SCREENING OF ACID LACTIC BACTERIA ISOLATED FROM MEAT WITH INHIBITORY POTENTIAL TOWARDS ENTEROHAEMORRAGIC ESCHERICHIA COLI O157:H7

CISNEROS, L.; VIGNOLO, G.; FADDA, S.

Tucuman

Simposio; V International Symposium on Lactic Acid Bacteria (SIBAL). Benefitting from lactic Acid Bacteria. Progress in Health and Food.; 2016

CERELA-CONICET

Escherichia coli enterohaemorragic (EHEC) is responsible for hemorrhagic colitis and hemolytic uremic syndrome (HUS). In Argentina, the HUS, mainly caused by EHEC, constitutes the most common cause of acute renal failure and kidney transplantation in children and teenagers. EHEC associated disease is due to the pathogen´s ability to produce and release a potent shiga toxin (Stx). Several studies can confirm the role of cattle as the main reservoir of Shiga toxin producing E. coli (STEC ), especially the serotype O157:H7. Therefore, fresh meat is also considered vehicle of this pathogen. The microbiological quality of meat is highly dependent on the initial contamination of carcasses (80 %) and the rest (20 %) is the result of cross-contamination of food in contact with surfaces during processing. Consequently, a great concern about this pathogen, which affects both public health and meat industry, exists in worldwide and to find a sustainable solution to control and/or mitigate EHEC in meat products and processing surfaces is imperative. It is know the ability of some lactic acid bacteria (LAB) to inhibit the growth of certain pathogens. Indeed its use as bioprotective agents is a feasable strategy. In this work the antagonistic effect against E. coli O157: H7 of different LAB strains was evaluated using the spot on lawn method. Fifty seven LAB strains (CERELA) isolated from meat and fermented meat sausages were analyzed. The strains registered the highest EHEC inhibitory activity belonged to Lactobacillus plantarum, L. curvatus, Pediococcus acidilactici, L. acidophilus, L. brevis, L. sakei and L. salivarus. In contrast, the strains that registered low inhibitory potential corresponded to L. paracassei subsp tollerans, L. pentosus, L. fermentum, Lactobacillus sp., Lactococcus lactis subsp lactis, Carnobacterium sp., P. pentosaceus, and Weissela viridescens. In addition it was observed that only fresh cultures or washed cells presented positive inhibitory action, towards EHEC, with variable inhibitory halo sizes depending on the strain. On the contrary, in the spots where the heated or neutralized culture supernatants were seeded no signs of pathogen inhibition was detected. In summary a high proportion of assayed strains produced EHEC inhibition. Moreover, it can be concluded that the presence of intact and viable LAB cells was required to inhibit EHEC. In fact, metabolites such as the lactic acid present in the free cell supernatant were insufficient to inhibit the evaluated E. coli strain. Other assays to expand the selection of LAB with ability to mitigate EHEC are in progress in view to undertake more detailed studies of its action towards EHEC biofilms on processing surfaces (stainless steel).