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66 Cards in this Set
- Front
- Back
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Strep are part of the normal flora in what part of the body?
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Oral cavity, GI and genital tract.
Note: some species highly pathogenic in various parts of the body. |
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What is the morphology of strep?
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Spherical or oval cocci arranged in chains.
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What is the Gram stain of Strep?
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Gram + cocci in chains, become Gram variable as cells age and die.
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What effect can antibiotics have on the morphology of strep?
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Antibiotics can cause elongation of the strep shape.
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What is strep's relationship to oxygen?
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facultative anaerobe
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Classification for streptococcus is based on what?
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Type of hemolysis on blood agar.
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Non helomytic strep are said to have what type of hemolysis?
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Gamma hemolysis at 100X
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What is alpha hemolysis?
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Species with partial hemolysis of RBCs causing a green zone around the colony.
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Alpha hemolytic strep are also called what?
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Strep. viridans.
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Complete hemolysis is also called what?
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Beta hemolysis.
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Lancefield groupings are for which type of strep?
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Beta strep, based on cell wall antigens, groups identified by letters.
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Pyogenic strep are what?
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Strep that form pus, beta hemolytic strep, cause purulent infections.
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Beta hemolytic strep.
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Lyse sheep RBCs can infect skin, soft tissue and the CNS.
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Group A strep.
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type of beta hemolytic strep that is also called strep pyogenes.
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Pneumococcus
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A commonly used synonym for Strep pneumonia, contains a single species of Strep that is part of the alpha hemolytic group of strep.
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Viridans strep
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All remaining alpoha strep once strep pneumonia have been removed.
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Non-hemolytic strep
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Strep with low pathogenicity similar to viridans strep, genus enterococcus is in this group.
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Pneumococcus
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Refers to a single species: Strep pneumoniae, officially part of the alpha hemolytic group.
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Speciation of viridans strep requires what?
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Speciation for positives from multiple blood cultures.
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Group A strep.
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Strep pyogenes; beta hemolysis produced by streptolysin S (oxygen stable) Streptolysin O (O2 labile)
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To enhance hemolysis of Beta hemolytic strep you can do what?
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Incubate the plate anaerobically.
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Group A surface structure.
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Typical Gram + cell wall; group specific antigenic deteriminants raminose side chain on NAG; M protein associated with virulence; Protein F which binds mammalian cells.
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Group A biologically active products
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Hemolysins, toxins and biologically active extracellular products.
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Streptolysin O
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Type of hemolysin, pore forming toxin similar to alpha toxin in staph.
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ASO
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Individuals infected with Strep A make antibody to streptolysin O. A high ASO titer can be used to indicate a recent infection with group A strep. Elevated ASO Ab in ~85% people recently infected with group A strep for two weeks or more.
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Group A toxin.
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Also called pyogenic exotoxin; once called erythyrogenic toxin; stimulates cytokine release making a red rash on the skin (scarlet fever); toxin is carried on a phage; the majority of strains do not carry this toxin.
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Group A Biologically Active Extracellular Products.
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Streptokinase (lysis of fibrin clots), hyaluronidase (separates connective tisse barriers), DNAse, C5a peptidase degrades complement.
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Group A Strep Pharyngitis
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2-10% of the population are carriers, lasts 1-4 weeks or more after infection; organism in throat, sometimes anus, spread by direct contact or aerosols.
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Pathogenesis of pharyngitis
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Protein F and protein M play a role in binding. Once bound multiplication occurs. protein M prevents phagocytosis. organism continues to spread due to streptokinase, hyaluronidase, etc.
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Scarlet Fever
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Strep throat with a rash; Deep red color-cheeks temples buccal mucosa and a red tongue called strawberry tongue, punctate hemorrhages on palate; sandpaper rash on trunk arms and legs, rash due to toxin.
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Acute rheumatic fever
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Post streptococcal sequelae; inflammatory disease fever carditis, subcutaneous nodules, migratory polyarthritis; heart valve damage causing murmurs, cardiac enlargement, repeat infections lead to progressive damage.
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Mechanism of action for acute rheumatic fever
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M protein fragments from certain serotypes cross react with cardiac tissue, affected persons must be treated with penicillins to prevent recurrences.
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Acute glomerulonephritis
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Antigen antibody complexes deposited in kidney causing lesions of glomeruli, occurs 10 days after respiratory infections, recovery after weeks or months occasional kidney failure or death.
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Impetigo
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group A strep infection of the skin, starts as a minor insect bite or scratch; may coinfect with staph; small vesicles with erythema, become pustular and later crusted, glomerulonephritis a possible complocation.
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Erysipelas
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group A strep of skin and subcuatenous tissue; spreading areas of erythema and edema with rapidly advancing edges accompanied by pain fever lymphadenopothy.
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Group A beta hemolytic strep can also cause what freakin nasty horrible infection?
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Necrotizing fasciitis.
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Puerperal infections
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infection of endometrium at delivery, rapidly spreads to other organs and blood stream via lymphatics, rapidly fatal prevented by handwashing.
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Toxic Shock Like syndrome
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progressive infection with bacteremia, shock, diarrhea, rash renal impairment, respiratory failure. Multuple organs involved caused by strep pyrogenic exotoxin. Mortality is abotu 10-12%. desquamation.
