Flashcards in Streptococci and Enterococci Deck (54)
What are 2 key features of Streptococci?
1) catalase NEG
2) cocci in pairs and chaines (strep is a strip)
________ are aerobic while _____________ are anaerobic
How do you know if an organism is catalase positive or negative?
catalase positive - O2 bubbles up
What are the 3 hemolytic properties of strep?
1) COMPLETE hemolysis (beta)
2) incomplete hemolysis (alpha)
3) NO hymolysis (gamma)
What is the important strep species of Group A?
What is the important strep species of Group B?
What kind of infections are associated with S. pyogenes?
1) ACUTE PHARYNGITIS (resp droplets, 5-15 year old with fever, sore throat, headache, swollen lymph nodes)
2) IMPETIGO (2-5 child with localized skin disease)
3) ERYSIPELAS (spreading erythema with well demarcated edge on face or legs, fever and lymphadenopathy)
4) SCARLET FEVER
5) NEC FASC
What are 7 clinical manifestations of strep pyogenes infection?
1) Acute pharyngitis
4) Scarlet fever
5) Nec fas
6) Toxic shock-like syndrome
7) Puerperal sepsis
What two bacteria can cause toxic shock?
staph and strep (group A)
Which toxic shock like syndrome toxins belong to staph? strep?
staph = TSST-1
strep = SPE
What patient population do you see puerperal sepsis?
women following delivery
(bacteria from genital tract or obstetric personnel invade upper genital tract)
What are dangerous sequelae after strep?
Rheumatic fever (1-5 weeks after)
Acute glomerulonephritis (antigen+antibody+C deposited in glomeruli)
Why can rheumatic fever be dangerous?
cardiac lesions called Aschoff bodies and vascular damage leads to possible endocarditis later in life
What are 4 accomplishments of group A strep that help promote virulence?
1. adhere to surface of host cells
2. invade epithelial cells
3. avoid opsonization/phagocytosis
4. produce variety of toxins/enzymes
What are the 7 S. pyogenes virulence factors?
What are the 2 hemolysins of S. pyogenes?
Streptolysin S (oxygen stable, non-antigenic)
Streptolysin O (oxygen labile, ASO antibodies)
What is SPE?
streptococcal pyrogenic exotoxins
superantigens of s. pyogenes; stimulate cytokine response leading to shock
responsible for rash in scarlet fever (erythrogenic exotoxin)
What protein is absolutely required for the pathogenesis of s. pyogenes?
What does the M protein do?
- binds to epidermal cells
- allows bacteria to survive
- degrades complement C3b
What 2 proteins of s. pyogenes allows for spread of bacteria in tissues?
True or false: there are antibiotic resistant strep pyogenes?
What drugs do you use to treat s. pyogenes?
erythromycin (for pen allergic patient)
What does strep agalactiae cause?
- neonatal pneumonia, sepsis, meningitis
- skin/wound infections in adult diabetic patients
Is strep agalactiae normal on the body anywhere?
throat, vaginal and GI tract
How can baby get GBS (group b strep)?
normal maternal colonization of vagina or rectum exposes baby at delivery
leads to meningitis, bacteremia, pneumoniae
How do you prevent babies from getting GBS at delivery?
culture mom at 35-37 weeks and treat mom as if she is positive
How do you treat GBS?
gentamicin to enhance killing
clindamycin for pen allergic
Aside from s. pyogenes and s. agalactiae, what are the other beta hemolytic strep?
Group C (vet infections, pharyngitis in college kids, sepsis)
Group F (abscesses)
Group G (pharyngitis, sepsis in neonates)
How do you diagnose GBS?
antibody detection (ASO, Anti-DNase)
True or false: if GBS strep test comes up negative, pt is negative
FALSE; always do a back up culture
What are Viridans Streptococci?
alpha or gamma hemolytic (NO BETA)
major cause of dental caries
important cause of endocarditis
causes sepsis in neutropenic cancer patient
What are the 5 groups of viridans strep?
What is included in the bovis group? What does it cause?
non-enterococcal group D strep
bacteremia, meningits, endocarditis
Isolation of s. bovis from blood is associated with what?
carcinoma of colon
What bacteria has butterscotch scent on agar plates? also requires CO2 for isolation and makes pinpoint colonies
Where are strep milleri infections usually found?
cause pyogenic infections of cardiac, abdominal, skin and CNS tissues
Where is strep milleri usually found?
mouth, oropharynx, GI tract, vagina
Where is strep pneumoniae usually found?
upper resp tract
What can strep pneumo cause?
- paranasal sinusitis
- otitis media
- septic arthritis
For which bug is a polysaccharide capsule important virulence factor?
Name the 5 virulence factors of strep pneumoniae
- sIgA protease
- Teichoic acid/peptidoglycan
What does sIgA protease do?
prevent IgA mediated binding of pneumococcal cells to mucus
What does teichoic acid/peptidoglycan do?
activates complement by alt pathway --> mediates inflammation
What is the most common cause of CA acute bacterial pneumonia? Also most common cause of bacterial meningitis
What is responsible for the highest rate of meningitis in kids under 2?
What does s. pneumoniae look like?
lancet shaped cocci
What does s. pneumoniae look like on blood agar?
dimes, alpha hemolytic
What inhibits s. pneumoniae growth in the lab?
How do you decide how to treat strep pneumococcal infections?
look at MIC for susceptibility
What 3 drugs can you give for susceptible pneumococcal infections?
What are some characteristics of enteroccus?
a, B, y hemolytic
What are the 2 classes of entercoccus virulence factors?
- aggregation substance
- carbohydrate adhesins
true or false: there are some vancomycin resistant enterococci
TRUE (E. faecium)
Van A - plasmid mediated
Van B - chromosomal
Van C - intrinsic
Makes YELLOW colonies