mounted units and 1 ceiling-mounted UVC unit.
The UVC irradiance levels were measured with a UVX radiometer with a sensor calibrated at 254 nm (UVP Products). Calculations of total UVC doses were performed for all the UVC measurements by using the following formula: UVC dose (J/m2) = irradiance (W/m2) x exposure time (in seconds). A total of 165 measurements were taken at different positions in isolation unit 101—the floors, on top of and under shelves and the bed, and other open areas. On the floors in the patient room, anteroom, and bathroom, the UVC irradiance was measured every 0.5 m starting 0.1 m from the wall, giving 133 single points in total. In addition, the UVC dose was monitored at 32 different positions, aside from floors (Table 1).The UVC disinfection time used in the study was approximately 40 minutes (variation, 33-47 minutes because of hospital daily activities). A schematic drawing of the distribution of UVC on the floor is shown in Figure 2. On the floor in the isolation unit 101 UVC irradiance levels varied from 0.08 to 3.2 W/m2 (Table 1). Average ± SD values of 1.95 ± 0.65 W/m2 (n = 133) was found for all samples; 2.2 ± 0.5 W/m2 (n = 70) was found in the patient room, 2.0 ± 0.7 W/m2 (n = 31) in the anteroom, and 1.4 ± 0.5 W/m2 (n = 32) in the bathroom. At other positions in the isolation unit the UVC output varied from 0.08 to 6.82 W/m2 (Table 1). The isolation units were exposed to UVC for a mean of 40 minutes (range, 33-47 minutes). The shortest exposure time corresponds to UVC doses ranging from 160 to 13,500 J/m2, and the longest irradiation results in a dose of 230-19,200 J/m2.
UV C light (UVC; wavelength, 200-280 nm) has a germicidal effect on microorganisms in water, on surfaces, and in air, and it is used for disinfection both inside and outside hospitals.9-19 UVC is lethal to bacteria, bacterial spores, viruses, mold, mold spores, yeast, and algae, but the doses needed to inactivate them vary.20 UVC is absorbed by organic materials, and its ability to penetrate is low. Therefore, cleaning of visibly soiled surfaces is necessary before UVC disinfection. Also, chemical disinfection agents such as chlorine or chloramines may have reduced effect in the presence of organic materials. As a separate procedure, soil and visible organic materials are always removed immediately when they are detected by the staff during “spot cleaning” and disinfection.8 When the final disinfection is done, all visible organic materials and soil have been removed first. Chloramine disinfection of surfaces in rooms is always followed by standard hospital environmental cleaning, to remove the chemical agent.8
In the present study, we tested the bactericidal effect of UVC from ceiling- and wall-mounted units in negative air- pressure isolation units for patients with airborne infections. The main aim was to see whether UVC could be used for final surface disinfection in patient rooms.
METHODS
Four identical negative air-pressure isolation units for patients with infectious diseases were studied with respect to the effect of final disinfection after a patient has been discharged. The isolation rooms were used for patients with, for example, methicillin-resistant Staphylococcus aureus (MRSA) infection, tuberculosis of the lung, and other airborne infections. Standard hospital environmental cleaning with non-antibacterial soap and water was done daily during each patient’s hospitalization. Mop heads were changed between each procedure. Used mop heads and water containers were decontaminated at 85°C after each cleaning and placed in the patient decontamination room. The equipment was not used in other patient rooms. Soil and visible organic materials were removed immediately by the ward staff when they were detected, by spot cleaning and disinfection.8 Final disinfection (after the patient was discharged) was done with the water container and chloramine prediluted to 5%, for 1 hour, using a cloth on walls and equipment and the mop on the floor. This was followed by standard hospital environmental cleaning to remove the chloramine.8 Each unit consisted of an anteroom, a patient room, and a bathroom/decontamination room, as shown in Figure 1. Negative air pressure (approximately -45 Pa) was provided with inward airflow and an air change rate in the patient room of 5-6 air changes per hour. All exhaust air from the rooms was disinfected with filtration and UVC exposure.
All rooms were supplied with stainless steel UVC units for the exposure of walls, floors, and equipment: the ceiling-mounted Z-300 unit (fan capacity, 170 m3/h; UVC lamps, 10 x 30 W Osram HNS OFR; power supply, 230 V single-phase AC; power consumption, 391 W; current, 1.7 A; dimensions, 1205 x 505 x 100 mm; weight, approximately 30 kg) and wall-mounted Z-30 unit (no fan; UVC lamps, 1 x 30 W Osram HNS OFR; power supply, 230 V single-phase AC; power consumption, 30 W; current, 0.15 A; dimensions, 1180 x 150 x 79 mm; weight, approximately 7 kg) (Figure 1) (Klean ASA System).19 The system has been tested and approved by Norwegian technical authority (NEMCO). The patient room had 9 wall-mounted and 2 ceiling-mounted UVC units, the anteroom had 5 wall-mounted units and 1 ceiling-mounted unit, and the bathroom had 3 wall-mounted units and 1 ceiling-mounted UVC unit.
