Microbial Pathogenesis and infection

Microbial Pathogenesis and infection
Pathogenesis: The process of pathogenesis involves various steps and stages beginning with the transmission of the infectious agent (bacterial) to the host, till the progression or resolution of the disease .So the important stages of bacterial pathogenesis are:
? Transmission from an external source into the portal of entry.
? Evasion of primary host defenses.
? Adherence to mucous membranes.
? Colonization by growth of the bacteria at the site of adherence.
? Disease symptoms.
? Host responses.
? progression or resolution of the disease.

Infection is the presence and multiplication of pathogenic microbe within human body, and cause symptoms of infection. The infection differs from other diseases is that caused by living microbial pathogens.
Infection is determined by balance between number and virulence of microbe (degree of pathogenicity) and competency of that host defense (resistance). If microbes are overcome, the disease results.
Pathogen: micro-organism has ability to cause disease, some are highly pathogenic and some are not; depending on their virulence factors.
Opportunistic pathogen: organisms that take advantage of an opportunity of reduced immunity and cause infection in immunocompromised individuals, it is frequently a member of the body’s normal flora.
ID50: infectious dose required to cause disease in 50% of inoculated test animals.