Which of the following is a pathogen that could not be identified by the original koch’s postulates?
staphylococcus aureus
pseudomonas aeruginosa
human immunodeficiency virus
salmonella enterica serovar typhimurium

Human immunodeficiency Virus.

Explanation:

According to Koch postulates the The microorganisms can be grown on pure culture( postulate 2).

But the human immunodeficiency virus cannot be grown on pure culture. Without a suitable not human host a researcher cannot evaluate postulate 2.

Human immunodeficiency virus needs host cell to grow it does not use any other animal as a host cell so this virus does not follows Koch postulates.

is this a psat question, if so do not cheat try your best.