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Streptococci
gram-positive bacteria, chapter 4
37
Microbiology
Graduate
12/29/2009

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Term
How do you differentiate between streptococci and staphylococci?
Definition
staphylococci: catalase +
streptococci: catalase -
Term
Divide streptococci into three groups depending on hemolytic ability
Definition
* beta-hemolytic: completely lyse RBC
* alpha-hemolytic: incomplete/partial, green-colored hemoglobin metabolite
* gamma-hemolytic: non-hemolytic
Term
What are "Lancefield antigens"?
Definition
Antigenic C carbohydrate found on the cell wall. A ~ S
Term
What are 5 most significant human pathogenic streptococci species?
Definition
Lancefield group A, B, and D.
Streptococcus pneumoniae
Viridans group streptococci.
Term
Which streptococcus species has Lancefield group A, and is beta-hemolytic?
Definition
Streptococcus pyogenes
(pus-producing)
Term
4 diseases that streptococci pyogenes cause
Definition
strep throat, scarlet fever, rheumatic fever, post-streptococcal glomerulonephritis
Term
What is "M protein?"
Definition
Antigenic cell wall component of group A streptococcus. Inhibits activation of complements, but is a target of antibodies of the host.
Term
Enzymes in streptococcus pyogenes (group A, beta-hemolytic)
Definition
* streptolysin O: lyses RBC, WBC; antigenic. INactivated by oxygen
* streptolysin S: Oxygen stable. Hemolytic but not antigenic
* Pyrogenic exotoxin (erythrogenic toxin): in a few strains; cause scarlet fever; some are superantigens that lead to toxic shock syndrome
* streptokinase, hyaluronidase, DNAses, anti-C5a peptidase
Term
4 diseases by local invasion and/or exotoxin release of streptococcus pyogenes?
Definition
1. streptococcal pharyngitis
2. streptococcal skin infections
3. scarlet fever
4. streptococcal toxic shock syndrome
Term
2 delayed antibody mediated diseases by streptococcus pyogenes:
Definition
1. rheumatic fever
2. glomerulonephritis
Term
How to diagnose streptococcal pharyngitis?
Definition
1. Rapid Antigen Detection Test (for antigenic C carbohydrate)
2. throat culture
Term
How do you treat streptococcal skin infection?
Definition
With dicloxacillin (penicillinase resistant penicillin), which covers both Streptococcus pyogenes and Staphylococcus aureus
Term
What is erysipelas?
Definition
Streptococcal pyogenes infection of the superficial skin (dermis). Unlike cellulitis, rarely caused by Staph. aureus
Term
Virulent factor of Strep. pyogenes that causes necrotizing fasciitis?
Definition
M protein--block phagocytosis, allowing the bacteria to move rapidly through tissue, along the fascia.
Term
Fournier's gangrene?
Definition
A form of necrotizing fasciitis involving the male genital area and perineum.
Can be caused by Strep. pyogenes
Term
Scarlet fever's rash spares which part of the body?
Definition
face
Term
How to treat Streptococcus pyogenes infection?
Definition
* penicillin G
* clindamycin, which inhibits bacterial ribosome ---> blocks pyrogenic toxin and M protein syntheses
Term
Rheumatic fever follows:
Definition
beta-hemolytic group A streptococcal pharyngitis (not skin infection)
Term
Clinical features of acute post-streptococcal glomerulonephritis
Definition
* fluid retention
* dark urine (hematuria)
Term
Group B streptococci (also beta-hemolytic) are called:
Definition
Streptococcus agalactiae
Term
Streptococcus agalactiae can cause what diseases in neonates (< 3 mo. old)
Definition
meningitis, pneumonia, sepsis
Term
Clinical features of neonatal meningitis
Definition
nonspecific: fever, vomiting, poor feeding, irritability
Term
Three most common bacteria that cause neonatal meningitis:
Definition
* Listeria monocytogenes
* Escherichia coli
* Streptococcus agalactiae (group B)
Term
two most common bacteria that cause meningitis between maternal Ab and synthesis of new Ab?
Definition
* Neisseria meningitides
* Haemophilus influenzae
Term
Where are Viridans group streptococci found?
Definition
GI tract, esp. in the mouth
Term
3 infections caused by Viridans group streptococci:
Definition
* dental infections
* endocarditis
* abscesses
Term
subacute and acute endocarditis are caused by:
Definition
subacute: viridans streptococci
acute: staphylococcal infection
Term
Streptococcus intermedius and anginosus
Definition
immediately assess for abscess (CAT scan with contrast). viridans group
Term
Group D streptococci: hemolysis type and divisions
Definition
* alpha-hemolytic
* enterococci (faecalis and faecium) and non-enterococci (S. bovis and S. equinus)
Term
Enterococci result in...
Definition
urinary tract infections, biliary tract infections, bacteremia, subacute bacterial endocarditis, target hospitalized patients.
Term
Enterococci are not resistant to:
Definition
ampicillin and vancomycin
Term
How do you grow Streptococcus bovis (group D, non-enterococci)?
Definition
In 40% bile (but not in 6.5% NaCl)--enterococci grow in either 40% bile or 6.5% NaCl
Term
Which bacterial infection is associated with colon cancer?
Definition
Streptococcus bovis
Term
Streptococcus pneumoniae (pneumococcus) cause which diseases?
Definition
bacterial pneumonia and meningitis in adults; otitis media in children
Term
How to ID pneumococcus?
Definition
1. Quellung reaction (capsule)
2. Optochin sensitivity (Strep. viridans is also alpha-hemolytic)
Term
3 most common bacteria that cause otitis media:
Definition
1. Streptococcus pneumoniae
2. Haemophilus influenzae
3. Moraxella catarrhalis
Term
Who should get pneumovax (pneumococcal vacine)?
Definition
immunocompromised (HIV), elderly, no spleen
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