Positive-pressure isolation and the prevention of invasive aspergillosis. What is the evidence?

COVID-19-Associated Pulmonary Aspergillosis at an Academic Medical Center in the Midwestern United States

Pulmonary aspergillosis has been reported at high rates in patients with coronavirus disease 2019 (COVID-19) and is associated with high morbidity and mortality. We retrospectively assessed all patients admitted to an intensive care unit during the early COVID-19 surge (3/17/20–5/10/20) at our medical center in the midwestern USA for the presence of COVID-19-associated pulmonary aspergillosis (CAPA). Patients were not routinely screened for CAPA; diagnostic work-up for fungal infections was pursued when clinically indicated. Among 256 patients admitted to the ICU with severe COVID-19, 188 (73%) were intubated and 62 (24%) ultimately expired within 30 days of admission to the ICU. Only three patients (1%) were found to have CAPA; diagnosis was made by tracheal aspirate cultures in two cases and by bronchoalveolar lavage fluid Aspergillus galactomannan in one case. None of the patients who developed CAPA had classic risk factors for invasive fungal infection. The occurrence of CAPA was much lower than that reported at other centers, likely reflecting the local epidemiology.

CFD investigation on the effects of wind and thermal wall-flow on pollutant transmission in a high-rise building

The solar radiation can heat the building outer surface, and then cause the upward natural convection flows adjacent to the wall. This phenomenon is especially obvious on a windless sunny day. The near wall thermal plume can drive gaseous pollutants released from lower floors to upper floors. Combined with the effect of ambient approaching wind, the transmission routes will be very complicated. The paper aims to investigate the airflow patterns and pollutant transmission within a building under the effects of wind and thermal forces. A hypothetical twenty-storey slab-shape high-rise building in Shanghai with single-sided natural ventilation is set as the research object in the present study. The intensity of solar radiation on a typical day during transition season is theoretically analysed. The temperature difference between the heated building envelope and the ambient air is calculated by a simplified heat balance model. Finally, the tracer gas method is employed in the numerical simulation to analyse the influence of the wind and wall thermal plume flow on the inter-flat pollutant transmission characteristics. The results show that, the temperature difference between sunward and shady side wall is about 10 K at noon on the designate day. When the source is set as a point with steady intensity and the buoyancy is stronger than or approximately equivalent to the wind, the reentry ratio of the flat immediately above the source can be around 25%.

Analyzing the risk factors influencing surgical site infections: the site of environmental factors

BACKGROUND

Addressing surgical site infection (SSI) is accomplished, in part, through studies that attempt to clarify the nature of many essential factors in the control of SSI. We sought to examine the link between multiple risk factors, including environmental factors, and SSI for prevention management.

METHODS

We conducted a longitudinal prospective study to identify SSIs in all patients who underwent interventions in 2014 in 8 selected hospitals on the Mediterranean coast of Spain. Risk factors related to the operating theatre included level of fungi and bacterial contamination, temperature and humidity, air renewal and differential air pressure. Patient-related variables included age, sex, comorbidity, nutrition level and transfusion. Other factors were antibiotic prophylaxis, electric versus manual shaving, American Society of Anaesthesiologists physical status classification, type of intervention, duration of the intervention and preoperative stay.

RESULTS

Superficial SSI was most often associated with environmental factors, such as environmental contamination by fungi (from 2 colony-forming units) and bacteria as well as surface contamination. When there was no contamination in the operating room, no SSI was detected. Factors that determined deep and organ/space SSI were more often associated with patient characteristics (age, sex, transfusion, nasogastric feeding and nutrition, as measured by the level of albumin in the blood), type of intervention and preoperative stay. Antibiotic prophylaxis and shaving with electric razor were protective factors for both types of infection, whereas the duration of the intervention and the classification of the intervention as "dirty" were shared risk factors.

CONCLUSION

Our results suggest the importance of environmental and surface contamination control to prevent SSI.

