Clade Related Estrogen Response among Candida albicans Isolates

Objective: Estrogen enhances Candida albicans growth, although the exact mechanism has not been established. Estrogen also induces the ability to survive heat shock at 48°C and upregulates a gene encoding for antifungal resistance. Distinct genetic clades of C. albicans have been described, of which 4 are commonly found among South African isolates. Estrogen response has not been performed in relation to the different C. albicans clades and the objective of this study was to determine whether increased growth and resistance to heat, in response to estrogen, is related to any of the identified C. albicans clades. Methods: Six isolates from each clade was exposed to 10-9M estrogen. Growth was expressed as Optical Density(OD). After growth in estrogen the isolates were exposed to heat at 48oC for 0, 15, 30 and 60 min., 50µl cell suspension plated and colony forming units (CFUs) counted to determine survival. The t-test was applied to determine any statistically significant differences. Results: Although some isolates responded much better to estrogen than others, there was no statistically significant difference between the mean OD values of the different clades. At time zero, before heat exposure, a similar survival was observed for both control and test isolates. No control isolates survived after 15 min. of heat exposure while the number of CFUs was also markedly less among the test isolates after 30 min. heat exposure. No isolates survived exposure for 60 min. at 48°C. Heat shock survival also proved to be strain related rather than clade related. Conclusion: No significant difference in estrogen growth response and heat shock survival was observed between isolates representing the different C. albicans clades. This study on the largest number of isolates yet, confirms the strain relatedness of estrogen response.