Awoman had life-threatening salmonellosis that was successfully treated with anti-salmonella. why did this treatment work, when antibiotics and her own immune system failed?

Because anti-salmonella the woman's immune system to recognize the pathogen (salmonella) and kills it.

Explanation:

Anti-salmonella is a serum containing inactive salmonella serotypes. They are effective in cases of salmonella infection where antibiotic use did not work and the patient's immune system was unable to recognize the pathogen and kill it. Anti-salmonella serum allows the patient's immune system to adapt, recognize the pathogen and get it expelled from the patient's body.