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Lab Diagnosis of Group A strep.
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Rapid Group A Stret, immunological assays for group A antigen. 80-90% sensitive- must do a culture on the negatives, 99% specific no need to culture the positives.
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CDC recommendations regarding throat cultures for adults.
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Throat cultures not recommended for adults or to confirm negative rapid tests. Throat cultures OK if Neisseria gonorhhea is suspected.
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Antibody tests for group A Strep
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used in post stret sequalae used in acute rheumatic fever and glomerulonephritis, antibody high but cultures are negative ASO main test. antihyaluronidase is an alternate test. Streptozyme detects antibody to 5 extracellular products.
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Treatment of group A strep.
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pharyngitis with penicillin G or erythromycin. Impetigo, since S. aureus often accompanies treatment is with cephalosporins or oxacillin.
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Group B Strep (Strep agalactiae)
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Up to 30% women carry GBS as part of normal vaginal flora. Neonate can acquire while passing through the birth canal.
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Neonatal group B Strep diseases.
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Neonatal sepsis and meningitis in 1980's 1-3 cases per 1000 births. mortality 10-60% IN 1998 GBS was one of leading causes of death in neonates.
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Group B strep infections
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neonatal disease: lethargy, fever sepsis meningitis, respiratory disease, older children and adults puerperal fever at delivery, gynecological surgery infections, skin and soft tissue infections.
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Prevention of Group B Strep Infections
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Routinely culture pregnant women during the last month of delivery. If culture + then give penicillin at birth, treat baby if premature rupture of membranes, any sign of lethargy or abnormality. (DNA probe for group B)
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Strep pneumoniae morphology
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Gram + diplococci wider range of shapes, round to oval to lancet shape, encapsulated organism, alpha hemolytic colonies on blood agar, mucoid in appearance.
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Pneumococcal disease
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Most common cause of bacterial pneumonia in adults, vaccine avail.; encapsulated bacteria in adults and children causes meningitis, middle ear infection, sinusitis, abdominal or wound infection.
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Pneumococcal Vaccine
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need each capsule type to be included in vaccine. 23 strains in current adult vaccine, 88% invasive pneumococcal disease associated with these 23 strains.should be given to adults greater than 65 years of age. for children there is a special vaccine pneumococcal disease is the leading cause of vaccine preventable death worldwide in children under age 5.
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pediatric pneumococcal vaccine
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13 valents, prevents pneumococcal disease and otitis media and pneumonia. 7 valent original disease associated with invasive disease. serotype 19A associated with antibiotic resistance and prevalent in many parts of the world.
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Who should receive the 23 valent pneumococcal vaccine?
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Adults 65 and older.
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Who should receive PCV13?
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children 6 weeks to 5 years especially those with chronic heart or lung disorders. vaccine can be started as early as 6 weeks.
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Viridans Strep
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All the alpha hemolytic strep once strep pneumoniae has been removed. does not include beta or non hemolytic organisms, normal flora of mouth, gut and genitalia.
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Strep milleri group
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clinically associated with brain and liver abscesses, split into angiosus, constellatus and intermedius.
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Viridans strep species
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All can cause subacute bacterial endocarditis, s mutans also causes cavities, S mitis, S salivarius, detect with blood cultures, treat with penicillin for weeks,
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Viridans strep on heart valves
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initially adhere to tiny imperfections of heart valve, usually sensitive to penicillin G if gievn for weeks. pen given as prophylaxis for dental procedures.
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Nutritionally deficient strep: abiotrophia defectiva and Granulicatella adiacens
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will not grow on ordinary blood agar, need special vitamins, resembles viridans, causes bacterial endocarditis, difficult to detect by culture but can make easier by adding a feeder colony.
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Group D Strep:S bovis
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non hemolytic strep in the gut positive in blood cultures in patients with colon cancer.
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Entercoccus
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gram positive cocci in chains, natural habitat is the gut, very resistant to bile salts acid, NaCl. Infections caused: Endocarditis, UTIs, opportunistic hospital infections.
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E. faecalis
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most common clinical isolate of entercoccus. Susceptible to ampicillin
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E. faecium
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resistant to ampicillin, more likely resistant to vancomycin
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Enterococcus classification
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non-hemolytic on sheeps blood agar, beta hemolytic on horse blood agar, positive growth on bile esculin agar, growth in 6.5% NaCl broth(separates from non-hemolytic strep)
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Enterococcus diseases
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Opportunistic: cause infection after broad spectrum antibiotics wipe out normal flora, wound and soft tissue infections, bacteremia related to indwelling lines, hard to treat endocarditis, 5% outpatient UTIs, 10-30% inpatient UTIs associated with urinary tract manipulations
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Enterococcus treatment
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E. faecalis use amplicillin UTIs, use amp+getamycin for endocarditis, E. faecium used to use Vanco becoming resistant.
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Vancomycin resistant enterococus
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20% enterococci.
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Enterococcus
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Gram + chains, non hemolytic, grows on bile causes UTI subactute bacterial endocarditis and opportunistic hospital infections.
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