Oral itraconazole may alter the gastrointestinal microbiome in healthy cats

To determine if and how oral itraconazole alters the gastrointestinal microbiome of cats.

This was a single-arm, longitudinal exploratory study performed in a university setting. Healthy cats were administered 5 mg/kg/day of itraconazole solution orally with food during alternating weeks over a 5-week time period. Rectal swabs were collected at 2 time points before treatment and serially during and after treatment over 31 weeks. Bacterial and fungal populations were quantified by 16S and internal transcribed spacer 3 and 4 sequencing, respectively. Changes in α diversity, β diversity, and differential abundance were evaluated over time.

There were no significant changes in bacterial α diversity, β diversity (R2 = 0.0077; P = .550), or relative abundance between the 2 pretreatment time points indicating stable microbial populations before itraconazole exposure in 16 cats. Time was a significant determinant of β diversity during and after itraconazole treatment (R2 = 0.0181; P = .002), and several α-diversity indices significantly decreased in the posttreatment timeframe. Ruminococcus torques (-1.916; 95% CI, -2.971 to -0.861), Acidaminococcus spp (-1.291; 95%, CI -1.866 to -0.716), and Blautia hansenii (-1.475, 95% CI, -2.295 to -0.691) relative abundances were significantly decreased at weeks 1, 5, and 9, respectively. The final fungal internal transcribed spacer dataset only included 5 taxa limiting analysis and interpretation.

These findings provide preliminary evidence for possible dysbiosis in the feline gastrointestinal tract during itraconazole treatment. However, many changes in differential abundance were small and no longer significant posttreatment.

Itraconazole administration might induce gastrointestinal bacterial dysbiosis in cats. Alternate methods for fungal microbiome assessment should be used in future feline studies.