Pathogenicity and Bacterial Pathogens

Study Notes

Pathogenicity is the ability of an agent to cause disease
Key attributes include transmissibility, survival in a new host, infectivity, and virulence
Virulence is a variable and multifactorial concept, relating to the ability of a pathogen to harm the host in relation to the host’s resistance.
Pathogenesis includes initiation of infection and mechanisms leading to disease symptoms.

Primary pathogens establish infection in healthy individuals.
Opportunistic pathogens cause disease in individuals with weakened immune systems.
Examples of opportunistic pathogens include coagulase-negative staphylococci and Escherichia coli, which are part of normal human flora.

Infection: The multiplication of an infectious agent within the body; multiplication of normal flora is generally not considered infection.
Invasion: The process where bacteria (and other pathogens) enter cells and tissues to spread.
Microbiota: The normal microbial flora in healthy individuals.
Nonpathogen: Microorganisms that do not cause disease, often part of the normal microbiota.
Pathogen: Microorganisms capable of causing disease.

Congenital: Pathogens cross the placental barrier, infecting the fetus in utero (e.g., syphilis).
Iatrogenic and Laboratory Infections: Pathogen transmission occurs during procedures such as injections, lumbar punctures, and dialysis or through contact with infectious material (e.g., laboratory personnel).
Nosocomial infections: Infections acquired from hospital personnel.
Clinical manifestations, like diarrhea, cough, promote transmission. (e.g. Vibrio Cholera)