Ventilation grilles as a potential source of methicillin-resistant Staphylococcus aureus causing an outbreak in an orthopaedic ward at a district general hospital

Identifying and elucidating the resistance of Staphylococcus aureus isolated from hospital environment to conventional disinfectants

BACKGROUND

Staphylococcus aureus is a nosocomial pathogen, detection and elucidation of its resistance mechanisms to conventional disinfectants may aid in limiting its spread on environmental surfaces in health care settings. In the current study, disinfectant susceptibility of S. aureus strains isolated from the hospital environment as well as possible associations between the presence of disinfectant-resistance genes and reduced susceptibility to disinfectants was investigated.

METHODS

A total of 245 samples were collected from the hospital environmental surfaces. The minimum inhibitory (MIC) and bactericidal concentrations (MBC) of disinfectants against S. aureus isolates were determined using the micro-broth dilution method. The qac genes (qacA, qacE, and qacΔE1) were detected by PCR and confirmed by sanger sequencing.

RESULTS

A total of 47 S. aureus strains were isolated, with more than 85% of them showing methicillin resistance. The qacA, qacE, and qac∆E1 genes were found in 23.4%, 29.7%, and 4.2% isolates respectively. All the isolates with qac genes had higher MIC and MBC values to selected disinfectants.

CONCLUSIONS

Significant methicillin resistant S. aureus (MRSA) contamination in the hospital environment was detected. Furthermore, higher qac gene frequencies were found in MRSA isolates that also correlated with higher MIC/MBC values to different disinfectants. The study proposes that hospitals should develop policies to determine disinfectant MICs against the common environmental isolates to contain the spread of resistant strains.

Designing a new fast solution to control isolation rooms in hospitals depending on artificial intelligence decision

Decreasing the COVID spread of infection among patients at physical isolation hospitals during the coronavirus pandemic was the main aim of all governments in the world. It was required to increase isolation places in the hospital's rules to prevent the spread of infection. To deal with influxes of infected COVID-19 patients’ quick solutions must be explored. The presented paper studies converting natural rooms in hospitals into isolation sections and constructing new isolation cabinets using prefabricated components as alternative and quick solutions. Artificial Intelligence (AI) helps in the selection and making of a decision on which type of solution will be used. A Multi-Layer Perceptron Neural Network (MLPNN) model is a type of artificial intelligence technique used to design and implement on time, cost, available facilities, area, and spaces as input parameters. The MLPNN result decided to select a prefabricated approach since it saves 43% of the time while the cost was the same for the two approaches. Forty-five hospitals have implemented a prefabricated solution which gave excellent results in a short period of time at reduced costs based on found facilities and spaces. Prefabricated solutions provide a shorter time and lower cost by 43% and 78% in average values respectively as compared to retrofitting existing natural ventilation rooms.

Effects of air-conditioning systems in the public areas of hospitals: A scoping review

Almost all hospitals are equipped with air-conditioning systems to provide a comfortable environment for patients and staff. However, the accumulation of dust and moisture within these systems increases the risk of transmission of microbes and have on occasion been associated with outbreaks of infection. Nevertheless, the impact of air-conditioning on the transmission of microorganisms leading to infection remains largely uncertain. We conducted a scoping review to screen systematically the evidence for such an association in the face of the coronavirus disease 2019 epidemic. PubMed, Embase and Web of Science databases were explored for relevant studies addressing microbial contamination of the air, their transmission and association with infectious diseases. The review process yielded 21 publications, 17 of which were cross-sectional studies, three were cohort studies and one case−control study. Our analysis showed that, compared with naturally ventilated areas, microbial loads were significantly lower in air-conditioned areas, but the incidence of infections increased if not properly managed. The use of high-efficiency particulate air (HEPA) filtration not only decreased transmission of airborne bioaerosols and various microorganisms, but also reduced the risk of infections. By contrast, contaminated air-conditioning systems in hospital rooms were associated with a higher risk of patient infection. Cleaning and maintenance of such systems to recommended standards should be performed regularly and where appropriate, the installation of HEPA filters can effectively mitigate microbial contamination in the public areas of hospitals.

Ventilation-Associated Particulate Matter Is a Potential Reservoir of Multidrug-Resistant Organisms in Health Facilities

Most healthcare-associated infections (HCAIs) develop due to the colonisation of patients and healthcare workers by multidrug-resistant organisms (MDRO). Here, we investigated whether the particulate matter from the ventilation systems (Vent-PM) of health facilities can harbour MDRO and other microbes, thereby acting as a potential reservoir of HCAIs. Dust samples collected in the ventilation grilles and adjacent air ducts underwent a detailed analysis of physicochemical properties and biodiversity. All Vent-PM samples included ultrafine PM capable of reaching the alveoli. Strikingly, >70% of Vent-PM samples were contaminated, mostly by viruses (>15%) or multidrug-resistant and biofilm-producing bacterial strains (60% and 48% of all bacteria-contaminated specimens, respectively). Total viable count at 1 m from the ventilation grilles was significantly increased after opening doors and windows, indicating an association between air flow and bacterial contamination. Both chemical and microbial compositions of Vent-PM considerably differed across surgical vs. non-surgical and intensive vs. elective care units and between health facilities located in coal and chemical districts. Reduced diversity among MDRO and increased prevalence ratio in multidrug-resistant to the total Enterococcus spp. in Vent-PM testified to the evolving antibiotic resistance. In conclusion, we suggest Vent-PM as a previously underestimated reservoir of HCAI-causing pathogens in the hospital environment.

COVID-19 Outbreak and Hospital Air Quality: A Systematic Review of Evidence on Air Filtration and Recirculation

The outbreak of SARS-CoV-2 has made us all think critically about hospital indoor air quality and the approaches to remove, dilute, and disinfect pathogenic organisms from the hospital environment. While specific aspects of the coronavirus infectivity, spread, and routes of transmission are still under rigorous investigation, it seems that a recollection of knowledge from the literature can provide useful lessons to cope with this new situation. As a result, a systematic literature review was conducted on the safety of air filtration and air recirculation in healthcare premises. This review targeted a wide range of evidence from codes and regulations, to peer-reviewed publications, and best practice standards. The literature search resulted in 394 publications, of which 109 documents were included in the final review. Overall, even though solid evidence to support current practice is very scarce, proper filtration remains one important approach to maintain the cleanliness of indoor air in hospitals. Given the rather large physical footprint of the filtration system, a range of short-term and long-term solutions from the literature are collected. Nonetheless, there is a need for a rigorous and feasible line of research in the area of air filtration and recirculation in healthcare facilities. Such efforts can enhance the performance of healthcare facilities under normal conditions or during a pandemic. Past innovations can be adopted for the new outbreak at low-to-minimal cost.

