PURPOSE: To obtain an infection-protecting agent containing a specific microorganism or its bacterial cell as an active ingredient. CONSTITUTION: This protecting agent contains a microorganism belonging to Lactobacillus acidophilus complex and having affinity for asialo GM1 or its bacterial cell as an active ingredient. A protein having activity to protect infection from a pathogen is capable of extracting from the bacterial cell of the microorganism using an alkali salt aqueous solution or a surfactant and has affinity for the asialo GM1 and has activity to protect infection from pathogen. The pathogen is a microorganism having affinity for asialo GM1 and belonging to enteropathogenic Escherichia coli, Pseudomonas aeruginos, Pseudomonas cepacia, Campyrobacter or Rota virus or Polio virus. The active ingredient is used in a large amount in foods, etc., as lactobacillus and has extremely high safety.