Molecular Epidemiology of Scedosporium apiospermum Infection Determined by PCR Amplification of Ribosomal Intergenic Spacer Sequences in Patients with Chronic Lung Disease

Abstract

Respiratory tract colonization with Scedosporium apiospermum in patients with chronic suppurative lung disease is a significant concern for lung transplantation candidates, since Scedosporium infections occurring posttransplantation are usually untreatable. Up to 10% of patients with cystic fibrosis attending our respiratory medicine unit have had Scedosporium organisms isolated from sputum samples. We therefore developed a molecular typing method to examine these isolates. Typing by PCR amplification of ribosomal intergenic spacer sequences demonstrated 20 different types from 52 isolates collected from the respiratory medicine unit and elsewhere in Australia. A single common type was isolated from 11 respiratory medicine unit inpatients. Two other types were isolated from more than one source: one from two respiratory medicine unit inpatients and one from two epidemiologically linked nonhuman sources. Multiple isolates were obtained from nine patients. This method demonstrated persistent carriage of isolates of the same type in one patient for 7 months. Two patients showed carriage of isolates with multiple typing patterns within a 3-month period. The high rate of isolation and the predominance of isolates with a single typing pattern from respiratory medicine unit patients may suggest transmission to patients from a source in the unit. There was no epidemiological evidence of direct patient-to-patient spread, and Scedosporium organisms were not isolated from dust, soil, or air samples from the unit. The source and route of transmission have yet to be determined.

Genotyping Study of Scedosporium apiospermum Isolates from Patients with Cystic Fibrosis

“…PCR-based ribotyping was the first molecular method that was proposed for the analysis of Scedosporium isolates (8,10,13,24,25). However, RAPD, which has been used successfully for numerous epidemiological purposes in medical mycology, also proved its efficiency for the characterization of Scedosporium prolificans isolates (17,18).…”

Molecular Typing of AustralianScedosporiumIsolates Showing Genetic Variability and NumerousS. aurantiacum

“…Our preliminary observations indicate that the epidemiology and clinical relevance of recovering S. aurantiacum may be similar to that of S. apiospermum. S. aurantiacum has been reported to colonize the respiratory tract of at-risk patients (8). In addition to PCR fi ngerprinting, we applied AFLP analysis to investigate the possibility of 2 case clusters caused by S. prolifi cans.…”

“…Molecular typing techniques now provide the means to elucidate the epidemiology of Scedosporium infections and to investigate potential case clusters (16,18,19). Strains recovered from patients with cystic fi brosis have demonstrated a high degree of genetic variability (10,20), although a single genetic profi le predominated in 1 study (8). The degree of genetic variation within S. prolifi cans is more controversial.…”

“…aurantiacum S. apiospermum infections occur worldwide, ranging from localized mycetomas to deep-seated disease such as cerebral abscesses (6,7). This species also colonizes the respiratory tract of ≈10% of patients with cystic fi brosis and chronic suppurative lung disease (8)(9)(10). On the basis of genetic data, a new species, S. aurantiacum, was proposed for a subset of isolates previously identifi ed as S. apiospermum (11).…”

Diagnosis of Invasive Fungal Infections – Current Limitations of Classical and New Diagnostic Methods

“…In general, assays targeting multicopy genes have better detection limits than those targeting single copy genes. 135 Although PCR may become a diagnostic modality to identify Mucorales, [136][137][138] Scedosporium, [139][140][141] and several other fungi, [142][143][144][145][146][147][148][149][150][151] no commercial test is available to date. These techniques hold promise, but they are not yet standardised or readily available in most clinical laboratories.…”