Françoise Symoens

Occurrence and relevance of filamentous fungi in respiratory secretions of patients with cystic fibrosis — a review

The colonization of airways by filamentous fungi and the development of respiratory infections require some predisposing factors as encountered in patients with cystic fibrosis (CF). Indeed, the defective mucociliary clearance which characterizes the disease is associated with local immunological disorders. In addition, the prolonged therapy with antibiotics and the use of corticosteroid treatments also facilitate fungal growth. An important fungal biota has been described in respiratory secretions of patients suffering from CF. Aspergillus fumigatus, Scedosporium apiospermum and Aspergillus terreus for filamentous fungi and Candida albicans for yeasts are the main fungal species associated with CF. Although less common, several fungal species including Aspergillus flavus and Aspergillus nidulans may be isolated transiently from CF respiratory secretions, while others such as Exophiala dermatitidis and Scedosporium prolificans may chronically colonize the airways. Moreover, some of them like Penicillium emersonii and Acrophialophora fusispora are encountered in humans almost exclusively in the context of CF. As fungal complications in CF patients are essentially caused by filamentous fungi the present review will not include works related to yeasts. In CF patients, fungi may sometimes be responsible for deterioration of lung function, as occurs in allergic broncho-pulmonary aspergillosis (ABPA) which is the most common fungal disease in this context. Additionally, although the clinical relevance of the fungal airway colonization is still a matter of debate, filamentous fungi may contribute to the local inflammatory response, and therefore to the progressive deterioration of the lung function.

Melanin is an essential component for the integrity of the cell wall of Aspergillus fumigatus conidia.

BackgroundAspergillus fumigatus is the most common agent of invasive aspergillosis, a feared complication in severely immunocompromised patients. Despite the recent commercialisation of new antifungal drugs, the prognosis for this infection remains uncertain. Thus, there is a real need to discover new targets for therapy. Particular attention has been paid to the biochemical composition and organisation of the fungal cell wall, because it mediates the host-fungus interplay. Conidia, which are responsible for infections, have melanin as one of the cell wall components. Melanin has been established as an important virulence factor, protecting the fungus against the hosts immune defences. We suggested that it might also have an indirect role in virulence, because it is required for correct assembly of the cell wall layers of the conidia.ResultsWe used three A. fumigatus isolates which grew as white or brown powdery colonies, to demonstrate the role of melanin. Firstly, sequencing the genes responsible for biosynthesis of melanin (ALB1, AYG1, ARP1, ARP2, ABR1 and ABR2) showed point mutations (missense mutation, deletion or insertion) in the ALB1 gene for pigmentless isolates or in ARP2 for the brownish isolate. The isolates were then shown by scanning electron microscopy to produce numerous, typical conidial heads, except that the conidia were smooth-walled, as previously observed for laboratory mutants with mutations in the PKSP/ALB1 gene. Flow cytometry showed an increase in the fibronectin binding capacity of conidia from mutant isolates, together with a marked decrease in the binding of laminin to the conidial surface. A marked decrease in the electronegative charge of the conidia and cell surface hydrophobicity was also seen by microelectrophoresis and two-phase partitioning, respectively. Ultrastructural studies of mutant isolates detected considerable changes in the organisation of the conidial wall, with the loss of the outermost electron dense layer responsible for the ornamentations seen on the conidial surface in wild-type strains. Finally, analysis of the conidial surface of mutant isolates by atomic force microscopy demonstrated the absence of the outer cell wall rodlet layer which is composed of hydrophobins.ConclusionThese results suggest that, in addition to a protective role against the hosts immune defences, melanin is also a structural component of the conidial wall that is required for correct assembly of the cell wall layers and the expression at the conidial surface of adhesins and other virulence factors.

Purification and characterization of a fibrinogenolytic serine proteinase from Aspergillus fumigatus culture filtrate

A fibrinogenolytic proteinase has been isolated from Aspergillus fumigatus culture filtrate by ammonium sulfate precipitation followed by successive chromatographics on Sephadex G‐75 and immobilized phenylalanine. The purified proteinase exhibited a molecular weight of about 33 kDa. When analysed by SDS‐polyacrylamide gels containing co‐polymerized fibrinogen, the proteinase appeared as a broad band at the top of the gels, which could correspond to polymerization of the enzyme, as suggested by SDS‐PAGE analysis of the unboiled eluate. The isoelectric point was 8.75 and the enzyme was not glycosylated. Proteinase activity was optimum at pH 9 and between 37 and 42°C, although a decrease in activity was observed above 37°C. PMSF and chymostatin markedly inhibited the proteinase activity, and good kinetic constants were obtained for the synthetic substrate, N‐Suc‐Ala‐Ala‐Pro‐Phe‐pNA. These results provide direct evidence that this enzyme belongs to the chymotrypsin‐like serine proteinase group.

