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89 Cards in this Set

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