Evaluation of Mutant Prevention Concentrations of Cephalosporin antibiotics for fecal Escherichia coli isolated in Keffi, Nigeria

Mutant Prevention Concentration (MPC) concept provides in vitro justification of a dosing regimen of antimicrobial agent that can prevent the emergence of least susceptible resistant mutant. This study evaluates the MPC of cephalexin, cefuroxime, ceftazidime and cefepime under two different temperature conditions for E. coli isolated from stool of patients. The study also investigates effect of temperature on the selection of resistance mutants. A total of fifty (50) isolates of E. coli was isolated and identified by standard procedure from stool of patients attending Nasarawa State University Health Centre Keffi, Nigeria. MPCs and mutant recovery were determined at 37°C and 41°C by standard methods. MPC at both 37°C and 41°C were the same for each of the drugs. MPCs for 50% of the isolates (MPC50) were: cephalexin (421.4 µg/ml[6.2 x MIC]), cefuroxime (209.0 µg/ml[3.3 x MIC]), ceftazidime (81.0 µg/ml[2.2 x MIC]) and cefepime (30.6 µg/ml[1.4 x MIC]); MPC for 90% of the isolates (MPC90) were: cephalexin (471.8 µg/ml[3.9 x MIC]), cefuroxime (465.0 µg/ml[3.8 x MIC]), ceftazidime (454.8 µg/ml[4 x MIC]) and cefepime (438.4 µg/ml[7.2 x MIC]). The MPC50/MIC50 ratios at both 37°C and 41°C were in the order: cephalexin>cefuroxime>ceftazidime>cefepime; but MPC90/MIC90 ratios were in the reverse order.