Strep 1 Flashcards
(88 cards)
slide 3 for the classification of stpah, strep and enterococci
gram—- and shape
gram positive cocci
arranged—-
linearily or in pairs or in chains
catalase?/respiration?/capsule?
negative/facultative anaerobe/some are encapsulated
motile? sporulating?/part of commensal flora?
non-motile/non-sporulating/may be part of commnesal flora
since strep are so diverse and heterp, one method of classification is not enough:
1) lancefield (based on cell wall carbs)
2) hemolysis
3) biochemical properties
lancefield group carb antigen is a —/ serological grouping into groups: ——
dimer of N-acetyl glucosamine and rhamnose: important for identification / A to H and K to U
method of lanecefield identification:
1) lysis of strep cells with enzyme to destry the cell wall
2) then we treat the sample wih antisera (antibody) specific to the C-antigen (precipitin test)
slide 11 to know the classification based on blood hemolysis and slide 12
slide 13: types of virulence factors 3and group A strep
strep pyogenes capsule is encaspsulated with—
hyaluronic acid so it’s a poor immunogen since GAS capsular hyaluronate is chemically similar to that found
in human connective tissue and no antibodies has been observed
virulence factors of GAS:
1)capsule: prevents oponized phagocytosis by neutrophiles or macrophages/ is nonantigenic since it’s chemically similar to tissues of hostso bacteria goes unrecognized by host and hides its antigens
2)M protein>120 serotype:next flaschard
3)lipoteichoic acid: mediate bactrial adherence to host epithethelial cells and mucosal surfaces
4)peptidoglycan: composed of polymers of repeating subunits of N acetylglucosamine and
N acetylmuramic acid. The peptidoglycan provides rigidity to the cell wall
explain the casue of antigenic drift and shift
Antigenic shift and antigenic drift are ways that pathogens (like viruses or bacteria) change over time to escape the immune system.
antigenic drift= small changes due to mutations
antigenic shift= big changes due to the swapping of genetic material between strains
what about the M protein as a virulence factor?
M protein (>120 serotype):
* is the major cause of antigenic shift and antigenic drift in the Group A streptococci
* M protein also binds fibrinogen from serum and blocks the binding of complement to
the underlying peptidoglycan—-inhibit phagocytosis so it uses firbrinogen to cover itself ta ma yeje 3leya l complement
* Antibody againt M protein is durable. (long lasting protection)
IP of GAS:
2-4 days
pharyngitiys caused by—is primaryily a disease of —
S.pyogenes/ a disease of children between the ages of 5 and 15
this pathogen is spread from person to person through—-/thete are coincidences where the organisms is inroudced into the —
respiratory droplets particulary duirng the winter months (crowding, daycare facilities)/spuerficical or deep tissues throygh a break in the skin
streptococcal diseases:
1) impetigo
2)rheumatic fever
3)cellulitis
4)scarlet fever (rash and lesions)
5)sore throat (strep pharyngitis or tonsilitis)
6) glumerulnphiritis
transmission of phrangitis:
droplets, saliva or nasal secretions
often a colonizer in——
asymptomatic perople (high in children)
symptoms of pharyngitis:
1-Sore throat (2-4 days post exposure),malaise, high grade fever, headache,
2-Lymphoid hyperplasia of the posterior portion of the pharynx
* enlarged tonsils
* Intense nasopharyngitis
* tonsillitis
* redness/edema of mucus membranes with purulent exudates (Purulent exudates refer to thick, pus-containing fluid that forms at the site of infection or inflammation.)
3- Lymph nodes enlarge
4-High CRP (C-reactive protein (CRP) is a protein made by the liver that increases in response to inflammation. )and WBC count
scarlet fever is a complication of ——. its—
phrayngitis/ it’s severe pharingitis/ skin infection and high grade fever
it’s characterized by —
red rash on trunk that may spread to extrimities after 24 hours of illness/Diffuse red spots over upper part of the chest-spread to remainder of the trunk, neck
and extremities, face flushed./pharyngitism, tonsilitism and hemorrhagic spots on the hard and soft palates (white
strawberry tongue)
it involves the acquisition of a —-
bacteriophage that mediate sthe production of a pyrogenic exotoxin