Mouse thigh infection model.

The in vivo PA-SME was determined using the neutropenic mouse thigh infection model as described (34). Mice were rendered neutropenic (polymorphonuclear leukocyte count, <100/mm³) by intraperitoneal (i.p.) injection of cyclophosphamide (Sigma-Aldrich) at 4 days (150 mg/kg of body weight) and 1 day (100 mg/kg) prior to intramuscular injection into the posterior thigh of a 0.1-ml bacterial inoculum (concentration, 1 × 10⁷ CFU/ml). Mice were dosed intravenously (i.v.) into the lateral tail vein with CF-301 at 10 to 15 mg/kg beginning 2 h postinfection. Dosing was based on previously determined EC₅₀ values (12). Buffer-treated mice served as controls. Groups of 3 mice were treated with each dosing regimen. Immediately after infection (T = 0) and at eight time points thereafter (T = 0.5, 1, 2, 4, 6, 24, 27, and 30 h), mice were euthanized and each thigh was aseptically removed, weighed, and homogenized in PBS using a Precellys24 high-throughput tissue homogenizer (Bertin Corporation, Rockville, MD). Serial 10-fold dilutions of the homogenized material were plated on TSAB plates for determinations of CFU per gram of tissue. Each symbol in the figures represents the data from three mice (six thighs).