Vol.53 No.1 January 2005
Initial bactericidal activity of β -lactam antibiotics against Pseudomonas aeruginosa
1)Clinical Development Institute, Banyu Pharmaceutical CO., Ltd., Okachi-Kayabacho Building, 1-3-12 Nihonbashi-Kayabacho, Chuo-ku, Tokyo, Japan
2)Department of Microbiology, Kitasato University School of Medicine
Abstract
Initial bactericidal activity was defined as log10 of bacteria killed in 1 hour of exposure to antibiotics. Initial bactericidal activity of carbapenems depended on substrate concentration, whereas the initial bactericidal activity of ceftazidime (a cephem antibiotics) did not depend on concentration within tested concentrations (0.5 μ M to 80 μ M). Initial bactericidal activity of 4 carbapenems (imipenem, meropenem, panipenem, and biapenem) and 3 cephem antibiotics (ceftazidime, cefepime, and cefpirome) against Pseudomonas aeruginosa PAO1 was measured at 20 μ M of each antibiotic. Carbapenems other than meropenem showed above 2 log reduction in viable count in 1 hour, but cephem antibiotics and meropenem showed under 0.5 log reduction in viable counts in 1 hour. Imipenem showed exceptional initial bactericidal activity. Initial bactericidal activity of carbapenem and cephem antibiotics was assessed using 47 strains of P. aeruginosa clinical isolates. The rate of P. aeruginosa clinical isolates showing≥ 2 log10 reduction in viable counts per hour was 68.0% for imipenem, 53.2% for panipenem, 36.2% for biapenem, 31.9% for meropenem, 23.4% for cefepime, 19.1% for cefpirome, and 0% for ceftazidime. The geometric MIC mean for 47 strains of P. aeruginosa was 0.612 μ g/mL for meropenem, 1.02 μ g/mL for biapenem, 1.67 μ g/mL for imipenem, 3.61 μ g/mL for cefepime, 4.12 μ g/mL for ceftazidime, and 5.87 μ g/mL for panipenem. Initial bactericidal activity did not correlate with MIC. This study thus requires further study of the relationship between initial bactericidal activity and clinical efficacy.
Key word
Initial bactericidal activity, Pseudomonas aeruginosa, carbapenem, cephem antibiotic
Received
October 7, 2004
Accepted
November 24, 2004
Jpn. J. Chemother. 53 (1): 1-4, 2005
