Is Nosocomial infection a food infection?

It could be but usually is not. Nosocomial simply means that the infection [caused by any type of pathogen, including food-borne germs] was acquired in a health care setting, such as a hospital, lab, surgical center, doctor's office or clinic, etc. It could be viral, bacterial, fungal, parasitic or any type of infection as long as it was "caught" in a health care location. Food-borne infections are very rare in the closely controlled kitchens of hospitals, but not unheard of.