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[Cryptococcus spp. DNA extraction from environmental samples]
Alexandra Castañeda1, Juan McEwen, Marylin Hidalgo
1Grupo de Microbiología, Instituto Nacional de Salud, Bogotá, DC, Colombia.
Abstract:
The genus Cryptococcus encompasses 38 species, but only 3 are associated with disease in humans and animals, Cryptococcus laurentii, Cryptococcus albidus and Cryptococcus neoformans. The last one is the most frequently reported. The disease is acquired by the inhalation of infectious propagules present in the environment. The habitat has been established using extraction techniques with buffer supplemented with antibiotics and plating in selective media. The aim of this work was to evaluate several DNA extraction techniques for Cryptocococus spp. from environmental samples. The control isolates were C. neoformans, C. albidus, C. laurentii and Paracoccidiodes brasiliensis. We also used vermiculita and soil samples contaminated with different yeast concentrations (10 to 10(6) cells/g) and samples naturally contaminated with C. neoformans. DNA was extracted with physical and chemical methods and with a commercial kit, and the DNA was purified with agarose blocks and silica columns. For the PCR amplification we used the CN4-CN5 primers, which are specific for C. neoformans. Only the commercial kit allowed DNA extraction and amplification from contaminated soil samples up to a concentration of 10 cells/g and from one sample naturally colonized. With this work we extracted and amplified DNA from Cryptococcus spp. from environmental samples with appropriate PCR specificity, it will be a tool to establish the ecological areas of C. neoformans in our country.
Insights
A commercial DNA extraction kit effectively isolated Cryptococcus spp. DNA from environmental soil samples, enabling specific PCR amplification. This method aids in identifying the ecological distribution of Cryptococcus neoformans.
Area of Science:
- Medical Mycology
- Environmental Microbiology
- Molecular Biology
Background:
- The genus Cryptococcus includes 38 species, with Cryptococcus neoformans being the most frequently reported cause of human and animal disease.
- Cryptococcal infections are acquired through inhalation of infectious propagules found in the environment.
- Current methods for habitat determination rely on specific extraction and culture techniques.
Purpose of the Study:
- To evaluate various DNA extraction techniques for Cryptococcus spp. from environmental samples.
- To optimize DNA extraction for subsequent PCR amplification.
- To develop a tool for establishing the ecological niches of Cryptococcus neoformans.
Main Methods:
- Environmental samples (soil, vermiculita) were artificially contaminated with Cryptococcus spp. at varying concentrations (10-10^6 cells/g) and tested with naturally contaminated samples.
- DNA extraction was performed using physical, chemical, and a commercial kit.
- PCR amplification was conducted using CN4-CN5 primers specific for C. neoformans.
Main Results:
- The commercial DNA extraction kit was the only method successful in extracting and amplifying Cryptococcus spp. DNA from soil samples down to 10 cells/g.
- The kit also enabled amplification from one naturally colonized environmental sample.
- Successful PCR amplification demonstrated appropriate specificity for C. neoformans.
Conclusions:
- A commercial DNA extraction kit provides an effective method for isolating Cryptococcus spp. DNA from environmental samples.
- This technique facilitates specific PCR amplification, crucial for epidemiological studies.
- The optimized method can serve as a valuable tool for mapping the environmental distribution of C. neoformans.
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