Flashcards
Bacterial adhesins and toxin-mediated diseases
Flashcards do conjunto (11)
- 1Toxin mediated diseases, Tetanus and BotulismGram positive spore forming anaerobic rods.
- 2C. difficileGram positive bacillus, spore forming, anaerobic.
- 3Adhesins - Pili (long & fat), fimbriae shorter and thinner.Type 1 - common, chromosomally derived, binds mannose, UPEC, plasmid borne,
Type IV - retractile, gram positive species EPEC, EPHEC, homopolymer of same pilin subunit.
Chaperone usher pili - E. coli P pilus (pap) - binds digalactoside, UPEC, Pap G = Tip, Pap C + D transport from periplasm to membrane. cpxA cpxR regulated in response to environmental stim. - 4Other types of adhesincurli - newly discovered class of amloid adhesive, enterobacteriaceae, highly aggregated form major component of ECM, pro inflammatory
- 5C. DiptheraeGram positive, adheres to pharyngeal cells via pili comprised of 3 subunits Spa A/B/C, generated by sortase machinery - links pili subunits
- 6Yersinia InfectionGram –ve Enterobacteriaceae:
Y. pestis (bubonic plague).
Y. pseudotuberculosis (mesenteric lymphadenitis & septicaemia).
Y. enterocolitica (enteritis & mesenteric lymphadenitis).
Possesses invasin (Inv) which was the first bacterial invasion protein ever described.
Chromosomally encoded.
Invasin binds to β1 integrins on host cells. - 7EPEC AdherenceAlthough not considered invasive, enteropathogenic E. coli cause profound cell alterations when they interact with epithelial cells.
Attachment results in:
Microvillus effacement.
Cytoskeletal arrangement.
Pedestal formation.
Initial attachment via pilus - 8EPEC adherenceThe adhesin intimin mediates close contact with the host cell.
The receptor for intimin is Tir:
Bacterial protein delivered to cell via TTSS.
Firmly anchors bacterium to cell.
Tir recruits host cell proteins involved in actin rearrangement. - 9Salmonella invasionS. Typhimurium triggers dramatic
response from epithelial cells:
Cell surface extends outwards.
Membrane ruffling.
Macropinocytosis.
Actin filaments rearranged.
Invasion occurs within minutes – Salmonella appear in membrane bound vacuoles shortly after making contact with the cell.
Host actin and cell surface return to normal post-invasion. - 10Salmonella invasionUses TTSS.
SipC is part of the TTSS and drives actin polymerisation.
SopE and B activates Rho GTPases causing actin polymerisation and membrane ruffling.
SipA inhibits cofilin.
SptP deactivates Rho GTPases, inhibiting actin polymerisation and allowing cell membrane to close after invasion. - 11Shigella invasionClosely resembles Salmonella invasion.
Translocates TTSS effectors into target cell to induce invasion.
IpaC is part of the TTSS and drives actin polymerisation.
VirA stimulates Rho GTPases causing actin polymerisation.
IpgD promotes membrane ruffling.
IpaA activates host protein vinculin causing actin depolymerisation and allowing cell membrane to close after invasion.
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