Genotyping Study of Scedosporium apiospermum Isolates from Patients with Cystic Fibrosis

ABSTRACT Usually a saprophyte, Scedosporium apiospermum often colonizes the respiratory tracts of patients with cystic fibrosis (CF). In order to improve our understanding of the molecular epidemiology of the airway colonization, 129 sequential and multiple isolates collected from January 1998 to March 1999 from nine CF patients monitored in three hospitals in France were typed by random amplification of polymorphic DNA with primers GC70, UBC-701, and UBC-703. Among these primers, UBC-703 was the most discriminating, allowing the differentiation of 14 genotypes. Combining the results obtained with this three-primer set resulted in the differentiation of 16 genotypes. No common genotype was found among the different patients, and no clustering according to geographic origin of the isolates was seen. In addition, five of the patients were colonized by a single genotype. The others usually exhibited a predominant genotype accompanied by one or two others, which were found occasionally and were genetically close to the predominant genotype. Thus, our study demonstrates the persistence of the fungus despite antifungal treatments and therefore reinforces the need for the development of new antifungals that are more efficient against this species.

Proposed nomenclature for Pseudallescheria, Scedosporium and related genera

As a result of fundamental changes in the International Code of Nomenclature on the use of separate names for sexual and asexual stages of fungi, generic names of many groups should be reconsidered. Members of the ECMM/ISHAM working group on Pseudallescheria/Scedosporium infections herein advocate a novel nomenclature for genera and species in Pseudallescheria, Scedosporium and allied taxa. The generic names Parascedosporium, Lomentospora, Petriella, Petriellopsis, and Scedosporium are proposed for a lineage within Microascaceae with mostly Scedosporium anamorphs producing slimy, annellidic conidia. Considering that Scedosporium has priority over Pseudallescheria and that Scedosporium prolificans is phylogenetically distinct from the other Scedosporium species, some name changes are proposed. Pseudallescheria minutispora and Petriellidium desertorum are renamed as Scedosporium minutisporum and S. desertorum, respectively. Scedosporium prolificans is renamed as Lomentospora prolificans.

Genetic Polymorphism of Aspergillus fumigatus in Clinical Samples from Patients with Invasive Aspergillosis: Investigation Using Multiple Typing Methods

ABSTRACT The genotypes of 52 strains of Aspergillus fumigatusisolated from 12 patients with invasive aspergillosis were investigated using three typing methods (random amplified polymorphic DNA, sequence-specific DNA polymorphism, and microsatellite polymorphism) combined with multilocus enzyme electrophoresis. Isolates were from patients hospitalized in three different geographic areas (Lyon, France; Grenoble, France; and Milan, Italy). In each case, the genetic polymorphism of several colonies (two to five) within the first respiratory clinical sample was studied. For the 52 isolates tested, random amplified polymorphic DNA identified 8 different genotypes, sequence-specific DNA polymorphism identified 9 different types, and microsatellite polymorphism identified 14 types. A combination of these results with multilocus enzyme electrophoresis study identified 25 different types within the sample studied. We identified 3 patients (of the 12 studied) who carried a single genotype; 6 patients were infected by two genotypes, 1 patient had four genotypes, while the last patient had five. A combination of typing methods provided better discrimination than the use of a single method. Typing methods revealed a population structure within each geographical site, suggesting that the epidemiology of A. fumigatus should be considered separately for each of these geographic areas. This study demonstrates the usefulness of combining several typing methods in reaching an understanding of the epidemiology of A. fumigatus and clarifies whether it is sufficient to type one isolate from each specimen to determine the strain involved in invasive aspergillosis.

Molecular epidemiology of airway colonisation by Aspergillus fumigatus in cystic fibrosis patients.

A total of 109 sequential and multiple Aspergillus fumigatus isolates corresponding to 41 samples from seven cystic fibrosis (CF) patients was typed by random amplification of polymorphic DNA (RAPD) with the primer NS3 from the fungal ribosomal gene 18S subunit, and by sequence-specific DNA primer (SSDP) analysis. RAPD typing of the isolates revealed 10 different genotypes, whereas nine genotypes were identified by SSDP. Combination of the two typing methods permitted the differentiation of 25 overall genotypes. The colonisation typing patterns differed greatly between patients colonised for <1 year by A. fumigatus and long-term colonised patients. Two of three recently colonised patients presented a large number of types even in the same sample, unlike the chronically colonised patients, who harboured a limited number of genotypes. In the latter, the occurrence of a dominant genotype, usually the overall genotype 2, tended to reflect to the duration of colonisation. Moreover, anti-catalase antibodies to A. fumigatus appeared in most cases to be in response to genotype 2. These findings suggest that some strains of A. fumigatus may be selected during prolonged colonisation of the airways in CF patients.

