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Title: Diagnosis and epidemiology of Aspergillus fumigatus and Aspergillus flavus infections by molecular techniques in haematology patients
Author: Yeghen, Tullie
ISNI:       0000 0001 3574 9407
Awarding Body: University of London
Current Institution: University College London (University of London)
Date of Award: 2000
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Invasive pulmonary aspergillosis (IPA) remains difficult to diagnose. Two polymerase chain reactions (PCR) for A. fumigatus introduced in 1993 were potentially powerful new diagnostic tools in the management of IPA. The clinical management of a group of 87 haematology patients with IPA was analysed restrospectively, while Aspergillus isolates and bronchoalveolar lavage (BAL) fluid from these patients and others were studied using the new PCR methodology. The radiological detection of LISA (lesion with imaging suggestive of aspergillosis) had a 90% positive predictive value for IPA in a subgroup of 39 patients who underwent lung resections based on the presence of LISA. Analysis of the survival of these 87 patients by Cox's proportional hazard model showed a significant negative association between the presence of LISA and death, and a significant association of relapsed haematological disease and death, while other factors, particularly surgical treatment, had no independent effect. The sensitivity of a PCR using primers based on the alkaline protease gene (2 pg) was superior to that of one based on the 26S/intergenic spacer region of the rDNA complex (200 pg), and the former assay was used for subsequent experiments. DNA recovery experiments from BAL fluid demonstrated a 3 log DNA loss during the extraction process. A variable DNA loss of up to 50 fold from suspensions of conidia in water was demonstrated, and the overall sensitivity of the extraction/PCR was equivalent to that of culture. PCR was performed on 68 Aspergillus culture negative BAL's, including 39 from haematology patients pulmonary infiltrates. Only 16 positive results were obtained from 228 validated reactions, and none were reliably reproducible, even in patients with subsequently proven IPA. The method cannot be recommended for clinical use. PCR, followed by SSCP of the products, with or without prior restriction, was insufficiently discriminatory as a typing method for A. fumigatus strains.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available