Pharmacodynamic effects of amikacin, ciprofloxacin and imipenem on growing and non-growing Escherichia coli and Pseudomonas aeruginosa

ObjectiveTo compare control-related effective regrowth times (CERTs) and postantibiotic effects (PAEs) of amikacin, ciprofloxacin and imipenem on growing and non-growing Escherichia coli and Pseudomonas aeruginosa.MethodsCERTs and PAEs of amikacin, ciprofloxacin and imipenem were determined with bioluminescence assay of bacteriai ATP and viable counts.ResultsNegative viable count PAEs of amikacin and imipenem occurred on growing bacteria, but bioluminescence PAEs were positive. CERTs were equal with both methods. Amikacin and ciprofloxacin induced long, concentration-dependent CERTs on growing and non-growing cultures. Amikacin (32 mg/L) prevented regrowth of E. coli and induced a CERT of 6.0 h on P. aeruginosa; corresponding CERTs on non-growing bacteria were 3.4 h and 3.3 h, respectively. Ciprofloxacin (8 mg/L) prevented regrowth of both strains in growing cultures and induced CERTs of 5.1 h on non-growing E. coli and 13.3 h on P. aeruginosa. Imipenem induced a concentration-dependent CERT on growing bacteria and no CERT on non-growing cultures. Imipenem (16 mg/L) induced a CERT of 5.3 h on growing P. aeruginosa and 3.2 h on E. coli.ConclusionAmikacin and ciprofloxacin induced strong pharmacodynamic effects on growing and non-growing E. coli and P. aeruginosa, while imipenem was only effective on growing cultures