CENTRO DE REFERENCIA PARA LACTOBACILOS
Unidad Ejecutora - UE
Inhibition of Staphylococcus aureus by H202-producing Lactobacillus gasseri isolated from the vaginal tract of catle.
MARIA CLAUDIA OTERO,; MARIA ELENA NADER-MACIAS
ANIMAL REPRODUCTION SCIENCE
Lugar: Amsterdam; Año: 2006 vol. 96 p. 35 - 35
Staphylococcus aureus is one of the pathogens associated with infectious diseases in postpartum cows. Antibiotics are usually applied to treat these infections of udder and uterus. The disadvantages of this therapy are presence of residues in foods, development of bacterial resistance, increase of production costs and alteration of defence mechanisms in the host. Probiotic products could help to decrease the application of antibiotics in these situations. Lactobacillus is one of the genera present in the bovine vaginal tract. They can prevent the pathogen colonization by different mechanisms such as production of antagonistic substances, for example lactic acid, H2O2 and bacteriocins. The present paper describes the selection of H2O2 generating lactobacilli among 72 strains isolated from the bovine vagina. Lactobacillus gasseri CRL 1421 and Lactobacillus gasseri CRL 1412, which share some probiotic properties, produce H2O2 detected by the plate colorimetric method. They were chosen to study the kinetics of H2O2 production evaluating different culture conditions. Both microorganisms produced higher levels of H2O2 in aerated cultures than in static cultures. As L. gasseri CRL 1421 showed higher capacity to generate H2O2, associative cultures with this strain and S. aureus were performed. A significant decrease in the pathogens growth was detected from 6 hours culture, being higher in aerated conditions. The addition of catalase to the mixed cultures abolished partially the inhibition, being this effect attributed to the combined action of H2O2 and other antagonistic metabolites. The simultaneous addition of catalase and NaOH restored the S. aureus growth obtained in control cultures. This observation induces to suppose that the inhibition is produced by the combination of hydrogen peroxide and lactic acid liberated from Lactobacillus. Electronic microphotographies showed the damage produced by the lactobacilli supernatant on the pathogen cells. The treatment of S. aureus with lactic acid and hydrogen peroxide showed that each metabolite produced a different type of morphological damage. The number of viable cells obtained is coincident with the microphotographys observations. L. gasseri CRL 1421 could be included in a probiotic product to prevent S. aureus infections, either acute metritis or mastitis.