Role of Human Factors Engineering in Infection Prevention: Gaps and Opportunities

Human factors engineering (HFE), with its focus on studying how humans interact with systems, including their physical and organizational environment, the tools and technologies they use, and the tasks they perform, provides principles, tools, and techniques for systematically identifying important factors, for analyzing and evaluating how these factors interact to increase or decrease the risk of Healthcare-associated infections (HAI), and for identifying and implementing effective preventive measures. We reviewed the literature on HFE and infection prevention and control and identified major themes to document how researchers and infection prevention staff have used HFE methods to prevent HAIs and to identify gaps in our knowledge about the role of HFE in HAI prevention and control. Our literature review found that most studies in the healthcare domain explicitly applying (HFE) principles and methods addressed patient safety issues not infection prevention and control issues. In addition, most investigators who applied human factors principles and methods to infection prevention issues assessed only one human factors element such as training, technology evaluations, or physical environment design. The most significant gap pertains to the limited use and application of formal HFE tools and methods. Every infection prevention study need not assess all components in a system, but investigators must assess the interaction of critical system components if they want to address latent and deep-rooted human factors problems.

Quantification of the fungal fraction released from various preloaded fibrous filters during a simulated ventilation restart

This study aimed to demonstrate that particles, especially those associated with fungi, could be released from fibrous filters used in the air-handling unit (AHU) of heating, ventilation and air-conditioning (HVAC) systems during ventilation restarts. Quantification of the water retention capacity and SEM pictures of the filters was used to show the potential for fungal proliferation in unused or preloaded filters. Five fibrous filters with various particle collection efficiencies were studied: classes G4, M5, M6, F7, and combined F7 according to European standard EN779:2012. Filters were clogged with micronized rice particles containing the fungus Penicillium chrysogenum and then incubated for three weeks at 25°C and 90% relative humidity. The results indicated that the five clogged tested filters had various fungal growth capacities depending on their water retention capacity. Preloaded filters were subjected to a simulated ventilation restart in a controlled filtration device to quantify that the fraction of particles released was around 1% for the G4, 0.1% for the M5 and the M6, and 0.001% for the F7 and the combined F7 filter. The results indicate that the likelihood of fungal particle release by low efficiency filters is significantly higher than by high efficiency filters.

Hospital Environments and Epidemiology of Healthcare-Associated Infections

Today, hospitals are facing difficult challenges: increasing proportion of immunologically vulnerable patients often affected by diseases requiring high complex level of healthcare; rapidly evolving medical technologies and healthcare models; and budget restrictions. All these features interfere with healthcare and can modify the risk of acquiring healthcare-associated infections (HCAIs). Therefore, HCAI prevention is a high priority for healthcare systems. Authors describe human and environmental origin of HCAIs, focusing on the modality of transmission of those airborne pathogens, including the new insight derived from the recent acquisitions about SARS and Ebola epidemiology. They also describe the state of the art about microorganism concentration (infective dose) required to determine a HCAI and the role played by other virulence factors. Finally, the effective control measures used for the prevention of airborne pathogen transmission are described, focusing mainly on the risk assessment and infection control.

A Study of the Relationship Between Environmental Contamination with Methicillin-ResistantStaphylococcus aureus(MRSA) and Patients' Acquisition of MRSA

Objective.

The study aimed to examine the presence of methicillin-resistantStaphylococcus aureus(MRSA) in the environment and its relationship to patients' acquisition of MRSA.

Design.

A prospective study was conducted in a 9-bed intensive care unit for 14 months. At every environmental screening, samples were obtained from the same 4 sites in each bed space. Patients were screened at admission and then 3 times weekly. All environmental and patient strains were typed using pulsed-field gel electrophoresis.

Results.

MRSA was isolated from the environment at every environmental screening, when both small and large numbers of patients were colonized. Detailed epidemiological typing of 250 environmental and 139 patient isolates revealed 14 different pulsed-field gel electrophoresis profiles, with variants of EMRSA-15 being the predominant type. On only 20 (35.7%) of 56 occasions were the strains isolated from the patients and the strains isolated from their immediate environment indistinguishable. There was strong evidence to suggest that 3 of 26 patients who acquired MRSA while in the intensive care unit acquired MRSA from the environment.

Conclusions.

This study reveals widespread contamination of the hospital environment with MRSA, highlights the complexities of the problem of contamination, and confirms the need for more-effective cleaning of the hospital environment to eliminate MRSA.

Prevalence of Methicillin Resistant Staphylococcal Bioaerosols in and around Residential Houses in an Urban Area in Central India

Methicillin resistant staphylococci (MRS) commonly found in clinical samples or associated environment pose a major health challenge globally. The carriage rate of MRS in human population is high, especially in India but research on airborne distribution of MRS is scanty. The present study aimed to evaluate the prevalence of MRS in indoor and outdoor environment of residential houses. Air samples were collected using impactor air sampler. The total counts of viable bacteria, staphylococci, and MRS along with the particles of various sizes were determined from indoor and outdoor environment of 14 residential houses. MRS bacteria were identified as methicillin resistant S. aureus (MRSA) or coagulase negative staphylococci (CNS) employing biochemical and PCR assays. The average concentration of MRS inside and outside of the houses was 5.9% and 4.6% of the total bacteria, respectively. The maximum correlation of total indoor and outdoor bacteria with particulate matter was 10 μm (r = 0.74) and 5 μm (r = 0.84), respectively. Statistically, significant positive correlation of staphylococci and MRS was found with particles of 10–25 μm inside the houses. Molecular surveillance, antibiotic stewardship programme, and infection control policies can help to manage increasing MRS burden in developing countries.

