Bacterial pathogenesis

Bacterial Pathogenesis I
Prof Shahina Yasmin

, Bacterial Pathogenesis I - LOs
• Define the following terms:
– pathogen, opportunistic pathogen, pathogenicity,
virulence, virulence factors, pathogenesis, infectious
dose, infection, latent infection, subclinical infection
• Explain the various modes of transmission of bacteria
with examples.
• Explain the important aspects of each stage of
bacterial pathogenesis

, Bacterial Pathogenesis – I -Definitions
• Pathogen: A microorganism capable of causing disease in individuals
including immuno-competent people.
• Opportunistic pathogens: Microbes that do not cause disease in
healthy person but can cause disease in immuno-compromised, when
host defenses are reduced. Body flora are frequently the cause.
• Pathogenesis: mechanism of disease production
• Pathogenicity: ability of an infectious agent to cause disease
• Virulence: quantitative ability of an infectious agent to cause disease.
measured by number of organisms required to cause disease,
expressed as:
– 50% Lethal dose LD50 Number of organisms required to kill half of
the hosts.
– 50% Infectious dose ID50 Number of organisms required to cause
infection in half of the hosts.
– Less the number, more the virulence