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61 Cards in this Set
- Front
- Back
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what kind of metabolic bacteria are streptococcus pyogenes
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anaerobes but are aerotolerant
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what kind of group of streptococcus cause a variety of invasive systemic infections and local infections sometimes followed by severe sequelae
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group A beta hemolytic streptococcus pyogenes
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what is the morphology of streptococci
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gram positive cocci often found in long chains
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how do alpha and beta hemolysis differ when observed on an agar plate
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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. |
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gamma hemolysis refers to what observation on the agar plate
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no hemolysis
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a test which places the beta hemolytic streptococci in groups lettered A through O
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a test which tests for C-carbohydrate in cell wall - its a ppt test and the C is the antigen
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the Lancefield test which further divides group A streptococci detects what
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cell wall protein antigens (analysis of their M proteins which are fimbriae)
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what kind of capsule does streptococci pyogenes have
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hyaluronic acid capsule
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infection of the uterus immediately after childbirth. once common and frequently fatal. now uncommon in developing countries - caused by strept
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puerperal fever
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what is the treatment for acute pharyngitis and tonsillitis (mild form - "strep-throat")
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penicillin (prevents sequela rheumatic fever)
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scarlet fever is caused by
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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) |
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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?
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lysogenic bacteriophage
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does immunity to the exotoxin in scarlet fever mean immunity to infectino with streptococcus p.
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no
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a minor superficial skin infection usually in children where streptococci enter through a pre-existing superficail skin lesion
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impetigo (pyoderma)
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what bacteria is a more important cause of impetigo than strep
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staph. aureus
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a severe cellulitis of the dermis and underlying tissue caused by strept pyogenes
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erysipelis
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What is the principal cause of toxic shock syndrome caused by strep. pyogenes.
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exotoxins speA, speB, and speC - which act as superantigens
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exotoxins produced by st. pyogenes cause the massive overproduction of
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lymphokines (they blunt specific host T cell response)
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when strep pyogenes produces rapidly progressing highly destructive muscle infections that are life-threatening, this is called
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necrotizing faciitis "flesh eating bacteria"
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how does the invasiveness of group A beta hemolyic streptococcal differ from the invasiveness of staph
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infection spreads through tissues rather than being walled off as in staph abscesses
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hemolytic enzymes secreted by group A hemolytic str. pyogens which lyses or injures other cells and causes beta hemolysis in blood agar
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streptolysins O and S
O is O2 labile S is O2 stable |
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what kind of titers are important labrotory diagnostic technique in detecting streptolysin O
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ASO (antistreptolysin O) titers
streptolysins are produced by stre.pyogenes |
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triggers the proteolytic system of the blood that destroys fibrin clots and is secreted by s. pyogenes
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streptokinase
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What are the two factors which play a role in streptococcus pyogenes infections because of their antiphagocytic activity
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1. hyaluronic acid capsule (capsuleless bacteria are non-pathogenic)
2. M proteins |
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cross reacting Ab to what part of strep may lead to rheumatic fever
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M protein
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how are rheumatic fever patients protected against reinfection
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prophylactic penicillin
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what is the major sign of rheumatic fever vs glomerulonephritis
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glomerulonephritis would lead to edem and r. fever to carditis
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what is the pathogenic mechanism begind the development of glomerulonephritis caused by a stretococcal infection
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deposition of antigen-antibody complexes in the kidneys
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are viable streptococcus pyogenes found in the damgaged tissue in rheumatic fever or glomerulonephritis
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no - its due to the immunological response
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a sensitivity to bacitracin correlates well with what kind of strept\\
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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
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a physicians office test for group A strep uses tiny plastic beads coated with what which causes agglutivation in pharyngeak exudate
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anti-group A streptococcal -
another test uses ELISA - based antigen-recognition assay that yields a colored product. reasonably specific but not as sensitive |
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An ASO titer higher than what suggests recent infection
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160 - an increase in titer, comparing acute and convalescent sera is better evidence of infetion. detects streptolysins produced by strep. pyogenes
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what is the mode of transmission of streptococcal pyogenes which causes pharyngitis -
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respiratory droplets - large incolum is need
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why are chronically carried strains of streptococcus pyogens less pathogenic
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prolonged carriage selescts bacteria that produce less M-protein probably because these bacteria with a lot of M protein are opsonized by specific antibody
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the most important group B beta-hemolytic streptococcus is
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streptococcus agalactiae
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neonatal infection w/ what strain of strep includes septicemia, meningitis, penumonia, and death
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group B streptococcal
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there are two epidemiological patters for group B streptococci. early onset neonatal disease (w/in the first week) is correlated with infection from what
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vaginal bacteria during birth.
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Pregnant women who have positive vaginal or rectal cultures for Group B streptococci are treated with what before giving birth
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penicillin or ampicillin
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later onset neonatal disease caused by group B streptococci correlate w/
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infant to infant spread w/in nursery with less fulminant course thatn early onset and lower motorality
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besides neonatal infection the other high risk age group for group B streptococci infections is
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over 65
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enterococci (enterococcus faecalis) is what group of streptococci
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group D
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a group of streptocci which are resistant to sever growth conditions (high salt, high temp, nearly all antibiotics that inhibit most streptococci)
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enterococci
common inhabitants of GI tract may cause UTIs |
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nearly universal inhabitants of mouth, nose, and pharynx
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viridans streptococci (alpha hemolytic streptococci)
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the most frequent cause of infective endocarditis
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alpha hemolytic streptococci (vridan streptococci)
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how might the alpha hemolytic strep of the motuth cause transient bacteremia
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through minor oral trauma.
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how does infective endocarditis caused by viridans streptococci develop
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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
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vegetation in infective endocarditis caused by viridans stretptococci can be detected by
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ultrasound (echocardiogram)
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gram positive diplococci where the short dimensions are opposed
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streptococcus pneumoniae
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what is the most useful test in distinguishing viridans streptoocci from streptococcus pneumoniae
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Optochin sensitivity in pneumonococcus. (this is a drug which OTHER alpha hemolytic streptococci are resitant to)
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nearly 100 types of pneumococci which are identified by their antigenically distinct
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polysaccharide capsules
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a genetic marker in DNA mediated transformation of pneumococi
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polysaccharide capsule
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pneumococci in clinical samples can be identified as to type by
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quelling reaction (when specific antibody reacts w/ pneuymococcal capsule, the capsule swells enough to allow the difference to be seen microscopically
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Dicks test tests for
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exotoxin Ab - a negative test means immunity to toxin not necesarily infection
useful in detected scarlet fever |
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with respect to their metabolism strep. pygenes is
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anaerobic but aerotolerant
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a super antigen links what two cells
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T cell receptor w/ MHC class II cell
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group A beta hemolytic streptococci
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stretococcus pyogenes
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sensitvity to bacitracin
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Stretococcus pyogenes
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what amount of inoculum is needed for an infection y stretococcus pyogenes
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millions of organisms
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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
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enterococci
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pneumococci are common inhabitants of the
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throat (and usually the source of pulmonary infection)
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what kind of gram stain - listera monocytogenes
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gram positive rod
it is facultative intracellular and has intracellular motility using host actin |