Environmental contamination and hospital-acquired infection: factors that are easily overlooked

There is an ongoing debate about the reasons for and factors contributing to healthcare-associated infection (HAI). Different solutions have been proposed over time to control the spread of HAI, with more focus on hand hygiene than on other aspects such as preventing the aerial dissemination of bacteria. Yet, it emerges that there is a need for a more pluralistic approach to infection control; one that reflects the complexity of the systems associated with HAI and involves multidisciplinary teams including hospital doctors, infection control nurses, microbiologists, architects, and engineers with expertise in building design and facilities management. This study reviews the knowledge base on the role that environmental contamination plays in the transmission of HAI, with the aim of raising awareness regarding infection control issues that are frequently overlooked. From the discussion presented in the study, it is clear that many unknowns persist regarding aerial dissemination of bacteria, and its control via cleaning and disinfection of the clinical environment. There is a paucity of good-quality epidemiological data, making it difficult for healthcare authorities to develop evidence-based policies. Consequently, there is a strong need for carefully designed studies to determine the impact of environmental contamination on the spread of HAI.

Development of a ubiquitously transferrable silver-nanoparticle-loaded polymer nanosheet as an antimicrobial coating

Ultra-thin polymer films (nanosheets) fabricated by a layer-by-layer (LbL) method possess unique properties such as high flexibility, adhesive strength, and transparency, and can be peeled off from a substrate and attached to various surfaces via a water-soluble supporting film. Therefore, flexible and transferrable LbL nanosheets are convenient tools as coating materials. Here, we fabricated a novel antimicrobial coating material by embedding silver nanoparticles (AgNPs) in an LbL nanosheet composed of layers of chitosan and sodium alginate (Ag-LbL nanosheet) by means of a photo-reduction method. Optimizing the amount of irradiated energy applied led to robust antimicrobial efficacy against methicillin-resistant Staphylococcus aureus (MRSA), sufficient to meet ISO standards (ISO 22196), while maintaining the flexibility and adhesive potency of the LbL nanosheet. Thus, the Ag-LbL nanosheet is a promising coating material that can provide antimicrobial efficacy to various surfaces.

Microbiological assessment of indoor air quality at different hospital sites

Poor hospital indoor air quality (IAQ) may lead to hospital-acquired infections, sick hospital syndrome and various occupational hazards. Air-control measures are crucial for reducing dissemination of airborne biological particles in hospitals. The objective of this study was to perform a survey of bioaerosol quality in different sites in a Portuguese Hospital, namely the operating theater (OT), the emergency service (ES) and the surgical ward (SW). Aerobic mesophilic bacterial counts (BCs) and fungal load (FL) were assessed by impaction directly onto tryptic soy agar and malt extract agar supplemented with antibiotic chloramphenicol (0.05%) plates, respectively using a MAS-100 air sampler. The ES revealed the highest airborne microbial concentrations (BC range 240-736 CFU/m(3) CFU/m(3); FL range 27-933 CFU/m(3)), exceeding, at several sampling sites, conformity criteria defined in national legislation [6]. Bacterial concentrations in the SW (BC range 99-495 CFU/m(3)) and the OT (BC range 12-170 CFU/m(3)) were under recommended criteria. While fungal levels were below 1 CFU/m(3) in the OT, in the SW (range 1-32 CFU/m(3)), there existed a site with fungal indoor concentrations higher than those detected outdoors. Airborne Gram-positive cocci were the most frequent phenotype (88%) detected from the measured bacterial population in all indoor environments. Staphylococcus (51%) and Micrococcus (37%) were dominant among the bacterial genera identified in the present study. Concerning indoor fungal characterization, the prevalent genera were Penicillium (41%) and Aspergillus (24%). Regular monitoring is essential for assessing air control efficiency and for detecting irregular introduction of airborne particles via clothing of visitors and medical staff or carriage by personal and medical materials. Furthermore, microbiological survey data should be used to clearly define specific air quality guidelines for controlled environments in hospital settings.

Hospital ward design and prevention of hospital-acquired infections: A prospective clinical trial

BACKGROUND

Renovation of a general medical ward provided an opportunity to study health care facility design as a factor for preventing hospital-acquired infections.

OBJECTIVE

To determine whether a hospital ward designed with predominantly single rooms was associated with lower event rates of hospital-acquired infection and colonization.

METHODS

A prospective controlled trial with patient allocation incorporating randomness was designed with outcomes on multiple 'historic design' wards (mainly four-bed rooms with shared bathrooms) compared with outcomes on a newly renovated 'new design' ward (predominantly single rooms with private bathrooms).

RESULTS

Using Poisson regression analysis and adjusting for time at risk, there were no differences (P=0.18) in the primary outcome (2.96 versus 1.85 events/1000 patient-days, respectively). After adjustment for age, sex, Charlson score, admitted from care facility, previous hospitalization within six months, isolation requirement and the duration on antibiotics, the incidence rate ratio was 1.44 (95% CI 0.71 to 2.94) for the new design versus the historic design wards. A restricted analysis on the numbers of events occurring in single-bed versus multibed wings within the new design ward revealed an event incidence density of 1.89 versus 3.47 events/1000 patient-days, respectively (P=0.18), and an incidence rate ratio of 0.54 (95% CI 0.15 to 1.30).

CONCLUSIONS

No difference in the incidence density of hospital-acquired infections or colonizations was observed for medical patients admitted to a new design ward versus historic design wards. A restricted analysis of events occurring in single-bed versus multibed wings suggests that ward design warrants further study.

Staphylococcus aureus dispersal from healthy volunteers

BACKGROUND

Understanding Staphylococcus aureus dispersal from human carriers is vital for preventing transmission and colonization of this organism in health care settings. This study investigated the S aureus supershedder hypothesis in relation to attributes of healthy volunteers.

METHODS

Microbial aerosol generation from volunteers was quantified within a controlled environmental chamber during walking or sitting activities. Biological air samplers were used to determine numbers of total S aureus colony-forming units disseminated during these activities.

RESULTS

A total of 17 volunteers was sampled on 3 occasions. Hairstyle (long hair tied up or a shaved head) was the only significant predictor of dissemination of S aureus (5% significance level). No other significant effects were found at the 5% level. A negative binomial distribution provides the best fit with respect to S aureus.

CONCLUSION

We found that, in the context of our small sample size, hairstyle (long hair tied up or a shaved head) statistically affected levels of bacteria shed from volunteers. However, we found no evidence for "supershedders" or "cloud adults," suggesting they are at an extreme end of a continuous distribution.

Bioaerosol sampling for airborne bacteria in a small animal veterinary teaching hospital

BACKGROUND

Airborne microorganisms within the hospital environment can potentially cause infection in susceptible patients. The objectives of this study were to identify, quantify, and determine the nosocomial potential of common airborne microorganisms present within a small animal teaching hospital.

