Fungal aerobiology: how, when and where?

Infection Prevention and Control Issues After Solid Organ Transplantation

Infections are an important cause of morbidity and mortality in solid organ transplant recipients. Consequently, infection prevention is an essential component of any organ transplant program. Given their frequent and often prolonged contact with the healthcare system, solid organ transplant recipients are at high risk for healthcare-associated infections, including those caused by antibiotic-resistant organisms. In this chapter we review several different healthcare-associated infections of importance to transplant recipients, including those caused by bacterial, viral, and fungal organisms. We also describe infection prevention and control strategies applicable to this patient population. These practices focus on clinical interventions and environmental controls designed to prevent the spread of potentially pathogenic organisms in the healthcare setting. We also describe post-exposure interventions applicable to solid organ transplant recipients exposed to potential pathogens in order to reduce their risk of subsequent infection.

Prevention of Fungal Infections in Hematology Patients

Endogenous infections such as candidiasis can be minimized by oral fluconazole prophylaxis, although oral or intravenous amphotericin, or itraconazole, are suitable for certain patients. Exogenous fungal infections most commonly are transmitted by the airborne route, but the benefits of high-efficiency particulate air-filtered room air probably are diminishing as broad-spectrum prophylaxis againstAspergillusspecies and other fungi improves. However, high-risk environmental sources such as construction work always must be avoided near neutropenic patients. Reactivation of quiescent pulmonaryAspergillusinfection can be prevented by surgical resection during remission, or by systemic amphotericin prophylaxis during subsequent neutropenic episodes.

Environmental sampling of particulate matter and fungal spores during demolition of a building on a hospital area

Demolition or renovation works adjacent to hospitals pose risks of fungal airborne infections. During November 2005 and March 2006 an old building with three floors was demolished on the area of University Hospital of Essen. To prevent dust exposure the building was sealed up by impermeable plastic foil and mechanical disruption of structures was accomplished using excavators. Dust emission was minimised by water jet. To determine if there were any infectious risks for patients from emissions from the demolition work we monitored particle and fungal concentration of the air before and during demolition. Air sampling was performed at seven positions around the building and weather conditions were monitored at the same time. Concentrations of ultrafine particles, particles > or =0.3, > or =0.5 and > or =1 microm were significantly higher during demolition than before, but only by small factors (ultrafine particles 1.6-fold, particles > or =0.3 microm 1.6-fold, particles > or =0.5 microm 2.9-fold and particles > or =1 microm 3.3-fold). Concentrations of moulds which could be cultured at 37 degrees C did not differ between the two periods (median before demolition: 66 cfu/ m3; median during demolition: 80 cfu/m3). Concentrations of moulds which grew at 22 degrees C correlated significantly with temperature and humidity and were significantly higher before (median: 510 cfu/m3) than during the demolition period (median: 210 cfu/m3). We conclude that the fungal infection risks for patients during demolition work in hospital areas is not increased by demolition if protective measures are in place.

Indoor air studies of fungi contamination at the Department of Pulmonology and Internal Medicine in Kavala Hospital in Greece

PURPOSE

The aim of the study was to assess the presence of airborne fungi and the fungal flora of the walls in the Departments of Pulmonary and Internal Medicine in Kavala Hospital (Greece).

MATERIAL AND METHODS

The study was carried out at the Department of Pulmonology and Internal medicine in Kavala Hospital. Materials for the tests were: the air samples (in front of the building and the selected rooms) and swabs from the walls. The air pollution was determined using SAS SUPER 100 (Pbi International). The microbial flora from walls was assessed using the Count-Tact applicator and the plate Count-Tact (BioMerieux). Humidity and temperature were evaluated by a thermo-hygrometer.

RESULTS

The following fungal pathogens isolated from air were Aspergillus, Candida albicans, Candida spp., and Penicillium species in the Department of Pulmonary. Similar pathogens in the air of Department and Internal Medicine were found. Mean number of fungi colonies isolated from air in the Department of Pulmonology was significantly (p<0.001) higher compared to the Department of Internal Medicine. No significant correlations between CFU of fungi in air and temperature in both Departments were found.

