The surface of Aspergillus fumigatus conidia, the first structure recognized by the host immune system, is covered by rodlets. We report that this outer cell wall layer contains two hydrophobins, RodAp and RodBp, which are found as highly insoluble complexes. The RODA gene was previously characterized, and ⌬rodA conidia do not display a rodlet layer (N. Thau, M. Monod, B. Crestani, C. Rolland, G. Tronchin, J. P. Latgé, and S. Paris, Infect. Immun. 62:4380-4388, 1994). The RODB gene was cloned and disrupted. RodBp was highly homologous to RodAp and different from DewAp of A. nidulans. ⌬rodB conidia had a rodlet layer similar to that of the wild-type conidia. Therefore, unlike RodAp, RodBp is not required for rodlet formation. The surface of ⌬rodA conidia is granular; in contrast, an amorphous layer is present at the surface of the conidia of the ⌬rodA ⌬rodB double mutant. These data show that RodBp plays a role in the structure of the conidial cell wall. Moreover, rodletless mutants are more sensitive to killing by alveolar macrophages, suggesting that RodAp or the rodlet structure is involved in the resistance to host cells.The surface of many fungal conidia is covered by a thin layer of regularly arranged rodlets. This structure, which favors air buoyancy and dispersion of the conidia by air currents (2), is mainly proteinaceous (3,(8)(9)(10)16). The proteins present in the cell wall of aerial structures of fungi responsible for this rodlet configuration are the hydrophobins, a family of small, moderately hydrophobic proteins characterized by the conserved spacing of eight cysteine residues (42, 44). For the human opportunistic pathogen Aspergillus fumigatus, the presence of a rodlet layer has been visualized and the RODA gene has been previously shown to be involved in the formation of the rodlets of its conidia (41). In plants, hydrophobins have been associated with the virulence of phytopathogenic fungi (38). Although it has been repeatedly shown that cell wall and associated structures help human fungal pathogens to resist host defense reactions (22), to date no studies have analyzed the role of the rodlet layer in the resistance of the conidia to phagocytosis. Even though the rodlet layer of the conidia of Neurospora crassa, Beauveria bassiana, and Magnaporthe grisea contained a single hydrophobin (5, 39, 40), A. nidulans, a species phylogenetically close to A. fumigatus, has two conidial hydrophobins, RodAp and DewAp (35,36). These data have prompted us to reexamine the surface layer of the conidia of A. fumigatus with a view to (i) analyzing exhaustively hydrophobins present on the surface of the conidia and (ii) studying their role in resistance to phagocytosis. A. fumigatus is a good model for the later study, since conidia, which are a main component of the airborne thermophilic fungal florae (1), are all engulfed and killed by lung alveolar macrophages (AM) following their inhalation (11; B. Philippe, O. Ibrahim-Granet, M. C. Prévost, M. A. Gougerot-Pocidalo, J. Roes, M. SanchezPerez, A. Van der Meer...

Anti-infectious lock is an emerging therapeutic option for preventing and/or controlling catheter-associated infection. Ethanol has widespread bactericidal activity, limited side effects, and low risk of inducing antimicrobial resistance. However, concerns have been raised about ethanol-induced catheter structural degradation. In this study, silicone catheters were immersed at 37 degrees C in three different solvents: 0.9% sodium chloride, 60% ethanol, and 95% ethanol for 4 h, 15 days and 15 days after a first storage of 4 h. Scanning electron microscopy (magnification 1000-20 000 times) of the inner surface of the catheter revealed no damage to the lumen surfaces of catheters immersed in 95% ethanol for 15 days compared with the reference catheter. Gas chromatography/mass spectrometry (GC/MS) and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS) analysis of the storage solutions revealed a significant release of polydimethylsiloxanes having a number of dimethylsiloxane units lower than 30 in the 95% ethanol solution and a structure highly consistent with a cyclic structure. Most release occurred within the first 4 h of exposure. In contrast, there was no difference in the small amounts of silicone released in 0.9% sodium chloride as reference and 60% ethanol solution, whatever the exposure time. These results should allow the development of clinical trials to assess the efficacy of the 60% ethanol lock technique in preventing or controlling the infectious complications of silicone dialysis catheters.

No abstract

No abstract

No abstract