Evaluation of the in vitro and in vivo dimorphism ofSporothrix schenckii,Blastomyces dermatitidis, andParacoccidioides brasiliensisisolates after preservation in mineral oil

Abstract

Morphological differentiation has commanded attention for its putative impact on the pathogenesis of invasive fungal infections. We evaluated in vitro and in vivo the dimorphism from mycelial to yeast-phase of Sporothrix schenckii, Blastomyces dermatitidis and Paracoccidioides brasiliensis isolates, two strains for each species, preserved in mineral oil. S. schenckii strains showed typical micromorphology at 25 degrees C but one strain was unable to complete the dimorphic process in vitro. After in vivo passage through mice the strains had the ability to turn into yeast-like cells and to form colonies on brain-heart infusion medium at 36 degrees C. B. dermatitidis strains grew as dirty white to brownish membranous colonies at 25 degrees C and their micromorphology showed thin filaments with single hyaline conidia. At 36 degrees C the colonies did not differ from those grown at 25 degrees C, but produced a transitional micromorphology. P. brasiliensis strains grew as cream-colored cerebriform colonies at 25 degrees C showing a transitional morphology. B. dermatitidis and P. brasiliensis strains did not turn into yeast-like cells in vivo. The present results demonstrate that B. dermatitidis and P. brasiliensis strains were unable to complete the dimorphic process even after in vivo passage, in contrast to the S. schenckii strain.

Molecular and phenotypic reidentification of Sporothrix schenckii clinical isolates preserved under mineral oil for 34 to 64 years in a culture collection in Brazil

“…In relation to thermotolerance, all isolates in this study produced cigar-shaped budding yeasts when cultured at 37°C. IOC 2993 isolate performed a slower conversion from mycelial to yeast form, probably due to the prolonged stress of the preservation process as described in the literature ( Borba et al., 1992 ; Lima and Borba 2001 ; Lima et al., 2004 ) , but it was able to turn into yeast-like cells. Lima et al.…”

“…IOC 2993 isolate performed a slower conversion from mycelial to yeast form, probably due to the prolonged stress of the preservation process as described in the literature ( Borba et al., 1992 ; Lima and Borba 2001 ; Lima et al., 2004 ) , but it was able to turn into yeast-like cells. Lima et al. (2004) showed irreversible alterations in dimorphic fungi such as Blastomyces dermatitidis and Paracoccidioides brasiliensis preserved in mineral oil even after in vivo passage, in contrast to S. schenckii isolates that demonstrated greater resistance.…”

“…Although this method of preservation has the advantages of being simple and requiring few resources, there are disadvantages, such as the need for frequent monitoring of fungal colonies and the relative and laborious frequency of subculturing. Furthermore, there are reports of changes in the biochemical activity, morphological stability, and virulence profile of S. schenckii after storage ( Borba et al., 1992 ; Lima and Borba 2001 ; Lima et al., 2003 , 2004 ). Moreover, Mendes da Silva et al.…”

Aplicação de metodologias de preservação e caracterização de fungos na coleção de culturas do Instituto de Medicina Tropical de São Paulo

“…Um aspecto relevante do estudo foi a observação da perda da capacidade de reversão de fase (dimorfismo térmico) de diversos isolados de P. brasiliensis, S. schenckii e B. dermatitidis, provavelmente devido à manutenção das culturas sob repiques sucessivos; este fato já havia sido descrito em estudos anteriores realizados na micoteca, pela avaliação de sete isolados de P. brasiliensis, com apenas três revertendo para a fase leveduriforme (Cavalcanti et al, 2005). anos, verificando que mesmo após a passagem em animal, este processo não pode ser revertido (Lima et al, 2004 (Nakasone et al, 2004).…”

“…As metodologias mais adequadas para a preservação dos microorganismos por períodos prolongados baseiam-se na redução do metabolismo até um nível de dormência artificial; no entanto, a escolha do método deve levar em consideração a estabilidade genética, a manutenção dos caracteres morfológicos, metabólicos, antigênicos, de patogenicidade e virulência, além da viabilidade das culturas (Smith, 2003;Lima et al, 2004).…”