CONCLUSIONS

The main fungal pathogens isolated from the air samples were Aspergillus and Candida albicans in the Departments of Pulmonary and Internal Medicine in Kavala Hospital. Fungal occurrence in the air of rooms and walls varied between the both departments of the same hospital.

The efficiency of an air filtration system in the hospital ward

A study was conducted to ascertain the efficiency and effectiveness of an air filtration system (Electromedia Model 100C, Clean Air UK, UK) in the hospital ward. The sampling was conducted using a portable Surface Air Sampler (Cherwell Laboratories, Bicester, UK) in conjunction with settle plates. Samples were taken two days before and two days following activation of the filtration system and results compared. A clear, demonstrable, statistically significant reduction in microbial organisms following the activation of the filtration systems is evident (81% settle plates; 24% Surface Air Sampler). This study has implications for the improved health and welfare of patients and healthcare workers who may benefit through the implementation of such a system.

Impact of portable air filtration units on exposure of haematology-oncology patients to airborne Aspergillus fumigatus spores under field conditions

We undertook a one-year study to investigate the impact of the NSA model 7100A/B portable air filtration unit on exposure of haematology-oncology patients to airborne Aspergillus fumigatus spores under field conditions. Weekly measurements for airborne A. fumigatus were conducted in indoor and outdoor air, and surveillance for invasive aspergillosis was based on a combination of ward liaison, targeted chart review and consultation with the medical staff. The mean indoor A. fumigatus counts (8.1 cfu/m3; range, <0.8 to 42 cfu/m3) reflected the fungal load of outdoor air (9.4 cfu/m3; range, <0.8 to 50 cfu/m3), and were reduced by only about one third in rooms with portable air filtration units (5.3 cfu/m3; range, <0.8 to 41 cfu/m3). During the study period, a total of five cases (incidence density, 0.8 per 1000 patient-days) of invasive aspergillosis (one proven case, four suspected cases; case fatality rate 40%) were recorded. None of these five patients was allocated to a room with portable air filtration unit, however, the difference between incidence densities in rooms with and without portable air filtration units was non-significant (Fisher's exact test, P=0.33). Due to the noise level and thermal discomfort, patient compliance with the air filtration units was poor. We conclude that under field conditions this air filtration unit cannot be recommended for prevention of invasive aspergillosis in neutropenic haematology-oncology patients.

Pathogenic Aspergillus species recovered from a hospital water system: a 3-year prospective study

Nosocomial aspergillosis, a life-threatening infection in immunocompromised patients, is thought to be caused primarily by Aspergillus organisms in the air. A 3-year prospective study of the air, environmental surfaces, and water distribution system of a hospital in which there were known cases of aspergillosis was conducted to determine other possible sources of infection. Aspergillus species were found in the hospital water system. Significantly higher concentrations of airborne aspergillus propagules were found in bathrooms, where water use was highest (2.95 colony-forming units [cfu]/m(3)) than in patient rooms (0.78 cfu/m(3); P=.05) and in hallways (0.61 cfu/m(3); P=.03). A correlation was found between the rank orders of Aspergillus species recovered from hospital water and air. Water from tanks yielded higher counts of colony-forming units than did municipal water. An isolate of Aspergillus fumigatus recovered from a patient with aspergillosis was genotypically identical to an isolate recovered from the shower wall in the patient's room. In addition to the air, hospital water systems may be a source of nosocomial aspergillosis.