Infectious diseases in allogeneic haematopoietic stem cell transplantation: prevention and prophylaxis strategy guidelines 2016

Infectious complications after allogeneic haematopoietic stem cell transplantation (allo-HCT) remain a clinical challenge. This is a guideline provided by the AGIHO (Infectious Diseases Working Group) of the DGHO (German Society for Hematology and Medical Oncology). A core group of experts prepared a preliminary guideline, which was discussed, reviewed, and approved by the entire working group. The guideline provides clinical recommendations for the preventive management including prophylactic treatment of viral, bacterial, parasitic, and fungal diseases. The guideline focuses on antimicrobial agents but includes recommendations on the use of vaccinations. This is the updated version of the AGHIO guideline in the field of allogeneic haematopoietic stem cell transplantation utilizing methods according to evidence-based medicine criteria.

En-suite bathrooms in protected haematology wards: a source of filamentous fungal contamination?

BACKGROUND

In spite of 25 recently built high-risk haematology rooms with a protected environment and fitted with en-suite bathrooms in our university hospital centre in 2008, sporadic cases of hospital-acquired invasive aspergillosis remained in these wards.

AIM

This study aimed to identify unsuspected environmental sources of filamentous fungal contamination in these rooms.

METHODS

Over two months, environmental fungal flora in the air (150 samples) as well as air particle counting and physical environmental parameters (airspeed, temperature, humidity, pressure) were prospectively monitored twice on the sampling day in all 25 protected rooms and en-suite bathrooms in use, and on bathroom surfaces (150 samples).

FINDINGS

In rooms under laminar airflow, in the presence of patients during sampling sessions, fungi were isolated in two samples (4%, 2/50) with a maximum value of 2cfu/500L (none was Aspergillus sp.). However, 88% of the air samples (44/50) in the bathroom were contaminated with a median range and maximum value of 2 and 16cfu/500L. Aspergillus spp. were involved in 24% of contaminated samples (12/44) and A. fumigatus in 6% (3/44). Bathroom surfaces were contaminated by filamentous fungi in 5% of samples (8/150).

CONCLUSION

This study highlighted that en-suite bathrooms in protected wards are likely to be a source of fungi. Before considering specific treatment of air in bathrooms, technicians have first corrected the identified deficiencies: replacement of high-efficiency particulate air filters, improvement of air control automation, and restoration of initial technical specifications. Assessment of measure effectiveness is planned.

Spatial and temporal variations in indoor environmental conditions, human occupancy, and operational characteristics in a new hospital building

The dynamics of indoor environmental conditions, human occupancy, and operational characteristics of buildings influence human comfort and indoor environmental quality, including the survival and progression of microbial communities. A suite of continuous, long-term environmental and operational parameters were measured in ten patient rooms and two nurse stations in a new hospital building in Chicago, IL to characterize the indoor environment in which microbial samples were taken for the Hospital Microbiome Project. Measurements included environmental conditions (indoor dry-bulb temperature, relative humidity, humidity ratio, and illuminance) in the patient rooms and nurse stations; differential pressure between the patient rooms and hallways; surrogate measures for human occupancy and activity in the patient rooms using both indoor air CO₂ concentrations and infrared doorway beam-break counters; and outdoor air fractions in the heating, ventilating, and air-conditioning systems serving the sampled spaces. Measurements were made at 5-minute intervals over consecutive days for nearly one year, providing a total of ∼8×10⁶ data points. Indoor temperature, illuminance, and human occupancy/activity were all weakly correlated between rooms, while relative humidity, humidity ratio, and outdoor air fractions showed strong temporal (seasonal) patterns and strong spatial correlations between rooms. Differential pressure measurements confirmed that all patient rooms were operated at neutral pressure. The patient rooms averaged about 100 combined entrances and exits per day, which suggests they were relatively lightly occupied compared to higher traffic environments (e.g., retail buildings) and more similar to lower traffic office environments. There were also clear differences in several environmental parameters before and after the hospital was occupied with patients and staff. Characterizing and understanding factors that influence these building dynamics is vital for hospital environments, where they can impact patient health and the survival and spread of healthcare associated infections.

