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The Scientific World Journal
Volume 2012, Article ID 109795, 4 pages
Research Article

Colistin Resistance in Escherichia coli and Salmonella enterica Strains Isolated from Swine in Brazil

1Laboratório de Sanidade Suína e Virologia, Faculdade de Medicina Veterinária e Zootecnia (FMVZ), Universidade de São Paulo (USP), 05508 270 São Paulo, SP, Brazil
2Instituto de Pesquisas Veterinárias Especializadas-IPEVE, Rua Esmeralda, 786, 304111-191 Belo Horizonte, MG, Brazil
3Laboratório de Enterobactérias, FIOCRUZ, Avenida Brasil, 4365, Pavilhão Rocha Lima, 3°andar, Manguinhos, 21040-360 Rio de Janeiro, RJ, Brazil

Received 8 May 2012; Accepted 22 July 2012

Academic Editors: L. L. Barton and G. C. Ulett

Copyright © 2012 Adriano Savoia Morales et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


Reports about acquired resistance to colistin in different bacteria species are increasing, including E. coli of animal origin, but reports of resistance in wild S. enterica of different serotypes from swine are not found in the literature. Results obtained with one hundred and twenty-six E. coli strains from diseased swine and one hundred and twenty-four S. enterica strains from diseased and carrier swine showed a frequency of 6.3% and 21% of colistin-resistant strains, respectively. When comparing the disk diffusion test with the agar dilution test to evaluate the strains, it was confirmed that the disk diffusion test is not recommended to evaluate colistin resistance as described previously. The colistin MIC 90 and MIC 50 values obtained to E. coli were 0.25 μg/mL and 0.5 μg/mL, the MIC 90 and MIC 50 to S. enterica were 1 μg/mL and 8 μg/mL. Considering the importance of colistin in control of nosocomial human infections with Gram-negative multiresistant bacteria, and the large use of this drug in animal production, the colistin resistance prevalence in enterobacteriaceae of animal origin must be monitored more closely.