METHODS

Bioaerosol sampling was done initially in all 11 rooms and, subsequently, weekly samples were taken from selected rooms over a 9-week period. Samples were collected twice (morning and afternoon) at each site on each sampling day. The rooms were divided into two groups: Group 1, in which morning sampling was post-cleaning and afternoon sampling was during activity, and Group 2, in which morning sampling was pre-cleaning and afternoon sampling was post-cleaning. The total aerobic bacterial plate counts per m(3) and bacterial identification were done using standard microbiological methods.

RESULTS

A total of 14 bacterial genera were isolated with the most frequent being Micrococcus spp. followed by species of Corynebacterium, Bacillus, and Staphylococcus. There was a significant interaction between location and time for rooms in Group 1 (p=0.0028) but not in Group 2 (p>0.05). Microbial counts for rooms in Group 2 were significantly greater in the mornings than in the afternoon (p=0.0049). The microbial counts were also significantly different between some rooms (p=0.0333).

CONCLUSION

The detection of significantly higher airborne microbial loads in different rooms at different times of the day suggests that the probability of acquiring nosocomial infections is higher at these times and locations.

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.

Distribution of airborne microbes and antibiotic susceptibility pattern of bacteria during Gwalior trade fair, Central India

BACKGROUND/PURPOSE

Research into the distribution of bioaerosols during events associated with huge groups of people is lacking, especially in developing countries. The purpose of this study was to understand the distribution pattern of bioaerosols during an annual trade fair in the historical city of Gwalior, central India, a very important historical fair that was started by the King of Gwalior Maharaja Madho Rao in 1905.

METHODS

Air samples were collected from six different sites at the fair ground and three different sites in a residential area before/during/after the fair using an impactor sampler on microbial content test agar and rose bengal agar for total bacteria and fungi, respectively. The representative strains of bacteria and fungi were further identified and selected bacterial strains were subjected to antibiotic susceptibility testing according to US Clinical and Laboratory Standards Institute (CLSI) guidelines.

RESULTS

The bacterial bioaerosol count [colony-forming units (CFU)/m(3)] at fair sites was found to be 9.0 × 10(3), 4.0 × 10(4), and 1.0 × 10(4) before the start of the fair, during the fair, and after the fair, respectively. The fungal bioaerosol count at fair sites was 2.6 × 10(3) CFU/m(3), 6.3 × 10(3) CFU/m(3), and 1.7 × 10(3) CFU/m(3) before the fair, during the fair, and after the fair, respectively. Bacterial/fungal bioaerosols during-fair were increased significantly from the bacterial/fungal bioaerosols of the before-fair period (p < 0.05); they were also significantly higher than the bacterial/fungal bioaerosols at non-fair sites during the event (p < 0.0001). The proportion of antibiotic-resistant bacteria over the fair ground was significantly increased during-fair and was still higher in the after-fair period. Methicillin-resistant staphylococci (MRS) were also reported at the fair ground.

CONCLUSION

The study indicates significantly higher bacterial and fungal bioaerosols during the fair event. Therefore, further research is needed to explore the health aspects and guidelines to control microbial load during such types of events.

Does improving surface cleaning and disinfection reduce health care-associated infections?

Contaminated environmental surfaces provide an important potential source for transmission of health care-associated pathogens. In recent years, a variety of interventions have been shown to be effective in improving cleaning and disinfection of surfaces. This review examines the evidence that improving environmental disinfection can reduce health care-associated infections.

Air quality monitoring of the post-operative recovery room and locations surrounding operating theaters in a medical center in Taiwan

To prevent surgical site infection (SSI), the airborne microbial concentration in operating theaters must be reduced. The air quality in operating theaters and nearby areas is also important to healthcare workers. Therefore, this study assessed air quality in the post-operative recovery room, locations surrounding the operating theater area, and operating theaters in a medical center. Temperature, relative humidity (RH), and carbon dioxide (CO₂), suspended particulate matter (PM), and bacterial concentrations were monitored weekly over one year. Measurement results reveal clear differences in air quality in different operating theater areas. The post-operative recovery room had significantly higher CO₂ and bacterial concentrations than other locations. Bacillus spp., Micrococcus spp., and Staphylococcus spp. bacteria often existed in the operating theater area. Furthermore, Acinetobacter spp. was the main pathogen in the post-operative recovery room (18%) and traumatic surgery room (8%). The mixed effect models reveal a strong correlation between number of people in a space and high CO₂ concentration after adjusting for sampling locations. In conclusion, air quality in the post-operative recovery room and operating theaters warrants attention, and merits long-term surveillance to protect both surgical patients and healthcare workers.

Role of MRSA reservoirs in the acute care setting

Background  Nosocomial infection remains the most common complication of hospitalisation. Despite infection control efforts, nosocomial methicillin-resistant Staphylococcus aureus (MRSA) transmission continues to rise. The associated costs of increased hospital stay and patient mortality cause considerable burden to the health system. Objectives  This review sought to evaluate the role of reservoirs, particularly the environment and equipment commonly found in the clinical area, in the transmission of MRSA within the acute hospital. This review updates a review previously completed by the authors and published by the Joanna Briggs Institute (2002). Search strategy  A systematic search for relevant published or unpublished literature was undertaken using electronic databases, the reference lists of retrieved papers and the Internet. This extended the search published in the original review. Databases searched included  Medline (1966-August Week 1 2005), CINAHL (1982-August Week 1 2005), EMBASE (1996-Week 33), as well as the Cochrane Library (Issue 3, 2005) and the Joanna Briggs Institute Evidence Library (August 2005). Selection criteria  All research reports published between 1990 and August 2005 in the English language that focused on the role of the environment and equipment commonly found in the clinical area on the nosocomial MRSA transmission in adult, paediatric or neonatal acute care settings were considered. Data collection and analysis  Two reviewers assessed each paper against the inclusion criteria and a validated quality scale. Studies that scored less than the mean quality score were excluded from the review. Data extraction was undertaken using a tool designed specifically for this review. Statistical comparisons of findings were not possible, so findings are presented in a narrative form. Results  Forty-two papers met the review inclusion criteria, of which 18 obtained a quality score above the threshold and are included in this review. Seven studies reported general investigations of MRSA in the clinical environment and 11 studies explored specific environmental aspects. All studies used exploratory, descriptive or comparative designs. The evidence suggests that MRSA strains within the environment often match those found in patients within that environment. MRSA can be found in the air around MRSA colonised or infected patients. The degree of airborne contamination is significantly increased by activities that promote airflow. Although the site of MRSA colonisation or infection can influence the degree of environmental contamination, these data are inconsistent. Therefore, there is limited evidence for tailoring infection control interventions based on the sites of MRSA colonisation or infection. The evidence suggests that the type of materials used in clinical equipment can influence the effectiveness of cleaning techniques. Current routine cleaning practices, including conventional terminal cleaning, do not necessarily effectively eradicate MRSA from the environment. This review demonstrates that there is a link between the environment and hospital equipment and the transmission of MRSA within the acute hospital setting. Further well-designed research is urgently required to explore the efficacy of specific cleaning and decontamination methods, staff compliance with infection control practices and the range of factors that affect the incidence of MRSA contamination of the environment and equipment commonly found in the clinical area.

