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40 Cards in this Set
- Front
- Back
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what is the cause of most infections? ex?
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viruses (40-60%)
adeno, rhino, coxsackie, parainfluenza, coronavirus, HSV |
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what is the most common bacterial throat infection caused by? what are some other ex?
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strep throat (serious cause of pharyngitis) is usually caused by Group A beta hemolytic streptococcus (GAS, GABHS) aka. strep pyogenes
corynebacterium diphtheria, haemophilus influenza, moraxella catarrhalis |
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signs and symptoms of pharyngitis
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SORE THROAT
pain swallowing fever swollen lymph nodes (anterior cervical) runny nose, postnasal drip headache trouble breathing (serious) |
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what are the complications and sequelae surrounding step throat?
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complication (during infection): scarlet fever, bacteremia and strep TSS
sequelae (after infection): rheumatic fever, glomerulonephritis |
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what is the route of entry for strep pyogenes?
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respiratory (respiratory droplet spread)
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pathogenesis of strep pyogenes
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pharyngitis
otitis sinusitis tonsilitis adenitis pneumonia scarlet fever rheumatic fever glomerulonephritis |
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general charac of strep pyogenes
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G+ cocci
facultative anaerobe extracellular upper respiratory tract catalase neg toxigenic (streptolysin O) non-motile non spore forming |
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what type of hemolysis on blood agar plate?
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beta hemolysis (via streptolysin)
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epidemiology of strep pyogenes
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15-20% asx carriers (URT colonization)
respiratory droplet spread; crowded conditions some ppl at risk for scarlet/rheumatic fever |
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virulence factors for strep pyogenes
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M protein (50 Lancefield serotypes)
lipoteichoic acid Grp A (carbohydrate) capsule (hyaluronic acid) enzyme (hyaluronidase) pyrogenic (erythrogenic) exotoxins |
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how does the capsule prevent phagocytosis? how do we override this evasion mxn?
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made of hyaluronic acid; mimics BM
give type-specific Ig to M protein |
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S/S of GABHS pharyngitis
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fever
tonsillar exudate NO COUGH tender anterior cervical lymphadenopathy |
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clinical disease in pharyngitis
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abrupt onset: sore throat, fever, malaise, headache
posterior pharynx: erythematous cervical lymphadenopathy (50% w/ pharyngeal, tonsillar exudates) |
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what might streptococcal pharyngitis be confused with? why?
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viral pharyngitis
both have exudate |
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what is required for diagnosis?
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rapid strep, culture, serology
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scarlet fever will result during infection with what type of strep species?
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lysongenized strep species w/ pyrogenic (erythrogenic)exotoxin (super Ag)
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when do sx of of scarlet fever occur and how long do they last?
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occur 1-2 days after onset pharyngitis
last 5-7 days |
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what are the sx of scarlet fever?
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erythematous rash on upper chest
->extremities; blanch with pressure; pastia's lines (skin folds); sandpaper feel strawberry tongue high fever nausea, vomiting |
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when does rheumatic fever occur?
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2-3 weeks after pharyngitis
AUTOIMMUNE sequelae w/ untreated, asx pharyngitis |
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what are the S/S for rheumatic fever?
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endocarditis (heart valves)
pericarditis myocarditis fever rash carditis arthritis |
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how is rheumatic fever diagnosed?
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Jones criteria
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how do you prevent rheumatic fever?
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tx patient within 10 days of onset of pharyngitis
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what triggers rheumatic fever lesions?
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cross-reactivity b/w strep Ag and Ag on myocardium etc
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what is the Jones criteria?
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diagnosing rheumatic fever
1 required, 2 major, 0 minor OR 1 required, 1 major, 2 minor |
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what are required, major and minor criteria for rheumatic fever?
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required: lab diagnosis (strep Ig, culture, ASO etc)
major: carditis, sydenham's chorea (involuntary movements), polyarthitis, subQ nodules, erythema marginatum (pale center ans round margins) minor: fever, previous RF, acute phase reactions, prolonged PR interval |
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what is erythema marginatum? and what might it indicate?
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erythematous lesion
pale center rounded margin rheumatic fever |
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where are subcutaneous nodules usually found? what are they assoc with?
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extensor surfaces (knee, wrist, elbow)
rarely seen; assoc with sever carditis |
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how is glomerulonephritis assoc with GABHS?
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sequelae (post infection)for pharyngitis or impetigo (superficial skin infection from s. pyogenes)
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charac of glomerulonephritis
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IC deposited between epithelium and BM
autoimmune (crossreactive w/ s. pyogenes or rel of contained Ag) parietal and mesangial cells grow and proliferate (restrict lumen of capillaries; affect GFR and RBF) can lead to irreversible damage in adults NOT prevented by tx of pharyngitis or impetigo |
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s/s of glomerulonephritis
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edema
HTN hematuria proteinuria |
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lab diagnosis of s. pyogenes pharyngitis
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leukocytes WITH s. pyogenes
rapid test culture beta-hemolysis catalas neg bacitracin sensitive PYR test positive |
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are the rapid strep tests specific or sensitive? what does this require?
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high specificity (98), low sensitivity(90)
more FN (10%) so if have negative result must be confirmed; if positive, can give antibiotics |
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what is the PYR test?
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smear bacteria on filter paper containing PYR (chemical)
bacteria prod enzyme the hydrolizes PYR to give color |
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describe the bacitracin test for s. pyogenes
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diagnostic test-separates different types of strep
bacitracin on paper disk put on lawned agar; if bacteria are sensitive to it, they will be killed and a plaque will form; diameter is determined by MIC |
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what are the methods for the rapid strep test?
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extraction (enzyme, acid) and identification (immunoassay, latex agglutination)
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which type of extraction is more sensitive? which is faster?
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enzyme-more sensitive
acid-faster |
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when are throat cultures required?
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not for primary test
used to CONFIRM when had negative rapid NOT recommended for adults with pharyngitis |
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which method of identification is used more frequently?
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enzyme immunoassay (one step);
latex agglutination can detect different lancefield groups of strep |
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when do we do a rapid strep? when do we treat?
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test with 2 or more s/s of GABHS; treat with pos test OR when presumed GABHS with 3-4 s/s without test
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what is the treatment for GABHS?
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penicillin G
erythromycin cephalosporin (oral) may req 2nd round tx immediately to prevent rheumatic fever (not glomerulonephritis) req for rheumatic fever pts in subsequent procedures |
