Antibiotic treatment using amoxicillin-clavulanic acid impairs gut mycobiota development through modification of the bacterial ecosystemOriginal paper
Karen Pendergrass is a microbiome researcher specializing in microbiome-targeted interventions (MBTIs). She systematically analyzes scientific literature to identify microbial patterns, develop hypotheses, and validate interventions. As the founder of the Microbiome Signatures Database, she bridges microbiome research with clinical practice. In 2012, based on her own investigative research, she became the first documented case of FMT for Celiac Disease, four years before the first published case study.
Read MoreWhat was studied?
This study tested how the common antibiotic amoxicillin-clavulanic acid affects the gut fungal community, or mycobiota, not just bacteria. It challenged the assumption that antibiotics always let fungi bloom. Bacterial and fungal loads were measured by qPCR, and communities were profiled by 16S rRNA and ITS2 amplicon sequencing. In vitro co-cultures and in vivo gavage tested bacterial-fungal interactions. The team combined conventional mice, human microbiota-associated mice, fungus-colonized mice, and an infant sample cohort to test consistency across models.
Who was studied?
The work used mice and humans. Mice were 6-week-old female C57BL/6J, including conventional, human microbiota-associated, and Candida albicans-colonized animals, with 5 to 16 per group. The human samples came from 7 antibiotic-naive infants (all male, median age 2 to 4 months), sampled before and during amoxicillin given for otitis media following respiratory syncytial virus infection. Additional in vitro assays used isolated Enterobacteriaceae strains cultured with the yeasts Candida albicans and Saccharomyces cerevisiae.
What were the most important findings?
Amoxicillin-clavulanic acid significantly lowered fungal load in mouse ileum, cecum, and feces, and in infant feces, the opposite of the four-antibiotic cocktail, which raised fungal load. The drug enriched Enterobacteriaceae. Screening isolates from treated mice, 9 of 13 bacteria suppressed Candida albicans growth (p less than 0.001), and all were Enterobacteriaceae. Enterobacter hormaechei was the most potent, forming pili-like contacts with yeast and, when gavaged alone into mice, significantly reducing gut fungal load, recapitulating the antibiotic effect.
What are the greatest implications of this study?
The findings overturn the idea that all antibacterial treatment favors fungal overgrowth. The effect on fungi depends on which bacteria expand afterward, not on removing bacterial competition alone. A bloom of Enterobacteriaceae can suppress fungi through live-cell mechanisms including nutrient competition and adhesion, not secreted toxins, since dead cells and supernatants had no effect. Because human evidence came from a small infant cohort, the authors caution these results need larger human studies before informing clinical practice.