The Koch's postulates that are used for judging if a bacteria is the cause of the diseases and for identification of the disease-causing bacteria include:
Although the postulates cannot be applied to all pathogenic bacteria and viruses, some bacteria like tuberculosis fit these postulates. As a result, according to the results of the experiments, Koch successfully isolated tuberculosis bacteria from the infected individuals and incubated the microorganism in a culture. Healthy individuals did not contain the bacteria, while experimental animals could be infected using isolated and reisolated microbes. However, some organisms cannot be isolated in the culture (i.e., Mycobacterium leprae) and do not fulfil the pustulates.
Bacterial toxins can be distinguished by their nature and mechanism of action. Two main groups of bacteria toxins are:
More specifically, toxins can induce the lysis of the host membrane, block synaptic neurotransmission, activate cellular adenylyl cyclase stimulating diarrhea, block protein synthesis, and inhibitors of cells adhesion.