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Antimicrobial Agents and Chemotherapy, April 2000, p. 885-890, Vol. 44, No. 4
Service
d'Anesthésie-Réanimation, Hôpital Paul Brousse,
Assistance Publique-Hôpitaux de Paris, Faculté de
Médecine de Paris-Sud, 94804 Villejuif
Cédex,1 Service de
Bactériologie-Virologie, Hôpital de Bicêtre,
Assistance Publique-Hôpitaux de Paris, Faculté de
Médecine de Paris-Sud, 94275 Le Kremlin-Bicêtre
Cédex,2 and Crépit 93 Centre de Recherche en Pathologie Infectieuse et Tropicale,
Faculté de Médecine de Paris-Nord, 93009 Bobigny
Cédex,3 France
Received 3 May 1999/Returned for modification 5 October
1999/Accepted 10 January 2000
The antibacterial activities of imipenem-cilastatin,
meropenem-cilastatin, cefepime and ceftazidime against
Enterobacter cloacae NOR-1, which produces the
carbapenem-hydrolyzing
0066-4804/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.
Efficacies of Imipenem, Meropenem, Cefepime, and Ceftazidime in
Rats with Experimental Pneumonia Due to a Carbapenem-Hydrolyzing
-Lactamase-Producing Strain of Enterobacter
cloacae
-lactamase NmcA and a
cephalosporinase, and against one of its in vitro-obtained ceftazidime-resistant mutant were compared by using an experimental model of pneumonia with immunocompetent rats. The MICs of the
-lactams with an inoculum of 5 log10 CFU/ml were as
follows for E. cloacae NOR-1 and its ceftazidime-resistant
mutant, respectively: imipenem, 16 and 128 µg/ml,
meropenem, 4 and 32 µg/ml, cefepime, <0.03 and 1 µg/ml,
and ceftazidime, 1 and 512 µg/ml. The chromosomally located
cephalosporinase and carbapenem-hydrolyzing
-lactamase NmcA were inducible by cefoxitin and meropenem in
E. cloacae NOR-1, and both were stably overproduced in the
ceftazidime-resistant mutant. Renal impairment was induced (uranyl
nitrate, 1 mg/kg of body weight) in rats to simulate the human
pharmacokinetic parameters for the
-lactams studied. Animals were
intratracheally inoculated with 8.5 log10 CFU of E. cloacae, and therapy was initiated 3 h later. At that time,
animal lungs showed bilateral pneumonia containing more than 6 log10 CFU of E. cloacae per g of tissue. Despite the relative low MIC of meropenem for E. cloacae NOR-1, the carbapenem-treated rats had no decrease in
bacterial counts in their lungs 60 h after therapy onset compared
to the counts for the controls, regardless of whether E. cloacae NOR-1 or its ceftazidime-resistant mutant was inoculated.
A significant decrease in bacterial titers was observed for the
ceftazidime-treated rats infected with E. cloacae NOR-1
only. Cefepime was the only
-lactam tested effective as treatment
against infections due to E. cloacae NOR-1 or its
ceftazidime-resistant mutant.
*
Corresponding author. Mailing address: Service
d'Anesthésie-Réanimation, Hôpital Paul
Brousse, 12, ave. Paul Vaillant-Couturier, 94804 Villejuif Cédex,
France. Phone: 33 1 45 59 32 19. Fax: 33 1 45 59 38 34. E-mail:
olivier.mimoz{at}pbr.ap-hop-paris.fr.
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