Lecture 2: Microbial Pathogenesis Flashcards
(15 cards)
3 things that have to happen before an infection results in disease:
- est. a focus of infection
- spread to adjacent or other tissues
- cause change from normal health or function
2 main types of transmission of infectious dose from reservoir to portal of entry
communicable and non-communicable
3 ways bacteria resist innate host defenses
- produce leukocidins
- escape phagocytosis
- live intracellulary
Methods of bacterial spread (5)
- penetrate beneath surface (collagenase, protease, lecithinase, lipase to damage EM)
- direct spread (hyaluronidase, sialidase, mucinase to damage extracellular matrix)
- “trojan horse” inside phagocyte
- enter circ. system
- tissue tropism
mechanisms of bacterial LOCAL damage
- chemical/enzymatic/mechanical
- acids/peroxides/collagenase/protease/lecithinase/hemolysin/glycosidases
- induced endocytosis
- biofilms
Mechs. of bacterial SYSTEMIC damage
- exotoxins (released from living bacteria)
- endotoxins (released from bacteria when dead or phagocytized)
physical properties of exotoxins
- proteins
- immunogenic
- toxic in small doses
- heat-labile (susceptible)
- have specific mechs. of action and specific effects on targets
compare/contrast boulinum toxin with tetanus toxin
have similar molec. structures and act on the same receptor, but have opposite effects. Botulinum toxins blocks excitation via preventing release of ACh from pre-synaptic receptor, and tetanus toxin blocks inhibition by blocking release of GABA
phys. properties of endotoxins
- lipopeptides/lipopolysaccharies
- non-immunogenic
- toxic in high doses
- heat-stable
indirect systemic effects of endotoxins
- cytokine storm of interleukins, interferons, prostaglandins
- coagulation
- fibrinolysis
- complement and kinin activation –> smooth m. contraction, increased vascular permeability histamine release
- inflammation –> vasodilation increased vasc. permeability
- fever
lipid A endotoxin can activate:
tol-receptors
most common inflammatory disease
mastitis
discospondylitis is caused by
bacteria getting inoculated into the bone, where immune system can’t infiltrate
T/F: mucocutaneous junction prone to infection
T
How do bacteria establish FOCUS?
- transmission of infectious dose from reservoir
- compete with normal flora
- resist innate host defense
