Purpureocillium lilacinum an emergent pathogen: antifungal susceptibility of environmental and clinical strains.

Purpureocillium lilacinum is a filamentous and hyaline fungus cosmopolitan, saprophytic, largely used in the biological control of plant-parasitic nematodes and insects, also considered an emerging and opportunistic human pathogen. The standard treatment for hyalohyphomycosis caused by P. lilacinum is not yet defined, since this fungus is resistant to different antifungals, in vitro and in vivo. The aim of this study was to evaluate and compare in vitro antifungal activity against environmental and clinical P. lilacinum isolates and our results demonstrated that these isolates can be resistant to newer generation triazoles, such as voriconazole, and to caspofungin, a drug of the echinocandin class. In summary, we highlight the importance of knowing the different susceptibility profiles of P. lilacinum isolates, and besides that, the emergence of uncommon human and animal opportunistic fungi, such P. lilacinum, especially during COVID-19, highlight the need for antifungal susceptibility testing of isolates since empirical therapy with different treatment schedules failed in great number of patients.

Paracoccidioides brasiliensis: virulence and an attempt to induce the dimorphic process with fetal calf serum.

The virulence of Paracoccidioides brasiliensis strains and the induction of the dimorphic process of the fungus were investigated. The strains were kept under mineral oil for different periods of time, except for one that was successively subcultured on agar slants. Four strains with transitional morphology at room temperature were avirulent to experimental animals. Two strains with typical morphology at 36 degrees C, one of them preserved under mineral oil for 16 years and the other maintained by successive subcultures for 10 years, were virulent to mice. These strains caused macro- and microscopic lesions in various organs, with enlargement of the spleen and heart. An attempt to induce the dimorphic process with fetal calf serum (FCS) in P.brasiliensis strains with transitional morphology failed. FCS was probably unable to stimulate the synthesis of Y cell wall alpha-1,3-glucan. The results demonstrate that keeping strains under mineral oil for a long period of time may have altered the enzymatic activities of the proteinases and other virulence factors that participate in the transition process and in pathogenesis.

Viability, morphological characteristics and dimorphic ability of fungi preserved by different methods.

The viability, morphological characteristics and dimorphic ability of fungi were evaluated. Strain subcultures were maintained under mineral oil and in soil for different periods of time, ranging from 49 to eight years. Of the 16 Blastomyces dermatitidis strains, four maintained viability and were able to complete the dimorphic process to the M phase producing a large amount of conidia, but were unable to form Y cells at 36 degrees C. Of the 15 Histoplasma capsulatum var. capsulatum strains, only one was viable but it was impossible to check its identity because it lost sporulating and dimorphic ability. Of the 53 Sporothrix schenckii strains, 37 were viable, 28 able to sporulate and 12 of them completed the whole M <=> Y dimorphic process. All subcultures in soil became inviable. The results demonstrate that the preservation methods used here affected the morphology and sporulating and dimorphic ability of the strains. B. dermatitidis and S. schenckii were considered to be species that survive better than H. capsulatum var. capsulatum under mineral oil. Thus, it is necessary to establish routine monitoring and appropriate environmental and culture conditions, using less widely spaced transplants and choosing the exact time of intervention to induce growth and development restriction in each strain.

Viability and sporulating capability of Coelomycetes preserved under a range of different storage regimes.

The viability and sporulating capability of 45 Coelomycetes strains were evaluated. Strain subcultures were maintained under mineral oil, in soil and on agar slant for different periods of time lasting as long as 50 years, 39 years and 2 years, respectively. Of the 34 strains preserved under mineral oil, 20 maintained their viability but lost the sporulating capability with exception of one strain of Pestalotiopsis guepinii. Of the 16 strains also preserved in soil only one was viable and it was not able to sporulate. All 12 endophytic strains, 11 preserved on agar slant and one under mineral oil remained viable; however, the strain preserved under mineral oil lost its sporulating capability, while the strains on agar slant were only able to sporulate after culturing on sterilized alfalfa twigs. The results demonstrate that routine monitoring, and the use of different preservation methods, specially with the addition of sterilized plant tissue on the culture media for promoting conidiomata formation, is necessary for the success of the Coelomycetes long-term preservation.

Evaluation and comparison of the growth and viability of yeast-like cells of Paracoccidioides brasiliensis.

The growth and viability of two Paracoccidioides brasiliensis strains were evaluated in PYG and MMcM media containing no boric acid. The two P. brasiliensis strains exhibited a similar growth pattern in PYG medium, which was considered to be good compared with the growth curves in defined MMcM medium without boric acid. Calculation of cell generation time in the media studied demonstrated that the cells had greater difficulty in forming new generations in MMcM medium containing no boric acid. The present data confirm the literature view that PYG medium is the most complete in terms of nutritive substances for the growth and development of P. brasiliensis.