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89 Cards in this Set
- Front
- Back
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What is the gram stain morphology of streptococci?
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Gram pos cocci in chains
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What are the 3 most pathogenic streps?
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-Strep pneumo
-Strep group A (pyogenes) -Strep group B (agalactiae) |
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What is Strep used in?
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Industrial and dairy products
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What is the nomenclature of Streps (A/B/D) based on?
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Lancefield serotyping of cell wall components
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What is the most common infection caused by Strep A pyogenes?
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Pharyngitis (strep throat)
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What are 2 diseases associated with Strep B agalactiae?
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-Neonatal meningitis
-Sepsis |
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What diseases are associated with Enterococcus and S. bovis?
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-Biliary / UTI
-Endocarditis |
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What disease is caused by Strep viridans? What species?
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Endocarditis / Dental caries
-S. mutans |
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What does S. pneumoniae cause?
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lobar pneumonia
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What are the 7 acute infections that Strep A causes?
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SISTEEN
-Strep throat -Impetigo -Scarlet fever -toxic shock (LIKE) -Endocarditis -Erysipelas -Necrotizing fasciitis |
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What are the 2 late sequelae infections that result from Strep A infections?
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-Glomerulonephritis
-Rheumatic fever |
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How does scarlet fever develop and manifest?
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From pharyngitis; a red rash develops.
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What is impetigo?
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An infection of the superficial layers of the skin
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What is erysipelas?
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An infection of the skin and subcutaneous tissues
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What are the general features seen in erysipelas?
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-Edema
-Induration -Distinct advancing border |
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What is the progression of Streptococcal Toxic Shock?
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1. Focal infection
2. Bactermia 3. Shock hypotension 4. and 2/more other symptoms |
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What are 5 complications that will normally follow Strep Toxic shock?
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-Coagulopathy
-ARDS -Renal impairment -Liver abnormality -Rash/desquamation |
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What is the worst skin infection caused by Strep group A?
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Necrotizing fasciitis
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How deep does Necrotizing fasciitis go?
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Into the fascia
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What are the results of necrotizing fasciitis?
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-Extensive necrosis
-Gangrene |
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What causes Strep A to sometimes advance into later sequelae?
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The cell-mediated adaptive immune response that occurs later in response to infection.
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What does rheumatic fever often follow?
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Respiratory infections
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What IS rheumatic fever?
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A type II hypersensitivity reaction of antibodies against Strep A that cross react with heart tissue antigens.
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What are the 3 symptoms of rheumatic fever?
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-Fever
-Polyarthritis -Carditis |
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What does glomerulnephritis follow?
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Either pharyngeal or cutaneous infections
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What is glomerulnephritis?
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Hypersensitivity reaction to immune complexes that get stuck and deposit in the glomerular basement membrane.
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What are the symptoms of glomerulonephritis?
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-Fever
-Hematuria -Edema |
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Why do Streps bud linearly instead of in clusters?
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Because they are encapsulated
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What type of capsule does Strep pneumoniae have?
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Polysaccharide
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What type of capsule does Strep A have?
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Hylauronic acid
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How does Strep A bud?
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In long chains
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How does Strep pneumo bud?
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In lancet shaped diplocci
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How do we differentiate streps from staph?
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Via catalase
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Are streps motile?
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no
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Where are Strep A and B normal flora?
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In the nasopharynx
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Is S. pneumoniae normal flora?
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In some
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In what patients are Strep infections most frequently seen?
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Young and Old
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When does the rash in Scarlet fever occur?
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12-48 hours after the start of fever
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Where does the rash in scarlet fever start out?
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Below the ears, neck, chest, armpits, and groin.
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What are the first signs of the rash in Scarlet fever?
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Goose pimples
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What are the epidemiological markers on Group A strep?
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R and T proteins
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What are M proteins?
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The virulence determinant on Group A strep that encodes its ability to evade phagocytosis
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What mediates attachment of Strep A to host cells?
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Lipotechoic acid
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What are the antigenic epitopes on Group A strep that cross react with host CT?
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The hyaluronic acid capsule
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What is the major virulence factor on Strep pneumo?
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The polysaccharide capsule
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How does the polysaccharide capsule mediate virulence of strep pneumo?
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It confers anti-phagocytic properties.
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What happens if Strep pneumo is unencapsulated?
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It is avirulent
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Can we make a vaccine against Strep A?
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No - the regions that determine its virulence are HYPERVARIABLE
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Can we make a vaccine against Strep pneumo? How?
