Antifungal Susceptibility of Oral Candida Isolates from Mother-Infant Dyads to Nystatin, Fluconazole, and Caspofungin

The carriage of Candida albicans in children’s oral cavities is associated with a higher risk for early childhood caries, so controlling this fungus in early life is essential for preventing caries. In a prospective cohort of 41 mothers and their children from 0 to 2 years of age, this study addressed four main objectives: (1) Evaluate in vitro the antifungal agent susceptibility of oral Candida isolates from the mother-child cohort; (2) compare Candida susceptibility between isolates from the mothers and children; (3) assess longitudinal changes in the susceptibility of the isolates collected between 0 and 2 years; and (4) detect mutations in C. albicans antifungal resistance genes. Susceptibility to antifungal medications was tested by in vitro broth microdilution and expressed as the minimal inhibitory concentration (MIC). C. albicans clinical isolates were sequenced by whole genome sequencing, and the genes related to antifungal resistance, ERG3, ERG11, CDR1, CDR2, MDR1, and FKS1, were assessed. Four Candida spp. (n = 126) were isolated: C. albicans, C. parapsilosis, C. dubliniensis, and C. lusitaniae. Caspofungin was the most active drug for oral Candida, followed by fluconazole and nystatin. Two missense mutations in the CDR2 gene were shared among C. albicans isolates resistant to nystatin. Most of the children’s C. albicans isolates had MIC values similar to those from their mothers, and 70% remained stable on antifungal medications from 0 to 2 years. For caspofungin, 29% of the children’s isolates showed an increase in MIC values from 0 to 2 years. Results of the longitudinal cohort indicated that clinically used oral nystatin was ineffective in reducing the carriage of C. albicans in children; novel antifungal regimens in infants are needed for better oral yeast control.