Fungal spore concentrations in two haematopoietic stem cell transplantation (HSCT) units containing distinct air control systems

Invasive fungal diseases have emerged as important causes of morbidity and mortality in haematological patients. In this study air samples were collected in two haematopoietic stem cell transplantation (HSCT) units, in which distinct air-control systems were in place. In hospital 1 no high-efficiency particulate air (HEPA) filter was available whereas in hospital 2 HSCT rooms were equipped with HEPA filters, with positive air pressure in relation to the corridor. A total of 117 samples from rooms, toilets and corridors were obtained during December 2009 to January 2011, using a six-stage Andersen sampler. In both hospitals, the concentration of potentially pathogenic fungi in the air was reduced in patients' rooms compared to corridors (P < 0·0001). Despite the presence of a HEPA filter in hospital 2, rooms in both hospitals showed similar concentrations of potentially pathogenic fungi (P = 0·714). These findings may be explained by the implementation of additional protective measures in hospital 1, emphasizing the importance of such measures in protected environments.

Environmental prevention of infection in stem cell transplant recipients: a survey of the Infectious Diseases Working Party of the European Group for Blood and Marrow Transplantation

BACKGROUND

The developments of peripheral blood stem cells in autologous hematopoietic stem cell transplantation (auto-HCT), and of reduced-intensity conditioning (RIC) regimens in allogeneic HCT (allo-HCT), have considerably changed the transplant approach. Prolonged neutropenia combined with severe mucosal damage and organ dysfunction is no longer the rule in the early post-HCT pancytopenic phase. Although strict isolation during pancytopenia was followed by most HCT units in the past, this may not be the current practice.

METHODS

In 2008, a questionnaire was sent out to the 463 European Group for Blood and Marrow Transplantation centers, enquiring about their current environmental protection procedures; 89 (20%) returned the questionnaire.

RESULTS

Most centers housed auto-HCT recipients in high-efficiency particulate air (HEPA)-filtered rooms without (52%) or with laminar air flow (LAF) (29%) after total body irradiation (TBI), whereas HEPA-filtered rooms were used in 53% of auto-HCT conditioned without TBI. During the initial pancytopenic phase after allo-HCT, patients were housed in HEPA/LAF rooms in 50% and 42% of the centers, if a high-dose myeloablative conditioning regimen or a RIC regimen was used, respectively. Surprisingly, 8-24% of the centers reported that no isolation procedures were used in patients colonized or infected with highly transmissible pathogens (i.e., Clostridium difficile, respiratory viruses, and varicella zoster virus).

CONCLUSION

In conclusion, universal recommendations for infected or colonized patients may be poorly known or applied in many HCT units.

Impact of two-way air flow due to temperature difference on preventing the entry of outdoor particles using indoor positive pressure control method

Maintaining positive pressure indoors using mechanical ventilation system is a popular control method for preventing the entry of outdoor airborne particles. The idea is, as long as the supply air flow rate is larger than return air flow rate, the pressure inside the ventilated room should be positive since the superfluous air flow must exfiltrate from air leakages or other openings of the room to the outdoors. Based on experimental and theoretical analyses this paper aims to show the impact of two-way air flow due to indoor/outdoor temperature difference on preventing the entry of outdoor particles using positive pressure control method. The indoor positive pressure control method is effective only when the size of the opening area is restricted to a certain level, opening degree less than 30° in this study, due to the two-way air flow effect induced by differential temperature. The theoretical model was validated using the experimental data. The impacts of two-way air flow due to temperature difference and the supply air flow rate were also analyzed using the theoretical model as well as experimental data. For real houses, it seems that the idea about the positive pressure control method for preventing the entry of outdoor particles has a blind side.

Risk factors for invasive aspergillosis in acute myeloid leukemia patients prophylactically treated with posaconazole

Invasive aspergillosis (IA) is an important cause of morbidity and mortality in neutropenic patients with hematological malignancies. To investigate the immediate and mid-term benefits of posaconazole prophylaxis in AML patients undergoing first induction chemotherapy and to study the infection risk factors, we prospectively studied the IA incidence in these patients at our hospital between years 2007 and 2008; then we compared them to a matched control group without prophylaxis. There were 55 and 66 patients in each group respectively. At day 32 post-induction, two probable cases (3.6%) were scored in the prophylaxis group compared to 8 cases (12.1%) in the control group (4 possible and 4 probable). At day 100, it reached 7.27% and 15.5% respectively. Kaplan-Meier analysis at day 100 showed lower mortality rate in the prophylaxis group compared to the control group [3.64% (n = 2, none due to IA) and 10.61% (n = 7, four due to IA) respectively, P = 0.002]. Multivariate analysis showed age and lack of response to induction as independent infection risk factors. Posaconazole prophylaxis resulted in lower incidence of IA and significantly improved survival. Patient's age and response to induction treatment are two independent infection risk factors, and need more attention during future clinical trials linked to antifungal prophylaxis.

