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Applied and Environmental Microbiology, August 2007, p. 4785-4790, Vol. 73, No. 15
0099-2240/07/$08.00+0     doi:10.1128/AEM.00252-07
Copyright © 2007, American Society for Microbiology. All Rights Reserved.

Impact of Three Ampicillin Dosage Regimens on Selection of Ampicillin Resistance in Enterobacteriaceae and Excretion of blaTEM Genes in Swine Feces{triangledown}

D. Bibbal,1 V. Dupouy,1 J. P. Ferré,1 P. L. Toutain,1 O. Fayet,2 M. F. Prère,2 and A. Bousquet-Mélou1*

UMR181 Physiopathologie et Toxicologie Expérimentales, INRA, ENVT, Ecole Nationale Vétérinaire de Toulouse, 23 Chemin des Capelles, BP 87 614, 31076 Toulouse Cedex 3, France,1 UMR5100 Microbiologie et Génétique Moléculaires, CNRS, UPS, Laboratoire de Microbiologie et Génétique Moléculaires, Université Paul Sabatier, 118 Route de Narbonne, 31062 Toulouse Cedex 9, France2

Received 31 January 2007/ Accepted 3 June 2007

The aim of this study was to assess the impact of three ampicillin dosage regimens on ampicillin resistance among Enterobacteriaceae recovered from swine feces by use of phenotypic and genotypic approaches. Phenotypically, ampicillin resistance was determined from the percentage of resistant Enterobacteriaceae and MICs of Escherichia coli isolates. The pool of ampicillin resistance genes was also monitored by quantification of blaTEM genes, which code for the most frequently produced ß-lactamases in gram-negative bacteria, using a newly developed real-time PCR assay. Ampicillin was administered intramuscularly and orally to fed or fasted pigs for 7 days at 20 mg/kg of body weight. The average percentage of resistant Enterobacteriaceae before treatment was between 2.5% and 12%, and blaTEM gene quantities were below 107 copies/g of feces. By days 4 and 7, the percentage of resistant Enterobacteriaceae exceeded 50% in all treated groups, with some highly resistant strains (MIC of >256 µg/ml). In the control group, blaTEM gene quantities fluctuated between 104 and 106 copies/g of feces, whereas they fluctuated between 106 to 108 and 107 to 109 copies/g of feces for the intramuscular and oral routes, respectively. Whereas phenotypic evaluations did not discriminate among the three ampicillin dosage regimens, blaTEM gene quantification was able to differentiate between the effects of two routes of ampicillin administration. Our results suggest that fecal blaTEM gene quantification provides a sensitive tool to evaluate the impact of ampicillin administration on the selection of ampicillin resistance in the digestive microflora and its dissemination in the environment.

* Corresponding author. Mailing address: UMR181 Physiopathologie et Toxicologie Expérimentales, INRA, ENVT, Ecole Nationale Vétérinaire de Toulouse, 23 Chemin des Capelles, BP 87 614, 31076 Toulouse Cedex 3, France. Phone: 33 (0) 561 193 925. Fax: 33 (0) 561 193 917. E-mail: a.bousquet-melou{at}envt.fr

{triangledown} Published ahead of print on 8 June 2007.

Applied and Environmental Microbiology, August 2007, p. 4785-4790, Vol. 73, No. 15
0099-2240/07/$08.00+0     doi:10.1128/AEM.00252-07
Copyright © 2007, American Society for Microbiology. All Rights Reserved.



This article has been cited by other articles:

  • Alexander, T. W., Reuter, T., Sharma, R., Yanke, L. J., Topp, E., McAllister, T. A. (2009). Longitudinal Characterization of Resistant Escherichia coli in Fecal Deposits from Cattle Fed Subtherapeutic Levels of Antimicrobials. Appl. Environ. Microbiol. 75: 7125-7134 [Abstract] [Full Text]  
  • Bibbal, D., Dupouy, V., Prere, M. F., Toutain, P. L., Bousquet-Melou, A. (2009). Relatedness of Escherichia coli Strains with Different Susceptibility Phenotypes Isolated from Swine Feces during Ampicillin Treatment. Appl. Environ. Microbiol. 75: 2999-3006 [Abstract] [Full Text]  


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