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Mixed mould species in laboratory cultures of respiratory specimens: how should they be reported, and what are the indications for susceptibility testing?
  1. J Purcell1,
  2. J McKenna1,
  3. P Critten1,
  4. D W Denning2,
  5. I A Hassan1
  1. 1Department of Microbiology, Clinical Sciences Building, University Hospital of South Manchester, Wythenshawe Hospital, Manchester, UK
  2. 2National Aspergillosis Centre, Education and Research Centre, University Hospital of South Manchester (Wythenshawe Hospital), Manchester, UK
  1. Correspondence to Dr Ibrahim A Hassan, Department of Microbiology, Clinical Sciences Building, University Hospital of South Manchester, Wythenshawe Hospital, Manchester M23 9LT, UK; ibrahim.hassan{at}


Aims To investigate how clinical microbiology laboratories should report and interpret mixed mould isolates including Aspergillus species from clinical samples and the criteria for susceptibility testing of the isolates.

Methods Retrospectively collected data from our laboratory information system of moulds isolated between January 2005 and December 2007. Patient case notes were also reviewed.

Results A total of 502 isolates (from 273 patients) were found. 20 patients with clinical diagnosis of a probable fungal infection had mixed Aspergillus species.

Conclusions In most instances, the isolation of Aspergillus species from non-sterile sites does not represent clinical disease, but only colonisation/contamination. However, for high-risk patients including transplant recipients, a positive culture is associated with invasive disease. Our tertiary centre routinely reports single fungal isolates and mixed cultures with appropriate comments, and those considered significant will also have susceptibility testing carried out. The correlation of culture results with clinical features can differentiate between invasive disease and contamination.

  • Aspergillus
  • moulds
  • laboratory
  • cultures
  • immunocompromised
  • aspergillosis
  • fungi
  • microbiology
  • mycology

Statistics from


  • Preliminary data from this work were presented orally at the British Society for Medical Mycology Conference in London (March 2009).

  • Competing interests None.

  • Provenance and peer review Not commissioned; externally peer reviewed.

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