Protocol for administering antibiotics by gavage effectively reduces intestinal bacterial contents.

<p>(<b>A</b>) Enumeration of cultivable fecal bacteria (mean ± SEM) in untreated mice. (<b>B</b>) Efficacy of successful depletion (<1 cfu/mg feces) of cultivable gut microbiota and distribution of aerobe, anaerobe, and fungal overgrowth (def.: ≥1 cfu/mg feces) after 13 and 24 days of treatment with vancomycinm (V), neomycin (N), metronidazol (M), and amphotericin-B (Amf-B) every 12 hours by gavage with ampicillin <i>ad libitum</i> in drinking water (A), n = 43. (<b>C</b>) Bacterial 16S DNA load (mean ± SD) in fecal pellets. 16S DNA determined by quantitative PCR for the V2 and V6 regions and normalized to total mouse genomic DNA in the same pellets of mice treated 13 and 24 days with VNMAmf-B +A compared with water controls, n = 7 for water controls, 40 for 13 days, and 35 for 24 days.