Phenotypical characterization and molecular identification of clinical isolates of Candida tropicalis

Candida tropicalis is an increasingly important human pathogen which usually affects neutropenic oncology patients with common hematogenous seeding to peripheral organs and high mortality rates. Candida pathogenicity is facilitated by several virulence attributes, including secretion of hydrolytic enzymes; however, little is known regarding the C. tropicalis ability to secrete them and their role in the disease.

To confirm by molecular means the identification of 187 clinical isolates (127 from blood, 52 from urine, and 8 from diverse clinical origins) phenotypically identified as C. tropicalis, and to investigate their in vitro aspartyl proteinase, phospholipase, esterase, hemolysin, DNase and coagulase activities.

The molecular confirmation was performed by ITS sequencing, and the enzymatic determinations were conducted using plate assays with specific substrates, with the exception of coagulase, which was determined by the classical tube test.

The majority of the strains exhibited a very strong or strong activity of aspartyl proteinase, phospholipase and esterase. A 4.7% of the bloodstream isolates were hemolysin producers, and all were negative for the coagulase and DNase assays.

Very strong activities of aspartyl proteinase, phospholipase and esterase profiles were detected, and a statistical association between phospholipase production and blood and urine isolates was found.