Question

What is the class of exposures that Koch’s Postulates addresses?

Answer 1

Answer)-Advances in knowledge have included
the discovery of viruses, chlamydiae, and rickettsiae as new
classes of microbes that cannot be propagated in pure culture
but that require other cells for reproduction. The spectrum of
bacterial, fungal, and protozoan pathogens has been expanded
with improved culture techniques and the development of adavanced imaging methods. For example, light microscopy has
been refined with the use of immunohistochemical or immuanofluorescent stains to detect specific molecules in the host or
pathogen.

**********Koch’s postulates ******************can
be summarized from his presentation before the Tenth International Congress of Medicine in Berlin in 1890 (53, 95).
(i) The parasite occurs in every case of the disease in question and under circumstances which can account for the pathological changes and clinical course of the disease.
(ii) The parasite occurs in no other disease as a fortuitous
and nonpathogenic parasite.
(iii) After being fully isolated from the body and repeatedly
grown in pure culture, the parasite can induce the disease
anew.

Considerations of host, environment, microbial adaptation,and the complexities of host-parasite relationships suggest that

we change our perspective on microbial causation. Definitions

should address the difference between ‘‘necessary’’ and ‘‘suffi-

cient’’; that is, the presence of a microbial pathogen or its

products (at some point in time) may be necessary but not

sufficient to produce disease in a given host. As Alfred Evans

noted (30), ‘‘...failure to fulfill the Henle-Koch postulates does

not eliminate a putative microbe from playing a causative role

in a disease. It did not at the time of Koch’s presentation in

1890 and it certainly does not today. Postulates of causation

must change with the technology available to prove them and

with our knowledge of the disease.’