Techniques for the detection of pathogenic Cryptococcus species in wood decay substrata and the evaluation of viability in stored samples

• Published in: Memórias do Instituto Oswaldo Cruz Vol. 108; no. 1; pp. 126 - 129
• Main Authors: Alvarez, Christian, Barbosa, Glaucia Gonçalves, de Oliveira, Raquel de Vasconcellos Carvalhaes, Morales, Bernardina Penarrieta, Wanke, Bodo, Lazéra, Márcia dos Santos
• Format: Journal Article
• Language: English
• Published: Brazil Fundação Oswaldo Cruz, Fiocruz 01.02.2013; Instituto Oswaldo Cruz, Ministério da Saúde; Fundação Oswaldo Cruz (FIOCRUZ)
• Subjects: Colony Count, Microbial; Cryptococcus; Cryptococcus gattii; Cryptococcus gattii - growth & development; Cryptococcus gattii - isolation & purification; Cryptococcus neoformans; Cryptococcus neoformans - growth & development; Cryptococcus neoformans - isolation & purification; Environmental Microbiology; isolation techniques; isolation techniques - Cryptococcus neoformans - Cryptococcus gattii - wood decay substrata; Microbial Viability; PARASITOLOGY; Specimen Handling - methods; Technical Notes; TROPICAL MEDICINE; Wood - microbiology; wood decay substrata; Cryptococcus gattii; isolation techniques; Cryptococcus neoformans; wood decay substrata
• ISSN: 1678-8060; 0074-0276; 1678-8060; 0074-0276
• DOI: 10.1590/S0074-02762013000100023

In this study, we evaluated several techniques for the detection of the yeast form of Cryptococcus in decaying wood and measured the viability of these fungi in environmental samples stored in the laboratory. Samples were collected from a tree known to be positive for Cryptococcus and were each inoculated on 10 Niger seed agar (NSA) plates. The conventional technique (CT) yielded a greater number of positive samples and indicated a higher fungal density [in colony forming units per gram of wood (CFU.g-1)] compared to the humid swab technique (ST). However, the difference in positive and false negative results between the CT-ST was not significant. The threshold of detection for the CT was 0.05.103 CFU.g-1, while the threshold for the ST was greater than 0.1.103 CFU-1. No colonies were recovered using the dry swab technique. We also determined the viability of Cryptococcus in wood samples stored for 45 days at 25ºC using the CT and ST and found that samples not only continued to yield a positive response, but also exhibited an increase in CFU.g-1, suggesting that Cryptococcus is able to grow in stored environmental samples. The ST.1, in which samples collected with swabs were immediately plated on NSA medium, was more efficient and less laborious than either the CT or ST and required approximately 10 min to perform; however, additional studies are needed to validate this technique.