Mechanisms of Microbial
Pathogenesis
, Introduction
Pathogens
•Organisms capable of producing
disease, are usually referred to
‘pathogens’
,Pathogenesis
• Pathogenesis is the chain of events that lead to development of
diseases in the host.
What are the stages of pathogenesis?
• Stages of Pathogenesis. To cause disease, a pathogen must
successfully achieve four steps or stages of pathogenesis: exposure
(contact), adhesion (colonization), invasion, and infection.
, Determinants of Pathogenicity
• 1. Invasiveness is the ability to invade tissues
• 2.Toxigenesis is the ability to produce toxins.
Bacteria may produce two types of toxins called
exotoxins and endotoxins. Exotoxins are released
from bacterial cells and may act at tissue sites removed
from the site of bacterial growth. Endotoxins are cell-
associated substance.
• 3.Fimbria/pili-adherence to surface
• 4. Capsule- adhere to surface, prevent phagocytosis,
impart virulence .
• 5. Flagella-organ motility.
Pathogenesis
, Introduction
Pathogens
•Organisms capable of producing
disease, are usually referred to
‘pathogens’
,Pathogenesis
• Pathogenesis is the chain of events that lead to development of
diseases in the host.
What are the stages of pathogenesis?
• Stages of Pathogenesis. To cause disease, a pathogen must
successfully achieve four steps or stages of pathogenesis: exposure
(contact), adhesion (colonization), invasion, and infection.
, Determinants of Pathogenicity
• 1. Invasiveness is the ability to invade tissues
• 2.Toxigenesis is the ability to produce toxins.
Bacteria may produce two types of toxins called
exotoxins and endotoxins. Exotoxins are released
from bacterial cells and may act at tissue sites removed
from the site of bacterial growth. Endotoxins are cell-
associated substance.
• 3.Fimbria/pili-adherence to surface
• 4. Capsule- adhere to surface, prevent phagocytosis,
impart virulence .
• 5. Flagella-organ motility.
