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Microbiology

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General Microbiology

Question
4 out of 97
 

Which of the following is not one of Koch's postulates?(AIIMS Nov 2009)


A The organism is regularly found in lesions of the disease
B The organism can be isolated from diseased tissues in pure culture on artificial media
C Inoculation of this pure culture produces a similar disease in experimental animals
D Treatment of the disease with a broad spectrum oral antimicrobial dependably eradicates the organism and cures the disease

Ans. D Treatment of the disease with a broad spectrum oral antimicrobial dependably eradicates the organism and cures the disease

The Koch’s postulates are:

  1. The bacterium should be constantly associated with the lesions of the disease
  2. It should be possible to isolate the bacterium in pure culture from the lesions
  3. Reproduction of lesions by inoculation of this pure culture into suitable lab animals
  4. It should be possible to reisolate the bacterium in pure culture from the lesions in the lab animals
  5. Specific antibodies to the bacterium should be demonstrable in the serum of patients suffering from the disease

Table - Guidelines for Establishing the Causes of Infectious Diseases

Koch's Postulates

Molecular Koch's Postulates

Molecular Guidelines for Establishing Microbial Disease Causation

1. The microorganism should be found in all cases of the disease in question, and its distribution in the body should be in accordance with the lesions observed

1. The phenotype or property under investigation should be significantly associated with pathogenic strains of a species and not with nonpathogenic strains

1. The nucleic acid sequence of a putative pathogen should be present in most cases of an infectious disease, and preferentially in anatomic sites where pathology is evident

2. The microorganism should be grown in pure culture in vitro (or outside the body of the host) for several generations

2. Specific inactivation of the gene or genes associated with the suspected virulence trait should lead to a measurable decrease in pathogenicity or virulence

2. The nucleic acid sequence of a putative pathogen should be absent from most healthy controls. If the sequence is detected in healthy controls, it should be present with a lower prevalence as compared with patients with disease, and in lower copy numbers

3. When such a pure culture is inoculated into susceptible animal species, the typical disease must result

3. Reversion or replacement of the mutated gene with the wild-type gene should lead to restoration of pathogenicity or virulence

3. The copy number of a pathogen-associated nucleic acid sequence should decrease or become undetectable with resolution of the disease (eg, with effective treatment) and should increase with relapse or recurrence of disease

4. The microorganism must again be isolated from the lesions of such experimentally produced disease

4. The presence of a pathogen-associated nucleic acid sequence in healthy subjects should help predict the subsequent development of disease

5. The nature of the pathogen inferred from analysis of its nucleic acid sequence should be consistent with the known biologic characteristics of closely related organisms and the nature of the disease. The significance of a detected microbial sequence is increased when microbial genotype predicts microbial morphology, pathology, clinical features of disease, and host response

General Microbiology Flashcard List

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