Ten-year air sample analysis of Aspergillus prevalence in a university hospital.

Airborne fungal samples were collected on a monthly basis for 10 years, from 1995 to 2005, at a tertiary university hospital. Paired samples were cultured at 25 and 37 degrees C. Data were interpreted according to the air filtration systems serving each location. Samples cultured at 37 degrees C from the patient care areas had a mean recovery of 18% of the mean recovery from outdoor air (22 versus 122cfu/m(3)). Recovery of Aspergillus spp. at 37 degrees C in the high-efficiency particulate air (HEPA)-filtered locations was positive for Aspergillus spp. approximately one-third of the time; the rest of the patient care areas were positive half of the time and the outdoor samples were positive 95% of the time. We found 48 sporadic bursts at 37 degrees C which produced counts >3 SD above the mean. Hospital-acquired infection was related to high recovery of Aspergillus fumigatus on at least one occasion. We have found it impossible, without implementing impractical measures, to provide an environment completely devoid of Aspergillus spp. We conclude that routine air sampling is not an effective means of predicting hospital-acquired infections. However, a transient spike, or burst, may be useful in identifying an in-house source of contamination and may be used to consider additional interventional treatments for patients at risk. Emphasis should be placed on maintaining high-efficiency filtration of the outside air and on ensuring that other environmental control methods are used to prevent dissemination of environmental opportunistic fungal spores.

Extrinsic risk factors for pneumonia in the patient at high risk of infection.

Most nosocomial pathogens cause pneumonia through the following sequence: transit to the patient on the hands of medical personnel or perhaps in food, proliferation in the nasopharynx, and subsequent pulmonary aspiration. There are three exceptional pathogens, each of particular concern as a cause of pneumonia in the immunocompromised patient, which follow atypical routes. Important recent advances in understanding these routes permit more rational preventive measures. This report examines the evidentiary basis for the following pathophysiolgic propositions about these three pathogens: Aspergillus, Pneumocystis carinii, and Legionella. Aspergillus spores are almost ubiquitous. Spore generation, except in very unusual circumstances, takes place outside the hospital. Most spores enter the hospital borne in air by infiltration or because of incomplete filtration. Air filtration systems of moderate efficiency remove Aspergillus spores. Nosocomial pulmonary and disseminated aspergillosis arises from inhalation of airborne spores. A nasopharygeal colonization intermediate step before pulmonary disease has not yet been solidly established. It is now firmly established that airborne Pneumocystic carinii transmission occurs between animals. Airborne acquisition probably occurs early in human life. However, in-hospital, person-to-person transmission has yet to be convincingly demonstrated. Most or all cases of pneumocystosis in adults are due to reactivation of endogenous pulmonary organisms. Intensive diagnostic efforts reveal that Legionella is a common cause of community-acquired and nosocomial pneumonia in hospitals where it had not previously been recognized. However, there are at least a few hospitals where it is an uncommon source of pneumonia. Several hospitals have demonstrated a temporal association between the presence of Legionella in hot water systems and nosocomial cases of Legionella pneumonia. The mechanism or mechanisms of transmission to the patient remain to be delineated. It is also not determined if all hospital hot water systems should be maintained Legionella free.

Refinements of environmental assessment during an outbreak investigation of invasive aspergillosis in a leukemia and bone marrow transplant unit.

