2. The organism must be isolated in pure cultures in vitro.
3. Organism must be producing the disease when injected in to laboratory animals.
4. The organism must be isolated from the laboratory animals .Tubercle bacilli cause T.b. Tubercle bacilli isolate from 100 cases for ex: then injected in to lab animals so T.b lesion occurs, isolated of tubercle bacilli from the infected lab animal.
f. Define the following :
Infection: growth and multiplication of a microbe in or on the body with or without the production of disease.
The capacity of a bacterium to cause disease reflects its relative “Pathogenicity.”
Virulence is the measure of the pathogenicity of a microorganism.
Adherence of bacterium to epithelial or endothelial cells allow them to colonize the tissue.
Common adhesins: pili (fimbriae), slime, lipoteichoic acid, surface proteins or lectins.
Biofilm, formed on a surface by the bacteria that are bound together within a sticky web of polysaccharide, is a special bacterial adaptation that facilitates colonization on the surgical appliances (e.g., artificial valves or indwelling catheters) and dental plaque. It can protect the bacteria from host defenses and antibiotics.
o. Lipid A of lipopolysaccharide is responsible for endotoxin activity
Q2 Enuemerate the following :
Pathological Mechanisms of Bacterial Infections
Bacterial virulence factors
=> bacterial factors causing diseases
Bacterial Virulence Mechanisms:
Microbial defenses against host immunologic clearance.
Encapsulation (Inhibition of phagocytosis and serum bactericidal effect)