Specific antibody to the bacterium should be detectable in the serum during the course of the disease. It has not been possible to fulfil every one of Koch’s postulates, but by adhering to them as closely as possible, serious errors have been prevented.
Exceptions to Koch s postulates
Many healthy people carry pathogens but do not exhibit symptoms of the disease.
Some microbes are very difficult or impossible to grow in vitro(in the laboratory) in artificial media. Eg. Treponema pallidum
Many species are species specific. Eg. Brucella abortus cause abortion in animals but no report in humans.
Certain diseases develop only when an opportunistic pathogen invades immunocompromised host.
1.2. THE MICROBIAL WORLD
TAXONOMIC CLASSIFICATION OF ORGANISMS
TAXONOMY is the science of organisimal classification. Classification is the assignment of organisms (species) into anorganised scheme of naming .idealy these schemes are based on evolutionary relationships (i.e the more similar the name, the closer the evolutionary relationships). Thus, classification is concerned with:-
The establishment of criteria for identifying organisms & assignment to groups (what belongs where)