In Vitro Acid Resistance of Pathogenic Species in Simulated Gastric Fluid.

Background And Aims: Although species in the fungal genus are often commensal residents of the gastrointestinal (GI) tract, they can also cause high-mortality systemic candidiasis. Most pathogenic species are dimorphic fungi that exist predominantly in filamentous forms in the invading tissues. is the most prominent pathogen among species, but nonalbicans species have also emerged as important pathogens. The stomach is the most acidic niche in the GI tract and is maintained at pH 1-2 in healthy individuals. The aim of the present study was to determine whether species can survive in gastric fluid and to observe their morphology under varied pH conditions.

Methods: We investigated the in vitro survival of the pathogenic species and in simulated gastric fluid.

Results: We first described that a portion of the 4 species can survive under highly acidic conditions. Moreover, dimorphic species, namely, and exhibited yeast-hyphal transition in simulated gastric fluid with elevated pH. Pathogenic filamentous cells had lower acid resistance than yeast cells.

Conclusion: These findings may illuminate the migration to the lower GI tract by commensal fungi of the oral cavity.