Escherichia coli O157:H7 isolated from feedlot-ground beef: bactericidal activity of APCECT7121 and synergistic effect with colistin

GARCÍA ALLENDE L; DELPECH G; SPARO M; CECI M

JOURNAL OF VETERINARY PHARMACOLOGY AND THERAPEUTICS

WILEY-BLACKWELL PUBLISHING, INC

Año: 2018 vol. 41 p. 126 - 126

0140-7783

Introduction/Objective: The emergence of multidrug-resistant Escherichia coli strains highlights a need for new therapeutic options. An old antimicrobial, colistin, is frequently indicated for infections caused by multi-drug resistant enterobacteria in animal species that are used for livestock production, such as cattle. Toxic effects of colistin can be potentially reduced using this drug combined with bacteriocins. In Argentina, feedlot systems have acquired a significant relevance as providers of meat products, such as ground beef. E. coli O157:H7 is one of the most important foodborne pathogens, with major implications in meat products industry. AP-CECT7121 is a bacteriocin produced by the probiotic strain Enterococcus faecalis CECT7121. In this study we aimed to investigate its bactericidal activity against E. coli O157:H7 isolated from feedlot-ground beef and the synergistic effect with colistin. Materials and Methods: E. coli O157:H7 (n: 3) were isolated and characterized from feedlot-ground beef sold in markets in Tandil County (Argentina). Minimum Inhibitory Concentration (MIC) for AP-CECT7121 (AP), colistin (C) and their combination against E. coli was assayed (micro-dilution method). In vitro bactericidal activity of AP-CECT7121 alone or combined with colistin (MIC/4), for assessing a synergistic effect, was studied carrying out time-kill curves. Samples were obtained for viable cell counts (0, 4, 8 and 24 h). MIC and time-kill curves were carried out three times. Results were expressed as their average values.Results: E. coli were uniformly resistant to AP-CECT7121 (MICAP > 128 mg l−1); colistin presented anti-E. coli activity in all strains (MICC 0.3 mg l−1). AP-CECT7121 combined with colistin showed bactericidal activity against E. coli (MICAP/C 16/0.02 mg l−1). A synergistic effect was observed at 4?8 and 24 h (−2.4 to −4.5 Δlog10 CFU ml−1). Conclusions: AP-CECT7121 constitutes a candidate as a natural tool in combination with colistin, against E. coli O157:H7. Colistin increases the permeability of the cell membrane, allowing APCECT7121 to have a bactericidal effect against E. coli, which leads to lower MIC and a potential reduction of colistin toxicity, to be further studied.