Investigation of virulence factors of candida strains isolated from different clinical specimens

The incidence and prevalence of Candida infections has been increasing in recent years. Development of drug resistance increases the requirement of new antifungal drug targets. Identification of virulence factors helps to clear the fungal pathogenesis and supports the development of new drug targets. In this study we aimed to determine the biofilm production, phospholipase, gelatinase and haemolytic activities in various Candida species isolated from different clinical specimens and to investigate the differences of these virulence factors according to Candida species and clinical specimens. A total number of 409 strains consisting of C. albicans (n=171), C. glabrata (n=73), C. parapsilosis (n=81) and C. tropicalis (n=94) isolated from blood, urine oral cavity and tracheal secretion cultures in Dokuz Eylul University Hospital Mycology Laboratory between 2011 July- 2012 November were included in our study. Biofilm and phospholipase activities were investigated by petri adherence, modified microplate and egg-yolk agar plate assays, respectively. Haemolytic and gelatinase activities of the strains were examined by using Sabouraud dextrose agar supplemented with 7% blood and same medium supplemented with 1% gelatin, respectively. Thirty-five percent (n=143) and 31.3% (n=128) of Candida isolates were determined to be biofilm positive by petri adherence and modified microplate assay, respectively. Biofilm production was mostly detected among C. tropicalis isolates. The overall agreement between the two biofilm detection methods was found to be 68.5 %. The biofilm production by both methods was detected to be statistically significant among different Candida species. In our study, highest biofilm production was determined among Candida strains which had been isolated from urine samples when compared with the strains isolated from other sites. Statistically important differences were observed between species and clinical specimen groups with both methods. Twenty-seven point one percent of Candida isolates showed phospholipase activity and most of them were C. albicans. Phospholipase activity was not observed among C. tropicalis isolates. Statically significant difference was detected between the phospholipase activities of different species in favor of C. albicans (X2=153,3; P=0,00). The positivity rate of phospholipase activity was found to be highest among the isolates obtained from oral cavity specimens and positivity rates declined respectively among the isolates cultured from tracheal secretion, blood and urine specimens. Statistically significant difference was observed between species and clinical specimen groups (X2=33,2; p=0,00). Ninety-three point six percent of the isolates (n=383) showed haemolytic activity while 51.1 %of them had only alpha and 42.5% of them had alpha and beta haemolysis together. Alpha haemolysis was observed mostly in strains isolated from urine, alpha and beta haemolysis were mostly observed among oral cavity isolates. There were not statically significant differences between Candida species and clinical specimens that the strains had been cultured (X2=7.3; p=0.06). None of the Candida strains had gelatinase activity. Insight of these findings it can be concluded that biofilm production, phospholipase and haemolytic activities play important roles while gelatinase doesn't seem to play a role in virulence of Candida isolates included in this study. Key Words: Candida, biofilm, phospholipase, haemolytic activity, gelatinase.