Changes in the Staphylococcus aureus transcriptome during early adaptation to the lung

Staphylococcus aureus is a common inhabitant of the human nasopharynx. It is also a cause of life-threatening illness, producing a potent array of virulence factors that enable survival in normally sterile sites. The transformation of S. aureus from commensal to pathogen is poorly understood. We analyzed S. aureus gene expression during adaptation to the lung using a mouse model of S. aureus pneumonia. Bacteria were isolated by bronchoalveolar lavage after residence in vivo for up to 6 hours. S. aureus in vivo RNA transcription was compared by microarray to that of shake flask grown stationary phase and early exponential phase cells. Compared to in vitro conditions, the in vivo transcriptome was dramatically altered within 30 minutes. Expression of central metabolic pathways changed significantly in response to the lung environment. Gluconeogenesis (fbs, pckA) was down regulated, as was TCA cycle and fermentation pathway gene expression. Genes associated with amino acid synthesis, RNA translation and nitrate respiration were upregulated, indicative of a highly active metabolic state during the first 6 hours in the lung. Virulence factors regulated by agr were down regulated in vivo and in early exponential phase compared to stationary phase cells. Over time in vivo, expression of ahpCF, involved in H₂O₂ scavenging, and uspA, which encodes a universal stress regulator, increased. Transcription of leukotoxic α and β-type phenol-soluble modulins psmα1-4 and psmβ1-2 increased 13 and 8-fold respectively; hld mRNA, encoding δ-hemolysin, was increased 9-fold. These were the only toxins to be significantly upregulated in vivo. These data provide the first complete survey of the S. aureus transcriptome response to the mammalian airway. The results present intriguing contrasts with previous work in other in vitro and in vivo models and provide novel insights into the adaptive and temporal response of S. aureus early in the pathogenesis of pneumonia.

Effect of enhanced ultraviolet germicidal irradiation in the heating ventilation and air conditioning system on ventilator-associated pneumonia in a neonatal intensive care unit

OBJECTIVE

The objective of this study was to test the hypothesis that enhanced ultraviolet germicidal irradiation (eUVGI) installed in our neonatal intensive care unit (NICU) heating ventilation and air conditioning system (HVAC) would decrease HVAC and NICU environment microbes, tracheal colonization and ventilator-associated pneumonia (VAP).

STUDY DESIGN

The study was designed as a prospective interventional pre- and post-single-center study. University-affiliated Regional Perinatal Center NICU. Intubated patients in the NICU were evaluated for colonization, and a high-risk sub-population of infants <30 weeks gestation ventilated for ≥ 14 days was studied for VAP. eUVGI was installed in the NICU's remote HVACs. The HVACs, NICU environment and intubated patients' tracheas were cultured pre- and post-eUVGI for 12 months. The high-risk patients were studied for VAP (positive bacterial tracheal culture, increased ventilator support, worsening chest radiograph and ≥ 7 days of antibiotics).

RESULT

Pseudomonas, Klebsiella, Serratia, Acinetobacter, Staphylococcus aureus and Coagulase-negative Staphylococcus species were cultured from all sites. eUVGI significantly decreased HVAC organisms (baseline 500,000 CFU cm(-2); P=0.015) and NICU environmental microbes (P<0.0001). Tracheal microbial loads decreased 45% (P=0.004), and fewer patients became colonized. VAP in the high-risk cohort fell from 74% (n=31) to 39% (n=18), P=0.04. VAP episodes per patient decreased (Control: 1.2 to eUVGI: 0.4; P=0.004), and antibiotic usage was 62% less (P=0.013).

CONCLUSION

eUVGI decreased HVAC microbial colonization and was associated with reduced NICU environment and tracheal microbial colonization. Significant reductions in VAP and antibiotic use were also associated with eUVGI in this single-center study. Large randomized multicenter trials are needed.

Community-associated meticillin-resistant Staphylococcus aureus strains as a cause of healthcare-associated infection

Community-associated meticillin-resistant Staphylococcus aureus (CA-MRSA) was first noticed as a cause of infection in community-based individuals without healthcare contact. As the global epidemic of CA-MRSA has continued, CA-MRSA strain types have begun to emerge as a cause of healthcare-associated infections (HAIs) and hospital outbreaks have occurred worldwide. In areas where CA-MRSA clones have become established with high prevalence, for example USA300 (ST8-IV) in the USA, CA-MRSA are beginning to supplant or overtake traditional healthcare-associated MRSA strains as causes of HAI. The emergence of CA-MRSA as a cause of HAI puts a wider group of hospitalised patients, healthcare workers and their community contacts potentially at risk of MRSA infection. It also exposes CA-MRSA strains to the selective pressure of antibiotic use in hospitals, potentially resulting in increased antibiotic resistance, challenges traditional definitions of CA-MRSA and hampers control efforts due to the constant re-introduction of MRSA from an emerging community reservoir. There is thus an urgent need to clarify the definitions, prevalence and epidemiology of CA-MRSA and to develop systems for the identification and control of these organisms in the community, in hospitals and other healthcare facilities, and at the community-hospital interface.