The UVC irradiance levels were measured with a UVX radiometer with a sensor calibrated at 254 nm (UVP Products). Calculations of total UVC doses were performed for all the UVC measurements by using the following formula: UVC dose (J/m2) = irradiance (W/m2) x exposure time (in seconds). A total of 165 measurements were taken at different positions in isolation unit 101—the floors, on top of and under shelves and the bed, and other open areas. On the floors in the patient room, anteroom, and bathroom, the UVC irradiance was measured every 0.5 m starting 0.1 m from the wall, giving 133 single points in total. In addition, the UVC dose was monitored at 32 different positions, aside from floors (Table 1).The UVC disinfection time used in the study was approximately 40 minutes (variation, 33-47 minutes because of hospital daily activities). A schematic drawing of the distribution of UVC on the floor is shown in Figure 2. On the floor in the isolation unit 101 UVC irradiance levels varied from 0.08 to 3.2 W/m2 (Table 1). Average ± SD values of 1.95 ± 0.65 W/m2 (n = 133) was found for all samples; 2.2 ± 0.5 W/m2 (n = 70) was found in the patient room, 2.0 ± 0.7 W/m2 (n = 31) in the anteroom, and 1.4 ± 0.5 W/m2 (n = 32) in the bathroom. At other positions in the isolation unit the UVC output varied from 0.08 to 6.82 W/m2 (Table 1). The isolation units were exposed to UVC for a mean of 40 minutes (range, 33-47 minutes). The shortest exposure time corresponds to UVC doses ranging from 160 to 13,500 J/m2, and the longest irradiation results in a dose of 230-19,200 J/m2.
figure 1.
Schematic drawing of isolation unit 101. Each isolation unit consists of an anteroom, a patient room, and a bathroom/decontamination room. Negative air pressure is provided, with inward airflow and an air change rate in the patient room of 5-6 air changes per hour. All exhaust air from the rooms was disinfected with filtration and exposure to UV C light (UVC). All rooms were supplied with ceiling-mounted (Z-300) and wall-mounted (Z-30) UVC units for exposure of walls, floors, and equipment.
table 1. UV C Light (UVC) Levels Elsewhere Than the Floor in the Isolation Unit
Schematic drawing of isolation unit 101. Each isolation unit consists of an anteroom, a patient room, and a bathroom/decontamination room. Negative air pressure is provided, with inward airflow and an air change rate in the patient room of 5-6 air changes per hour. All exhaust air from the rooms was disinfected with filtration and exposure to UV C light (UVC). All rooms were supplied with ceiling-mounted (Z-300) and wall-mounted (Z-30) UVC units for exposure of walls, floors, and equipment.
table 1. UV C Light (UVC) Levels Elsewhere Than the Floor in the Isolation Unit
Before microbiological surface samples were obtained, any objects left by the patient and any equipment that had been used were placed in plastic bags and removed from the rooms.8 Bacterial samples from surfaces were taken at 26 different, preset positions in each of the 4 isolation units. They were taken immediately after tidying, cleaning and disinfection. To evaluate the disinfection efficiency of UVC, samples were taken from areas directly exposed and not directly exposed to UVC. Sampling was performed at approximately the same positions before and after disinfection. Standard contact plates (area, approximately 20 cm2) filled with 15 mL of trypticase soy agar (Becton Dickinson) and a Count-Tact applicator (Medinor) were used. The plates were coded and sent to an accredited external laboratory where they were incubated at 37°C for 48 hours and the colony-forming units counted. No identification was done. The upper limit of detection was 250 cfu per plate.
The isolation rooms were tidied, and all visible organic materials and soils were removed before they were either disinfected or cleaned with non-antibacterial soap and water and then disinfected. The cleaning staff was an experienced team, trained in surface disinfection and working at the isolation unit. Disinfection was either done manually with 5% chloramine with 1 hour exposure and then removed by cleaning with soap and water or with UVC for approximately 40 minutes. Microbial samples were taken immediately (within 10 minutes) after tidying, cleaning, and disinfection. Microbial samples with overgrowth (>250 cfu/plate) were registered and included in the figures, but those data were exempted from the mean summary of the experiments. The UVC units were activated only when people were not present in the rooms.
RESULTS
UVC markedly reduced the number of bacteria on un-cleaned surfaces in isolation unit 101, from a mean of 29.5 cfu per sample before to 2.0 cfu per sample after UVC disinfection, and to 1.6 cfu per sample after additional chloramine disinfection (P < .001 for both, using Poisson-distributed variables) (Figure 3). The most soiled areas were the console for electricity and gas, the bedside table, the TV screen, and the floor by the toilet. After standard cleaning of isolation units 102 and 104, the additional use of UVC disinfection significantly reduced the numbers of colony-forming units from a mean of 8.5 and 47 cfu per sample, respectively, before UVC disinfection to 1 and 2.6 cfu per sample, respectively, immediately after UVC disinfection (P < .001 for both). On surfaces not directly exposed to UVC, a maximum of 18 cfu per 20 cm2 was counted. In most other areas, between 0 and 5 cfu per sample were found after UVC treatment.
