P Vergidis1, C B Moore2, L Novak-Frazer3, R Rautemaa-Richardson4, A Walker5, D W Denning6, M D Richardson7. 1. National Aspergillosis Centre, Wythenshawe Hospital, Manchester University NHS Foundation Trust, Manchester Academic Health Science Centre, Manchester, UK; Division of Infection, Immunity and Respiratory Medicine, School of Biological Sciences, Faculty of Biology, Medicine and Health, University of Manchester, Manchester, UK; Division of Infectious Diseases, Mayo Clinic, Rochester, MN, USA. 2. Mycology Reference Centre Manchester, ECMM Excellence Centre, Wythenshawe Hospital, Manchester University NHS Foundation Trust, Manchester, UK. 3. Division of Infection, Immunity and Respiratory Medicine, School of Biological Sciences, Faculty of Biology, Medicine and Health, University of Manchester, Manchester, UK; Mycology Reference Centre Manchester, ECMM Excellence Centre, Wythenshawe Hospital, Manchester University NHS Foundation Trust, Manchester, UK. 4. National Aspergillosis Centre, Wythenshawe Hospital, Manchester University NHS Foundation Trust, Manchester Academic Health Science Centre, Manchester, UK; Division of Infection, Immunity and Respiratory Medicine, School of Biological Sciences, Faculty of Biology, Medicine and Health, University of Manchester, Manchester, UK; Mycology Reference Centre Manchester, ECMM Excellence Centre, Wythenshawe Hospital, Manchester University NHS Foundation Trust, Manchester, UK. 5. Division of Infection, Immunity and Respiratory Medicine, School of Biological Sciences, Faculty of Biology, Medicine and Health, University of Manchester, Manchester, UK. 6. National Aspergillosis Centre, Wythenshawe Hospital, Manchester University NHS Foundation Trust, Manchester Academic Health Science Centre, Manchester, UK; Division of Infection, Immunity and Respiratory Medicine, School of Biological Sciences, Faculty of Biology, Medicine and Health, University of Manchester, Manchester, UK. 7. Division of Infection, Immunity and Respiratory Medicine, School of Biological Sciences, Faculty of Biology, Medicine and Health, University of Manchester, Manchester, UK; Mycology Reference Centre Manchester, ECMM Excellence Centre, Wythenshawe Hospital, Manchester University NHS Foundation Trust, Manchester, UK. Electronic address: malcolm.richardson@manchester.ac.uk.
Abstract
OBJECTIVES: Sputum culture is an insensitive method for the diagnosis of pulmonary aspergillosis. Growth of the organism allows identification of the causative species and susceptibility testing, both of which can inform treatment choices. The current practice is to culture an aliquot of diluted sputum. We assessed the value of culturing large volumes of unprocessed sputum, a method that we have termed high-volume culture (HVC). METHODS: Specimens were processed by conventional culture (using an aliquot of homogenized, diluted sputum on Sabouraud agar at 37°C and 45°C for up to 5 days) and HVC (using undiluted sputum on Sabouraud agar at 30°C for up to 14 days). A separate specimen was tested by quantitative real-time PCR. Antifungal susceptibility testing was performed by the EUCAST standard. RESULTS: We obtained sputum specimens from 229 individuals with the following conditions: chronic pulmonary aspergillosis (66.8%, 153/229), allergic bronchopulmonary aspergillosis (25.3%, 58/229) and Aspergillus bronchitis (7.9%, 18/229). Individuals with invasive pulmonary aspergillosis were not included. The positivity rate of conventional culture was 15.7% (36/229, 95% CI 11.6%-21.0%) and that of HVC was 54.2% (124/229, 95% CI 47.7%-60.5%) (p < 0.001). The higher positivity rate of HVC was demonstrated regardless of administration of antifungal treatment. Quantitive real-time PCR had an overall positivity rate of 49.2% (65/132, 95% CI 40.9%-57.7%), comparable to that of HVC. CONCLUSION: Detection of Aspergillus spp. in sputum is greatly enhanced by HVC. HVC allows for detection of azole-resistant isolates that would have been missed by conventional culture. This method can be performed in any microbiology laboratory without the need for additional equipment.
OBJECTIVES: Sputum culture is an insensitive method for the diagnosis of pulmonary aspergillosis. Growth of the organism allows identification of the causative species and susceptibility testing, both of which can inform treatment choices. The current practice is to culture an aliquot of diluted sputum. We assessed the value of culturing large volumes of unprocessed sputum, a method that we have termed high-volume culture (HVC). METHODS: Specimens were processed by conventional culture (using an aliquot of homogenized, diluted sputum on Sabouraud agar at 37°C and 45°C for up to 5 days) and HVC (using undiluted sputum on Sabouraud agar at 30°C for up to 14 days). A separate specimen was tested by quantitative real-time PCR. Antifungal susceptibility testing was performed by the EUCAST standard. RESULTS: We obtained sputum specimens from 229 individuals with the following conditions: chronic pulmonary aspergillosis (66.8%, 153/229), allergic bronchopulmonary aspergillosis (25.3%, 58/229) and Aspergillus bronchitis (7.9%, 18/229). Individuals with invasive pulmonary aspergillosis were not included. The positivity rate of conventional culture was 15.7% (36/229, 95% CI 11.6%-21.0%) and that of HVC was 54.2% (124/229, 95% CI 47.7%-60.5%) (p < 0.001). The higher positivity rate of HVC was demonstrated regardless of administration of antifungal treatment. Quantitive real-time PCR had an overall positivity rate of 49.2% (65/132, 95% CI 40.9%-57.7%), comparable to that of HVC. CONCLUSION: Detection of Aspergillus spp. in sputum is greatly enhanced by HVC. HVC allows for detection of azole-resistant isolates that would have been missed by conventional culture. This method can be performed in any microbiology laboratory without the need for additional equipment.
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