Variation of Slime Production and Ultrastructural Analysis in Clinical and Soil Isolates ofCandida parapsilosis

Abstract

The slime production of 46 isolates of Candida parapsilosis from clinic (blood and vaginal) and soil sources was investigated. The cells were grown in liquid broth, testing several concentrations of glucose ranging from 0.9% (w/v) up to 20% in polystyrene tubes, and the presence of biofilm was checked by visual inspection of the internal wall of the tubes, scoring being: 0, no production; 1, weak; 2, moderate; 3, strong production. Each isolate had an identical slime value at the glucose concentration of 0.9% and 2%. All the blood isolates produced slime. Only the 25% of the vaginal isolates, on the other hand, produced slime, the carriage isolates producing more as compared with the isolates from acute vaginitis (20% vs 5%). The soil isolates produced no slime at all. Increasing the glucose concentration from 2% to 8%, 13 isolates increased their slime value. Increasing the glucose concentration up to 20%, no variations of slime value were observed. Isolates representative of all clinical sources and slime values found at 0.9% glucose were selected for scanning electron microscopy (SEM) analysis with or without Concanavalin (Con A) treatment, a lectin specific for mannan or mannoprotein constituents. In slime positive isolates, photomicrographs revealed cells adhering to one another, assembled in clumps, increasing with the increment of the slime value, or in files resembling a pseudohyphal state. An extracellular matrix of flocculent or fibrillar material covered the cells, increasing, surprisingly, with the increments of slime value in blood but not in vaginal isolates. This difference in amount of the extracellular material (perhaps not Con A binding) differentiates the two clinic sources, suggesting different slime depending pathogenic power. Keywords : Candida parapsilosis , slime production, Concanvalin A, scanning electron microscope.