Moulds are ubiquitous in nature and reproduce by making spores able to travel through air. They can cause illness, in particular the thermotolerant Aspergillus species that produce numerous conidia 2-4 m in diameter. Invasive aspergillosis (IA) is a major opportunistic infection among patients with severe and prolonged neutropenia. Spore inhalation is the usual route of infection, but other routes may exist. The nosocomial origin of aspergillosis has been demonstrated in epidemic situations with airborne spore transmission via unfiltered air, and massive environmental contamination during construction and renovation work both inside and outside the hospital. Air control measures are currently the more effective way of significantly reducing the incidence of nosocomial aspergillosis. Patient rooms should have adequate capacity to minimize accumulation of fungal spores using high-efficiency particulate air filtration, laminar air flow systems, high rates of room-air changes, positive pressure, and well-sealed rooms. Innovative systems producing purified air may represent an interesting alternative to the air filtration. Monitoring of environmental fungal contamination is strongly recommended to detect increases in conidia density and to assess air filtration efficiency. The follow-up of the air and surface fungal loads is highly recommended in hospital units, which benefit from air control measures, in addition to specific investigations in case of Aspergillus infection. It requires efficient biocollectors, adequate surface sampling methods and suitable culture conditions that must be evaluated before. Progress in terms of air filtration leaded to decrease of IA in neutropenic patients during the first few weeks after bone marrow transplantation, but delayed IA still occur. The sources and routes of spore transmission remain unclear, and alternative sources of contamination should be more investigated and controlled. Opportunistic fungal pathogens have been recovered from several hospital water distribution systems in the USA and authors suggested that aspergillosis is waterborne. However, the environmental risk of IA linked to water should be interpreted according to the local situation, because differences in water collection and treatment exist. Besides, several foods can be colonized by moulds and can lead to spore absorption or aerosolization and subsequent systemic infection. It has been previously recommended that immunocompromised patients should avoid such contaminated foods but one alternative is to disinfect potentially contaminated foods, especially with regard to A. fumigatus. Lastly, the clothing of visitors and medical staff, and carriage by personal and medical materials are potential vectors of spores. Preventive measures might then be appropriate.
Full conference title:
16th European Congress of Clinical Microbiology and Infectious Diseases
- ECCMID 16th (2006)