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68 Cards in this Set
- Front
- Back
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what does beta hemolytic strep do
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completely lyse RBC leaving a clear zone of hemolysis around the colony
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what does alpha hemolytic do
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partially lyse the RBC leaving a greenish discoloration of culture medium surrounding the colony (green has unlysed RBC &green-metabolite of hemoglobin)
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what is gamma hemolytic
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unable to hemolyze the RBC and shouldn't be called that
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how else can streptococci be classified based on antigenic characteristic beside hemolysis
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C carbohydrate (carb on cell wall)
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What are the C carbohydrates called
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Lancefield antigens (A, B,D)
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Group A beta-hemolytic streptococci what Lancfield
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group A, beta-hemolytic, on blood agar "pus producing"
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what are all the diseases group A strep can cause
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strep throat, scarlet fever, rheumatic fever, & post-strep glomerulonephritis
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What is the major virulence for group A streptococcus
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M protein- inhibits activation of complement and protects the organism from phagocytosis, weakest point in the organisms defense bc plasma B cells generate antibodies against M protein abs. bind to M protein (opsonize) aid in destruction of organism by macrophages & neutrophils
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streptolysin O stand for
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oxygen labile, inactivated by oxygen..enzyme destroys RBC & WBC and reason the beta-hemolytic to happen, also antigenic--> anti-strep O antibodies develop (titers)
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Streptolysin S
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stands for oxygen sbile- responsible for beta-hemolysis but not antigenic
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Pyrogenic exotoxin found
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only in few strains of beta-hemolytic A group strep, but they can cause scarlet fever..some are superantigens--> exotoxins directly superstim T cells pours out inflammatory cytokines, streptococal toxic shock syndrome
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Streptokinase
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activate protelyutic enzyme plasmina--> breaks fibrin blood clots
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4 types of diseases by local invasion or exotoxin release by strep group A
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streptococcal pharyngitis, streptococcal skin infections, scarlet fever, streptococcal toxic shock syndrome
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beta hemolytic also causes 2 delayed antibody mediated diseases
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rheumatic fever & glomerulonephritis
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describe streptococcal pharyngitis
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classic strep throat w red swollen tonsils & pharynx, purulent exudate on tonsils, high T, & swollen LN..5 days, tx w penicilin
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Skin infections caused by strep group A
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folliculitis (infect hair) cellulitis (deep of skin) impetigo (vesicular, blister erupt in kids crust/flake around mouth) also caused by staph areus, penicillinase resistant like dicloaxcillincovers both group A and staph
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necrotizing fasciitis caused by this
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"flesh-eating strep" certain M proteins block phagocytosis, allowing bacteria to rapidly invade, enter through a break in the skin by trauma... and follow path on fascia..btwn subcut & muscle swell, heat, & red
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what is the skin color with NF
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red--> purple--> blue and large blisters (bullae) form later skin dies and muscle can become infected (myositis)
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How do you remove the fascia w necrotizing fasciity
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surgically remove it and rapid antibiotic therapy
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how do you treat group A causing NF
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penicillin G + clindamycin to shut down strep metabolism & toxin production
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how does group A cause scarlet fever
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produces pyrogenic toxin/erythrogenic toxin...acuquired by lysogenic conversion- produces a fever, causes scarlet-red rash..begins on trunk/neck and spread to extremities/sparing the face, skin can peal
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streptococcal toxic shock syndrome
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beta hemolytic group A causes same as staph areus, mediated by release ph pyrogenic toxin..add clindamycin to penicillin G as the former rapidly shut strep met and toxin prod
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Delayed- Ab-mediated disease: rheumatic fever
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w advent of penicillin rheumatic fever is now uncommon, stirikes kids 5-15 yr, whe nit happens follows untreated beta-hemoltyics group A strep pharyngitis
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6 major manifestations of rheumatic fever
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fever, mycoarditis (heart inflammation), joint swelling (arthritis), & chorea (uncontrol dance moves), subacute nodules rash erthema marginatum red margin sprea dfrom center (JONES)
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how does rheumatic fever happen
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antibody-mdiated, antigens in heart similar to the antigens in group A beta-hemolytic strep...antigens forming for this can cross-react w heart= myocarditis, chest pain
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how does the heart start to become damage with rheumatic fever
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recurrent infectoin w strep makes a permanent damage, usually Mitral valve--> aortic valve happens after a while
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intially you see myocarditis and then
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rheumatic valvular heart disease develops
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to avoid the recurrent rheumatic fever what is recommended to give prophylactically
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penicillin
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describe acute post-strep glomerulonephritis
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nephritigenic strains from pharyngitis etc. can gross into the kidney, antigen-antibody deposit in glomerular BM--> activate complement cascade, glomerular destruction in kidney
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how will a kid present with glomerulonephritis from strep?
