Mechanisms of bacterial pathogenesis 2

Question 1

consequences of bacterial infection on the host

Answer 1

acute inflammatory changes, damage by bacterial enzymes, endotoxins, sepsis, immunopathology

Question 2

reasons for the local symptoms of acute inflammation

Answer 2

mainly consequence of local bv changes eg inc blood flow to area (redness and heat), inc permeability to fluid and plasma proteins (swelling), inc stickiness of vascular endothelium, emigration of phagocytes to site

Question 3

local symptoms of acute infection

Answer 3

redness, swelling, warmth, pain, loss of function, sometimes pus

Question 4

systemic symptoms of acute inflammation

Answer 4

fevers, riggers, chills, tachycardia, tachypnoea

Question 5

cause of local inflammatory response

Answer 5

triggered by release pf bacterial products (toxins/enzymes). is amplified by release of inflammatory products from host

Question 6

what are infections that cause a lot of pus called

Answer 6

pyogenic infections, caused by pyogenic organisms inc. staphylococci, streptococci, meningococci

Question 7

what is pus

Answer 7

accumulation of phagocytes (neutrophils and macrophages) forming exudate and pus
dead/dying neutrophils = pus

Question 8

what is an abscess

Answer 8

a localised area of pus

Question 9

damage to host by bacterial enzymes - streptococci

Answer 9

streptococci releases hyaluronidase. breaks down hyaluronic acid (component of ECM_ .’. bacteria can spread deeper into tissues and can spread

Question 10

damage to host by bacterial enzymes - clostridium perfringens (gram +ve bacillus/rod)

Answer 10

releases a-lecithinase which splits lecithin found on the surface of hosts .’. can kill/damage cells .’. cause major tissue damage

Question 11

ways in which bacterial exotoxins can affect host

Answer 11

enzymatic lysis, pore formation, inhibit protein synthesis, hyperactivation, effects on nerve muscle transmission

Question 12

what is a bacterial exotoxin

Answer 12

proteins that are secreted out of the bacteria

Question 13

what is a bacterial endotoxin

Answer 13

an integral part of bacterial structure. only found ion gram -ve bacteria bc is formed from the lipopolysaccharide in the outer membrane of the bacteria

Question 14

mechanism of endotoxin action

Answer 14

the endotoxin sticks out of of lipopolysaccharide wall, which can be recognised by the immune system and evoke a response

Question 15

endotoxin cytokine effects

Answer 15

endotoxin can activate macrophages/monocytes .’. release IL1/IL6/IL8/PAF/TNF .’. stimulate production go PG and Leukotrienes. also act on endothelium .’. becomes more permeable .’. blood leaks out of circulation .’. bv decreases .’. prevent organ perfusion .’. organ failure/shock

Question 16

endotoxin, complement/coagulation effects

Answer 16

activate complement via the alternative pathway. activate clotting cascade .’. can get uncontrolled clotting all over the body.
clotting factors are used up .’. can also get more bleeding
so have clots and blood leaking all the time

Question 17

examples of endotoxin mediated disease

Answer 17

N. meningitides, meningococci, E.Coli, Psuedomonas aeuginosa

Question 18

what is bacteraemia

Answer 18

bacteria in the blood

Question 19

what is septicaemia

Answer 19

bacteria in the blood with symptoms

Question 20

what is sepsis

Answer 20

body’s response to infection causes injury to its own tissues and organs. aused by an immune response triggered by an infection.

Question 21

what is toxic shock syndrome

Answer 21

potentially fatal illness caused by a gram +ve bacterial EXOtoxin.
eg staph. aureus (TSST toxin) or strep pyogenes (SPE toxin)

Question 22

what are superantigens

Answer 22

a class of antigens OF GRAM +VE =non-specific activation of T-cells .’. polyclonal T cell activation and massive cytokine release (cytokine storm) and huge inflammation (similar to that of endotoxins)

Question 23

what are the two classes of adaptive immune response

Answer 23

Humoral immunity -> production of antibodies by B-lymphocytes
Cellular immunity -> CD8+ lymphocytes
Both regulated by Th cells

Question 24

what is impetigo

Answer 24

a bacterial infection that involves the superficial skin. caused by Staphylococcus aureus or Streptococcus pyogenes

Question 25

type 3 hypersensitivity reaction of impetigo

Answer 25

when infected we produce antibodies. antibody and antigen bind= immune complexes (IC), are big, may get deposited around body. IC = deposited in glomerular capillary wall .’. activation of complement .’. influx of inflammatory cells .’. release of tissue damaging enzymes .’. damage to kidney = glomerulonephritis

Question 26

what is molecular mimicry

Answer 26

when surface antigens of bacteria are similar to host proteins, antigens produced may start to react against our own host cells .’. get inflammation.

Question 27

what is rheumatic heart disease/fever

Answer 27

disease caused due to cross-reactivity of antibodies. antibodies produced on throat infection with group A streptococcus. antibodies may cross react against self-antigens in heart and joints. Bc antigen of strep is similar to glycoprotein of heart valve.

Question 28

what is rheumatoid arthritis

Answer 28

cross-reaction of antibodies in the joints/synovium = inflammation of joints