Host parasite interactions

Table 28-1

Table 28-2

Fig. 1-15KOCH’S POSTULATES

Tools:Diseasedanimal

Healthyanimal

Redbloodcell

Observeblood/tissueunder themicroscope

Redbloodcell

The Postulates:

1. The suspected pathogenic organism should be present in all cases of the disease and absent from healthy animals.

2. The suspected organism should be grown in pure culture.

Suspectedpathogen

Microscopy, staining

Noorganismspresent

Streak agar platewith sample from eitherdiseased orhealthy animalColonies of

suspectedpathogen

Laboratory culture

3. Cells from a pure culture of the suspected organism should cause disease in a healthy animal.

Experimental animal

Diseased animal

Inoculate healthy animal withcells of suspected pathogen

Remove blood or tissue sampleand observe by microscopy

Laboratoryculture

Suspectedpathogen

Laboratory reisolation4. The organism should be reisolated and shown to be the same as the original.

Pure culture(must besameorganismas before)

Table 28-3

Table 28-4