The present invention pertains to a lactic acid bacterium belonging to the genus Lactococcus and having a receipt number NITE ABP-01694 with the Patent Microorganisms Depositary (NPMD) of the National Institute of Technology and Evaluation (NITE), a natural immunostimulant having this lactic acid bacterium as an active ingredient, a food or drink containing this lactic acid bacterium or this natural immunostimulant, and yogurt containing lactic acid bacteria, wherein the yogurt has resistance to at least one bacterium selected from the group comprising methicillin-sensitive Staphylococcus aureus, methicillin-resistant Staphylococcus aureus, Pseudomonas aeruginosa, and Enterococcus mundtii.
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