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Yes - by combining antigenic epitopes from 23 different variants.
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Are symptoms of strep infections caused by the invasiveness of the bacterium?
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No; moreso by the widespread secretion of its toxins.
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What is the structure of the M protein on Strep A like? Where is it anchored?
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-Highly alpha helical
-Anchored in the cell wall and membrane -Hypervariable regions at its N-terminus |
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What are 6 types of toxins secreted by Strep A?
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-Leukotoxins
-Hyaluronidase -Streptokinases -Streptodornases A-D -Protease -Pyrogenic exotoxins |
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What are the 3 leukotoxins?
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-Streptolysin S
-Streptolysin O -NADase |
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What is streptolysin S?
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Oxygen stable hemolysin
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What is streptolysin O?
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Reversible oxygen labile hemolysin
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What do we have to do to be able to see oxygen labile hemolysins?
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Stab the agar plate to get bugs down under the surface where they're protected from oxygen.
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What does Hyaluronidase do?
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Breaks up host connective tissue (and the capsule)
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What does Streptokinase do?
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Lyses fibrin - dissolves clots
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What are the Streptodornases A-D?
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DNases
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Why would streps want DNase?
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Because when they damage cells and they spill their genomes, it makes a big glob; DNase allows them to get through the glob.
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What are the Pyrogenic exotoxins?
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Streptococcal Pyrogenic Exotoxins A, B, and C
SUPERANTIGENS |
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How do the superantigens SPE A/B/C work?
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By nonspecifically binding the beta hypervariable subunit of TCR and MHC II on APCs to stimulate cytokine release.
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What specific disease process are the pyrogenic exotoxins associated with?
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Necrotizing fasciitis
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Where are the pyrogenic exotoxins encoded?
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BY BACTERIOPHAGE
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Are pyrogenic exotoxins only produced by Strep A?
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No, also by Strep B, C, F, and G
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Do super antigens bind the TCR and MHC II within the peptide binding domain?
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No; it's on the side of the two receptors.
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What do all the degradative enzymes secreted by Streps allow?
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Rapid spread through tissues
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What is NOT a useful mechanism for neutralizing the degrading damage caused by strep toxins?
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Antibodies and vaccines.
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With which streps do postinfectious sequelae occur?
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Strep A only
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When do postinfecious sequelae begin?
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1-3 weeks after the acute illness
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What type of infection does Rheumatic fever follow? Glomerulonephritis?
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RF: only after pharyngitis
GN: after throat OR skin infections |
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What type of sequelae requires life-long antibiotic prophylaxis for invasive procedures?
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Rheumatic fever
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What are the 2 most prominent infections associated with Strep group B?
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-Neonatal meningitis
-Pneumonia in elderly |
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What type of pathogens are Group D streps?
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Opportunistic
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What is Strep bovis associated with?
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Bowel disease and colon cancer
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What is strep viridans (mutans) associated with?
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It causes dental caries
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What are the 2 enterococci that are common commensals in the intestines?
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-E. faecalis
-E. faecium |
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Why are Enterococci bad?
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They are highly resistant to antiobiotic treatment
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What antibodies can the host immune system make against
-Strep pyogenes -Strep pneumo |
Strep A: Anti-M protein
Strep pneumo: Anti-polysaccharide capsule |
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Why can't we give vaccines against Strep A if the body makes an Anti-M protein?
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Because this molecule has the hypervariable N-terminus and thus infection with a different strain would not be protected against by a vaccine.
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How does the Pneumococcal vaccine work?
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It is polyvalent and contains antibodies against epitopes from 23 different strains.
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What is Quellung?
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A capsular swelling test used to identify Strep pneumo
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What is the drug of choice for streating Strep A?
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Penicililin
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What is happening to Strep pneumo?
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It is becomining resistant to penicillin
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What are 3 other drugs commonly used to treat Strep infections?
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-Erythromycin
-Tetracyclin -Clindamycin |
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What is the treatment for Necrotizing fasciitis or myositis?
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-Surgical wound debridement
-Antibiotics |
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What is required for treating Group D strep infections?
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A dual combination of Penicillin to weaken the cell wall, and Clindamycin to inhibit protein synthesis.
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What test differentiates Strep pneumo from Strep viridans?
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Optichin - Strep pneumo is sensitive
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What test differentiates Strep grp A from Strep B?
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Bacitracin - Strep A is sensitive
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