Experimental Germ Tube Induction in Candida albicans: An Evaluation of the Effect of Sodium Bicarbonate on Morphogenesis and Comparison with Pooled Human Serum

OBJECTIVE The potential of NaHCO3 versus human serum to induce germ tube formation in Candida albicans was investigated. SPECIMENS A total of 100 isolates were obtained from oral swabs of patients presenting with thrush. Approval for the study was granted by the Joint Research Ethics Committee (JREC/23/08). METHOD Confirmed C. albicans isolates by routine methods were tested for germ tube induction using 5 different concentrations of Tris-maleate buffered NaHCO3 and Tris-maleate buffer control. Standard control strains included were C. albicans (ATCC 10231) and C. krusei (ATCC 6258). Microculture was done in 20 μL inoculums on microscope slides for 3 hours at 37°C. The rate of germ tube formation at 10-minute intervals was determined on 100 isolates using the optimum 20 mM Tris-maleate buffered NaHCO3 concentration. Parallel germ tube formation using human serum was done in test tubes. RESULTS The optimum concentration of NaHCO3 in Tris-maleate buffer for germ tube induction was 20 mM for 67% of isolates. Only 21% of isolates formed germ tubes in Tris-maleate buffer control. There was no significant difference in induction between human serum and Tris-maleate buffered NaHCO3. CONCLUSION Tris-maleate buffered NaHCO3 induced germ tube formation in C. albicans isolates at rates similar to human serum.