Question

Among these, Koch’s postulates are not applicable to
A. PolioVirus
B. Treponema pallidum
C. Mycobacterium leprae
D. All of the above

Answer 1

Hint: Viruses are causative agents for many human diseases. Viruses replicate and proliferate in a living host cell using proteins and material of the host cell. Viruses cannot be cultured in laboratories or controlled environmental conditions.

Complete answer: The postulates given by Koch were:
1. The microorganism must be found in the sick-diseased or affected creatures, and not found in a healthy one.
2. The microorganism must be extracted and segregated from the sick creature and in this manner filled in culture.
3. The microorganism must reason sickness when acquainted with a solid trial creature.
4. The microorganism must be separated from the infected trial creature and shown to be a similar microorganism that was initially isolated from the principal unhealthy creature.
According to Koch, only if the above conditions are fulfilled, the microorganism can be accepted as the causative agent. These postulates are not true for viruses, because viruses do not replicate in cell culture and, therefore, viruses as a causative agent cannot be studied using animal models.
Hence, the correct answer is option D.

Additional information: Few human viral diseases are:

Disease	Pathogen
Influenza(Flu)	Myxovirus influenza
Common cold( one of the most infectious human disease)	Rhinovirus
Poliomyelitis(polio/infantile paralysis)	Poliovirus (Enterovirus)
Chikungunya	Chikungunya virus
Dengue fever(Break bone fever)	Arbovirus
Hepatitis B	HBV(DNA virus)

Note: Viruses are ultramicroscopic infectious particles. They contain either DNA or RNA, which is encircled by a protein coat. In some viruses, the protein coat is covered by a protein (virus) and lipid (host) envelope. Viruses are without protoplasm. They multiply within living host cells and are not affected by antibiotics.