OBJECTIVES: To investigate an outbreak of aspergillosis in a leukemia and bone marrow transplant (BMT) unit and to improve environmental assessment strategies to detect Aspergillus. DESIGN: Epidemiological investigation and detailed environmental assessment. SETTING: A tertiary-care university hospital with a 37-bed leukemia and BMT unit PARTICIPANTS: Leukemic or BMT patients with invasive aspergillosis identified through prospective surveillance and confirmed by chart review. INTERVENTIONS: We verified the diagnosis of invasive fungal infection by reviewing medical charts of at-risk patients, performing a case-control study to determine risk factors for infection, instituting wet mopping to clean all floors, providing N95 masks to protect patients outside high-efficiency particulate air (HEPA)-filtered areas, altering traffic patterns into the unit, and performing molecular typing of selected Aspergillus flavus isolates. To assess the environment, we verified pressure relationships between the rooms and hallway and between buildings, and we compared the ability of large-volume (1,200 L) and small-volume (160 L) air samplers to detect Aspergillus spores. RESULTS: Of 29 potential invasive aspergillosis cases, 21 were confirmed by medical chart review. Risk factors for developing invasive aspergillosis included the length of time since malignancy was diagnosed (odds ratio [OR], 1.0; P=.05) and hospitalization in a patient room located near a stairwell door (OR, 3.7; P=.05). Two of five A. flavus patient isolates were identical to one of the environmental isolates. The pressure in most of the rooms was higher than in the corridors, but the pressure in the oncology unit was negative with respect to the physically adjacent hospital; consequently, the unit acted essentially as a vacuum that siphoned non-HEPA-filtered air from the main hospital. Of the 78 samples obtained with a small-volume air sampler, none grew an Aspergillus species, whereas 10 of 40 cultures obtained with a large-volume air sampler did. CONCLUSIONS: During active construction, Aspergillus spores may have entered the oncology unit from the physically adjacent hospital because the air pressure differed. Guidelines that establish the minimum acceptable pressures and specify which pressure relationships to test in healthcare settings are needed. Our data show that large-volume air samples are superior to small-volume samples to assess for Aspergillus in the healthcare environment.

Infection control considerations during construction activities: land excavation and demolition.

Because current trends in hospital restructuring in North America, amalgamations and mergers, and the aging of health care facilities, the need to restructure physical buildings has become greater. Hospital construction carries with it risks to patients. One key concern is the risk of aspergillosis associated with hospital construction. Infection control practitioners must consider some key factors when addressing land excavation and building demolition, which differ in some ways from construction that occurs within a health care facility. The key factors to consider are project concept, risk assessment of patients, procedures and environment, air quality, routes of entry and egress, soil management, conducting inspections, contingency planning, housekeeping, and lines of cooperation and communication with various stakeholders. Considering these areas will help ensure that health care facility personnel and the workers have exercised diligence in patient care.

Significant factors in the disinfection and sterilization of flexible endoscopes.

BACKGROUND: Many nosocomial infection outbreaks have been linked to improper disinfection of the flexible endoscopes used in hospitals and clinics. The objective of this study was to evaluate the efficacy of scope disinfection with glutaraldehyde and hydrogen peroxide in manual and mechanical protocols. METHODS: Bacillus subtilis and Pseudomonas cepacia were the test organisms. Each channel in two different endoscopes was seeded and evaluated separately. Residual chemical germicide levels in the channels and in the work environment were also measured. RESULTS: Parametric analyses were carried out on log transformations of number of colony-forming units recovered. Repeated measures analysis demonstrated that both the type of disinfectant and the method of washing were significant factors for disinfection. CONCLUSIONS: Hydrogen peroxide proved to be more efficacious than glutaraldehyde for killing or removing B. subtilis in a 10-minute contact period. Automatic disinfection was more efficacious than manual disinfection for killing or removing B. subtilis in a 10-minute contact period. The channel being disinfected also proved to be a significant factor, with carbon dioxide and elevator channels the most difficult to disinfect consistently.

Collection of biological and non-biological particles by new and used filters made from glass and electrostatically charged synthetic fibers.