Geoclimatic influences on invasive aspergillosis after hematopoietic stem cell transplantation

BACKGROUND

Aspergillus species are ubiquitous. We hypothesized that climatic variables that affect airborne mold counts affect the incidence of invasive aspergillosis (IA).

METHODS

Patients who received hematopoietic stem cell transplants (HSCTs) in geographically and climatically diverse regions (Seattle, WA, and Houston, TX) were examined. Cumulative incidence function, Kaplan-Meier analysis, and Cox proportional hazards regression were performed to examine the association between IA and season. Poisson regression analysis was performed to evaluate the seasonal patterns in IA rates and association with spore counts and climate.

RESULTS

In Seattle, the 3-month incidence of IA was 4.6% (5.7% in allograft recipients and 0.8% in autograft recipients). During the 10-year study period, there was a decrease in the incidence of IA among allogeneic HSCT recipients, corresponding to decreased risks during the nonsummer months; receipt of HSCTs during the summer months was associated with an increased hazard for IA (hazard ratio, 1.87; 95% confidence interval, 1.25-2.81) after adjustment for other known risks. The person-month IA rate in Seattle was positively associated with environmental spore counts, which increased with high temperature and low precipitation. No seasonal effect on IA was observed in Houston, where total spore counts were lower and not variable by climate.

CONCLUSIONS

Climatic variables differentially affect airborne spore counts and IA risk in geographically disparate centers.

Recent advances in antifungal prevention and treatment

Invasive fungal infections are important causes of morbidity and mortality in patients with bone marrow failure syndromes and hematological malignancies, or who are undergoing allogeneic hematopoietic stem cell transplantation (HSCT). Current epidemiological trends indicate a shift toward infections by Aspergillus spp., non-albicans Candida spp., and previously uncommon fungal pathogens that have decreased susceptibility to the available antifungal agents. The last two decades have seen substantial improvements in the clinical, laboratory, and radiological diagnosis of these infections and the development of new antifungal compounds. Progress has been made in establishing disease definitions and paradigms for antifungal intervention and in the design and conduct of interventional clinical trials. Collectively, these advances have led to major but ongoing changes in the management of patients at risk of or being affected by invasive fungal infections. This article reviews current approaches to prevention and treatment of opportunistic fungal infections in immunocompromised patients with hematological disorders and discusses novel approaches to antifungal chemotherapy and adjunctive treatments.

Incidence of bacteremias and invasive mycoses in children undergoing allogeneic hematopoietic stem cell transplantation: a single center experience

We performed a retrospective single center study to define the epidemiology of bacteremias or invasive mycoses in pediatric allogeneic hematopoietic SCT (HSCT) from matched related donors (MRD) or alternative donors (AD). During 119 213 days of follow-up, 156 infections were observed: 130 bacteremias (27 in MRD-HSCT and 103 in AD-HSCT recipients) and 26 invasive mycoses (8 in MRD-HSCT and 18 in AD-HSCT recipients). Overall, the risk of bacteremia was fivefold that of invasive mycosis (P<0.001). AD-HSCT recipients had a higher percentage of infections (89 vs 27%; P<0.001), a higher rate/100 days of immunosuppression (infection rate (IR): 0.21 vs 0.06; P<0.001) and a higher proportion of repeated infections (44 vs 9%; P=0.001). In AD-HSCT, the relative risk of bacteremia was 2.87 in the pre-engraftment period, 5.84 in the early post-engraftment period and 6.46 in the late post-engraftment period (P<0.001) compared to MRD-HSCT. Only after 1 year did the epidemiology become similar. The epidemiology of invasive mycoses did not differ significantly between the two types of transplant.

Reduction of Invasive Aspergillosis Incidence among Immunocompromised Patients after Control of Environmental Exposure

BACKGROUND

The objective of the study was to assess the impact of the relocation of an adult hematological intensive care unit on invasive aspergillosis (IA) incidence.

