Correlation between fecal concentrations of ciprofloxacin and fecal counts of resistant Enterobacteriaceae in piglets treated with ciprofloxacin: toward new means to control the spread of resistance?

Abstract

We assessed in a piglet model the relationship between fecal ciprofloxacin concentrations and ciprofloxacin-resistant Enterobacteriaceae counts. Twenty-nine piglets were orally treated with placebo or with 1.5 or 15 mg ciprofloxacin/kg of body weight/day from day 1 (D1) to D5. Areas under the curve (AUC) of concentrations increased sharply with dose and correlated positively with AUC of resistant bacteria log counts between D1 and D9. Removing residual colonic quinolones could help to control the emergence of resistance in fecal flora.

Fig 1

Mean (and 95% confidence intervals) of ciprofloxacin concentrations (A) and of log counts of ciprofloxacin-resistant Enterobacteriaceae (B) as well as of percentages of Enterobacteriaceae resistant to ciprofloxacin (C) in fecal samples from piglets treated with placebo (n = 9) and 1.5 mg/kg/day (n = 10) and 15 mg/kg/day (n = 10) of oral ciprofloxacin from day 1 to day 9.

Fig 2

Relationship between individual AUC of fecal concentrations of ciprofloxacin (AUC_CIP) versus AUC of log counts of fecal ciprofloxacin-resistant Enterobacteriaceae (AUC_RES) (A) and versus AUC of percentages of ciprofloxacin-resistant Enterobacteriaceae (AUC_%RES) (B) for 29 piglets in 3 treatment groups. Each symbol represents the AUC_CIP and AUC_RES or AUC_%RES values for one piglet. The black curve among the symbols is the mean curve predicted by the E_max model.