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

Answer: 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.