A prospective study on factors influencing aspergillus spore load in the air during renovation works in a neonatal intensive care unit

The relationship between air contamination (cfu/m(3)) with fungal spores, especially Aspergillus spp., in three renovation areas of a neonatal intensive care unit (NICU) and colonization and infection rates in a high care area (HC) equipped with high efficiency particulate air (HEPA) filtration and a high pressure system, was evaluated. Data on the type and site of renovation works, outdoor meteorological conditions, patient crowding and nasopharyngeal colonization rate were collected. Factors not associated with Aspergillus spp. concentration were outdoor temperature, air pressure, wind speed, humidity, rainfall, patient density in the NICU, renovation works in the administrative area and in the isolation rooms. Multivariate analysis revealed that renovation works and air concentration of Aspergillus spp. spores in the medium care area (MC) resulted in a significant increase of the concentration in the HC of the NICU. The use of a mobile HEPA air filtration system (MedicCleanAir(R)Forte, Willebroek, Belgium) caused a significant decrease in the Aspergillus spp. concentration. There was no relationship between Aspergillus spp. air concentration and nasopharyngeal colonization in the neonates. Invasive aspergillosis did not occur during the renovation. This study highlights the importance of optimal physical barriers and air filtration to decrease airborne fungal spores in high-risk units during renovation works. The value of patient surveillance and environmental air sampling is questionable since no relationship was found between air contamination and colonization in patients.

Development and evaluation of a molecular viability assay for Pneumocystis carinii

Despite recent declines in incidence, Pneumocystis carinii pneumonia (PCP) remains the most commonly occurring opportunistic illness among persons with AIDS in the United States. While P. carinii DNA has been detected in patient respiratory specimens and in air samples collected from various indoor environments housing PCP patients, the viability of these organisms is unknown. For this reason, we have developed and evaluated a molecular viability assay for P. carinii. This method is based upon the detection of P. carinii mRNA by a reverse transcription-PCR that employs specific primers from a member of the heat shock protein 70 family. Under optimal assay conditions, these primers were capable of detecting as few as 100 viable trophozoites as determined by ethidium bromide staining, while no signal was obtained from 10(6) trophozoites killed by heat, desiccation, or UV radiation. This assay was also capable of distinguishing P. carinii from other common fungi present in the air. Therefore, this molecular viability assay may be useful in conjunction with standard bioaerosol collection devices and procedures for the detection of viable P. carinii collected from various indoor environments. It may also be useful in confirming the presence of viable trophozoites in respiratory specimens collected by noninvasive techniques from putatively infected individuals.

Density and molecular epidemiology of Aspergillus in air and relationship to outbreaks of Aspergillus infection

After five patients were diagnosed with nosocomial invasive aspergillosis caused by Aspergillus fumigatus and A. flavus, a 14-month surveillance program for pathogenic and nonpathogenic fungal conidia in the air within and outside the University Hospital in Rotterdam (The Netherlands) was begun. A. fumigatus isolates obtained from the Department of Hematology were studied for genetic relatedness by randomly amplified polymorphic DNA (RAPD) analysis. This was repeated with A. fumigatus isolates contaminating culture media in the microbiology laboratory. The density of the conidia of nonpathogenic fungi in the outside air showed a seasonal variation: higher densities were measured during the summer, while lower densities were determined during the fall and winter. Hardly any variation was found in the numbers of Aspergillus conidia. We found decreasing numbers of conidia when comparing air from outside the hospital to that inside the hospital and when comparing open areas within the hospital to the closed department of hematology. The increase in the number of patients with invasive aspergillosis could not be explained by an increase in the number of Aspergillus conidia in the outside air. The short-term presence of A. flavus can only be explained by the presence of a point source, which was probably patient related. Genotyping A. fumigatus isolates from the department of hematology showed that clonally related isolates were persistently present for more than 1 year. Clinical isolates of A. fumigatus obtained during the outbreak period were different from these persistent clones. A. fumigatus isolates contaminating culture media were all genotypically identical, indicating a causative point source. Knowledge of the epidemiology of Aspergillus species is necessary for the development of strategies to prevent invasive aspergillosis. RAPD fingerprinting of Aspergillus isolates can help to determine the cause of an outbreak of invasive aspergillosis.