host microbe

Microbes that cause noticeable damage to the host

Pathogens

Microbes that cause disease when defenses are weakened

Opportunistic pathogens

Mutualism

Both benefit (ex: gut bacteria making vitamin K)

Commensalism

One benefits, other unaffected

Parasitism

One benefits, host is harmed

Term for microbes routinely living on the body

Normal microbiota / microbiom

Microbiome imbalance

Dysbiosis

Competitive exclusion mechanisms

Cover binding sites, use nutrients, make toxins

What allows body to digest fibers?

Gut microbiota ferment them → short-chain fatty acids

What vitamins do gut bacteria make?

Vitamin K & B vitamins

Subjective disease effects

Symptoms

Objective evidence of disease

Signs

Primary vs secondary infection

First illness causing vulnerability → second infection

Pathogen that causes disease in healthy people

Primary pathogen

Traits that allow microbes to cause disease

Virulence factors

Infectious dose definition

# of microbes needed to cause disease

ID50

Dose that infects 50% of hosts

Disease stages

Incubation → Illness → Convalescence

People who spread disease while healthy

Carriers

Acute vs chronic vs latent

Rapid/short vs slow/long vs hiding w/ no symptoms

Localized infection

Small area

Systemic infection

Throughout body (fever, fatigue)

Bacteremia, toxemia, sepsis

Bacteria in blood; toxins in blood; systemic inflammation

First step in infection

Adherence

Structure for bacterial attachment

Adhesins on pili/fimbriae

What must bacteria do to colonize?

Multiply & compete with microbiota

Iron-binding proteins of host

Transferrin, lactoferrin

Bacterial iron-stealing molecules

Siderophores

Ways pathogens avoid IgA

IgA protease, antigenic variation, shedding pili

Enzyme that destroys C5a

C5a peptidase

How capsules prevent phagocytosis

Block opsonization

Bacteria that have Fc receptors

Staph aureus, Strep pyogenes

Pathogens that escape phagosomes

Shigella, Listeria

Why pathogens cause damage

To spread (e.g., diarrhea, coughing)

Pathogen causing cholera

Vibrio cholerae

Pathogen causing whooping cough

Bordetella pertussis