Lecture 11 Flashcards
(35 cards)
How are streptococci classified in the lancefield typing system?
Serology is used determined by the specific cell wall carbohydrates of each groups
What streptococci make up group A?
S.Pyogenes
What streptococci make up group B?
S.aglactiae
What streptococci make up group C?
S.equi, S.bovis
What streptococci make up group F?
S.intermedius
What streptococci make up group D?
S.Bovis
What streptococci can not be classified by the lancefield system?
S.Pneumoniae, viridans group (S.Mitis, S. Salivarius)
How can S.Pyogenes be identified?
Gram positive, catalase negative, beta haemolysis bacitracin sensitive
How can enterococcus spp. be identified?
Gram positive, catalase negative, gamma haemolysis, positive for bile esculine agar
How can viridans streptococci be identified?
Gram positive, catalase negative, alpha haemolysis, resistant to optochin
How can S.pneumoniae be identified?
Gram positive, catalase negative, alpha haemolysis and sensitivity to optochin
How can s.pyogenes be spread, and where does it colonize?
Spread through respiratory droplets, colonising the upper respiratory tract
What are the virulence factors of streptococci?
Microbial surface components recognizing adhesive matrix molecules, Pili, Streptolysin O and S, various spreading factors
What are the cyto toxins produced by streptococci?
Streptolysin O which forms membrane pores
Streptolysin S which lyses erythrocytes, plateltes and leukocytes
What spreading factor is different between S.Pyogenes and S.Aureus?
S.Pyogenes contains streptokinase fro fibrin breakdown as opposed to staphylokinase
What are the superantigens for S.Pyogenes and how are they different to S.Aureus?
Streptococcal pyogenic exotoxins, Streptococcal mitogenic exotoxin, they are different from S.Aureus super antigens as they do not cause food poisoning
What are the immune evasion factors for S.Pyogenes?
Protein M which prevents C3b opsonization, Capsule of hyaluronic acid, C5a peptidase which inhibits chemotaxis
What are the conditions that may result from a S.Pyogenes infection?
Impetigo, Pharyngitis, Scarlet Fever, Cellulitis, Necrotising fasciitis, Streptococcal toxic shock syndrome, rheumatic fever and rheumatic heart disease
What is Necrotising fasciitis?
A deep infection that causes desturction of muscle, having a high mortality rate
What is the difference between streptococcal toxic shock syndrome and staphylococcal toxic shock syndrome?
Streptococcal is more severe and faster, has a high mortality rate
What do most streptococci grow in as colonies and what is the exception?
Most grow in long chain, but S.Pnuemoniae forms ‘doublets’
What is the epidemiology of S.agalactiae?
Asymptomatic colonization of upper respiratory tract and genitourinary tract, most dangerous infections occur in uncolonised newborns with a weak immune system
What is the epidemiology of Viridans Streptococci?
Colonisation oropharynx, GI tract, and urinary tract, often seen in mouth flora as dental plaque
What are the virulence factors of Viridans Streptococci?
Has Pili allowing it to form dental film
