Typing and patterns of cellular morphological alterations inCryptococcus neoformansandCryptococcus gattiiisolates exposed to a panel of killer yeasts

Abstract

Cryptococcus neoformans and Cryptococcus gattii are encapsulated basidiomycetous yeasts that cause meningoencephalitis. The action of killer yeasts on the growth of one hundred genotypically characterized C. neoformans var. neoformans, C. neoformans var. grubii, and C. gattii clinical and environmental isolates was evaluated. Killer studies were performed on yeast malt-methylene blue (YM-MB) agar Petri dishes, and a dendrogram was obtained based on a quantitative data matrix using the diameter of the inhibition halo. The cellular morphological characteristics of dead cells within the halo were observed by means of optical and scanning electron microscopy. There was no formation of pores on the cell surface of the sensitive cells in contact with the toxins, at least for C. neoformans. The sensitivity patterns of clinical and environmental isolates to the killer toxins demonstrated that there is correlation between killer sensitivity of Cryptococcus species or varieties and some of the killer strains. In this case, the isolates were discriminated using the killer sensitivity patterns, and this could be used as a complementary tool to PCR-fingerprinting in epidemiological studies.

Susceptibility of species within the Sporothrix schenckii complex to a panel of killer yeasts

“…Although Fuentefria et al . observed differences between C. neoformans and C. gattii against a panel of killer yeasts obtained from raw milk and cheese , in our study those same killer yeasts were not able to differentiate the species within the S. schenckii complex, nor there was correlation between sensitivity and origin of the isolates (clinical, animal, and environmental). de Oliveira et al .…”

“…and 58% against Cryptococcus spp.). T. faecale QU100 (mean halo size 18.6 mm) showed inhibition haloes classified as C or D against approximately 74% of the S. schenckii isolates, the same percentage of Cryptococcus strains that were inhibited by this killer strain in the previous study . Finally, T. insectorum QU89 (syn.…”

“…This property has been used to control contaminating wild yeasts in food and pathogenic fungi in plants [7,8]. In the medical field, these yeasts have been used in the development of novel antimycotics for the treatment of human and animal fungal infections [9][10][11] and for the biotyping of pathogenic yeasts and yeast-like fungi [12,13]. The action of killer yeasts against S. schenckii has already been reported in the literatures [14,15], but this once considered a single species is presently recognized as a species complex.…”

“…Previous studies have shown that yeasts obtained from raw milk and cheese produce killer toxins against Cryptococcus neoformans and Cryptococcus gattii, and are promising for the development of new antifungal agents [13]. The aim of this study was to evaluate the action of 18 of these previously tested killer yeasts on the growth of 88 isolates of the S. schenckii species complex.…”

The Biology of Pichia membranifaciens Killer Toxins

“…Furthermore, Pichia acaciae , Kluyveromyces lactis and Debaryomyces robertsiae cytoplasmic virus like elements encode toxic anticodon nucleases along with specific proteins that confer toxin immunity [13,14]. The potential use of killer yeasts and their toxins has been intended for various fields of application such as the alcohol fermentation industries (brewery, winery, and distillery), fermented vegetables, biological control of post-harvest diseases, yeast bio-typing, as antimycotics in the medical field and they have been used as model systems to understand eukaryotic polypeptide processing and expression of eukaryotic viruses [10,11,12,13,14,15,16,17,18,19,20,21]. …”