strep, enterococ
Terms
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- gram stain of strep/entero generi (two genera)
-
NOT nice and round;
broth cultures give chains in gram stain.
a little messier than staphs - What are the growth characteristics of Streptococcus and Enterococcus?
-
Fastidious, facultative anaerobes (like Staphs, only fastidious)
Grows on BA in increased CO2 - What are the characteristic antigens on Streptococcus species?
-
C carbohydrates - use lancefield typing
M protein - protects from phagocytosis - 3 Ways Streps and Enterococcus are differentiated:
-
1. Hemolysis
2. Presumptive tests - biochemical
3. Definitive tests - imunological - gamma isolates of strep/enter
-
S. viridans
Enterococcus
Strep group D Non-Enterococcus - two tests on gamma isolates
-
-bile esculin (neg shows saprophyticus)
-6.5% NaCl (pos shows enterococ, neg shows strep D non-enter) - What test is an alternate to 6.5% NaCl?
- PYR HYDROLYSIS
- Where is S. viridans normal flora?
- mouth/vagina
-
What causes Bacterial Endocarditis?
-Acute
-Subacute -
Subacute caused by:
-Staphylococcus epidermidis
-Streptococcus viridans
Acute caused by:
Staphylococcus aureus - What is used to treat Streptococcus viridans infections?
- penicillin
- what is intrinsiclaly resistant to penicillin
- enterococcus; not due to beta lactamase, it just is
- 4 diseases caused by enterococci
-
bacteremia
endocarditis
wound infections
UTI -
treat with __ if an enterococcus is
-blactamase neg
-b-lactamase pos -
neg = ampicillin
pos = vancomycin -
VRE
(2 genes that encode it) -
vancomycin resistant enteroc
VanA
VanB - how do Van A and Van B mediate resistnc?
-
A - plasmid-mediated; worse cuz it can jump to other bugs
B - chromosomally-mediated; stays within the cell line. - know about Strep D non-enteroc:
- rare in humans, can cause endocarditis, treat w/ penicillin
- You have an alpha-hemolytic gram positive cocci; what tests do you inoculate?
-
1. bile esculin
2. salt
3. optichin - principle of optichin test
- disc contains ethylhydrocupreine HCl; if the bug is susceptible, zone of more or equal to 14 mm will show. resistant if less. (S. pneumonia and S. viridans are resistant)
- alpha hemolytic, bile esculin negative, optichin positive/negative: que es?
-
s. pneumoniae is pos
S. viridans is neg - what tests is alternate to optichin?
- bile solubility
- micro/macro morpho of strep pneumoniae
-
1. lancet shaped GPDC
2. if autolyzed, flat, mucoidy, checkers
MAKES A CAPSULE - What makes Strep pneumoniae pathogenic?
-
-capsule
-M-protein which makes it resist phagocytosis - lobar pneumonia pathology: what happens?
- bug enters, inflammatory response is WBC, fluid and RBC; can't breathe across alveoli - lobar consolidation
- high fever; shaking chills; sharp pleural pain; rusty sputum; what is it?
- lobar pneumoniae caused by strep pneum.
- why does s. pneumon cause red sputum?
- rbc's in it
- 3 diseases caused by strep pneumoniae:
-
lobar pneumonia
meningitis
otitis media - to treat s. pneumonia:
-
=penicillin or ciprofloxacin
vancomycin if necess - normal flora site of strep pneumoniae
- oral cavity, small numbers
- enterococcus normal flora site
- intestine
- how do you prevent streptococcal pneumoniae?
-
via vaccine;
pneumovax for over 2 years old,
PREVNAR FOR under 2 -
What test identifies S. viridans?
2 species and commonly caused disease (Kristine) -
Optichin neg (diff from s. pneumoniae)
S. MUTANS AND S. SANGUIR ASSOC. W/ DENTAL CARIES - tests done on beta strep
-
bile esculin
bacitracin or pyr
CAMP or hipp hydrolysis - bile esculin of beta strep diffs
-
positive is rare - nothing
negative do tests on - test to do on bile esc negative organisms:
-
CAMP - identifies beta strep B
Bacitracin - identifies beta strep A - does beta strep A resist or suscept to bacitracin?
- it's positive, so it resists it
- principle of CAMP test
- beta strep B produce compound that in conjunction with S. Aureus' hemolysin will cause complete hemolysis and an arrow shape
- alternate test for CAMP
- hippurate
-
Beta strep Antigen aka
how to test for it -
C- carbohydrate
flourescent antibody or latex agglutination - strep group A aka and its normal flora site:
- aka strep pyogenes; normally in oral cavity in 15% of population
- s. pyogenes produces what 6 pathogenic products:
-
streptokinase - digest fibrin, spread
streptodornase - break down dna
hylauronidase - break down connect tiss
erythrogenic toxin - red scarlet fever
hemolysins - break down RBC
M protein - resist phagocytosis - two hemolysins produced by s. pyogenes, strep group A:
-
Streptolysin S, O
ASO TEST tests for O by antibody action
O is O2 labile
S is O2 stabile - diseases caused by strep pyogenes (A)
-
strep throat
scarlet fever
erysipelas and cellulitis
impetigo
wound infections
pyogenic STrep A infections
post-strep diseases - what are pyogenic strep A infections?
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necrotizing fasciitis
toxic shoc-LIKE SYNDROME - what are post streptococcal diseases?
-
acute glomerulonephritis
rheumatic fever - how do you treat strep pyogenes (group a)
- with peniccilin
-
strep group B is aka
normal floral site? -
strep agalactiae
normally in oral cavity in low numbers, maybe vagina but abnormal and must protect fetus before delivery - what type of infection does s. agalactiae cause
-
neonatal infections:
-meningitis/sepsis
-respiratory distress syndrome
-osteomyelitis - direct specimen test for S. agalactiae
- group b Antigen test
- how do you treat group B strep? (s. agalactiae)
- with penicillin
- beta hemolytic strep other than A B or D
- normal flora, COULD cause phjaryngitis (streplike) but normal usually, susceptible to peniccilin
- what are 5 OTHER cat neg GPC?
-
=leukonostoc - rare, unusual to cause infection, only in compromised; INTRINSIC RESISTANCE TO VANCOMYCIN!
-aerococcus
-gemella
-pediococcus
-lactococcus - What are all streptococcus organisms treated with, and what is NOT treated with it?
- Enterococcus is intrinsically resistant, but everything else is susceptible to penicillin.