Phospholipase B enzyme expression is not associated with other virulence attributes in Candida albicans isolates from patients with human immunodeficiency virus infection

The extracellular phospholipases of Candida albicans are considered to play a significant role in the pathogenesis of human infections. Therefore 30 clinical isolates of C. albicans from human immunodeficiency virus (HIV)-infected individuals were screened for phospholipase production in vitro (using an egg-yolk-agar medium). Two groups of six isolates with positive (group A) or deficient (group B) phospholipase activity were then analysed for phospholipase B 1 (PLB1) gene expression both in egg-yolk-agar and yeast extract/peptone/dextrose (YPD) broth media. A total of four virulence attributes of these two groups were in turn characterized, namely their germ-tube formation, cell-surface-hydrophobicity (CSH), adhesion to buccal epithelial cells (ABEC) and haemolysin production, and these factors were subsequently correlated with PLB1 expression. In the phospholipase-producing isolates (group A) a positive correlation was demonstrated between phospholipase production and the degree of PLB1 expression in YPD medium (r = 0.96, P < 0.01). No such association was observed in group A isolates for PLB1 expression in egg-yolk-agar medium. Further, PLB1 expression in egg-yolk agar was less than that in YPD medium, although a positive correlation was seen between the expression levels on regression analysis (r = 0.86, P=0.026). Surprisingly, however, no significant associations were observed in either growth media between PLB1 expression and any of the four pathogenic attributes examined (P < 0.001). A significant correlation was seen between CSH and ABEC (r = 0.74) in group A isolates. The phospholipase-deficient group B, however, demonstrated a significant correlation between the latter parameters (r = +0.50) and also between germ-tube formation and ABEC (r = -0.59), and germ-tube formation and haemolysin production (r = +0.31). It appears that in oral C. albicans isolates in HIV infection there may be no significant association between the degree of PLB1 expression and other widely recognized major virulence attributes.