The dermatophyte species Arthroderma benhamiae: intraspecies variability and mating behaviour

Arthroderma benhamiae is a zoophilic dermatophyte belonging to the Trichophyton mentagrophytes species complex. Here, a population of A. benhamiae wild strains from the same geographical area (Switzerland) was studied by comparing their morphology, assessing their molecular variability using internal transcribed spacer (ITS) and 28S rRNA gene sequencing, and evaluating their interfertility. Sequencing of the ITS region and of part of the 28S rRNA gene revealed the existence of two infraspecific groups with markedly different colony phenotypes: white (group I) and yellow (group II), respectively. For all strains, the results of mating type identification by PCR, using HMG (high-mobility group) and α-box genes in the mating type locus as targets, were in total accordance with the results of mating type identification by strain confrontation experiments. White-phenotype strains were of mating type + (mt+) or mating type - (mt-), whilst yellow-phenotype strains were all mt-. White and yellow strains were found to produce fertile cleistothecia after mating with A. benhamiae reference tester strains, which belonged to a third group intermediate between groups I and II. However, no interfertility was observed between yellow strains and white strains of mt+. A significant result was that white strains of mt- were able to mate and produce fertile cleistothecia with the white A. benhamiae strain CBS 112371 (mt+), the genome of which has recently been sequenced and annotated. This finding should offer new tools for investigating the biology and genetics of dermatophytes using wild-type strains.

Fungal respiratory infections in cystic fibrosis: a growing problem

tions increases as the life expectancy of patients improves. But in contrast to bacterial respiratory infections, relatively little progress has been made with regards to fungal respiratory infections. Aspergillus fumigatus is by far the most common causative agent with a reported prevalence rate varying from 5.9% to 58.3%, but a wide range of fungi may colonize the respiratory tract of CF patients. For example, other Aspergillus species like Aspergillus terreus , as well as Scedosporium spp. and Exophiala dermatitidis are increasingly described in the CF context, but their prevalence is certainly underestimated. Additionally, whether the colonization of the airways by fungi/micromycetes constitutes a clinically relevant problem is still a matter of debate. However, recent studies have clearly indicated an increase in their prevalence rate, and a relationship with increased numbers of hospital admissions. Moreover, due to their thermotolerance and to their propensity to disseminate in immunocompromised hosts, prior colonization of the airways by fi lamentous fungi constitutes a serious risk factor for invasive infections in cases of lung transplantation. The latter remains the ultimate treatment of CF patients. Numerous questions are created by fungal colonization of the airways, and basic research on the ecology of the fungi, their biochemistry, and their pathogenic mechanisms should be promoted in order to defi ne prophylactic measures or to develop more effi cient antifungal drugs. To address these questions, the International Society for Human and Animal Mycology (ISHAM) launched in October 2006, a working group on “Fungal Respiratory Infections in Cystic Fibrosis”, whose fi rst formal meeting was held in Angers, France, on June 7-8, 2009. Altogether 65 clinicians, mycologists or scientists from 14 different countries participated to this meeting, as well as numerous PhD students to guarantee dynamic discussions. Thirtyeight presentations were provided by attendees, covering a wide variety of topics, including (a) “clinical surveillance All authors are members of the ISHAM working group on Fungal Respiratory Infections in Cystic Fibrosis. Correspondence: Jean-Philippe Bouchara, Groupe d’Etude des Interactions Hote-Pathogene, UPRES-EA 3142, Laboratoire de ParasitologieMycologie, CHU, 4 rue Larrey, 49933 Angers cedex 9, France. Tel: 33 (0)2 41 35 34 72; Fax: 33 (0)2 41 35 36 16; E-mail: jean-philippe. bouchara@univ-angers.fr Fungal respiratory infections in cystic fi brosis: a growing problem

High-resolution genotyping of Aspergillus fumigatus isolates recovered from chronically colonised patients with cystic fibrosis.

A series of 256 Aspergillus fumigatus isolates, recovered from eight patients with cystic fibrosis (CF), were genotyped using microsatellite-based typing. Only a limited number of genotypes were shared between patients and co-colonisation with multiple strains was indicated for all patients. Additionally, some genotypes were isolated recurrently, indicating that they are capable of prolonged colonisation.