All are true about Koch’s postulates except:

(Refer: Anantha Narayanan and Paniker’s Textbook of Microbiology, 9th edition, pg no: 4) Koch's postulates A microorganism to be accepted as the causative agent of an infectious disease has to satisfy the following conditions: The bacterium should be constantly associated with the lesions of the disease. It should be possible to isolate the bacterium in pure culture from the lesions. Inoculation of such pure culture into suitable laboratory animals should reproduce the lesions of the disease. It should be possible to re-isolate the bacterium in pure culture from the lesions produced in experimental animals. An additional criterion added later was that specific antibodies to the bacterium be demonstrable in the serum of patients suffering from the disease. Pathogenic organisms that do not obey the Koch's postulates Mycobacterium leprae Borrelia burgdorferi Treponema pallidum Tropheryma whippelii Rhinosporidium seeberi Rickettsia , Chlamydia Viruses Molecular form of Koch's postulates Phenotype of interest should be associated significantly more often with pathogenic members of a genus or pathogenic strains of a species than with non-pathogenic members or strains. Specific inactivation of the gene or genes associated with the suspected virulence trait should lead to a measurable decrease in virulence. Restoration of full pathogenicity should accompany replacement of the mutated version of the gene with the wild- type version in the strain of origin.