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Antimicrobial Agents and Chemotherapy, June 1999, p. 1406-1411, Vol. 43, No. 6
Clinique de Réanimation des Maladies
Infectieuses,
Received 28 September 1998/Returned for modification 3 February
1999/Accepted 7 April 1999
The effects of various regimens containing combinations of
0066-4804/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
In Vivo Efficacies of Combinations of
-Lactams,
-Lactamase Inhibitors, and Rifampin against Acinetobacter
baumannii in a Mouse Pneumonia Model
-lactams,
-lactam inhibitor(s), and rifampin were assessed in a
recently described mouse model of Acinetobacter baumannii
pneumonia (M. L. Joly-Guillou, M. Wolff, J. J. Pocidalo, F. Walker, and C. Carbon, Antimicrob. Agents Chemother. 41:345-351,
1997). Two aspects of the therapeutic response were studied: the
kinetics of the bactericidal effect (treatment was initiated 3 h
after intratracheal inoculation, and bacterial counts were determined over a 24-h period) and survival (treatment was initiated 8 h after inoculation, and the cumulative mortality rate was assessed on
day 5). Two clinical strains were used: a cephalosporinase-producing strain (SAN-94040) and a multiresistant strain (RCH-69). For SAN-94040 and RCH-69, MICs and MBCs (milligrams per liter) were as follows: ticarcillin, 32, 64, 256, and >256, respectively;
ticarcillin-clavulanate, 32, 64, and 512, and >512, respectively;
imipenem, 0.5, 0.5, 8, and 32, respectively; sulbactam, 0.5, 0.5, 8, and 8, respectively; and rifampin, 8, 8, 4, and 4, respectively.
Against SAN-94040, four regimens, i.e., imipenem, sulbactam,
imipenem-rifampin, and ticarcillin-clavulanate (at a 25/1
ratio)-sulbactam produced a true bactericidal effect
(
3-log10 reduction of CFU/g of lung). The best survival
rate (i.e., 93%) was obtained with the combination of
ticarcillin-clavulanate-sulbactam, and regimens containing rifampin
provided a survival rate of
65%. Against RCH-69, only regimens
containing rifampin and the combination of imipenem-sulbactam had a
true bactericidal effect. The best survival rates (
80%) were
obtained with regimens containing rifampin and sulbactam. These results
suggest that nonclassical combinations of
-lactams,
-lactamase
inhibitors, and rifampin should be considered for the treatment of
nosocomial pneumonia due to A. baumannii.
*
Corresponding author. Mailing address: Service de
Microbiologie, Hôpital Louis Mourier, 178 rue des Renouillers,
92701 Colombes, France. Phone: 33 1 47 60 60 13. Fax: 33 1 47 60 60 48. E-mail: marie-laure.joly-guillou{at}lmr.ap-hop-paris.fr.
Antimicrobial Agents and Chemotherapy, June 1999, p. 1406-1411, Vol. 43, No. 6
0066-4804/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
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