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61 Cards in this Set

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  • Back
what kind of metabolic bacteria are streptococcus pyogenes
anaerobes but are aerotolerant
what kind of group of streptococcus cause a variety of invasive systemic infections and local infections sometimes followed by severe sequelae
group A beta hemolytic streptococcus pyogenes
what is the morphology of streptococci
gram positive cocci often found in long chains
how do alpha and beta hemolysis differ when observed on an agar plate
1. Alpha hemolysis is seen as a cloudy green zone that contain intact red cells w/ chemically altered green heme pigment
2. Beta hemolysis appears as a clear zone in which all red cells are lysed. small zone of beta hemolysis may not look completely clear if the zone does not extend through the entire agar layer.
gamma hemolysis refers to what observation on the agar plate
no hemolysis
a test which places the beta hemolytic streptococci in groups lettered A through O
a test which tests for C-carbohydrate in cell wall - its a ppt test and the C is the antigen
the Lancefield test which further divides group A streptococci detects what
cell wall protein antigens (analysis of their M proteins which are fimbriae)
what kind of capsule does streptococci pyogenes have
hyaluronic acid capsule
infection of the uterus immediately after childbirth. once common and frequently fatal. now uncommon in developing countries - caused by strept
puerperal fever
what is the treatment for acute pharyngitis and tonsillitis (mild form - "strep-throat")
penicillin (prevents sequela rheumatic fever)
scarlet fever is caused by
streptococcal pyrogenic exotoxin.

it is a cutaneous rash

Dicks test will test for the Ab to the exotoxin and see if person has immunity to toxin (doesnt test for immunity against organism)
The ability for streptococcus pyogenes to produce the exotoxins speA, speB, and specC which may cause rash in scarlet fever is conferred by a bacteriophage or plasmid?
lysogenic bacteriophage
does immunity to the exotoxin in scarlet fever mean immunity to infectino with streptococcus p.
a minor superficial skin infection usually in children where streptococci enter through a pre-existing superficail skin lesion
impetigo (pyoderma)
what bacteria is a more important cause of impetigo than strep
staph. aureus
a severe cellulitis of the dermis and underlying tissue caused by strept pyogenes
What is the principal cause of toxic shock syndrome caused by strep. pyogenes.
exotoxins speA, speB, and speC - which act as superantigens
exotoxins produced by st. pyogenes cause the massive overproduction of
lymphokines (they blunt specific host T cell response)
when strep pyogenes produces rapidly progressing highly destructive muscle infections that are life-threatening, this is called
necrotizing faciitis "flesh eating bacteria"
how does the invasiveness of group A beta hemolyic streptococcal differ from the invasiveness of staph
infection spreads through tissues rather than being walled off as in staph abscesses
hemolytic enzymes secreted by group A hemolytic str. pyogens which lyses or injures other cells and causes beta hemolysis in blood agar
streptolysins O and S

O is O2 labile
S is O2 stable
what kind of titers are important labrotory diagnostic technique in detecting streptolysin O
ASO (antistreptolysin O) titers