The ventilation of multiple-bed hospital wards in the tropics: A review

Hospital and healthcare facilities have diverse indoor environment due to the different comfort and health needs of its occupants. Currently, most ventilation studies revolve around specialised areas such as operating rooms and isolation rooms. This paper focuses on the ventilation of multiple-bed hospital wards in the tropical climate, taking into account the design, indoor conditions and engineering controls. General ward layouts are described briefly. The required indoor conditions such as temperature, humidity, air movements and indoor air quality in the ward spaces are summarized based on the current guidelines and practices. Also, recent studies and engineering practices in the hospital indoor environment are elaborated. Usage of computational fluid dynamics tools for the ventilation studies is discussed as well. As identified during the review, there is an apparent knowledge gap for ventilation studies in the tropics compared with temperate climates, as fact studies have only been published for hospital wards in countries with a temperate climate. Therefore, it is highlighted that specific tropical studies along with novel engineering controls are required in addressing the ventilation requirements for the tropics.

Methicillin-resistant Staphylococcus aureus on surfaces of an Intensive Care Unit

OBJECTIVE: To evaluate the presence of methicillin-resistant Staphylococcus aureus (MRSA) in areas close to patients in a General Intensive Care Unit. METHODS: This is a cross-sectional study, in which microbiological samples were collected from five surfaces (left / right bed siderails, bed crank, table, buttons on the infusion pump, and cotton gowns) from each of ten patient rooms, totaling 63 samples. To collect samples, the Petri FilmTM Staph Express Count System 3M TM was used to screen for methicillin resistance, with the Mueller-Hinton agar supplemented with 4% sodium chloride and 6 µg / ml of oxacillin. Descriptive analysis was conducted to determine the frequency (n) and percentage (%) of contamination of environmental surfaces. RESULTS: Of 48 samples positive for Staphylococcus aureus, 29 (60.4%) were resistant to methicillin. The incidence on the siderails and bed cranks, table, buttons on the infusion pumps and aprons were, respectively, 55.5%, 57.1%, 57.1%, 60.0% and 75.0%. CONCLUSION: The results suggest that the surfaces around the patient constitute a major threat, as they represent secondary reservoirs of MRSA.

Rethinking hospital general ward ventilation design using computational fluid dynamics

Indoor ventilation with good air quality control minimises the spread of airborne respiratory and other infections in hospitals. This article considers the role of ventilation in preventing and controlling infection in hospital general wards and identifies a simple and cost-effective ventilation design capable of reducing the chances of cross-infection. Computational fluid dynamic (CFD) analysis is used to simulate and compare the removal of microbes using a number of different ventilation systems. Instead of the conventional corridor air return arrangement used in most general wards, air return is rearranged so that ventilation is controlled from inside the ward cubicle. In addition to boosting the air ventilation rate, the CFD results reveal that ventilation performance and the removal of microbes can be significantly improved. These improvements are capable of matching the standards maintained in a properly constructed isolation room, though at much lower cost. It is recommended that the newly identified ventilation parameters be widely adopted in the design of new hospital general wards to minimise cross-infection. The proposed ventilation system can also be retrofitted in existing hospital general wards with far less disruption and cost than a full-scale refurbishment.

Community-associated methicillin-resistant Staphylococcus aureus: epidemiology and clinical consequences of an emerging epidemic

Staphylococcus aureus is an important cause of skin and soft-tissue infections (SSTIs), endovascular infections, pneumonia, septic arthritis, endocarditis, osteomyelitis, foreign-body infections, and sepsis. Methicillin-resistant S. aureus (MRSA) isolates were once confined largely to hospitals, other health care environments, and patients frequenting these facilities. Since the mid-1990s, however, there has been an explosion in the number of MRSA infections reported in populations lacking risk factors for exposure to the health care system. This increase in the incidence of MRSA infection has been associated with the recognition of new MRSA clones known as community-associated MRSA (CA-MRSA). CA-MRSA strains differ from the older, health care-associated MRSA strains; they infect a different group of patients, they cause different clinical syndromes, they differ in antimicrobial susceptibility patterns, they spread rapidly among healthy people in the community, and they frequently cause infections in health care environments as well. This review details what is known about the epidemiology of CA-MRSA strains and the clinical spectrum of infectious syndromes associated with them that ranges from a commensal state to severe, overwhelming infection. It also addresses the therapy of these infections and strategies for their prevention.

Infection-free surgery: how to improve hand-hygiene compliance and eradicate methicillin-resistant Staphylococcus aureus from surgical wards

INTRODUCTION

Healthcare-associated infections cost the UK National Health Service 1 billion UK pounds per annum. Poor hand hygiene is the main route of transmission for methicillin-resistant Staphylococcus aureus (MRSA), leading to increased mortality and morbidity for infected patients. This study aims to quantify MRSA infection rates and compliance of alcohol gel application at the entrance to a surgical ward and assess how a simple intervention affects compliance.

SUBJECTS AND METHODS

Compliance was assessed via a discretely positioned close-surveillance camera at the ward entrance. Footage was reviewed to monitor compliance of all persons entering the ward over a 12-month period.

RESULTS

For the initial 6 months, mean alcohol gel compliance was 24% for all persons entering the ward. After this period, a conspicuous strip of bright red tape was positioned along the corridor approaching the ward entrance. The red line continued up the wall to an arrow head pointing to the two alcohol gel dispensers on the wall. Mean compliance over the subsequent 6 months significantly improved to 62% (P < 0.0001). Compliance improved for all persons entering the ward as follows (before - after, significance): doctors (0% - 54%, P < 0.01); nurses (24% - 75%, P < 0.05); porters (21% - 67%, P < 0.05); visitors (35% - 68%, P < 0.01); patients (23% - 44%, P > 0.05). There were two cases of MRSA bacteraemia in the initial 6 months and no cases in the following 6 months with the red line in situ.

CONCLUSIONS

This study demonstrates how a simple intervention significantly improves hand-hygiene compliance with associated eradication of MRSA.

The environment as a factor in methicillin-resistant Staphylococcus aureus transmission

In recent years, methicillin-resistant Staphylococcus aureus (MRSA) has become a leading cause of infectious disease morbidity and mortality in the United States. The epidemiology of the organism has changed, with novel strains emerging in the community among individuals lacking any healthcare contact. Although direct human-to-human transmission via skin contact is one way for this organism to spread, transmission via environmental contamination of fomites or through air are other potential ways that the organism can be acquired. As such, an improved understanding of MRSA transmission is needed to implement maximally effective control and prevention interventions. We review the research documenting the role of the environment in MRSA spread.

