Dataset Information

Keratitis due to Aspergillus flavus: clinical profile, molecular identification of fungal strains and detection of aflatoxin production.

ABSTRACT: PURPOSE: To document the clinical profile of patients with keratitis due to Aspergillus flavus and to elaborate on differences in the aflatoxin-producing potential of keratitis strains versus environmental strains of A. flavus. METHODS: Over a 6-month period, strains of Aspergillus flavus were isolated in culture from corneal scrape or biopsy material of patients who presented with suppurative keratitis (clinical isolates). The strains were confirmed to be A. flavus by molecular methods (amplification of the internal transcribed spacer 2 [ITS 2] region and direct sequencing followed by comparative GenBank analysis). The aflatoxin-producing potential of each strain was determined by thin-layer chromatography. The ability of each strain to form sclerotia in Czapek-Dox agar (CDA) after 7 days incubation at 30 degrees C in the dark and to produce a beige ring in yeast extract sucrose agar supplemented with methyl beta-cyclodextrin and sodium desoxycholate (YESD medium) after 3 days incubation at 30 degrees C was also assessed. For comparison, the tests were also run on 10 strains of A. flavus (identity confirmed by molecular methods) collected from local farming areas (environmental isolates). RESULTS: Aflatoxin B1 was detected in 16 (80%) of 20 culture filtrate or mycelial homogenate samples of the clinical isolates (mean concentration: 366.7+/-125.4 parts per billion [ppb]) but in only eight (40%) of 20 samples of environmental isolates (mean concentration: 306.6+/-125.4 ppb). Seven of the eight aflatoxin-producing clinical isolates and two of the four aflatoxin-producing environmental isolates formed sclerotia (>400 microm) and a beige ring in culture. CONCLUSIONS: Aflatoxin B1 was detected in a significantly higher percentage of growth samples of clinical isolates (80%) than growth samples of environmental isolates (40%) (chi(2)=6.667; p=0.0098); the therapeutic implications of this finding require further study. The production of sclerotia and a beige ring in culture appear to be useful markers of aflatoxin-producing potential in strains of A. flavus isolated from keratitis.

SUBMITTER: Leema G

PROVIDER: S-EPMC2866576 | biostudies-literature | 2010

REPOSITORIES: biostudies-literature

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Keratitis due to Aspergillus flavus: clinical profile, molecular identification of fungal strains and detection of aflatoxin production.

Leema George G Kaliamurthy Jayaraman J Geraldine Pitchairaj P Thomas Philip A PA

Molecular vision 20100511

<h4>Purpose</h4>To document the clinical profile of patients with keratitis due to Aspergillus flavus and to elaborate on differences in the aflatoxin-producing potential of keratitis strains versus environmental strains of A. flavus.<h4>Methods</h4>Over a 6-month period, strains of Aspergillus flavus were isolated in culture from corneal scrape or biopsy material of patients who presented with suppurative keratitis (clinical isolates). The strains were confirmed to be A. flavus by molecular met ...[more]

PMID: 20461152

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Project description:Aflatoxins are carcinogenic fungal secondary metabolites. Levels of aflatoxins in agricultural commodities are stringently regulated by many countries. A cluster of genes is responsible for aflatoxin biosynthesis by Aspergillus flavus and other closely related species. Expression of the clustered aflatoxin genes is governed by a complex network of regulatory mechanisms. To better understand the molecular events that are associated with aflatoxin production, transcription profiling by microarray analyses which compared three independent aflatoxigenic A. flavus strains to individual isogenic progenies that no longer produced aflatoxins after serial transfers was carried out. Twenty-two significantly differentially expressed features were identified. After physical mapping using the A. oryzae genome sequence as the reference, the number of unique genes was reduced to 16. Compared to the parental strains, changes in the aflatoxin gene expression levels in the progenies were not significant, which suggests that the inability to produce aflatoxins is not caused by decreased expression. The only gene showing higher expression levels in the progenies is homologous to glutathione S-transferease genes. Overexpression of this gene, named hcc, at six- to nine-fold in an aflatoxigenic A. flavus did not cause discernible changes in colony morphology or aflatoxin production. Loss of aflatoxin production after serial transfers may not result from a single event but caused by multiple factors. Keywords: Compartiave hybridization toxigenic and atoxigenic lines of Aspergillus Aspergillus flavus NRRL 29459, NRRL 29474, and NRRL 29490 are aflatoxigenic strains originated from soil collection in a peanut field (Terrell Co., Georgia, USA). Strains 459B-20-2, 474A-20, and 499A-20 were nonaflatoxigenic isolates obtained after 20 serial transfers of the parental strains on potato dextrose agar slants (Horn and Dorner 2002). Comparsions in each experiment consisted of one aflatoxigenic parental strain and one nonaflatoxigenic progeny, compared after 48- or 72-hr growth. Each comparison was repeated with duplicate dye-flip.

Dataset Information

Keratitis due to Aspergillus flavus: clinical profile, molecular identification of fungal strains and detection of aflatoxin production.

Publications

Keratitis due to Aspergillus flavus: clinical profile, molecular identification of fungal strains and detection of aflatoxin production.

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