Ch 34 Powerpoint summarized Pt1

What is pathogenicity?

the ability of a microorganism to cause disease

What is virulence?

the degree or intensity of pathogenicity

What is a reservoir in infectious disease?

the natural source of a pathogen (animate or inanimate)

What are zoonoses?

diseases transmitted to humans from animals

What is required for a pathogen to cause disease?

it must contact the host and survive within it

What is ID50?

the infectious dose that infects 50% of test organisms

What is LD50?

the lethal dose that kills 50% of test organisms

What influences a host’s susceptibility to infection?

• host immune status

• pathogen virulence

• exposure level

What are extracellular pathogens?

pathogens that grow outside host cells

What are obligate intracellular pathogens?

pathogens that must grow inside host cells to survive

What is adherence in infection?

the ability of a pathogen to attach to host tissues

What structures mediate pathogen adherence?

• fimbriae

• pili

• capsules

• spike proteins

Name four major portals of entry.

• skin

• respiratory tract

• GI tract

• urogenital tract

What is invasion?

the ability of pathogens to spread into host tissues

Is Clostridium tetani invasive?

no, it is non-invasive but highly virulent

Is Bacillus anthracis invasive?

yes

What is hyaluronidase?

an exoenzyme that breaks down hyaluronic acid, aiding spread

What organisms commonly produce hyaluronidase?

• staphylococcus

• streptococcus

• clostridium species

What does coagulase do?

converts fibrinogen to fibrin; produced by S. aureus

What does fibrinolysin (streptokinase) do?

breaks down fibrin clots

What does collagenase do?

breaks down collagen to aid tissue invasion

What are leukocidins?

toxins that lyse leukocytes

What are hemolysins?

toxins that lyse red blood cells

What organism produces many virulence factors including coagulase and protein A?

Staph aureus

What are exotoxins?

soluble, heat-labile proteins released by bacteria

Are most exotoxin producers Gram-positive or Gram-negative?

gram positive

What are antitoxins?

antibodies produced to neutralize exotoxins

What are toxoids?

inactivated toxins used as vaccines

What is an AB toxin?

a two-part exotoxin with an active (A) and binding (B) component

What does diphtheria toxin do?

inhibits protein synthesis by ADP-ribosylating EF-2

What is the capsule’s role in B. anthracis virulence?

it helps the bacterium evade the immune system

What do enterotoxins affect?

intestinal permeability, causing diarrhea or vomiting

What does cholera toxin do?

activates adenylate cyclase → increased cAMP → massive ion and water loss

What is a major virulence mechanism of EHEC (STEC)?

production of Shiga-like toxins

What is a T3SS (Type III secretion system)?

an injectisome used by bacteria to deliver effector proteins

What is a superantigen?

a toxin that overstimulates T cells, causing cytokine storm

What is endotoxin?

lipid A component of LPS in Gram-negative bacteria

What causes septic shock?

massive immune activation leading to severe hypotension and organ failure

What are mycotoxins?

toxic secondary metabolites produced by fungi

What fungus produces aflatoxin?

Aspergillus flavus or A. parasiticus

How do capsules help pathogens resist host defenses?

prevent phagocytosis

What are antigenic variations?

mutations that change surface antigens to evade immunity

How do biofilms aid pathogens?

they protect bacteria from immune cells and antibiotics

What is the main lesson from the chain of infection concept?

breaking any step in the chain can prevent disease

What is the chain of infection?

the series of events needed for an infection to occur

What are the five key factors in the chain of infection?

• agent identity

• virulence

• means of exposure

• dose

• host susceptibility

What is a reservoir?

the natural habitat of a pathogen

What are animate reservoirs?

living reservoirs such as humans or animals

What are inanimate reservoirs?

non-living sources like soil, water, or food