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BioMed Research International
Volume 2015, Article ID 618752, 8 pages
Research Article

Comparison of Antibiotic Resistance and Virulence Factors among Escherichia coli Isolated from Conventional and Free-Range Poultry

1Department of Microbiology, Laboratory of Basic and Applied Bacteriology, State University of Londrina (UEL), Rodovia Celso Garcia Cid, Caixa Postal 6001, 86051-980 Londrina, PR, Brazil
2Department of Pathology and Clinical and Toxicological Analysis, State University of Londrina (UEL), Avenida Robert Koch, No. 60, Vila Operária, 86038-350 Londrina, PR, Brazil
3Department of Zootechnia, State University of Londrina (UEL), Rodovia Celso Garcia Cid, Caixa Postal 6001, 86051-980 Londrina, PR, Brazil
4Laboratory of Bird Health, Fepagro Animal Health, Veterinary Research Institute Desidério Finamor (IPVDF), Estrada do Conde, No. 6000, 92990-000 Eldorado do Sul, RS, Brazil

Received 1 April 2015; Revised 28 September 2015; Accepted 30 September 2015

Academic Editor: Miguel Prieto

Copyright © 2015 Vanessa L. Koga 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.


Microbiological contamination in commercial poultry production has caused concerns for human health because of both the presence of pathogenic microorganisms and the increase in antimicrobial resistance in bacterial strains that can cause treatment failure of human infections. The aim of our study was to analyze the profile of antimicrobial resistance and virulence factors of E. coli isolates from chicken carcasses obtained from different farming systems (conventional and free-range poultry). A total of 156 E. coli strains were isolated and characterized for genes encoding virulence factors described in extraintestinal pathogenic E. coli (ExPEC). Antimicrobial susceptibility testing was performed for 15 antimicrobials, and strains were confirmed as extended spectrum of β-lactamases- (ESBLs-) producing E. coli by phenotypic and genotypic tests. The results indicated that strains from free-range poultry have fewer virulence factors than strains from conventional poultry. Strains from conventionally raised chickens had a higher frequency of antimicrobial resistance for all antibiotics tested and also exhibited genes encoding ESBL and AmpC, unlike free-range poultry isolates, which did not. Group 2 CTX-M and CIT were the most prevalent ESBL and AmpC genes, respectively. The farming systems of poultries can be related with the frequency of virulence factors and resistance to antimicrobials in bacteria.