Disinfection with chloramine yielded a mean of 25 cfu per sample in room 105. However, two samples from the chloramine disinfection study grew >250 cfu per sample, which may have been a result of contamination or an indication that the areas had not been disinfected before sampling. Standard hospital cleaning after chloramine disinfection yielded a mean of 4.1 cfu per sample, and, when UVC disinfection was used in addition, the mean count was 0.5 cfu per sample (P < .001 for both).
Table 2 shows the summary of the experiments from the 4 different isolation units. Four uncountable plates (valuesof >250 cfu per sample) were removed from the calculation: 1 from each of the tidying and cleaning experiments and 2 from the chloramine-only experiment. The measurements after tidying represented the original bacterial burden without any intervention, and the mean number of cfu per sample was 30.9. After cleaning only, the mean number was somewhat lower (22.0 cfu per sample); after UVC disinfection alone, it was 2.1 cfu per sample, and that after chloramine disinfection alone for 1 h was 1.3 cfu per sample.
Use of chloramine 5% for 1 h, followed by cleaning to remove the disinfectant, resulted in a mean of 4.1 cfu per sample, whereas UVC disinfection combined with precleaning or subsequent chloramine treatments gave the same results: 1.8 and 1.7 cfu per sample. After disinfection with chloramine for 1 hour, followed by cleaning and final UVC irradiation, the mean count was 0.5 cfu/plate. Compared with the original bacterial burden, both the use of UVC and of chloramine disinfection alone or in different combinations significantly reduced the amount of surface flora (P < .001 for both) (Table 2).
The isolation rooms were tidied, and all visible organic materials and soils were removed before they were either disinfected or cleaned with non-antibacterial soap and water and then disinfected. The cleaning staff was an experienced team, trained in surface disinfection and working at the isolation unit. Disinfection was either done manually with 5% chloramine with 1 hour exposure and then removed by cleaning with soap and water or with UVC for approximately 40 minutes. Microbial samples were taken immediately (within 10 minutes) after tidying, cleaning, and disinfection. Microbial samples with overgrowth (>250 cfu/plate) were registered and included in the figures, but those data were exempted from the mean summary of the experiments. The UVC units were activated only when people were not present in the rooms.
RESULTS
UVC markedly reduced the number of bacteria on un-cleaned surfaces in isolation unit 101, from a mean of 29.5 cfu per sample before to 2.0 cfu per sample after UVC disinfection, and to 1.6 cfu per sample after additional chloramine disinfection (P < .001 for both, using Poisson-distributed variables) (Figure 3). The most soiled areas were the console for electricity and gas, the bedside table, the TV screen, and the floor by the toilet. After standard cleaning of isolation units 102 and 104, the additional use of UVC disinfection significantly reduced the numbers of colony-forming units from a mean of 8.5 and 47 cfu per sample, respectively, before UVC disinfection to 1 and 2.6 cfu per sample, respectively, immediately after UVC disinfection (P < .001 for both). On surfaces not directly exposed to UVC, a maximum of 18 cfu per 20 cm2 was counted. In most other areas, between 0 and 5 cfu per sample were found after UVC treatment.
Disinfection with chloramine yielded a mean of 25 cfu per sample in room 105. However, two samples from the chloramine disinfection study grew >250 cfu per sample, which may have been a result of contamination or an indication that the areas had not been disinfected before sampling. Standard hospital cleaning after chloramine disinfection yielded a mean of 4.1 cfu per sample, and, when UVC disinfection was used in addition, the mean count was 0.5 cfu per sample (P < .001 for both).
Table 2 shows the summary of the experiments from the 4 different isolation units. Four uncountable plates (valuesof >250 cfu per sample) were removed from the calculation: 1 from each of the tidying and cleaning experiments and 2 from the chloramine-only experiment. The measurements after tidying represented the original bacterial burden without any intervention, and the mean number of cfu per sample was 30.9. After cleaning only, the mean number was somewhat lower (22.0 cfu per sample); after UVC disinfection alone, it was 2.1 cfu per sample, and that after chloramine disinfection alone for 1 h was 1.3 cfu per sample.
Use of chloramine 5% for 1 h, followed by cleaning to remove the disinfectant, resulted in a mean of 4.1 cfu per sample, whereas UVC disinfection combined with precleaning or subsequent chloramine treatments gave the same results: 1.8 and 1.7 cfu per sample. After disinfection with chloramine for 1 hour, followed by cleaning and final UVC irradiation, the mean count was 0.5 cfu/plate. Compared with the original bacterial burden, both the use of UVC and of chloramine disinfection alone or in different combinations significantly reduced the amount of surface flora (P < .001 for both) (Table 2).
figure 2.
