SAFETY CHARACTERISTICS OF LACTIC ACID BACTERIA ISOLATED FROM FEEDLOT TO BE INCLUDED IN A PROBIOTIC PRODUCT

MALDONADO, N.; ARISTIMUÑO FICOSECO, M.; MELIAN, C.; VIGNOLO, G.; NADER-MACIAS, M.E.F

Tucuman

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

CERELA-CONICET

Since 2006, European Union legislation has banned the use of antibiotics as growth promoters in animal husbandry. Antibiotic use may contribute to the emergence of antibiotic resistance bacteria in humans, because genes spreading through food chains may occur. Consequently, the addition of probiotics to diets has gained increasing importance in animal nutrition and health constituting a novel alternative to replace antibiotic growth promoters. As part of the research work, Lactic Acid Bacteria (LAB) were isolated and identified from feedlot environment and their beneficial properties were investigated. In this study, safety characteristics such as antibiotic resistance genes and virulence factors as hyaluronidase, gelatinase and/or hemolysis of LAB strains intended to be used as animal probiotic formula, were evaluated. The antibiotic resistance was examined by phenotypic and genetic assays using the following antimicrobials: Ampicillin, Tetracycline, Chloramphenicol, Gentamicin, Streptomycin, Kanamycin, Vancomycin and Erythromycin. The minimum inhibitory concentration (MIC) was determined by agar dilution method in LSM media. Forty LAB strains were evaluated (27 Lactobacillus, 12 Enterococcus and 2 Pediococcus acidilactici) and the European Food Safety Authority (EFSA) proposed cutoff values, were applied. By PCR using specific primers, the presence of antibiotic 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 and vanX) were evaluated, whereas phenotypic assays in agar solid media with specific substrates were used for virulence factors detection. Results showed different antibiotic susceptibility/resistance patterns displayed by LAB, all of them being sensitive to VAN and AMP while 80.5% of the strains resistant to TET were mostly isolated from animal feces. In addition, resistance to ERY (58%), CLI (38.5%), CHL (12%), STR (10%), KAN (3%) was found for LAB strains. Lactobacillus strains were more susceptible to CLI/ERY/GEN than Enterococcus. MIC values one dilution higher than the cutoff was observed for Lactobacillus and Enterococcus resistance to STR/GEN and GEN/CLI/ERY, respectively. With the exception of VAN genes, the presence of the coding genes for AMP/KAN/CHL/TET/ERY/STR was found. In addition, the majority of the analyzed LAB strains were free of virulence factors. The incidence of antibiotic resistance traits together with virulence factors helped to select LAB strains able to be involved in a probiotic formula for steers in feedlot.