Abstract
Poster session 3, September 23, 2022, 12:30 PM - 1:30 PM
Fungus collection is an essential approach to allow future studies, including molecular, and epidemiological characteristics, virulence factors, susceptibility profile, and others. Ideal methods should keep the isolates viable for long periods of storage. The mineral oil method is theoretically a secure and efficient method for the storage of filamentous and dimorphic fungi, including Sporothrix spp., for long periods.
Objective
We aimed to evaluate the recovery rate of isolates of Sporothrix spp. maintained for years through the mineral oil technique in a fungal collection.
Methods
Sporothrix spp. isolates were originally cultivated in tubes with potato dextrose agar, incubated at 30°C for at least 7 days, and covered by mineral oil, until around 1 cm above the surface, after the growth and sporulation of the colonies. Tubes were maintained at room temperature (∼25°C). A total of 238 isolates of Sporothrix spp. (mostly S. brasiliensis) maintained for 4-108 months (mean of 49.7 months) were included in the study, being 191 isolates from cats (80%), 31 from humans (13%), 14 from dogs (6%), and 2 (1%) from the environment. To evaluate the rate of recovery, a fragment of the colonies was cultivated in duplicate in plates with Sabouraud dextrose agar and incubated at 25°C until the fungal growth or for 30 days. To analyze the results, frequency, mean, and standard deviation (SD) were calculated, as well and the Kruskal-Wallis test was performed, using the SPSS statistical program.
Results
Only 14% (n = 34) of the fungal isolates were recovered from oil minerals after a mean of 64 months of storage (SD = 18.4), being 82% (n = 28) of the recovered isolates from cats, 12% (n = 4) from humans, and 6% (n = 2) from dogs (n = 1), or environment (n = 1). The 204 isolates that could not be recovered, were stored for a mean of 47 months (SD = 25.5) (P ˃ 0.05).
Conclusion
Disagreeing with previous reports, mineral oil was a failure method to keep Sporothrix spp. isolates viable independently of the period of storage. Therefore, optimization of this methodology is necessary, and/or other methods must be implemented to guarantee the preservation of Sporothrix spp. isolates in fungal collections.