Mechanisms of bacterial pathogenesis 2 Flashcards
consequences of bacterial infection on the host
acute inflammatory changes, damage by bacterial enzymes, endotoxins, sepsis, immunopathology
reasons for the local symptoms of acute inflammation
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
local symptoms of acute infection
redness, swelling, warmth, pain, loss of function, sometimes pus
systemic symptoms of acute inflammation
fevers, riggers, chills, tachycardia, tachypnoea
cause of local inflammatory response
triggered by release pf bacterial products (toxins/enzymes). is amplified by release of inflammatory products from host
what are infections that cause a lot of pus called
pyogenic infections, caused by pyogenic organisms inc. staphylococci, streptococci, meningococci
what is pus
accumulation of phagocytes (neutrophils and macrophages) forming exudate and pus
dead/dying neutrophils = pus
what is an abscess
a localised area of pus
damage to host by bacterial enzymes - streptococci
streptococci releases hyaluronidase. breaks down hyaluronic acid (component of ECM_ .’. bacteria can spread deeper into tissues and can spread
damage to host by bacterial enzymes - clostridium perfringens (gram +ve bacillus/rod)
releases a-lecithinase which splits lecithin found on the surface of hosts .’. can kill/damage cells .’. cause major tissue damage
ways in which bacterial exotoxins can affect host
enzymatic lysis, pore formation, inhibit protein synthesis, hyperactivation, effects on nerve muscle transmission
what is a bacterial exotoxin
proteins that are secreted out of the bacteria
what is a bacterial endotoxin
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
mechanism of endotoxin action
the endotoxin sticks out of of lipopolysaccharide wall, which can be recognised by the immune system and evoke a response
endotoxin cytokine effects
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
endotoxin, complement/coagulation effects
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
examples of endotoxin mediated disease
N. meningitides, meningococci, E.Coli, Psuedomonas aeuginosa
what is bacteraemia
bacteria in the blood
what is septicaemia
bacteria in the blood with symptoms
what is sepsis
body’s response to infection causes injury to its own tissues and organs. aused by an immune response triggered by an infection.
what is toxic shock syndrome
potentially fatal illness caused by a gram +ve bacterial EXOtoxin.
eg staph. aureus (TSST toxin) or strep pyogenes (SPE toxin)
what are superantigens
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)
what are the two classes of adaptive immune response
Humoral immunity -> production of antibodies by B-lymphocytes
Cellular immunity -> CD8+ lymphocytes
Both regulated by Th cells
what is impetigo
a bacterial infection that involves the superficial skin. caused by Staphylococcus aureus or Streptococcus pyogenes
