As a metabolite of aflatoxin (AF) B1, AFM1 is a potential granulotoxin, and in AFB1-exposed cows the metabolite appears everywhere, especially in milk. Neutrophils are pivotal for defense against mastitis; they have enormous potentials to finally eliminate engulfed pathogens. We have recently observed the antagonistic properties of a Lactobacillus (L.) fermentum, isolated from milk of healthy dairy cows, against Staphylococcus aureus (S. aureus). To investigate the effect of AFM1 on neutrophils killing activity against S. aureus, and to determine whether L. fermentum reverses the diminished effects of the AFM1 on neutrophils, healthy dairy cows were used as a source of neutrophils. The isolated blood neutrophils were exposed with: 1) only 25 ng/ml of AFM1 2) AFM1 plus overnight grown L. fermentum 3) only overnight grown L. fermentum and 4) none of them for 3 hours; their capacity to kill was then monitored by a bactericidal assay, accordingly, using in vitro challenge of S. aureus with above mentioned neutrophil groups for 1 h and then cfu counting of the S. aureus. Results from the bactericidal assay were expressed and compared as the percentage of killed S. aureus. The killing of S. aureus by AFM1-treated neutrophils was markedly minimal and improved significantly with application of the L. fermentum. Observed improved phagocytic activity of neutrophils sheds fresh light on the application of this lactobacillus as a good probiotic to prevent infection in immunocompromised periparturient dairy cows.

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