Streptococci Flashcards
1
Q
Streptococci occur in
A
Gpos cocci occuring in chains
2
Q
All Streptococci are
A
- Catalase negative
- Gpos cocci occuring in chains
- check for hemolysis pattern
3
Q
Types of Streptococci
6 listed
A
- Streptococcus pyogenes (Group A)
- Streptococcus agalactiae (Group B)
- Streptococcus pneumonae
- Streptococcus viridans
- Enterococcus (Group D)
- Streptococcus bovis
4
Q
Group A strep
A
Streptococcus pyogenes
5
Q
Group B strep
A
Streptococcus agalactiae
6
Q
Group D strep
A
Enterococcus
7
Q
Features of Streptococcus pyogenes
A
- Group A strep
- Pyrrolidonyl arylamidase (PYR) positive
- Substrate (L-napthylamide-beta-napthylamide) hydrolyzed by bacterial enzyme to beta-naphthylamide
- can be detected by color change with detection reagent
- M protein virulence factor
- inhibits phagocytosis
8
Q
Strep pyogenes illnesses
A
- infections
- Pharyngitis (strep throat)
- skin: Cellulitis, impetigo
- Toxin-mediated disease
- Scarlet fever
- Necrotizing fasciitis
- Toxic Shock Syndrome
- Immune-disease
- Rheumatic fever
- Post-strep glomerulonephritis
9
Q
Strep pharyngitis
A
- 15-30% of pharyngitis is due to S. pyogenes
- most cases are viral
- important to identify and treat S. pyogenes
- prevent transmission
- limit symptoms and severity
- prevent Rheumatic fever
- Dx
- Throat culture
- Rapid antigen test (useful if positive)
- Tx
- Penicillin
- Amoxicillin
- Cephalosporins
10
Q
Strep pyogenes skin infections
A
- cellulitis and impetigo
- can also be caused by Staph aureus so antibiotics need to cover both
11
Q
Strep pyogenes Scarlet fever
A
- Rash following pharyngitis
- Skin reaction to ***erythrogenic toxin***
- gene for toxin transferred by lysogenic bacteriophage (not found in bacterial genome)
- symptoms
- fever
- sore throat
- diffuse red rash
- strawberry tongue (can also get from Kawasaki Disease)
- also many small papules (“sandpaper” skin) (palms and soles usually spared)
- starts on the head/neck -> expands to cover the trunk
- Eventually skin desquamates (palms and soles usually spared)
12
Q
Differentiating Scarlet fever from Kawasaki disease
A
Look for a sore throat to determine Scarlet Fever
13
Q
Infectious rashes that involve the palms and soles
A
- Syphilis
- RMSF
- Coxsackie virus
14
Q
Necrotizing fasciitis
A
- Caused by Strep pyogenes strains that produce streptococcal pyrogenic exotoxin
- Infection of deep tissues
- muscle fascia/subcutaneous fat
- Streptococcal pyrogenic exotoxin released
- fulminant and deadly
- infection spreads along the muscular fascia and requires surgical debridement
15
Q
Necrotizing fasciitis toxin
A
Strep pyogenes that produce streptococcal pyrogenic exotoxin
16
Q
Type 1 Necrotizing fasciitis
A
- polymicrobial (Bacteroides, Clostridium, etc. anaerobes)
- occurs in diabetics, immunocompromised, post-surgery
17
Q
Type 2 Necrotizing fasciitis
A
- Group A strep
- sometimes Staph
- Occurs in otherwise heallthy people after skin injury
18
Q
Classic case of Type 2 Necrotizing fasciitis
A
- minor skin trauma
- redness/warmth (can be confused with cellulitis)
- pain out of proportion to exam
- fever
- hypotension
19
Q
Rheumatic fever
A
- A type II autoimmune reaction
- Follows Group A strep pharyngitis infection
- Streptococcus -> anti-strep antibodies cross react with tissue-antigens
- Dx: Jones criteria
20
Q
Rheumatic fever pathology
A
- Aschoff bodies (form of granuloma) ***Pathognomonic for rheumatic carditis***
- Anitschkow’s cells
- Elevated ASO titers (Anti-streptolysin O antibodies)
21
Q
Jones Criteria
A
- Major
- carditis
- polyarthritis
- chorea
- Erythema marginatum
- subcutaenous nodules
- Minor
- fever
- arthralgia
- prior RF
- elevated WBC, ESR, CRP
