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J Antimicrob Chemother. 2007 Nov;60(5):1045-50. Epub 2007 Sep 4.

Broad-spectrum beta-lactams for treating experimental peritonitis in mice due to Escherichia coli producing plasmid-encoded cephalosporinases.

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Service de Bactériologie-Virologie, Hôpital de Bicêtre, Assistance Publique-Hôpitaux de Paris, Faculté de Médecine de Paris-Sud, 94275 K.-Bicêtre, France.



To investigate the correlation between in vitro activity and in vivo efficacy of broad-spectrum beta-lactams for treating experimental infections due to Escherichia coli expressing two types of plasmid-mediated AmpC-type beta-lactamases, LAT-1 and FOX-1.


Susceptibility testing and time-kill curves were determined for piperacillin/tazobactam, ceftazidime, cefepime and imipenem. A mouse model of peritonitis was developed to determine 50% effective doses (ED(50)s) of beta-lactams against E. coli clinical strains producing recombinant plasmids pLAT-1 and pFOX-1.


MIC and MBC values correlated with the ED(50)s for ceftazidime, cefepime and imipenem. Among the beta-lactams tested, both cefepime and imipenem were effective for treating peritonitis caused by E. coli strains harbouring pLAT-1 or pFOX-1, whereas ceftazidime was effective only against E. coli (pLAT-1). Piperacillin/tazobactam was not effective for treating infections with either of these two strains.


Piperacillin/tazobactam was not efficacious for treating infections due to E. coli producing plasmid-mediated AmpC-type beta-lactamases, whereas cefepime and imipenem were efficacious.

[Indexed for MEDLINE]

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