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Antimicrobial Agents and Chemotherapy, Sep 1996, 2147-2151, Vol 40, No. 9
C Darras-Joly, JP Bedos, C Sauve, P Moine, E Vallee, C Carbon and E Azoulay-Dupuis
In vivo synergy with beta-lactam antibiotics and aminoglycosides has been
studied only with penicillin-susceptible Streptococcus pneumoniae strains.
We evaluated the interaction between amoxicillin (AMX) and gentamicin (GEN)
on the basis of in vitro checkerboard and time-kill curves and of findings
in a mouse model of acute bacteremic pneumonia due to a highly
penicillin-resistant and -tolerant S. pneumoniae strain of serotype 19
(penicillin and AMX MICs of 4 micrograms/ml; gentamicin MIC of 16
micrograms/ml). Checkerboard results at 18 h of incubation showed
indifference. With regard to AMX alone, in vitro time-kill curves
demonstrated synergy between AMX (1 microgram/ml) and GEN (16
micrograms/ml) at 5 and 8 h of incubation and for AMX (16 micrograms/ml) in
combination with GEN (16 micrograms/ml) at 3, 5, and 8 h of incubation. In
leukopenic mice, pulmonary killing curves after a single drug injection
demonstrated that AMX (100 mg/kg of body weight) with GEN (16 mg/kg) was
more effective than AMX alone (P = 10(-4). With repeated-dose treatment, a
synergy was apparent at 8 h after four injections with AMX (100 mg/kg) in
combination with GEN (8 or 16 mg/kg) (P < or = 0.05). The cumulative
survival rate with AMX (100 mg/kg) every 8 h, combined with GEN (4 or 8
mg/kg) every 8, 12, or 24 h, was better than with AMX alone. Combined use
of AMX and GEN may be a valuable therapeutic alternative for pneumococcal
pneumonia due to highly penicillin-resistant S. pneumoniae strains.
Copyright © 1996 by the American Society for Microbiology. All rights reserved.
Synergy between amoxicillin and gentamicin in combination against a highly penicillin-resistant and -tolerant strain of Streptococcus pneumoniae in a mouse pneumonia model
Institut National de la Sante et de la Recherche Medicale U 13, Paris, France.
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