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Molecular epidemiology of apparent outbreak of invasive aspergillosis in a hematology ward
A Leenders1, A van Belkum, S Janssen
1Department of Bacteriology, University Hospital Dijkzigt, Rotterdam, Netherlands.
Abstract:
During a 2-month period, five patients suffering from invasive infections caused by Aspergillus flavus or Aspergillus fumigatus were identified in the Hematology Department of the University Hospital Dijkzigt (Rotterdam, The Netherlands). To study the epidemiological aspects of invasive aspergillosis, strains from these patients and from the hospital environment, isolated during extensive microbiological screening, were subjected to genotyping. A novel DNA extraction technique, involving freezing, grinding, and direct lysis in guanidium isothiocyanate-containing buffers of mycelial material, was applied. DNA isolation was followed by typing by random amplification of polymorphic DNA (RAPD) analysis. This showed that strains isolated from all patients infected with the same fungal species were genotypically distinct, thus providing evidence against the possibility of an ongoing, single-source nosocomial outbreak. Strains could also be differentiated from strains of geographically diverse origins. However, an A. flavus strain from one of the patients was also frequently encountered in the hospital environment. As all environmental strains were collected after this patient had been diagnosed with invasive disease, the epidemiological value of this observation could not be ascertained. Intensive investigations showed no single source of A. flavus or other aspergilli. RAPD genotyping proved that the outbreak of invasive aspergillosis in the hematology ward consisted of a series of unrelated events and was not due to a common source within the hospital. RAPD fingerprinting of aspergilli may greatly facilitate future investigations of the epidemiology of invasive disease caused by these pathogens.
Insights
Invasive aspergillosis in hematology patients was studied using random amplification of polymorphic DNA (RAPD) genotyping. The analysis revealed distinct fungal strains, indicating multiple infection sources rather than a single hospital outbreak.
Area of Science:
- Medical Mycology
- Infectious Diseases
- Molecular Epidemiology
Background:
- Invasive aspergillosis poses a significant threat to immunocompromised patients, particularly in hematology wards.
- Understanding the sources and transmission routes of Aspergillus infections is crucial for effective control.
- Previous epidemiological studies often lacked precise strain differentiation methods.
Purpose of the Study:
- To investigate the epidemiological origins of invasive aspergillosis cases in a hospital setting.
- To determine if identified patient isolates and environmental strains were linked to a common source.
- To evaluate the utility of random amplification of polymorphic DNA (RAPD) for Aspergillus genotyping.
Main Methods:
- Collected Aspergillus flavus and Aspergillus fumigatus strains from five infected hematology patients.
- Conducted extensive microbiological screening of the hospital environment for Aspergillus.
- Developed and applied a novel DNA extraction technique followed by RAPD analysis for genotyping.
Main Results:
- Genotyping revealed that Aspergillus strains from patients with the same fungal species were genotypically distinct.
- This genetic diversity indicated that the cases represented unrelated infections, not a single nosocomial outbreak.
- While one A. flavus strain was found in the environment, its relevance could not be confirmed due to timing.
Conclusions:
- The invasive aspergillosis cases were a series of independent events, not originating from a common hospital source.
- Random Amplification of Polymorphic DNA (RAPD) genotyping is a valuable tool for differentiating Aspergillus strains.
- RAPD fingerprinting can significantly aid future investigations into the epidemiology of invasive aspergillosis.