Graphic presentation of the distribution of UV C light (UVC) irradiance on the floor in isolation unit 101: patient room, anteroom, and bathroom/decontamination room. The values were obtained from Table 1.
Graphic presentation of the distribution of UV C light (UVC) irradiance on the floor in isolation unit 101: patient room, anteroom, and bathroom/decontamination room. The values were obtained from Table 1.
figure 3.
The number of colony-forming units (cfu) per contact plate (20 cm2) cultured from samples of areas in isolation unit 101. Microbiological samples were taken from surfaces after tidying (red bars); after tidying and UV C light (UVC) disinfection for approximately 40 minutes (blue bars); and after tidying, approximately 40 minutes of UVC irradiation, and 1 hour exposure to 5% chloramine exposure (yellow bars).
table 2. Results of Statistical Analysis of Colony Counts on Contact Plates for Samples From 4 Isolation Units
The number of colony-forming units (cfu) per contact plate (20 cm2) cultured from samples of areas in isolation unit 101. Microbiological samples were taken from surfaces after tidying (red bars); after tidying and UV C light (UVC) disinfection for approximately 40 minutes (blue bars); and after tidying, approximately 40 minutes of UVC irradiation, and 1 hour exposure to 5% chloramine exposure (yellow bars).
table 2. Results of Statistical Analysis of Colony Counts on Contact Plates for Samples From 4 Isolation Units
discussion
UVC disinfection works by dissociating the DNA structure of living cells. Destruction of molecular chains requires a dose of UV light that is matched to the type of organism and that is at the germicidal wavelength of 253.7 nm. As the genetic structure of bacteria or viruses is exposed to the UVC, it will be destroyed. However, the success of surface disinfection using UVC depends greatly on the consistency of the material to be disinfected. In general, UVC rays must directly strike the microorganism to achieve lethal destruction. If the organism is hidden below the surface of a material or is not in the direct path of the UVC rays, it will not be destroyed.
UVC disinfection of surfaces has the advantage of being an automatic method—no manual labor is needed, and a relatively short exposure time is required.8,10,15 In addition, UVC leaves no residue in the indoor environment, and the new-style UVC light units are not subject to temperature limitations. However, UVC may have some destructive effect over time on materials such as plastic and vinyl and cause fading of colored paints and fabrics. It also has a low penetrating effect (1-2 mm), and means must be taken to reduce any shadowing that may occur. As with most chemical disinfection agents, the bactericidal effect is reduced in the presence of organic materials. Therefore, visually soiled surfaces (eg, stains left by blood, urine, and milk) will need to be cleaned before UVC disinfection. It is important that the room is empty during UVC disinfection, because accidental irradiation effects have been described.21-23
Manual labor is required in the use of most chemical methods, such as the chloramine disinfection method used in the present study. In addition, the chemical has to be removed by cleaning after use. However, recently a hydrogen peroxide vapor decontamination system was described by French et al. that was tested against MRSA.24 There was no effect of standard cleaning on MRSA; 74% of the swab samples obtained before and 66% of those obtained after cleaning yielded MRSA. In contrast, after hydrogen peroxide vapor decontamination, only 1.2% of swab samples yielded MRSA.24 The exposure time is, however, longer for hydrogen peroxide vapor—5 hours, compared with a mean of 40 minutes for UVC.
At present, there are insufficient data to support the effectiveness of UVC as a tool for infection control, because there is no evidence that routine use of UVC disinfection will reduce the rate of nosocomial infections. According to published UVC dosimetry data, the counts of surviving bacteria and bacterial spores are reduced by 90% with doses of 18-80 and 120 J/m2, respectively.20 The survival curve normally falls exponentially with increasing doses (ie, it follows a log-linear pattern). Several studies have shown that doses of UVC of 90-900 J/m2 may inactivate 99.999% (5-log) of bacteria. Jepson et al.20 have shown that a dose of 1,500 J/m2 may inactivate 99.99% of spores of Bacillus anthracis, 1,800-3,000 J/m2 inactivates protozoa, 16,800 J/m2 inactivates 90% of Cryptosporidium parvum, 3,000 J/m2 inactivates 99.99% of Candida albicans, 110-3,300 J/m2 inactivates 99.99% of fungi, and 10,000-20,000 J/m2 inactivates 99.99% of blue-green algae. The doses for virus inactivation varied from 190 to 11,500 J/m2. HIV showed a relatively high tolerance to UVC at doses of up to 11,500 J/m2.
In the present study, the isolation units were exposed to UVC for total doses of 160 J/m2 in the most shadowed area to 19,200 J/m2 (0.08-6.82 W/m2) in open, exposed areas. Thus, the output of the UVC units on surfaces in the isolation unit was high enough to inactivate most bacterial organisms, including their spores, and most virus and fungi, even on shadowed surfaces on the floor that were not directly reached by UVC.
