Soares, Maria Cristina Prudêncio PereiraBrito, Maria Luísa de CastroAmador, Maria Paula Pinto2011-01-252011-01-252010Amador, Maria Paula Pinto - Pesquisa e caracterização molecular de Beta-lactamases em bactérias isoladas de alimentos prontos-a-comer. Lisboa, Instituto Superior de Agronomia, 2010, 271 p.http://hdl.handle.net/10400.5/2856Doutoramento em Engenharia Agro-Industrial - Instituto Superior de AgronomiaThis study aimed to characterize b-lactam resistance genes in bacteria isolated from Ready-to-Eat (RTE) Portuguese food and to investigate in vitro transference of these genes to Escherichia coli. The numbers of ampicillin resistant bacteria from cheese and deli meats varied from < 3 Log CFU/g to 8 Log CFU/g. From 44 and 24 resistant phenotypes from cheese and deli meats, respectively, 31.4 and 35.9 % were multidrug resistant. The majority of the isolates from cheese (85%) and from deli meats (87.2%) belonged to Enterobacteriaceae. The blaTEM gene was detected in 80.9 % and 34.3% of the cheese and meat isolates, respectively. In addition, 6% of the meat isolates (Klebsiella oxytoca) harbour blaOXY-1, blaOXY-2 and blaOXY-5. Forty out of 128 b-lactams resistant bacteria from both types of foods proved to transfer resistance determinants to E. coli. The blaTEM-1 was detected in 85% of donors and transconjugants, while two new TEMs (TEM-179 and TEM-180) were identified. A phylogenetic inference based on TEM aminoacidic sequences showed that these sequences clustered with most of the TEM sequences of worldwide clinical isolates. These results suggest that the consumption of RTE foods, particularly with high levels of Enterobacteriaceae may contribute to the spread of b-lactam resistanceporready-to-eat foodcheesedeli meatsBeta-lactam-resistant enterobacteriaceaetransconjugation assaysphylogenetic analysisdoctoral thesis