definitions

• saprophytic: free living
• parasitic: requires host
• host range: number of higher order species where a microbe is able to exist
• commensal: neutral or beneficial relationship with host
• opportunistic: becomes pathogenic with certain conditions
• pathogenic: always causes disease
• disease: any condition in which the normal structure or functions of the body are damaged or impaired
• infection: successful colonization of host by a microorganism
• pathogens: organisms that cause disease
• virulence: degree of pathogenicity
• koch's postulates:

  the microorganism must be present in every case of the disease but absent from healthy organisms

  the suspected microorganisms must be isolated and grown in pure culture

  the same disease must result when the isolated microorganism is inoculated into a healthy host

  the same microorganisms must be isolated again from the diseased host
• exposure: encounter with pathogen
• adhesion: attachment to body cells
• local infection: confined to small area
• focal infection: spread of local infection to secondary location
• systemic: disseminated throughout the body
• secondary infection: infection by one pathogen leads to infection by another
• incubation period: between exposure and infection
• prodromal stage: multiplication of pathogen
• illness: immune system and pathogen causing symptoms
• convalescent period: mostly cleared infection but may still shed pathogen