Vol.56 No.2 March 2008
In-vitro effect of carbapenem antibiotics on endotoxin release from Pseudomonas aeruginosa
Department of Microbiology and Immunology, Aichi Medical University School of Medicine, 21 Karimata, Yasago, Nagakute, Aichi-gun, Aichi, Japan
Abstract
It is well known that carbapem antibiotic induces a low endotoxin release in the bacteriocidal action. In the present study we compared the endotoxin-releasing activity of imipenem(IPM), doripenem(DRPM) and meropenem(MEPM) against Pseudomonas aeruginosa PAO-1. P. aeruginosa PAO-1 was cultured in endotoxin-free fetal calf serum in the presence of the antibiotic. The endotoxin level was determined by an endotoxin-specific limulus assay. No significant endotoxin release was detected in any of the cultures containing IPM, DRPM, MEPM or ceftazidime(CAZ) at 2 MIC although high endotoxin levels were detected in the culture without any antibiotic. DRPM, MEPM and CAZ at 1/2 MIC induced marked endotoxin release, with the endotoxin level being higher than that in the untreated control. IPM at 1/2 MIC, however, induced much less endotoxin release. The endotoxin release was clearly detected at 8 h after the antibiotic treatment. IPM at 1/2 MIC converted the rod-shaped bacteria into spherical ones, whereas DRPM and MEPM at 1/2 MIC induced the formation of filaments. CAZ also induced long-filament formation in P. aeruginosa. It was suggested that the high endotoxin release induced by DRPM and MEPM at 1/2 MIC was closely associated with the filament formation.
Key word
carbapenem antibiotic, Pseudomonas aeruginosa, endotoxin, filament formation
Received
November 1, 2007
Accepted
November 19, 2007
Jpn. J. Chemother. 56 (2): 206-208, 2008