- prolong PR interval
Must have evidence of strep infection and 2 major or 1 major & 2 minor to diagnose Rheumatic fever
22
Q
Clues to diagnosing Rheumatic fever
A
Sore throat or URI followed by joint pain, new murmur
23
Q
Tx of Rheumatic fever
A
Penicillin (often indefinitely for prevention of recurrent infection)
24
Q
Cardiac involvement of Rheumatic fever
A
Acute RF -> severe valve disease, heart failure
Later -> mitral stenosis (rarely aortic or tricuspid valves)
25
Post-streptococcal GN
* Nephritic syndrome 2-3 weeks after GAS infection
* Nephritogenic strains of strep
* bacteria with particular M protein subtypes cause nephritis
* specific subtypes are associated with RF and others with post-streptococcal GN (so pts get on or the other but not both)
26
Strep agalactiae features
* Group B strep
* Beta-hemolytic (like GAS)
* Makes CAMP factor
* Staph aureus makes beta-hemolysin
* CAMP factor enhances lysis by beta-hemolysis
* hydrolyzes hippurate
* alters the color of hippurate test
* Colonizes the vagina
* causes infections in newborns
* babies infected in utero or during birth
* Pneumonia, meningitis, sepsis
* Pregnant women screened at 35-37 weeks
* GBS+ pregnant women recieve prophylaxis
* 4 hours pre-delivery
* Penicillin, ampicillin or cefazolin
27
Beta-hemolytic strep
* GAS (Strep pyogenes)
* GBS (Strep agalactiae)
28
Rapid Strep agalactiae test
Hippurate test
29
Step pneumonia features
* "Lancet-shaped" gram (+) cocci
* Makes IgA protease
* Key virulence factor: polysaccharide capsule
* prevents phagocytosis
* basis of vaccine from capsular material
* Asplenic patients at risk for sepsis
* splenectomy
* Sickle cell anemia
30
31
Step pneumonia illnesses
* Lobar pneumonia
* Meningitis
* Ottitis media
* Sinusitis
32
Strep viridans features
* group of similar bacteria
* No strep Lancefield grouping
* Normal mouth flora
33
Strep viridans illnesses
* Dental caries (Strep mutans)
* Subacute endocarditis (Strep sanguis)
34
Subacute endocarditis
* caused by Strep sanguis
* slow-onset of symptoms
* less sick pts
* often affects abnormal vales
* Dextran -\> fibrin
* Requires endothelial damage
* Mitral valve prolapse
* PEARL= Recent Dental Procedure
35
Dextran?
Strep viridans
36
Types of enterococcus
* E. faecalis
* E. faecium
37
Features of Enterococcus
* normal colonic bacteria
* Group D Strep (Lancefield Group D)
* Resistant to penicillin
* Vancomycin resistant Enterococcus (VRE)
* dangerous hospital acquired infection
38
Enterococcus illnesses
* UTIs
* Endocarditis (rare)
* VRE (Vancomycin Resistant Enterococcus)
* dangerous hospital acquired infection
39
Antibiotics for Enterococcus
* relatively resistant to cell wall agents (penicillin, ampcillin, vancomycin)
* Impermeable to aminoglycosides
* For bacteremia us synergystic therapy
* Vancomycin/Gentamycin
* Ampicillin/Gentamycin
* For VRE use
* Linezolid
* Daptomycin
* Micro lab sensitivities are very important for therapy
40
Enterococcus UTIs
* Often hospital acquired (associated with catheters)
* Removal of catheter alone may cure infection
* Urinalysis: negative for nitrites
41
UTIs negative for nitrites
only 2 bacteria do this
* Staph saprophyticus
* Enterococcus
42
Enterococcus Endocarditis
* Rare cause of endocarditis
* usually caused by GU tract manipulation
* TURP procedure for enlarged prostate
* Cystoscopy
* Vancomycin/Gentamycin often used for empiric therapy before culture data is available
43
Strep bovis features
normal colonic bacteria
44
Strep bovis illnesses
* Rare cause of bacteremia/endocarditis
* endocarditis or bacteremia infection is strongly associated with colon cancer (breakdown of the colon wall is how bovis got into the blood stream)
