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.
abstract: 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 74·1% 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.
authors: Centre of Studies of Animal and Veterinary Sciences, Vila Real, Portugal.
authors: N
authors: N
authors: Silva
authors: L
authors: L
authors: Costa
authors: A
authors: A
authors: Gonçalves
authors: M
authors: M
authors: Sousa
authors: H
authors: H
authors: Radhouani
authors: F
authors: F
authors: Brito
authors: G
authors: G
authors: Igrejas
authors: P
authors: P
authors: Poeta
mesh_terms: D000818:Animals; D002645:Chickens; D004926:Escherichia coli / Q000145:classification / Q000187:drug effects / Q000201:enzymology / Q000235:genetics*; D004927:Escherichia coli Infections / Q000453:epidemiology / Q000382:microbiology / Q000662:veterinary*; D029968:Escherichia coli Proteins / Q000235:genetics* / Q000378:metabolism; D008460:Meat / Q000382:microbiology*; D016133:Polymerase Chain Reaction / Q000662:veterinary; D011174:Portugal / Q000453:epidemiology; D011201:Poultry Diseases / Q000453:epidemiology / Q000382:microbiology*; D012307:Risk Factors; D017422:Sequence Analysis, DNA / Q000662:veterinary; D018440:beta-Lactam Resistance; D001618:beta-Lactamases / Q000235:genetics* / Q000378:metabolism; D047090:beta-Lactams / Q000494:pharmacology*
chemical_list: D029968:Escherichia coli Proteins; D047090:beta-Lactams; C412613:CTX-M-9 protein, E coli; D001618:beta-Lactamases