The water supply system as a potential source of fungal infection in paediatric haematopoietic stem cell units.

BACKGROUND: We conducted a prospective study to investigate the presence of microfungal contamination in the water supply system of the Oncology Paediatric Institute, São Paulo-Brazil after the occurrence of one invasive Fusarium solani infection in a patient after Haematopoietic Stem Cell Transplantation (HSCT). During a twelve-month period, we investigated the water supply system of the HSCT unit by monitoring a total of fourteen different collection sites. METHODS: One litre of water was collected in each location, filtered through a 0.45 µm membrane and cultured on SDA to detect the presence of filamentous fungi. Physicochemical analyses of samples were performed to evaluate the temperature, turbidity, pH, and the concentration of free residual chlorine. RESULTS: Over the 12 months of the study, 164 samples were collected from the water supply system of the HSCT unit, and 139 of the samples tested positive for filamentous fungi (84.8%), generating a total of 2,362 colonies. Cladosporium spp., Penicillium spp., Purpureocillium spp. and Aspergillus spp. were ranked as the most commonly found genera of mould in the collected samples. Of note, Fusarium solani complex isolates were obtained from 14 out of the 106 samples that were collected from tap water (mean of 20 CFU/L). There was a positive correlation between the total number of fungal CFU obtained in all cultures and both water turbidity and temperature parameters. Our findings emphasise the need for the establishment of strict measures to limit the exposure of high-risk patients to waterborne fungal propagules. CONCLUSIONS: We were able to isolate a wide variety of filamentous fungi from the water of the HSCT unit where several immunocompromised patients are assisted.

Molecular phylogeny and phenotypic variability of clinical and environmental strains of Aspergillus flavus.

Aspergillus flavus is the second most common cause of aspergillosis infection in immunocompromised patients and is responsible for the production of aflatoxins. Little is known about the population structure of A. flavus, although recent molecular and phenotypic data seem to demonstrate that different genetic lineages exist within this species. The aim of this study was to carry out a morphological, physiological, and molecular analysis of a set of clinical and environmental isolates to determine whether this variability is due to species divergence or intraspecific diversity, and to assess whether the clinical isolates form a separate group. The amdS and omtA genes were more phylogenetically informative than the other tested genes and their combined analysis inferred three main clades, with no clear distinction between clinical and environmental isolates. No important morphological and physiological differences were found between the members of the different clades, with the exception of the assimilation of d-glucosamine, which differentiates the members of the clade II from the others.

Aspergillus novoparasiticus: a new clinical species of the section Flavi.

During a survey on the incidence of Aspergillus in clinical environments, we found some interesting isolates that were morphologically similar to Aspergillus parasiticus, but differed in the color of the colonies and in the pattern of their conidial ornamentation. In the present study, those isolates were characterized using a polyphasic approach. A phylogenetic analysis was carried out, based on partial fragments of the acetamidase (amdS) and O-methyltransferase (omtS) genes and the internal transcribed spacer (ITS) region of rDNA. This information was combined with a detailed morphological and physiological study that included aflatoxin production and assimilation profiles of different carbon and nitrogen sources. The phenotypic and genotypic results support the proposal of a new species, Aspergillus novoparasiticus, phylogenetically placed in a distinct sister clade to that of A. parasiticus. The former has lobate-reticulate conidia and does not produce aspergillic acid on AFPA or organic acids on CREA, while A. parasiticus has echinulate conidia and produces aspergillic and organic acids. In addition, this new species, as well as A. parasiticus, produces aflatoxins B1, B2, G1 and G2.