The protein content on surfaces may absorb UV irradiation and cause varying disinfection efficacy for different organisms. Double-strand DNA viruses (ie, enteric adenoviruses) are more resistant than are single-strand RNA viruses (ie, poliovirus). In addition, some bacteria, and possibly adenoviruses, are capable of directly or indirectly repairing the damage caused by irradiation and reverting back to a viable state (“photoreactivation”). The extent of photoreactivation varies among microbes; therefore, more studies are needed to evaluate a wide range of pathogens and the effect that various UV doses have on a variety of microbes and to evaluate the durations of irradiation required after which photoreactivation can no longer occur.
To control the radiometric measurements, sampling of surface bacteria was done in the 4 isolation units in connection with the final disinfection, after patients were discharged. Both UVC and chloramine 5% disinfection were tested, in addition to standard hospital environmental cleaning using water and nonantibacterial soap. Compared with tidying these measurements represented the original bacterial burden without any intervention—cleaning the isolation rooms with soap and water only seemed to affect surface microorganisms: we measured a mean of 30.9 cfu per sample before and 22.0 cfu per sample after cleaning. This is in accordance with earlier findings; floor cleaning by wet mopping had no significant effect on bacterial counts on floors, whereas damp mopping reduced bacterial counts by 75%, which was significant (P < .01).2
The use of UVC or chloramine disinfection alone or in various combinations with or without cleaning significantly reduced the amount of surface flora (P < .001 for both). UVC disinfection reduced the number of colony-forming units to an average of 2.1 cfu per sample in an un-cleaned room and 1.8 cfu per sample in a cleaned room, (P < .001). The lowest average number, 0.5 cfu per sample, was measured after disinfection with chloramine followed by cleaning and removing of the chemical agent and final UVC irradiation. This latter method seemed to be more effective than the use of chloramine alone. Thus, UVC showed a significant germicidal effect on surface microorganisms in isolation units and markedly reduced the number of bacteria both on cleaned and un-cleaned surfaces. An effect of UVC was also registered in partly shadowed areas that were not directly exposed to UVC. After chloramine disinfection alone, an average of 1.3 ± 2.6 cfu per sample was measured (after the removal of 2 uncountable plates from calculations).
As shown in the present study, direct UVC irradiation may be an effective germicidal agent for whole-room disinfection. However, this method, like chemical disinfection methods, may be hampered by the fact that the bactericidal effect is reduced in the presence of organic materials. Surfaces with visible stains that contain organic matter will always need separate procedures for immediate spot cleaning and disinfection.8
Furthermore, UVC disinfection is not effective in completely shadowed areas, such as bed mattresses, closed bedrails, and lockers. These surfaces still have to be disinfected by other means. Therefore, UVC may not be used alone for disinfection, but it may be a good addition to chemical disinfection, to lower the biological burden of infectious agents in isolation units for high-risk infectious patients.
REFERENCES
1. Dancer SJ. Mopping up hospital infection. J Hosp Infect 1999; 43:85-100.
2. Andersen BM, Solheim N, Kruger Ø, Levy F, Sogn K, Moløkken I. Floor cleaning in patient rooms: effect of bacteria on soil and particles in air. Tidsskr Nor Lægeforen 1997; 117:838-841.
3. Griffith CJ, Cooper RA, Gilmore J, Davies C, Lewis M. An evaluation of hospital cleaning regimes and standards. J Hosp Infect 2000; 45:19-28.
4. Rutala WA, Weber DJ. Environmental interventions to control nosocomial infections. Infect Control Hosp Epidemiol 1995; 16:442-443.
5. Levin AS, Gobara S, Mendes C, Cursino R, Sinto S. Environmental contamination by multidrug-resistant Acinetobacter baumannii in an intensive care unit. Infect Control Hosp Epidemiol 2001; 22:717-720.
6. Garner JS. Guideline for isolation precautions in hospitals. The Hospital Infection Control Practices Advisory Committee. Infect Control Hosp Epidemiol 1996; 17:53-80
7. Sehulster L, Chinn RY, CDC, HICPAC. Guidelines for environmental infection control in health-care facilities: recommendations of CDC and the Healthcare Infection Control Practices Advisory Committee (HICPAC). MMWR Recomm Rep 2003; 52(RR-10):1-42.
8. Fjellet AL, Brubakk O, Hochlin K, Solheim N, Andersen BM. Isolation procedures. In: Andersen BM, ed. Handbook in Hygiene and Infection Control. Oslo: Ullevål University Hospital; 2003:100-127.
9. Sharp G. The lethal action of short ultraviolet rays on several common pathogenic bacteria. J Bacteriol 1939; 37:447-459.
10. Riley RL, Nardell EA. Clearing the air: the theory and application of ultraviolet air disinfection. Am Rev Respir Dis 1989; 139:1286-1294.
11. Riley RL, Mills CC, O’Grady FO, Sultan LU, Wittstadt F, Shivpuri DN. Infectiousness of air from tuberculosis ward. Ultraviolet irradiation of infected air: comparative infectiousness of different patients. Am Rev Respir Dis 1962; 85:511-525
12. Nardell EA. Interrupting transmission from patients with unsuspected tuberculosis: a unique role for upper-room ultraviolet air disinfection. AM J Infect Control 1995; 23:156-164.
