The aim of this study was to identify serologically and analyze the antimicrobial resistance profile of E. coli in foods of animal origin commercialized in Brazil, and its ability to produce extended-spectrum beta-lactamase (ESBL). Isolates from milk, beef, fish, pork and chicken (n=105) collected between 2006 and 2013 were analyzed. The serology of 101/105 isolates were applied by slide agglutination test. The disk diffusion susceptibility test was applied for resistance profile determination. The method of double disk synergy test (DDST) was used to confirm ESBL production. Thirteen percent of strains (13/101) were positive for diarrheagenic E. coli (EPEC, EIEC, EHEC). Multidrug resistance was observed in 48.5% (51/105) of isolates and 70% (74/105) were resistant to one or more antibiotics. The strains showed increased resistance to tetracycline (60/105) and greater sensitivity to amikacin (102/105). Twelve percent (13/105) of strains were positive for ESBL, 92% (12/13) of these coming from chicken.

In DDST, around a central disk of amoxycillin / clavulanic acid (A) cephalosporins discs, such as ceftriaxone (B1), ceftazidime (B2) and cefotaxime (B3) and aztreonam (C), are arranged distant 20 mm of the central disc (D). The result is considered positive for the production of β-lactamase extended spectrum (ESBL) if there is inhibition halo enlargement (E1) or forming an additional area (“ghost area”) (E2) between the central disc and either tested disks. Source: personal archive.

Results and Discussion

Among the analyzed isolates, 18/105 (17%) originated from dairy samples; 7/105 (7%) from beef; 61/105 (58%) from chicken and derivatives, 16/105 (15%) from fish, 1/105 (1%) from pig derived and 2/105 (2%) from mixed sausage collected in 19 cities of the State of Bahia.
Out of 105 isolates, 101 were tested serologically for diarrheagenic E. coli (DEC) identification, of which 13 (13%) were positive. Out of these, 7/13 (54%) were from chicken meat samples, 4/13 (31%) from dairy products, 1/13 (8%) from fish and 1/13 (8%) from mixed sausage . 6/101 (6%) of enteropathogenic E. coli (EPEC), 6/101 (6%) of enteroinvasive E. coli (EIEC) and 1/101 (1%) of enterohemorrhagic E. coli (EHEC) (Table 1) were identified. The EIEC isolates showed a higher frequency of resistance to ampicillin, tetracycline, amoxicillin and sulfazotrim (all with 67% resistance rate, 4/6); the highest frequency of resistance among EPEC isolates were amoxicillin and cefotaxime (both 50%, 3/3), and EHEC isolate was resistant to ampicillin, amoxicillin, chloramphenicol, cephalothin and sulfazotrim. Previous studies on food, animals, human or animal feces in several countries detected lower and higher resistance percentage than the present study, but all of them identified tetracycline and ampicillin as two of antimicrobials with higher resistance index in DEC isolates (Bii et al., 2005, Canizalez-Roman et al., 2013, Adenipekun et al., 2015, Hemmatinezhad et al., 2015, Shah et al. 2015).

We would like to thank MV Ms. Daniela Benevides Melo and the Laboratory of Animal Health of the Agricultural Protection Agency of Bahia for providing the isolates used in this study, and the Clinical Microbiology Laboratory of the Federal University of Bahia for giving control isolates. We also thank Prof. Dra. Lia Fernandes for providing the structure of the Poultry Health Laboratory of the Federal University of Bahia so that part of the analysis could be performed. This work was financially supported by CNPq - National Council for Scientific and Technological Development - Process 456165 / 2014-2.