chap 15

Question 1

basic steps of causing disease

Answer 1

• enter host
• penetrate/invade host defenses - using capsule, enzyme, and fimbriae/pili
• damage host - use toxins, intracellular pathogens
• exit host

Question 2

portals of entry

Answer 2

mucous membranes - respiratory tract; GI tract;
genitourinary tract

skin - hair follicles, sweat glands, conjunctiva

parenteral route - deposition of microbes directly
under skin or mucous membrane

Question 3

what is the preferred method of entry for pathogens?

Answer 3

respiratory tract and GI tract

Question 4

ID50

Answer 4

infectious dose needed to cause symptoms in 50% of experimental hosts

Question 5

LD50(lethal dose 50%)

Answer 5

dose of pathogen needed to kill 50% experimental animal hosts(measure potency)

Question 6

how specifically do pathogens enter the host

Answer 6

• bind via adhesion/ligands on pathogen to cell membrane

Question 7

biofilm formation

Answer 7

• microbial community contain in exopolysaccharide matrix
• adhere to surfaces
• very resistant
• dental plaque, catheters, ivs, heart valves

Question 8

factors that allow for penetration of host defenses

Answer 8

• capsule - impairs phagocytosis by host cells
• cell wall comp: mycolic acids in some
  M protien- for attachment,
  antiphagocytic, inactive complement
• extracellular enzymes
• antigenic variation - alter pathogen surface proteins;
  possess alternate genes
• opa protein - tight attachment for transcytosis

Question 9

extracellular enzymes to penetrate host

Answer 9

• coagulases: clot blood, isolate bacteria from host
• kinases: destroy blood clots
• collagenase: digests collagen in connective tissue,
  muscles, organs, tissues
• protein A - make antibodies inactive
• proteases - destroy host proteins; IgA protease

Question 10

process of opa protien(transcytosis)

Answer 10

• pilli anchor pathogen to epitheial cells
• opa protein attach for tight adherence
• pathogen travels through the cells to other cells and it keeps going

Question 11

penetration into cytoskeleton

Answer 11

• penetrate using actin filaments in cytoskeleton
• invasions(salmonella) - pathogen surface proteins
  that rearrange actin filaments
  - make membrane ruffling(pathogen engulfed
  into cell

Question 11

pathogen damage to host cells

Answer 11

• use host’s nutrients: pathogen get host
  siderophores(Fe chelators)
• cause direct dmg in vicinity of infection: intracellular
  pathogen(viral infection)
• production of toxins: transported by blood, lymph
  - inhibit protein synthesis
  - disruption of membrane
• induction of hypersensitivity reaction: overproduction
  of cytokines
• release of toxins

Question 12

exotoxins

Answer 12

• types: a-b toxins, membrane disrupting, superantigens
• secreted into environment
• water soluble proteins(lot enzymes); most plasmid
  based or in phages
• antitoxins: toxoid forms to provide immunity

Question 13

toxigenicity

Answer 13

ability for pathogen to produce substances that damage the host

Question 14

toxemia

Answer 14

disease caused by spread of bacteria and its toxins in blood steam

Question 15

a-b toxins

Answer 15

diphtheria toxin: inhibits proteins synthesis; phage
carries tox gene

botulism toxin: neurotoxin; prevents nerve impulses to
muscles; causes flaccid paralysis

tetanus toxin: neurotoxin tetanospasmin; blocks
inhibitory nerve impulses to muscles; cause
spasmodic contractions

vibrio enterotoxin: cholera toxin; causes cellular
secretion of fluids and electrolytes –> severe
diarrhea and dehydration

Question 16

membrane - disrupting toxin

Answer 16

• cause lysis host cells by disrupting the plasma
  membrane
  - leukocidins: kill phagocytic white
  - hemolysins: kill red blood cells

Question 16

superantigens

Answer 16

• stimulate intense immune response of T cells
• t cells stimulated to produce cytokines; regulate
  immune response

erythrogenic toxins: damage blood capillaries under
skin cause rash and scarlet fever

staphylococcal enterotoxin(s. aureus)

Question 17

endotoxin

Answer 17

• lipid protein(A) of LPS of gram neg -> released when
  cells die and lyse
• stimulates macrophages release too much cytokines
• can activate blood clotting proteins and induce fever
• endotoxic shock: drastic drop in blood pressure

Question 18

cytopathic effects

Answer 18

• visible effects of viral infection
  cytocidal effect: results in cell death
  - cytocidal viruses stop host biosynthesis and make
  cell lysosomes release contents
• syncytium formation
• granules formation
• virus infected cells form interferons(protects non-
  infected cells)
• antigenic changes on cell surface caused by virus

Question 19

what is syncytium and how is it formed?

Answer 19

multinucleate infected cell

• virus entry(membrane fusion)
• viral replication(viral envelope on outside)
• noninfected cell fuses w infected
• syncytium forms are more cells get fused

Question 20

what do oncogenic viruses do

Answer 20

transform cells into cancerous cells

Question 21

portal of exit

Answer 21

secretion, excretion, discharges, tissue that is shed

• related to part of the body that was infected
• usually same portal entry and exit