@article {18414,
	title = {Genetic characterisation of extended-spectrum β-lactamases in Escherichia coli isolated from retail chicken products including CTX-M-9 containing isolates: a food safety risk factor},
	journal = {British Poultry Science},
	volume = {53},
	year = {2012},
	month = {2012-11-07 00:00:00},
	pages = {747-755},
	publisher = {British Poultry Science},
	abstract = {<div>
<p>1. Bacterial resistance to β-lactam antibiotics has risen dramatically in Escherichia coli from food animals. In a previous study, 29 randomly selected chicken products, collected in Portugal, were analysed for the presence of extended-spectrum β-lactamases (ESBLs)-producing E. coli; and during this study the genetic characterisation of ESBLs genes was investigated. 2. The presence of genes encoding TEM, OXA, SHV, and CTX-M type beta-lactamases was studied by PCR followed by sequencing. Additionally, other mechanisms of antimicrobial resistance, phylogenetic groups and the presence of virulence determinants were evaluated among the isolates. 3. β-lactamases genes were identified as follows: bla (CTX-M-14) (n = 4), bla (CTX-M-1) (n = 2), bla (CTX-M-9) (n = 4) and bla (TEM-52) (n = 13). Mutations at positions -42, -18, -1, and +58 of ampC promoter region were identified in 4 non-ESBL-producing isolates. The tet(A) or tet(B) genes were identified in all tetracycline-resistant isolates; the aadA gene detected in 8 of 10 streptomycin-resistant isolates; the aac(3)-II gene in all gentamicin-resistant isolates; the cmlA gene in the chloramphenicol-resistant isolate; and sul1 and/or sul2 and/or sul3 genes were found in all trimethoprim-sulfamethoxazole-resistant isolates. The intI1 gene was detected in 8 trimethoprim-sulfamethoxazole-resistant isolates and the intI2 gene in 4 isolates; one gene cassette arrangements were identified among class 1 integrons (dfrA1 + aadA1) and among the class 2 integrons (dfrA1 + sat2 + aadA1). Among cefotaxime-resistant isolates, 16 belonged to A or B1 phylogenetic groups, while 11 isolates were classified into the D or B2 phylogroups. At least one virulence-associated gene (aer, fimA, or papC) was detected in 74{\textperiodcentered}1\% of the cefotaxime-resistant isolates. 4. Because ESBLs-producing bacteria are resistant to a broad range of β-lactams, infections caused by these organisms complicate therapy and limit treatment options.</p>
</div>},
	keywords = {E. coli, ESBL},
	doi = {10.1080/00071668.2012.740554.},
	url = {http://www.tandfonline.com/doi/abs/10.1080/00071668.2012.740554?url_ver=Z39.88-2003\&rfr_id=ori\%3Arid\%3Acrossref.org\&rfr_dat=cr_pub\%3Dpubmed\&},
	author = {Silva, N. and Costa, L. and Gon{\c c}alves, A. and Sousa, M. and Radhouani, H. and Brito, F. and Igrejas, G. and Poeta, P.}
}