Airborne transmission of disease in hospitals

Hospital-acquired infection (HAI) is an important public health issue with unacceptable levels of morbidity and mortality, over the last 5 years. Disease can be transmitted by air (over large distances), by direct/indirect contact or a combination of both routes. While contact transmission of disease forms the majority of HAI cases, transmission through the air is harder to control, but one where the engineering sciences can play an important role in limiting the spread. This forms the focus of this themed volume. In this paper, we describe the current hospital environment and review the contributions from microbiologists, mechanical and civil engineers, and mathematicians to this themed volume on the airborne transmission of infection in hospitals. The review also points out some of the outstanding scientific questions and possible approaches to mitigating transmission.

Mathematical models for assessing the role of airflow on the risk of airborne infection in hospital wards

Understanding the risk of airborne transmission can provide important information for designing safe healthcare environments with an appropriate level of environmental control for mitigating risks. The most common approach for assessing risk is to use the Wells-Riley equation to relate infectious cases to human and environmental parameters. While it is a simple model that can yield valuable information, the model used as in its original presentation has a number of limitations. This paper reviews recent developments addressing some of the limitations including coupling with epidemic models to evaluate the wider impact of control measures on disease progression, linking with zonal ventilation or computational fluid dynamics simulations to deal with imperfect mixing in real environments and recent work on dose-response modelling to simulate the interaction between pathogens and the host. A stochastic version of the Wells-Riley model is presented that allows consideration of the effects of small populations relevant in healthcare settings and it is demonstrated how this can be linked to a simple zonal ventilation model to simulate the influence of proximity to an infector. The results show how neglecting the stochastic effects present in a real situation could underestimate the risk by 15 per cent or more and that the number and rate of new infections between connected spaces is strongly dependent on the airflow. Results also indicate the potential danger of using fully mixed models for future risk assessments, with quanta values derived from such cases less than half the actual source value.

The role of healthcare personnel in the maintenance and spread of methicillin-resistant Staphylococcus aureus

Healthcare workers may acquire methicillin-resistant Staphylococcus aureus (MRSA) from patients, both hospital and home environments, other healthcare workers, family and public acquaintances, and pets. There is a consensus of case reports and series which now strongly support the role for MRSA-carrying healthcare personnel to serve as a reservoir and as a vehicle of spread within healthcare settings. Carriage may occur at a number of body sites and for short, intermediate, and long terms. A number of approaches have been taken to interrupt the linkage of staff-patient spread, but most emphasis has been placed on handwashing and the treatment of staff MRSA carriers. The importance of healthcare workers in transmission has been viewed with varying degrees of interest, and several logistical problems have arisen when healthcare worker screening is brought to the forefront. There is now considerable support for the screening and treatment of healthcare workers, but it is suggested that the intensity of any such approach must consider available resources, the nature of the outbreak, and the strength of epidemiological associations. The task of assessing healthcare personnel carriage in any context should be shaped with due regard to national and international guidelines, should be honed and practiced according to local needs and experience, and must be patient-oriented.

The ventilation of multiple-bed hospital wards: review and analysis

BACKGROUND

Although the merits of ventilating operating theatres and isolation rooms are well known, the clinical benefits derived from ventilating hospital wards and patient rooms are unclear. This is because relatively little research work has been done in the ventilation of these areas compared with that done in operating theatres and isolation rooms. Consequently, there is a paucity of good quality data from which to make important decisions regarding hospital infrastructure. This review evaluates the role of general ward ventilation to assess whether or not it affects the transmission of infection.

METHODS

A critical review was undertaken of guidelines in the United Kingdom and United States governing the design of ventilation systems for hospital wards and other multibed rooms. In addition, an analytical computational fluid dynamics (CFD) study was performed to evaluate the effectiveness of various ventilation strategies in removing airborne pathogens from ward spaces.

RESULTS

The CFD simulation showed the bioaerosol concentration in the study room to be substantially lower (2467 cfu/m(3)) when air was supplied and extracted through the ceiling compared with other simulated ventilations strategies, which achieved bioaerosol concentrations of 12487 and 10601 cfu/m(3), respectively.

CONCLUSIONS

There is a growing body of evidence that the aerial dispersion of some nosocomial pathogens can seed widespread environmental contamination, and that this may be contributing to the spread infection in hospital wards. Acinetobacter spp in particular appear to conform to this model, with numerous outbreaks attributed to aerial dissemination. This suggests that the clinical role of general ward ventilation may have been underestimated and that through improved ward ventilation, it may be possible to reduce environmental contamination and thus reduce nosocomial infection rates.

A Review of the Research Literature on Evidence-Based Healthcare Design

Objective:

This report surveys and evaluates the scientific research on evidence-based healthcare design and extracts its implications for designing better and safer hospitals.

Background:

It builds on a literature review conducted by researchers in 2004.

Methods:

Research teams conducted a new and more exhaustive search for rigorous empirical studies that link the design of hospital physical environments with healthcare outcomes. The review followed a two-step process, including an extensive search for existing literature and a screening of each identified study for the relevance and quality of evidence.

Results:

This review found a growing body of rigorous studies to guide healthcare design, especially with respect to reducing the frequency of hospital-acquired infections. Results are organized according to three general types of outcomes: patient safety, other patient outcomes, and staff outcomes. The findings further support the importance of improving outcomes for a range of design characteristics or interventions, including single-bed rooms rather than multibed rooms, effective ventilation systems, a good acoustic environment, nature distractions and daylight, appropriate lighting, better ergonomic design, acuity-adaptable rooms, and improved floor layouts and work settings. Directions for future research are also identified.

Conclusions:

The state of knowledge of evidence-based healthcare design has grown rapidly in recent years. The evidence indicates that well-designed physical settings play an important role in making hospitals safer and more healing for patients, and better places for staff to work.

MRSA and the environment: implications for comprehensive control measures

Environmental contamination with methicillin-resistant Staphylococcus aureus (MRSA) is established soon after colonized or infected patients become resident. There are many studies that detail the mechanisms of spread and environmental survival of methicillin-susceptible Staphylococcus aureus (MSSA); this knowledge translates directly into the same findings for MRSA. The potential ubiquity of MRSA in a health-care setting poses challenges for decontamination. Whereas patients and medical staff are important sources for MRSA spread, the environmental burden may contribute significantly in various contexts. Effective control measures must therefore include consideration for MRSA in the environment.

Role of MRSA reservoirs in the acute care setting

BACKGROUND

Nosocomial infection remains the most common complication of hospitalisation. Despite infection control efforts, nosocomial methicillin-resistant Staphylococcus aureus (MRSA) transmission continues to rise. The associated costs of increased hospital stay and patient mortality cause considerable burden to the health system.

