Extracellular Protease and DNase Activities in Clinical and Environmental Isolates of Cryptococcus neoformans Species Complex from Central India

Abstract

Enzymes are important not only for the growth and multiplication of the microorganism but also in the infection, penetration of the host tissue and encountering host defense mechanisms. This study aims to investigate extracellular protease and DNase activity in clinical (20) and 120 environmental isolates of C. neoformans species complex collected from different localities of central India. DNase test agar containing toluidine blue and Yeast Carbon Base (YCB) agar medium supplemented with 0.1% BSA + 0.01% polypeptone was employed for the screening of DNase and protease production respectively. DNase and protease production was detected by the appearance of clear zones around the colonies. On the basis of enzymatic activity and their Pz values, high protease production (Pz≤0.6) was observed by 14 (11.6 %) environmental and 4 (11.6 %) clinical strains on 5th day, whereas 35 (29.16 %) environmental and 8 (40 %) clinical strains were screened on 8th day of incubation. Similarly 13 (10.83%) environmental and 3 (15 %) clinical strains on the 5th day, however 32 (26.66%) environmental and 8 (40 %) clinical strains on the 8th day of incubation were found to be high DNase producing strains with low Pz value (Pz≤0.6). In the case of protease activity, no significant difference was observed whereas a significant difference has shown by clinical C. neoformans and C. gattii strains on the 5th day of DNase production (p < .001). Extracellular enzymes play a vital role in the pathogenicity and virulence of C. neoformans species complex, therefore, enzymes are considered as worthy targets for developing therapeutics.
 Keywords: Cryptococcus neoformans species complex, Extracellular enzymes, DNase, protease, virulence, Pz value

Transcription Factors Control the Virulence-Associated Metabolic Enzymes and Membrane Proteins in Response to Nutrient Bioavailability in Cryptococcal Infection

“…The release of DNases is generally correlated with the increased activity of ureases that degrade excessive nitrogenous compounds in most fungi except in a few isolates of Endomycopsis fibuligera and Lipomyces starkeyi [162]. Though not too many studies are available on the cryptococcal extracellular nucleases [162]; however, available few studies have predicted the inclusion of secreted nucleases as virulence factors [163,164] because it may play a role in innate immune evasion as found with Group A Streptococcus infection characterised with polymorphonuclear neutrophil infiltration at the inflammatory region caused by bacterial infection [165,166]. A wide range of cryptococcal strain assessments for the production of DNase showed that neoformans and gattii species could secrete DNase.…”

“…A wide range of cryptococcal strain assessments for the production of DNase showed that neoformans and gattii species could secrete DNase. Based on their natural environment, the clinical isolates usually produce higher levels of DNase than environmental isolates [163,164].…”