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Impact of three ampicillin dosage regimens on selection of ampicillin resistance in Enterobacteriaceae and excretion of blaTEM genes in swine feces

Bibbal, Delphine and Dupouy, Véronique and Ferré, JP and Toutain, Pierre-Louis and Fayet, O and Prère, MF and Bousquet-Mélou, Alain Impact of three ampicillin dosage regimens on selection of ampicillin resistance in Enterobacteriaceae and excretion of blaTEM genes in swine feces. (2007) Applied and Environmental Microbiology, vol. 7 (n° 15). pp. 4785-4790. ISSN 0099-2240

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Official URL: http://dx.doi.org/10.1128/AEM.00252-07

Abstract

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

Item Type:Article
Additional Information:Thanks to The American Society for Microbiology editor. The definitive version of the article is available at http://aem.asm.org/cgi/content/abstract/73/15/4785
Audience (journal):International peer-reviewed journal
Uncontrolled Keywords:
Institution:French research institutions > Institut National de la Recherche Agronomique - INRA
Université de Toulouse > Université Paul Sabatier-Toulouse III - UPS
Université de Toulouse > Ecole Nationale Vétérinaire de Toulouse - ENVT
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Deposited By:Delphine BIBBAL

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