13. Wallner-Pendleton EA, Summer SS, Froning GW, Stetson LE. The use of ultraviolet radiation to reduce Salmonella and psychotrophic bacterial contamination on poultry carcasses. Poult Sci 1994; 73:1327-1333.
14. Ishida H, Nahara Y, Tamamoto M, Hamada T. The fungicidal effect of ultraviolet light on impression materials. J Prosthet Dent 1991; 65:532-535.
15. Young AR, Björn LO, Moan J, Nultsch W, eds. Environmental UV Photobiology. New York: Plenum Press; 1993
16. Riley RL, Kaufman JE. Air disinfection in corridors by upper air irradiation with ultraviolet. Arch Environ Health 1971; 22:551-553.
17. Hart D, Durham NC. Bactericidal ultraviolet radiation in the operating room: twenty-nine year study for control of infections. JAMA 1960; 172:1019-1028.
18. Bånrud H, Moan J. The use of UCV for disinfection in operating rooms. Tidsskr Nor Lægeforen 1999; 119:2670-2673.
19. Technical Project Report: Air Quality, Destruction of Microbes, and Use of Negative-Pressure, Filter, and UVC Technology in Patient Isolates. Oslo: Klean, Siemens, Ullevål University Hospital; 2000.
20. Hyllseth B, Bånrud H. Literature concerning UVC (J/m2) inactivation of microbes. In: Technical Project Report: Air Quality, Destruction of Microbes, and Use of Negative-Pressure, Filter, and UVC Technology in Patient Isolates. Oslo: Klean, Siemens, Ullevål University Hospital; 2000 (attachment).
21. Moss CE, Seitz TA. Ultraviolet radiation exposure to health care workers from germicidal lamps. Appl Occup Environ Hyg 1991; 6:168-170.
22. Forsyth A, Ide CW, Moseley H. Acute sunburn due to accidental irradiation with UVC. Contact Dermatitis 1991; 24:141-142.
23. International Radiation Protection Association. IRPA Guidelines on Protection Against Non-ionizing Radiation: the Collected Publications of the IRPA Non-ionizing Radiation Committee. New York: Pergamon Press; 1991.
24. French GL, Otter JA, Shannon KP, Adams NM, Watling D, Parks MJ. Tackling contamination of the hospital environment by methicillin-resistant Staphylococcus aureus (MRSA): a comparison between conventional terminal cleaning and hydrogen peroxide vapour decontamination. J Hosp Infect 2004; 57:31-37.
From the Department of Hospital infections and Department of Internal Services, Ullevål University Hospital, Oslo (B.M.A., E.B.); Klean ASA, Rud (H.B., O.B.); and the Faculty of Technology, Sør-Trøndelag University College, Trondheim (F.D.), Norway
Received September 16, 2004; accepted January 4, 2005; electronically published June 2, 2006.
© 2006 by The Society for Healthcare Epidemiology of America. All rights reserved. 0899-823X/2006/2707-0015$15.00.
UVC disinfection works by dissociating the DNA structure of living cells. Destruction of molecular chains requires a dose of UV light that is matched to the type of organism and that is at the germicidal wavelength of 253.7 nm. As the genetic structure of bacteria or viruses is exposed to the UVC, it will be destroyed. However, the success of surface disinfection using UVC depends greatly on the consistency of the material to be disinfected. In general, UVC rays must directly strike the microorganism to achieve lethal destruction. If the organism is hidden below the surface of a material or is not in the direct path of the UVC rays, it will not be destroyed.
UVC disinfection of surfaces has the advantage of being an automatic method—no manual labor is needed, and a relatively short exposure time is required.8,10,15 In addition, UVC leaves no residue in the indoor environment, and the new-style UVC light units are not subject to temperature limitations. However, UVC may have some destructive effect over time on materials such as plastic and vinyl and cause fading of colored paints and fabrics. It also has a low penetrating effect (1-2 mm), and means must be taken to reduce any shadowing that may occur. As with most chemical disinfection agents, the bactericidal effect is reduced in the presence of organic materials. Therefore, visually soiled surfaces (eg, stains left by blood, urine, and milk) will need to be cleaned before UVC disinfection. It is important that the room is empty during UVC disinfection, because accidental irradiation effects have been described.21-23
Manual labor is required in the use of most chemical methods, such as the chloramine disinfection method used in the present study. In addition, the chemical has to be removed by cleaning after use. However, recently a hydrogen peroxide vapor decontamination system was described by French et al. that was tested against MRSA.24 There was no effect of standard cleaning on MRSA; 74% of the swab samples obtained before and 66% of those obtained after cleaning yielded MRSA. In contrast, after hydrogen peroxide vapor decontamination, only 1.2% of swab samples yielded MRSA.24 The exposure time is, however, longer for hydrogen peroxide vapor—5 hours, compared with a mean of 40 minutes for UVC.
