Evaluation of the antimicrobial activity of bacteriocins produced by regional yersinia strains

PASCUAL LOURDES INÉS; ESCUDERO MARÍA ESTHER; IRIARTE HEBE JORGELINA; MATTAR DOMINGUEZ MARÍA AIDA; FAVIER GABRIELA ISABEL

Congreso; Congreso Conjunto SAIB-SAMIGE 2021; 2021

Bacteriocins are extracellular peptides of ribosomal origin and encoded at the plasmid level. Pathogenic Yersinia enterocolitica strains belonging to biotypes (B) 1 to 5 are cause of gastrointestinal symptoms and immunological sequelae in humans by consumption of contaminated foods. Y. frederiksenii, Y. intermedia and strains of Y. enterocolitica B1A do not carry the virulence markers that characterize pathogenic Y. enterocolitica strains; however, they may produce bacteriocins that inhibit the growth or destroy these pathogenic strains. To contribute to food safety and the human health, the use of bacteria as biocontrol agents in food has been proposed since they offer safe advantages to the consumer. The aim of this study was to evaluate the antimicrobial activity of bacteriocins produced by Yersinia strains on pathogenic Y. enterocolitica strains isolated from various foods in our region by the plate titration method. Two Y. intermedia B1 (named 79 and 26), one Y. intermedia B6 (10) and three Y. enterocolitica B1A (66, 89, 90) were tested as bacteriocin-producing strains (BPS), and three Y. enterocolitica strains belonging to B2, B3 and B4 were used as indicator strains (IS) of the antimicrobial effect. The spot technique was performed on a double layer agar. BPS and IS were cultured in Luria Bertani broth (LB) with shaking at 25°C for 18 h, and inocula were adjusted to a concentration corresponding to an ODʎ610 0.2. From BPS, two-fold dilutions were made in LB, and 10 μl of each one was placed on Petri plates with semisolid agar previously inoculated with IS. Plates were incubated at 25°C and at 10°C for 18 h. The reciprocal of the highest dilution of BPS that produced total inhibition of IS was considered as the titer and expressed in arbitrary units per ml (AU ml -1). Results represent the average of three different experiments. At 25°C, the highest inhibition titers were observed for Y. enterocolitica B1A (90) on Y. enterocolitica B2 and B4, with values ​​of 12,800 + 0 AU ml-1 and 10,667 + 3,695 AU ml-1 (p > 0.05), respectively. At 10 ° C, the highest inhibition titers were showed by Y. intermedia B1 (79) on Y. enterocolitica B2 and B4, with values of 9,262 + 3,695 AU ml-1 and 6,400 + 0 AU ml-1 (p > 0.05), respectively. All BPS showed lower titers on Y. enterocolitica B3 than on Y. enterocolitica B2 and B4 (p < 0.05) at both temperatures. When comparing the two temperatures, most of titles produced by BPS were higher at 25°C than at 10°C (p < 0.05). Results obtained in this study demonstrate the capacity of regional Y. intermedia and Y. enterocolitica B1A strains to produce significant amounts of bacteriocins with inhibitory effect on pathogenic Y. enterocolitica strains, and highlight the great potential of these substances as antagonists of pathogenic or spoilage bacteria in food, even at refrigeration temperatures.