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puffy cheek, hypertension, dark urine"tea colored", hematuria
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Group B streptococci
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these are also beta-hemolytic, normal in the vagina, but in a neonate can cause meningitis, sepsis will show fever/vomit, poor feeding irrtability
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classic sign for meningitis in an adult?
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stiff neck
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e.coli, listeria monocytes, & group B commonly cause _____ in infants
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meningitis
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how to diagnose meningites?
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lumbar puncture
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what is the strep viridans group
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no lancefield group to classify
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most of the viridans are what type of hemolysis
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alpha
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what are the 3 main infections by viridans?
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dental, endocarditis, & abscesses
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main dental infector
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strep mutans, binds to teeth, ferments sugar, produces acids & dental carries
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endocarditis caused by
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dental send to bloodstream implant on endocardial, usually a damaged valve..produce extracelllular dextran..allow to cling, subacute bacterial endocardiits...pile on heart
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clinically how does an SBE present
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low-grad fevers, fatigue, anemia, and heart murmurs secondary to valve destruction
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acute infective endocarditis is caused by
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staphylococcal infection often secondary to IV drug abuse, characterized by an abrupt onset of shaking chills, high spiking fevers, & rapid valve destruction
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what cuases SBE the fastes?
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staph areus
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so an acute SBE is most likely caused by
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staph areus
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strep can work as a team strep pyogenes causes rheumatic fever and then rheumatic fever damages the heart valve--> now who infects
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now viridans strep or group D stick better on heart valves
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where is strep intermeius found
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subgroup of strep viridans, normal GI tract, oxygen hating critters...found in abscesses in brain/abdominal found alone in pur cultures or mixed w anaerobes
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if strep intermedius is in the blood you should suspect
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abscess in organ
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Group D streptococci are
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alpha-hemoltyic divide 2 groups enteroccii & non-enterococcie
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enterococci are their own
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genus bc vastly diff from strep but non-entero is still s. bovis & s. equinus
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where do the enterococcus reside
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human intestine, and normal bowel flora, alpha hemoltyic grow in 40% bile or 6.5% NaCL commonly found in UTI, biliary tract infections...SBE...not as virulent as strep pyogenes...aroun din GI and prey on weak hospitalized pts.
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what is the 2nd most common noscomial infection in US
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entercoccus
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enterococcus is now resistant to
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ampicilly & vancomycin
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how do we treat enterococcus
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ampicillin _ aminoglycoside
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how did VRE develop
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alter cell wall dipeptide- d-alanine-d alanine target of vanco, change to d-alanin-lactate
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pristinomycins can be used for
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enterococcus
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strep bovis doesnt grows in
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40% bile but not NaCl, lives in Gi tract..causes similiar diseases...important unique= colon cancer, is it a marker or the cause of the cancer?
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pneumococcus is
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important no lancefield, but bacterial pneumonia & meningitis in adults and otitis media in kids its the "group B" to adults as B is to babies
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how does pneumococcus appear under the microscope
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lancet-shaped gram-positive cocci arranged in pairs (diplococci)
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whats the major virulence factor of pneumococcus
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polysacchardide capsule, protects from phagocytosis, capsule is antigenic, and abs. specific neutralize it
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but whats the problem w capsules
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theres so many! you can be immune to one but not the 80 others
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important lab tests for pneumococcus
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quellung reaction & optochin sensitivity
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pneumococci on a slide smear w antiserum & methylene blue- capsule swells =
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quellung reaction + pneumoccocus
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strep pneum and strep viridan= alpha, to differentiate
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disc w optochin on agar- strep pneum growth is inhibits
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common signs of pneumonia
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shaking chills, high fevers ,chest pain, SOB, alveoli of lung lobe fill w WBC..chest X-ray white consolidated lobe cough up yellow-green phlegm gram += gram + positive lancet-shaped diplococci
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strep pneum MCC
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MOPS
(meningitis, otitis media, pneumonia, sinusitis) |
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pneumo vax is great for
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immunocompromised pts and HIV
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strep pneumonia is resistant to
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penicillin
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OVRPS
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optochin, veridan= resistance
pneumonia= sensitive |
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B-BRAS
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bacitracin
group B= resistant group A= sensitive |