METHODS

A quasi-experimental study, including a control group and an intervention group that both underwent pretest and posttest evaluations, was conducted in the 3 adult hematological intensive care units (each composed of 14 single rooms) in a university hospital from 14 April 2005 through 1 February 2006. One of these units was relocated from the main building to an adjoining modular construction. In this unit, 4 rooms were equipped with laminar airflow before relocation; all rooms were equipped with positive pressure isolation after relocation. The 2 other units (control group), each containing 8 rooms with laminar airflow, did not undergo environmental modification. The diagnostic criteria for IA were based on the criteria of the European Organization for Research and Treatment of Cancer.

RESULTS

In total, 356 hospitalized patients were included. Of the 21 cases of IA, 18 were nosocomial, and 3 were of undetermined origin. In the relocated unit, the incidence of IA decreased from 13.2% (9 patients) before relocation to 1.6% (1 patient) after relocation (P=.018). Eight of the 9 patients with IA before relocation stayed in rooms without specific air treatment. The rate of IA did not change in the control group. Patient characteristics were similar in each unit before and after relocation.

CONCLUSION

We detected a straightforward association between environmental modification and decreased IA incidence, which emphasizes the use of an environmental strategy, including high-efficiency air filtration, in the prevention of IA.

Hospital and community acquired infection and the built environment--design and testing of infection control rooms

Negative-pressure isolation rooms are required to house patients infected with agents transmissible by the aerosol route in order to minimise exposure of healthcare workers and other patients. Housing patients in a separate room provides a barrier which minimises any physical contact with other patients. An isolation room held at negative pressure to reduce aerosol escape and a high air-change rate to allow rapid removal of aerosols can eliminate transmission of infectious aerosols to those outside the room. However, badly designed and/or incorrectly operating isolation rooms have been shown to place healthcare workers and other patients at risk from airborne diseases such as tuberculosis. Few standards are available for the design of isolation rooms and no pressure differential or air-change rates are specified. Techniques such as aerosol particle tracer sampling and computational fluid dynamics can be applied to study the performance of negative-pressure rooms and to assess how design variables can affect their performance. This should allow cost-effective designs for isolation rooms to be developed. Healthcare staff should be trained to understand how these rooms operate and there should be systems in place to ensure they are functioning correctly.

Post-operative aspergillosis

While invasive aspergillosis occurs typically in severely immunocompromised patients, cases of surgical site infection have been reported in immunocompetent individuals. The Medline, LILACS and EMBASE databases were searched for descriptions of cases of post-operative aspergillosis, and references from relevant articles and conference abstracts were reviewed. More than 500 cases of post-operative aspergillosis were found. Cardiac surgery (n = 188), ophthalmological surgery (n > 90) and dental surgery (n > 100) were associated with the majority of cases. Other cases involved wound infections (n = 22), bronchial infections (n = 30), mediastinitis (n = 11), pleural aspergillosis (n = 1), infections following orthopaedic surgery (n = 42), vascular prosthetic surgery (n = 22), breast surgery (n = 5), abdominal surgery (n = 10) and neurosurgery (n = 25). In most patients, the source was presumed to be airborne infection during the surgical procedure. Prevention of these infections requires special care of the ventilation system in the operating room. Successful treatment requires rapid diagnosis, surgical debridement and antifungal therapy, often with voriconazole. In order to improve the outcome, better diagnostic methods are needed, particularly for cases of endocarditis and aortitis.

Factors involved in the aerosol transmission of infection and control of ventilation in healthcare premises

The epidemics of severe acute respiratory syndrome (SARS) in 2003 highlighted both short- and long-range transmission routes, i.e. between infected patients and healthcare workers, and between distant locations. With other infections such as tuberculosis, measles and chickenpox, the concept of aerosol transmission is so well accepted that isolation of such patients is the norm. With current concerns about a possible approaching influenza pandemic, the control of transmission via infectious air has become more important. Therefore, the aim of this review is to describe the factors involved in: (1) the generation of an infectious aerosol, (2) the transmission of infectious droplets or droplet nuclei from this aerosol, and (3) the potential for inhalation of such droplets or droplet nuclei by a susceptible host. On this basis, recommendations are made to improve the control of aerosol-transmitted infections in hospitals as well as in the design and construction of future isolation facilities.