At present, there are insufficient data to support the effectiveness of UVC as a tool for infection control, because there is no evidence that routine use of UVC disinfection will reduce the rate of nosocomial infections. According to published UVC dosimetry data, the counts of surviving bacteria and bacterial spores are reduced by 90% with doses of 18-80 and 120 J/m2, respectively.20 The survival curve normally falls exponentially with increasing doses (ie, it follows a log-linear pattern). Several studies have shown that doses of UVC of 90-900 J/m2 may inactivate 99.999% (5-log) of bacteria. Jepson et al.20 have shown that a dose of 1,500 J/m2 may inactivate 99.99% of spores of Bacillus anthracis, 1,800-3,000 J/m2 inactivates protozoa, 16,800 J/m2 inactivates 90% of Cryptosporidium parvum, 3,000 J/m2 inactivates 99.99% of Candida albicans, 110-3,300 J/m2 inactivates 99.99% of fungi, and 10,000-20,000 J/m2 inactivates 99.99% of blue-green algae. The doses for virus inactivation varied from 190 to 11,500 J/m2. HIV showed a relatively high tolerance to UVC at doses of up to 11,500 J/m2.
In the present study, the isolation units were exposed to UVC for total doses of 160 J/m2 in the most shadowed area to 19,200 J/m2 (0.08-6.82 W/m2) in open, exposed areas. Thus, the output of the UVC units on surfaces in the isolation unit was high enough to inactivate most bacterial organisms, including their spores, and most virus and fungi, even on shadowed surfaces on the floor that were not directly reached by UVC.
The protein content on surfaces may absorb UV irradiation and cause varying disinfection efficacy for different organisms. Double-strand DNA viruses (ie, enteric adenoviruses) are more resistant than are single-strand RNA viruses (ie, poliovirus). In addition, some bacteria, and possibly adenoviruses, are capable of directly or indirectly repairing the damage caused by irradiation and reverting back to a viable state (“photoreactivation”). The extent of photoreactivation varies among microbes; therefore, more studies are needed to evaluate a wide range of pathogens and the effect that various UV doses have on a variety of microbes and to evaluate the durations of irradiation required after which photoreactivation can no longer occur.
To control the radiometric measurements, sampling of surface bacteria was done in the 4 isolation units in connection with the final disinfection, after patients were discharged. Both UVC and chloramine 5% disinfection were tested, in addition to standard hospital environmental cleaning using water and nonantibacterial soap. Compared with tidying these measurements represented the original bacterial burden without any intervention—cleaning the isolation rooms with soap and water only seemed to affect surface microorganisms: we measured a mean of 30.9 cfu per sample before and 22.0 cfu per sample after cleaning. This is in accordance with earlier findings; floor cleaning by wet mopping had no significant effect on bacterial counts on floors, whereas damp mopping reduced bacterial counts by 75%, which was significant (P < .01).2
The use of UVC or chloramine disinfection alone or in various combinations with or without cleaning significantly reduced the amount of surface flora (P < .001 for both). UVC disinfection reduced the number of colony-forming units to an average of 2.1 cfu per sample in an un-cleaned room and 1.8 cfu per sample in a cleaned room, (P < .001). The lowest average number, 0.5 cfu per sample, was measured after disinfection with chloramine followed by cleaning and removing of the chemical agent and final UVC irradiation. This latter method seemed to be more effective than the use of chloramine alone. Thus, UVC showed a significant germicidal effect on surface microorganisms in isolation units and markedly reduced the number of bacteria both on cleaned and un-cleaned surfaces. An effect of UVC was also registered in partly shadowed areas that were not directly exposed to UVC. After chloramine disinfection alone, an average of 1.3 ± 2.6 cfu per sample was measured (after the removal of 2 uncountable plates from calculations).
As shown in the present study, direct UVC irradiation may be an effective germicidal agent for whole-room disinfection. However, this method, like chemical disinfection methods, may be hampered by the fact that the bactericidal effect is reduced in the presence of organic materials. Surfaces with visible stains that contain organic matter will always need separate procedures for immediate spot cleaning and disinfection.8
Furthermore, UVC disinfection is not effective in completely shadowed areas, such as bed mattresses, closed bedrails, and lockers. These surfaces still have to be disinfected by other means. Therefore, UVC may not be used alone for disinfection, but it may be a good addition to chemical disinfection, to lower the biological burden of infectious agents in isolation units for high-risk infectious patients.
REFERENCES
1. Dancer SJ. Mopping up hospital infection. J Hosp Infect 1999; 43:85-100.
2. Andersen BM, Solheim N, Kruger Ø, Levy F, Sogn K, Moløkken I. Floor cleaning in patient rooms: effect of bacteria on soil and particles in air. Tidsskr Nor Lægeforen 1997; 117:838-841.
3. Griffith CJ, Cooper RA, Gilmore J, Davies C, Lewis M. An evaluation of hospital cleaning regimes and standards. J Hosp Infect 2000; 45:19-28.
