Use of <i>Lactococcus lactis</i> Subsp. <i>Lactis</i> Strains to Inhibit the Development of Pathogens

Abstract

Bovine mastitis affects the udder health and thus causing significant economic losses. Probiotic products based on the use of lactic acid bacteria (LAB) to limit pathogens multiplication and pre-infection risks can be an interesting alternative to post infection allopathic treatment with antibiotics. <i> Lactococcus lactis</i> is one of the most important bacteria used in dairy technology. In this work, a total of 21 <i> Lactococcus lactis subsp. Lactis</i> strains , 20 from goat milk whey and one strain from cow milk were used to evaluate their antibacterial activity against four pathogenic germs responsible for mastitis: <i> Escherichia coli , Staphylococcus aureus , S treptococcus uberis</i> and <i> S treptococcus agalactiae</i> . The nisin-producing cow milk strain was active against <i> St . uberis</i> and <i> Str . Agalactiae</i> using the well diffusion method. For the strains isolated from goat milk whey, no antimicrobial effect was observed against these pathogens. However, a different approach based on the growth of pathogenic bacteria interacting with the <i> Lactococcus lactis</i> strains in a minimum medium was used to study the barrier effect of LAB. The <i> Lactococcus lactis</i> strains S1 and S2 from goat milk whey depleted the growth of <i> Sa . aureus , St . uberis</i> and <i> E . coli</i> during 8 h and stopped the development of <i> St . agalactiae</i> .