Safety characteristics of Lactic Acid Bacteria isolated from feedlot to be included in a probiotic product

MALDONADO NATALIA CECILIA; ARISTIMUÑO FICOSECO MARIA CECILIA; MELIAN CONSTANZA; MANSILLA FLAVIA; GRACIELA VIGNOLO; FÁTIMA NADER-MACIAS, MARÍA E.

San Muguel de Tucumán

Simposio; V International Symposium of Lactic Acid Bacteria; 2016

Since 2006,European Unionlegislation has banned the use of antibiotics as growth promotersin animal husbandry. Antibiotic use may contribute to the emergence ofantibioticresistance bacteria in humans, because genesspreading through foodchains may occur. Consequently, the addition of probioticsto diets has gainedincreasing importance in animal nutrition and health constituting a novelalternative to replace antibiotic growth promoters.As part of the researchwork, Lactic Acid Bacteria (LAB) were isolated and identified from feedlotenvironment and their beneficial properties were investigated. In this study,safety characteristics such as antibiotic resistance genes and virulencefactors as hyaluronidase, gelatinase and/orhemolysis of LAB strains intended tobe used as animal probiotic formula,were evaluated. The antibiotic resistancewas examined by phenotypic and genetic assays using the followingantimicrobials: Ampicillin, Tetracycline, Chloramphenicol, Gentamicin,Streptomycin, Kanamycin, Vancomycinand Erythromycin. The minimum inhibitoryconcentration (MIC) was determined by agar dilution method in LSM media. FortyLAB strains wereevaluated(27 Lactobacillus, 11Enterococcusand2Pediococcusacidilactici) and the European Food Safety Authority (EFSA) proposedcutoff valueswere applied. By PCRusing specific primers, the presence ofantibiotic resistance genes (bla,cat,erm(B),erm(C),aac(6´)-aph(2´´),aph(3´´)-III,strA,strB,aadA,aadE,ant(6),tet(M),tet(K),tet(L),tet(S),vanA,vanB andvanX)were evaluated, whereas phenotypic assays in agar solid media withspecific substrates were used for virulence factors detection.Results showeddifferent antibiotic susceptibility/resistance patternsdisplayed by LAB, all ofthem beingsensitive to VANand AMP, while80.5% of the strainsresistant toTETwere mostlyisolated from animal feces.In addition, resistance toERY (58%),CLI(38.5%), CHL (12%), STR (10%) andKAN(3%)was detected inLABstrains.Lactobacillusweremore susceptible to CLI/ERY/GEN than Enterococcus.MICvalues one dilution higher than the cutoffwere observed forLactobacillusandEnterococcusresistance to STR/GEN and GEN/CLI/ERY, respectively.With theexception of VAN genes, the presence of coding genes forAMP/KAN/CHL/TET/ERY/STRwas found. In addition, all of the assayed LAB strainswere free of virulence factors. The incidence of antibioticresistance traitstogether with the lack of virulence factors helped to select LAB strains to beincluded in the design of a probiotic formula for steers in feedlot.