streptolysins are produced by stre.pyogenes
triggers the proteolytic system of the blood that destroys fibrin clots and is secreted by s. pyogenes
What are the two factors which play a role in streptococcus pyogenes infections because of their antiphagocytic activity
1. hyaluronic acid capsule (capsuleless bacteria are non-pathogenic)
2. M proteins
cross reacting Ab to what part of strep may lead to rheumatic fever
M protein
how are rheumatic fever patients protected against reinfection
prophylactic penicillin
what is the major sign of rheumatic fever vs glomerulonephritis
glomerulonephritis would lead to edem and r. fever to carditis
what is the pathogenic mechanism begind the development of glomerulonephritis caused by a stretococcal infection
deposition of antigen-antibody complexes in the kidneys
are viable streptococcus pyogenes found in the damgaged tissue in rheumatic fever or glomerulonephritis
no - its due to the immunological response
a sensitivity to bacitracin correlates well with what kind of strept\\
3. sensitivity to bacitracin, a property that correlates very well with assignment to group A beta hemolytic strec. The other beta-hemolytic strept are relatively resistant
a physicians office test for group A strep uses tiny plastic beads coated with what which causes agglutivation in pharyngeak exudate
anti-group A streptococcal -
another test uses ELISA - based antigen-recognition assay that yields a colored product. reasonably specific but not as sensitive
An ASO titer higher than what suggests recent infection
160 - an increase in titer, comparing acute and convalescent sera is better evidence of infetion. detects streptolysins produced by strep. pyogenes
what is the mode of transmission of streptococcal pyogenes which causes pharyngitis -
respiratory droplets - large incolum is need
why are chronically carried strains of streptococcus pyogens less pathogenic
prolonged carriage selescts bacteria that produce less M-protein probably because these bacteria with a lot of M protein are opsonized by specific antibody
the most important group B beta-hemolytic streptococcus is
streptococcus agalactiae
neonatal infection w/ what strain of strep includes septicemia, meningitis, penumonia, and death
group B streptococcal
there are two epidemiological patters for group B streptococci. early onset neonatal disease (w/in the first week) is correlated with infection from what
vaginal bacteria during birth.
Pregnant women who have positive vaginal or rectal cultures for Group B streptococci are treated with what before giving birth
penicillin or ampicillin
later onset neonatal disease caused by group B streptococci correlate w/
infant to infant spread w/in nursery with less fulminant course thatn early onset and lower motorality
besides neonatal infection the other high risk age group for group B streptococci infections is
over 65
enterococci (enterococcus faecalis) is what group of streptococci
group D
a group of streptocci which are resistant to sever growth conditions (high salt, high temp, nearly all antibiotics that inhibit most streptococci)

common inhabitants of GI tract
may cause UTIs
nearly universal inhabitants of mouth, nose, and pharynx
viridans streptococci (alpha hemolytic streptococci)
the most frequent cause of infective endocarditis
alpha hemolytic streptococci (vridan streptococci)
how might the alpha hemolytic strep of the motuth cause transient bacteremia
through minor oral trauma.
how does infective endocarditis caused by viridans streptococci develop
through blood sets up a focus of infection in a pre-existing minor lesion on the endocardium usually on a valve. it adheres to the pre-existing lesion and multiplys w/in a mass of fibrin and platelets to yield very high bacterial concentrations. the resulting mass is called a vegetation
vegetation in infective endocarditis caused by viridans stretptococci can be detected by
ultrasound (echocardiogram)
gram positive diplococci where the short dimensions are opposed
streptococcus pneumoniae
what is the most useful test in distinguishing viridans streptoocci from streptococcus pneumoniae
Optochin sensitivity in pneumonococcus. (this is a drug which OTHER alpha hemolytic streptococci are resitant to)
nearly 100 types of pneumococci which are identified by their antigenically distinct
polysaccharide capsules
a genetic marker in DNA mediated transformation of pneumococi
polysaccharide capsule
pneumococci in clinical samples can be identified as to type by
quelling reaction (when specific antibody reacts w/ pneuymococcal capsule, the capsule swells enough to allow the difference to be seen microscopically
Dicks test tests for
exotoxin Ab - a negative test means immunity to toxin not necesarily infection

useful in detected scarlet fever
with respect to their metabolism strep. pygenes is
anaerobic but aerotolerant
a super antigen links what two cells
T cell receptor w/ MHC class II cell
group A beta hemolytic streptococci
stretococcus pyogenes
sensitvity to bacitracin
Stretococcus pyogenes
what amount of inoculum is needed for an infection y stretococcus pyogenes
millions of organisms
common inhabitants of the g.i. tract with a pattern of hemolysis which differs from strain to strain - they are resistant to the "last resort" antibiotic
pneumococci are common inhabitants of the
throat (and usually the source of pulmonary infection)
what kind of gram stain - listera monocytogenes
gram positive rod

it is facultative intracellular and has intracellular motility using host actin