OBJECTIVES

This review sought to evaluate the role of reservoirs, particularly the environment and equipment commonly found in the clinical area, in the transmission of MRSA within the acute hospital. This review updates a review previously completed by the authors and published by the Joanna Briggs Institute (2002).

SEARCH STRATEGY

A systematic search for relevant published or unpublished literature was undertaken using electronic databases, the reference lists of retrieved papers and the Internet. This extended the search published in the original review.Databases searched included Medline (1966-August Week 1 2005), CINAHL (1982-August Week 1 2005), EMBASE (1996-Week 33), as well as the Cochrane Library (Issue 3, 2005) and the Joanna Briggs Institute Evidence Library (August 2005).

SELECTION CRITERIA

All research reports published between 1990 and August 2005 in the English language that focused on the role of the environment and equipment commonly found in the clinical area on the nosocomial MRSA transmission in adult, paediatric or neonatal acute care settings were considered.

DATA COLLECTION AND ANALYSIS

Two reviewers assessed each paper against the inclusion criteria and a validated quality scale. Studies that scored less than the mean quality score were excluded from the review. Data extraction was undertaken using a tool designed specifically for this review. Statistical comparisons of findings were not possible, so findings are presented in a narrative form.

RESULTS

Forty-two papers met the review inclusion criteria, of which 18 obtained a quality score above the threshold and are included in this review. Seven studies reported general investigations of MRSA in the clinical environment and 11 studies explored specific environmental aspects. All studies used exploratory, descriptive or comparative designs. The evidence suggests that MRSA strains within the environment often match those found in patients within that environment. MRSA can be found in the air around MRSA colonised or infected patients. The degree of airborne contamination is significantly increased by activities that promote airflow. Although the site of MRSA colonisation or infection can influence the degree of environmental contamination, these data are inconsistent. Therefore, there is limited evidence for tailoring infection control interventions based on the sites of MRSA colonisation or infection. The evidence suggests that the type of materials used in clinical equipment can influence the effectiveness of cleaning techniques. Current routine cleaning practices, including conventional terminal cleaning, do not necessarily effectively eradicate MRSA from the environment. This review demonstrates that there is a link between the environment and hospital equipment and the transmission of MRSA within the acute hospital setting. Further well-designed research is urgently required to explore the efficacy of specific cleaning and decontamination methods, staff compliance with infection control practices and the range of factors that affect the incidence of MRSA contamination of the environment and equipment commonly found in the clinical area.

Environmental contamination makes an important contribution to hospital infection

Meticillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant enterococci (VRE) are capable of surviving for days to weeks on environmental surfaces in healthcare facilities. Environmental surfaces frequently touched by healthcare workers are commonly contaminated in the rooms of patients colonized or infected with MRSA or VRE. A number of studies have documented that healthcare workers may contaminate their hands or gloves by touching contaminated environmental surfaces, and that hands or gloves become contaminated with numbers of organisms that are likely to result in transmission to patients. Pathogens may also be transferred directly from contaminated surfaces to susceptible patients. There is an increasing body of evidence that cleaning or disinfection of the environment can reduce transmission of healthcare-associated pathogens. Because routine cleaning of equipment items and other high-touch surfaces does not always remove pathogens from contaminated surfaces, improved methods of disinfecting the hospital environment are needed. Preliminary studies suggest that hydrogen peroxide vapour technology deserves further evaluation as a method for decontamination of the environment in healthcare settings.

Evaluation of a new mobile system for protecting immune-suppressed patients against airborne contamination

BACKGROUND

Invasive aspergillosis is one of the most lethal airborne dangers for immune-suppressed subjects. Providing patient protection from such airborne threats requires costly and high-maintenance facilities. We herein evaluate a new self-contained mobile unit as an alternative for creating a patient protective environment.

METHODS

Airborne contamination levels were monitored for different simulated scenarios and under actual clinical conditions. Functional tests were used to challenge the unit under adverse conditions, and a preliminary clinical study with patients and staff present was performed at 2 different French hospitals.

RESULTS

Functional tests demonstrated that the unit can rapidly decontaminate air in the protected zone created by the unit and in the surrounding room. In addition, the protected zone is not sensitive to large disturbances that occur in the room. The clinical study included 4 patients with 150 accumulated days of testing. The protected zone created by the unit systematically provided an environment with undetectable airborne fungal levels (ie, <1 CFU/m(3)) regardless of the levels in the room or corridor (P < .01).

CONCLUSIONS

These tests show that the unit can be used to create a mobile protective environment for immune-suppressed patients in a standard hospital setting.

Decreasing airborne contamination levels in high-risk hospital areas using a novel mobile air-treatment unit

OBJECTIVE

To evaluate the performance of a new mobile air-treatment unit that uses nonthermal-plasma reactors for lowering the airborne bioburden in critical hospital environments and reducing the risk of nosocomial infection due to opportunistic airborne pathogens, such as Aspergillus fumigatus.

METHODS

Tests were conducted in 2 different high-risk hospital areas: an operating room under simulated conditions and rooms hosting patients in a pediatric hematology ward. Operating room testing provided performance evaluations of removal rates for airborne contamination (ie, particles larger than 0.5 microm) and overall lowering of the airborne bioburden (ie, colony-forming units of total mesophilic flora and fungal flora per cubic meter of air). In the hematology service, opportunistic and nonpathogenic airborne fungal levels in a patient's room equipped with an air-treatment unit were compared to those in a control room.

RESULTS

In an operating room with a volume of 118 m(3), the time required to lower the concentration of airborne particles larger than 0.5 microm by 90% was decreased from 12 minutes with the existing high-efficiency particulate air filtration system to less than 2 minutes with the units tested, with a 2-log decrease in the steady-state levels of such particles (P<.01). Concurrently, total airborne mesophilic flora concentrations dropped by a factor of 2, and the concentrations of fungal species were reduced to undetectable levels (P<.01). The 12-day test period in the hematology ward revealed a significant reduction in airborne fungus levels (P<.01), with average reductions of 75% for opportunistic species and 82% for nonpathogenic species.

CONCLUSION

Our data indicate that the mobile, nonthermal-plasma air treatment unit tested in this study can rapidly reduce the levels of airborne particles and significantly lower the airborne bioburden in high-risk hospital environments.