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 5^th day, whereas 35 (29.16 %) environmental and 8 (40 %) clinical strains were screened on 8^th day of incubation. Similarly 13 (10.83%) environmental and 3 (15 %) clinical strains on the 5^th day, however 32 (26.66%) environmental and 8 (40 %) clinical strains on the 8^th 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 5^th 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