UNLABELLED: Synthetic filters made from fibers carrying electrostatic charges and fiberglass filters that do not carry electrostatic charges are both utilized commonly in heating, ventilating, and air-conditioning (HVAC) systems. The pressure drop and efficiency of a bank of fiberglass filters and a bank of electrostatically charged synthetic filters were measured repeatedly for 13 weeks in operating HVAC systems at a hospital. Additionally, the efficiency with which new and used fiberglass and synthetic filters collected culturable biological particles was measured in a test apparatus. Pressure drop measurements adjusted to equivalent flows indicated that the synthetic filters operated with a pressure drop less than half that of the fiberglass filters throughout the test. When measured using total ambient particles, synthetic filter efficiency decreased during the test period for all particle diameters. For particles 0.7-1.0 mum in diameter, efficiency decreased from 92% to 44%. It is hypothesized that this reduction in collection efficiency may be due to charge shielding. Efficiency did not change significantly for the fiberglass filters during the test period. However, when measured using culturable biological particles in the ambient air, efficiency was essentially the same for new filters and filters used for 13 weeks in the hospital for both the synthetic and fiberglass filters. It is hypothesized that the lack of efficiency reduction for culturable particles may be due to their having higher charge than non-biological particles, allowing them to overcome the effects of charge shielding. The type of particles requiring capture may be an important consideration when comparing the relative performance of electrostatically charged synthetic and fiberglass filters. PRACTICAL IMPLICATIONS: Electrostatically charged synthetic filters with high initial efficiency can frequently replace traditional fiberglass filters with lower efficiency in HVAC systems because properly designed synthetic filters offer less resistance to air flow. Although the efficiency of charged synthetic filters at collecting non-biological particles declined substantially with use, the efficiency of these filters at collecting biological particles remained steady. These findings suggest that the merits of electrostatically charged synthetic HVAC filters relative to fiberglass filters may be more pronounced if collection of biological particles is of primary concern.

In-hospital source of airborne Penicillium species spores.

Between 16 July and 1 October 1984, prospectively monitored corridor air samples from a bone marrow transplant station revealed a marked increase in airborne thermotolerant Penicillium spores. Simultaneous cultures of outside air showed lower spore counts, which were unchanged before, during, and after the corridor outburst, establishing that the source was within the hospital. Although the corridor was equipped with recirculating high-efficiency particulate air filtration units which provided 16 air changes per h, the mean corridor air count rose to 64.4 thermotolerant Penicillium CFU/m3 during the outburst period. The in-hospital source was ultimately traced to rotting cabinet wood enclosing a sink with leaking pipes in the medication room. It produced approximately 5.5 X 10(5) thermotolerant Penicillium CFU/h. In a patient room supplied by corridor air, an in-room recirculating high-efficiency particulate air filter reduced the mean thermotolerant Penicillium count to 2.2 CFU/m3. No patient illness or colonization occurred as a result of this event, although the cabinet wood, after sterilization, was shown to sustain abundant growth of Aspergillus fumigatus and Aspergillus flavus. Wet organic substrates should be avoided in hospital areas with immunosuppressed patients.

Aspergillus fumigatus and other thermotolerant fungi generated by hospital building demolition.

On 13 September 1981, a 51-year-old seven-story building within our hospital complex was demolished by explosives. The concern that this event might release large numbers of thermotolerant fungi (TF), potentially hazardous to immunosuppressed patients, led us to seal hospital windows and doors. The air-handling systems were also manipulated. Concentrations of airborne TF, especially Aspergillus fumigatus, were determined before and after demolition, using Andersen and Cassella air samplers with inhibitory mold agar plates. Two outdoor and two hospital ward locations were sampled. The plates were incubated at 37 degrees C; the CFU per cubic meter were counted at 72 h. The outdoor concentration of TF increased at one site by an average of 1.8 log10 (10(2) to 10(5] over the predemolition level. A. fumigatus increased 3.3 log10 (10(0) to 10(4] at the other outdoor site. The indoor TF concentrations increased about 1 log10 (10(1) to 10(2] after demolition. Counts on the hospital wards were not remarkable when compared with previous surveillance air sampling. Protective measures apparently minimized the infiltration of TF during explosive demolition.

The evaluation and applications of hemodialyzers for pediatric patients.

It is difficult to determine which pediatric hemodialyzer to use in a given clinical situation since there is no comprehensive comparison of pediatric hemodialyzers. We evaluated five currently available disposable pediatric hemodialyzers in vitro and in vivo during treatment of pediatric patients. Two dialyzers, Gambro Mini-Minor and Viva Cell 0.2 are well suited to small pediatric patients weighing less than 10 kg. Three of the dialyzers are well suited to the pediatric patients weighing greater than 10 kg (Gambro Minor, Cordis Dow 0.6, Viva Cell 0.5). By considering the clinical status of the child and the performance characteristics of the dialyzer (solute removal, priming volume, ultrafiltration, etc.) it is possible to employ a hemodialyzer which more precisely meets the needs of the child without increasing risk factors associated with pediatric hemodialysis.