Clinico-microbiological Study of Candida Infections Focusing on Risk Factors, Species Identification, Virulence Factors and Antifungal Susceptibility Patterns

Abstract

Introduction: Infections caused by Candida species have been increasing along with the advancement in diagnostic and treatment interventions. Recently a shift from Candida albicans to non albicans species has also been observed. Infections by Candida species is aided by several virulence factors and prevalence of antifungal resistance. Aim: To speciate and study the virulence factors and determine susceptibility pattern of Candida isolates obtained from various clinical specimens. To determine the risk factors for infection with Candida species in patients admitted to a tertiary care hospital at Mangalore, Karnataka, India. Materials and Methods: This cross-sectional study was conducted at Department of Microbiology, Kasturba Medical College, Mangalore, Karnataka between October 2015 to September 2018. A total of 145 isolates from various clinical specimens were identified up to species level by germ tube test, chlamydospore formation, and growth characteristic on cornmeal agar, colour of colonies on chromogenic agar and carbohydrate fermentation tests. Virulence factors included were biofilm formation by microtitre plate method, phospholipase activity using egg yolk agar, proteinase activity using bovine serum albumin agar, haemolysin production, coagulase activity and production of true hyphae. Antifungal susceptibility test was performed as per CLSI 2009 M44-A2. The statistical analysis was done using statistical package version 16.0. The p-value less than 0.05 was considered as statistically significant. Results: Out of 145 Candida isolates C. tropicalis were 59 (40.6%) followed by C. albicans and other species. Presence of an intravenous catheter 124 (85.5%), treatment with broad spectrum antibiotics 121 (83.4%) and admission to ICU 113 (77.9%) were the most common risk factors identified in this study. Biofilm formation was detected in 80 (55.2%) of isolates, among which C. tropicalis (42 out of 59 71.1% p= 0.02) showed the highest propensity for biofilm formation. Phospholipase activity was highest among C. albicans 42 (79.2%, p= 0.001) whereas proteinase activity was highest in C. tropicalis 50 (84.7%, p=0.001). Coagulase production was detected in 14 isolates and 39 of our isolates had produced true hyphae. Production of true hyphae was observed more among C. tropicalis 25 (64.1%, p= 0.04). Non albicans species showed highest proteinase activity and true hyphae production of 69 (75.6% p= 0.002) and 25 (27.2% p=0.04) respectively. Fluconazole resistance was detected in 13.8% of the isolates. Conclusion: Study of risk factors and virulence factors will serve as a guideline for better understanding of the pathogenic mechanisms involved in fungal disease, which in turn will lead to better patient management and prognosis.

Keywords

• antifungal resistance
• biofilm
• candida albicans
• extracellular hydrolytic enzymes
• non albicans candida species