Itraconazole prophylaxis in pediatric cancer patients receiving conventional chemotherapy or autologous stem cell transplants

GOAL OF WORK

During the renovation works at our institution, the incidence density for invasive aspergillosis (IA) increased from <0.5 to 0.99/1,000 inpatient days in 2001. As a direct response to this increased environmental risk, itraconazole (ITC) was administered for primary prophylaxis in pediatric cancer patients for whom a particular high risk of IA was anticipated due to prolonged severe neutropenia (>10 days), autologous stem cell transplantation, acute myeloblastic leukemia or relapsed acute lymphoblastic leukemia, or high-dose steroids >3 weeks.

MATERIALS AND METHODS

In this open-label, prospective observational study, ITC was given in ITC solution or capsule. Trough concentrations were measured in plasma with high-performance liquid chromatography after at least 7 days of treatment. Doses were adjusted to target plasma trough ITC concentrations > or =0.5 mg/l.

RESULTS

From 2001 to 2005, 39 pediatric cancer patients received 44 prophylactic ITC cycles; 102 trough plasma concentrations were measured after oral administration. Plasma target concentrations >0.5 mg/l were achieved with both formulations. A median dose of 8 mg kg(-1) day(-1) (3.5-16.0 mg kg(-1) day(-1)) was necessary in pediatric oncology patients. The bioavailability of the liquid formulation was significantly lower when the solution was given by a feeding tube. Adverse effects (gastrointestinal, elevated transaminases, and one hemolysis) which led to the cessation of the ITC prophylaxis were reported in 11% of all courses. No breakthrough infection was seen in this pediatric population.

CONCLUSION

Oral ITC offers a feasible and inexpensive option for antifungal prophylaxis in selected pediatric cancer patients. Drug monitoring and meticulous consideration of possible interactions and adverse effects are mandatory.

Nosocomial aspergillosis in outbreak settings

Nosocomial aspergillosis represents a serious threat for severely immunocompromised patients and numerous outbreaks of invasive aspergillosis have been described. This systematic review summarizes characteristics and mortality rates of infected patients, distribution of Aspergillus spp. in clinical specimens, concentrations of aspergillus spores in volumetric air samples, and outbreak sources. A web-based register of nosocomial epidemics (outbreak database), PubMed and reference lists of relevant articles were searched systematically for descriptions of aspergillus outbreaks in hospital settings. Fifty-three studies with a total of 458 patients were included. In 356 patients, the lower respiratory tract was the primary site of aspergillus infection. Species identified most often were Aspergillus fumigatus (154 patients) and Aspergillus flavus (101 patients). Haematological malignancies were the predominant underlying diseases (299 individuals). The overall fatality rate in these 299 patients (57.6%) was significantly greater than that in patients without severe immunodeficiency (39.4% of 38 individuals). Construction or demolition work was often (49.1%) considered to be the probable or possible source of the outbreak. Even concentrations of Aspergillus spp. below 1 colony-forming unit/m(3) were sufficient to cause infection in high-risk patients. Virtually all outbreaks of nosocomial aspergillosis are attributed to airborne sources, usually construction. Even small concentrations of spores have been associated with outbreaks, mainly due to A. fumigatus or A. flavus. Patients at risk should not be exposed to aspergilli.

Prevention of systemic mycoses by reducing exposure to fungal pathogens in hospitalized and ambulatory neutropenic patients

PURPOSE/OBJECTIVES

To describe sources of fungal contamination that can incite invasive mycoses in hospitalized and ambulatory neutropenic patients and to discuss approaches to reduce exposure to pathogens.

DATA SOURCES

Published articles, books, and brochures.

DATA SYNTHESIS

Modifications of patient environments and lifestyles include hand hygiene for patients and healthcare workers, air filtration in hospitals, and reduction in exposure to plants, soil, standing water, and dusty environments. The effectiveness of dietary restrictions is controversial, although avoidance of pepper is recommended. These restrictions should be implemented prior to, during, and following neutropenia.

CONCLUSIONS

Mycoses can be hospital or community acquired; however, although guidelines for environmental and lifestyle modifications are well documented for the institutional setting, they are more limited for ambulatory patients.

IMPLICATIONS FOR NURSING

Nurses have a key role in the early identification of outbreaks of fungal infections, evaluation of hospital and home environments for sources of pathogens, education of patients on preventive measures, and research on neutropenic diets and improved technology to reduce exposure to fungal pathogens.