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66 Cards in this Set

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Strep are part of the normal flora in what part of the body?
Oral cavity, GI and genital tract.

Note: some species highly pathogenic in various parts of the body.
What is the morphology of strep?
Spherical or oval cocci arranged in chains.
What is the Gram stain of Strep?
Gram + cocci in chains, become Gram variable as cells age and die.
What effect can antibiotics have on the morphology of strep?
Antibiotics can cause elongation of the strep shape.
What is strep's relationship to oxygen?
facultative anaerobe
Classification for streptococcus is based on what?
Type of hemolysis on blood agar.
Non helomytic strep are said to have what type of hemolysis?
Gamma hemolysis at 100X
What is alpha hemolysis?
Species with partial hemolysis of RBCs causing a green zone around the colony.
Alpha hemolytic strep are also called what?
Strep. viridans.
Complete hemolysis is also called what?
Beta hemolysis.
Lancefield groupings are for which type of strep?
Beta strep, based on cell wall antigens, groups identified by letters.
Pyogenic strep are what?
Strep that form pus, beta hemolytic strep, cause purulent infections.
Beta hemolytic strep.
Lyse sheep RBCs can infect skin, soft tissue and the CNS.
Group A strep.
type of beta hemolytic strep that is also called strep pyogenes.
Pneumococcus
A commonly used synonym for Strep pneumonia, contains a single species of Strep that is part of the alpha hemolytic group of strep.
Viridans strep
All remaining alpoha strep once strep pneumonia have been removed.
Non-hemolytic strep
Strep with low pathogenicity similar to viridans strep, genus enterococcus is in this group.
Pneumococcus
Refers to a single species: Strep pneumoniae, officially part of the alpha hemolytic group.
Speciation of viridans strep requires what?
Speciation for positives from multiple blood cultures.
Group A strep.
Strep pyogenes; beta hemolysis produced by streptolysin S (oxygen stable) Streptolysin O (O2 labile)
To enhance hemolysis of Beta hemolytic strep you can do what?
Incubate the plate anaerobically.
Group A surface structure.
Typical Gram + cell wall; group specific antigenic deteriminants raminose side chain on NAG; M protein associated with virulence; Protein F which binds mammalian cells.
Group A biologically active products
Hemolysins, toxins and biologically active extracellular products.
Streptolysin O
Type of hemolysin, pore forming toxin similar to alpha toxin in staph.
ASO
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.
Group A toxin.
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.
Group A Biologically Active Extracellular Products.
Streptokinase (lysis of fibrin clots), hyaluronidase (separates connective tisse barriers), DNAse, C5a peptidase degrades complement.
Group A Strep Pharyngitis
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.
Pathogenesis of pharyngitis
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.
Scarlet Fever
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.
Acute rheumatic fever
Post streptococcal sequelae; inflammatory disease fever carditis, subcutaneous nodules, migratory polyarthritis; heart valve damage causing murmurs, cardiac enlargement, repeat infections lead to progressive damage.
Mechanism of action for acute rheumatic fever
M protein fragments from certain serotypes cross react with cardiac tissue, affected persons must be treated with penicillins to prevent recurrences.
Acute glomerulonephritis
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.
Impetigo
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.
Erysipelas
group A strep of skin and subcuatenous tissue; spreading areas of erythema and edema with rapidly advancing edges accompanied by pain fever lymphadenopothy.
Group A beta hemolytic strep can also cause what freakin nasty horrible infection?
Necrotizing fasciitis.
Puerperal infections
infection of endometrium at delivery, rapidly spreads to other organs and blood stream via lymphatics, rapidly fatal prevented by handwashing.
Toxic Shock Like syndrome
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.
Lab Diagnosis of Group A strep.
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.
CDC recommendations regarding throat cultures for adults.
Throat cultures not recommended for adults or to confirm negative rapid tests. Throat cultures OK if Neisseria gonorhhea is suspected.
Antibody tests for group A Strep
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.
Treatment of group A strep.
pharyngitis with penicillin G or erythromycin. Impetigo, since S. aureus often accompanies treatment is with cephalosporins or oxacillin.
Group B Strep (Strep agalactiae)
Up to 30% women carry GBS as part of normal vaginal flora. Neonate can acquire while passing through the birth canal.
Neonatal group B Strep diseases.
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.
Group B strep infections
neonatal disease: lethargy, fever sepsis meningitis, respiratory disease, older children and adults puerperal fever at delivery, gynecological surgery infections, skin and soft tissue infections.
Prevention of Group B Strep Infections
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)
Strep pneumoniae morphology
Gram + diplococci wider range of shapes, round to oval to lancet shape, encapsulated organism, alpha hemolytic colonies on blood agar, mucoid in appearance.
Pneumococcal disease
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.
Pneumococcal Vaccine
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.
pediatric pneumococcal vaccine
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.
Who should receive the 23 valent pneumococcal vaccine?
Adults 65 and older.
Who should receive PCV13?
children 6 weeks to 5 years especially those with chronic heart or lung disorders. vaccine can be started as early as 6 weeks.
Viridans Strep
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.
Strep milleri group
clinically associated with brain and liver abscesses, split into angiosus, constellatus and intermedius.
Viridans strep species
All can cause subacute bacterial endocarditis, s mutans also causes cavities, S mitis, S salivarius, detect with blood cultures, treat with penicillin for weeks,
Viridans strep on heart valves
initially adhere to tiny imperfections of heart valve, usually sensitive to penicillin G if gievn for weeks. pen given as prophylaxis for dental procedures.
Nutritionally deficient strep: abiotrophia defectiva and Granulicatella adiacens
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.
Group D Strep:S bovis
non hemolytic strep in the gut positive in blood cultures in patients with colon cancer.
Entercoccus
gram positive cocci in chains, natural habitat is the gut, very resistant to bile salts acid, NaCl. Infections caused: Endocarditis, UTIs, opportunistic hospital infections.
E. faecalis
most common clinical isolate of entercoccus. Susceptible to ampicillin
E. faecium
resistant to ampicillin, more likely resistant to vancomycin
Enterococcus classification
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)
Enterococcus diseases
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
Enterococcus treatment
E. faecalis use amplicillin UTIs, use amp+getamycin for endocarditis, E. faecium used to use Vanco becoming resistant.
Vancomycin resistant enterococus
20% enterococci.
Enterococcus
Gram + chains, non hemolytic, grows on bile causes UTI subactute bacterial endocarditis and opportunistic hospital infections.