4. Rutala WA, Weber DJ. Environmental interventions to control nosocomial infections. Infect Control Hosp Epidemiol 1995; 16:442-443.
5. Levin AS, Gobara S, Mendes C, Cursino R, Sinto S. Environmental contamination by multidrug-resistant Acinetobacter baumannii in an intensive care unit. Infect Control Hosp Epidemiol 2001; 22:717-720.
6. Garner JS. Guideline for isolation precautions in hospitals. The Hospital Infection Control Practices Advisory Committee. Infect Control Hosp Epidemiol 1996; 17:53-80
7. Sehulster L, Chinn RY, CDC, HICPAC. Guidelines for environmental infection control in health-care facilities: recommendations of CDC and the Healthcare Infection Control Practices Advisory Committee (HICPAC). MMWR Recomm Rep 2003; 52(RR-10):1-42.
8. Fjellet AL, Brubakk O, Hochlin K, Solheim N, Andersen BM. Isolation procedures. In: Andersen BM, ed. Handbook in Hygiene and Infection Control. Oslo: Ullevål University Hospital; 2003:100-127.
9. Sharp G. The lethal action of short ultraviolet rays on several common pathogenic bacteria. J Bacteriol 1939; 37:447-459.
10. Riley RL, Nardell EA. Clearing the air: the theory and application of ultraviolet air disinfection. Am Rev Respir Dis 1989; 139:1286-1294.
11. Riley RL, Mills CC, O’Grady FO, Sultan LU, Wittstadt F, Shivpuri DN. Infectiousness of air from tuberculosis ward. Ultraviolet irradiation of infected air: comparative infectiousness of different patients. Am Rev Respir Dis 1962; 85:511-525
12. Nardell EA. Interrupting transmission from patients with unsuspected tuberculosis: a unique role for upper-room ultraviolet air disinfection. AM J Infect Control 1995; 23:156-164.
13. Wallner-Pendleton EA, Summer SS, Froning GW, Stetson LE. The use of ultraviolet radiation to reduce Salmonella and psychotrophic bacterial contamination on poultry carcasses. Poult Sci 1994; 73:1327-1333.
14. Ishida H, Nahara Y, Tamamoto M, Hamada T. The fungicidal effect of ultraviolet light on impression materials. J Prosthet Dent 1991; 65:532-535.
15. Young AR, Björn LO, Moan J, Nultsch W, eds. Environmental UV Photobiology. New York: Plenum Press; 1993
16. Riley RL, Kaufman JE. Air disinfection in corridors by upper air irradiation with ultraviolet. Arch Environ Health 1971; 22:551-553.
17. Hart D, Durham NC. Bactericidal ultraviolet radiation in the operating room: twenty-nine year study for control of infections. JAMA 1960; 172:1019-1028.
18. Bånrud H, Moan J. The use of UCV for disinfection in operating rooms. Tidsskr Nor Lægeforen 1999; 119:2670-2673.
19. Technical Project Report: Air Quality, Destruction of Microbes, and Use of Negative-Pressure, Filter, and UVC Technology in Patient Isolates. Oslo: Klean, Siemens, Ullevål University Hospital; 2000.
20. Hyllseth B, Bånrud H. Literature concerning UVC (J/m2) inactivation of microbes. In: Technical Project Report: Air Quality, Destruction of Microbes, and Use of Negative-Pressure, Filter, and UVC Technology in Patient Isolates. Oslo: Klean, Siemens, Ullevål University Hospital; 2000 (attachment).
21. Moss CE, Seitz TA. Ultraviolet radiation exposure to health care workers from germicidal lamps. Appl Occup Environ Hyg 1991; 6:168-170.
22. Forsyth A, Ide CW, Moseley H. Acute sunburn due to accidental irradiation with UVC. Contact Dermatitis 1991; 24:141-142.
23. International Radiation Protection Association. IRPA Guidelines on Protection Against Non-ionizing Radiation: the Collected Publications of the IRPA Non-ionizing Radiation Committee. New York: Pergamon Press; 1991.
24. French GL, Otter JA, Shannon KP, Adams NM, Watling D, Parks MJ. Tackling contamination of the hospital environment by methicillin-resistant Staphylococcus aureus (MRSA): a comparison between conventional terminal cleaning and hydrogen peroxide vapour decontamination. J Hosp Infect 2004; 57:31-37.
From the Department of Hospital infections and Department of Internal Services, Ullevål University Hospital, Oslo (B.M.A., E.B.); Klean ASA, Rud (H.B., O.B.); and the Faculty of Technology, Sør-Trøndelag University College, Trondheim (F.D.), Norway
Received September 16, 2004; accepted January 4, 2005; electronically published June 2, 2006.
© 2006 by The Society for Healthcare Epidemiology of America. All rights reserved. 0899-823X/2006/2707-0015$15.00.
Posts
0 comments:
Post a Comment