Streptococci

Question 1

Streptococci occur in

Answer 1

Gpos cocci occuring in chains

Question 2

All Streptococci are

Answer 2

• Catalase negative
• Gpos cocci occuring in chains
• check for hemolysis pattern

Question 3

Types of Streptococci

6 listed

Answer 3

• Streptococcus pyogenes (Group A)
• Streptococcus agalactiae (Group B)
• Streptococcus pneumonae
• Streptococcus viridans
• Enterococcus (Group D)
• Streptococcus bovis

Question 4

Group A strep

Answer 4

Streptococcus pyogenes

Question 5

Group B strep

Answer 5

Streptococcus agalactiae

Question 6

Group D strep

Answer 6

Enterococcus

Question 7

Features of Streptococcus pyogenes

Answer 7

• 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

Question 8

Strep pyogenes illnesses

Answer 8

• infections
  
  • Pharyngitis (strep throat)
  • skin: Cellulitis, impetigo
• Toxin-mediated disease
  
  • Scarlet fever
  • Necrotizing fasciitis
  • Toxic Shock Syndrome
• Immune-disease
  
  • Rheumatic fever
  • Post-strep glomerulonephritis

Question 9

Strep pharyngitis

Answer 9

• 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

Question 10

Strep pyogenes skin infections

Answer 10

• cellulitis and impetigo
• can also be caused by Staph aureus so antibiotics need to cover both

Question 11

Strep pyogenes Scarlet fever

Answer 11

• 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)

Question 12

Differentiating Scarlet fever from Kawasaki disease

Answer 12

Look for a sore throat to determine Scarlet Fever

Question 13

Infectious rashes that involve the palms and soles

Answer 13

• Syphilis
• RMSF
• Coxsackie virus

Question 14

Necrotizing fasciitis

Answer 14

• 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

Question 15

Necrotizing fasciitis toxin

Answer 15

Strep pyogenes that produce streptococcal pyrogenic exotoxin

Question 16

Type 1 Necrotizing fasciitis

Answer 16

• polymicrobial (Bacteroides, Clostridium, etc. anaerobes)
• occurs in diabetics, immunocompromised, post-surgery

Question 17

Type 2 Necrotizing fasciitis

Answer 17

• Group A strep
  
  • sometimes Staph
• Occurs in otherwise heallthy people after skin injury

Question 18

Classic case of Type 2 Necrotizing fasciitis

Answer 18

• minor skin trauma
• redness/warmth (can be confused with cellulitis)
• pain out of proportion to exam
• fever
• hypotension

Question 19

Rheumatic fever

Answer 19

• A type II autoimmune reaction
• Follows Group A strep pharyngitis infection
• Streptococcus -> anti-strep antibodies cross react with tissue-antigens
• Dx: Jones criteria

Question 20

Rheumatic fever pathology

Answer 20

• Aschoff bodies (form of granuloma) ***Pathognomonic for rheumatic carditis***
• Anitschkow’s cells
• Elevated ASO titers (Anti-streptolysin O antibodies)

Question 21

Jones Criteria

Answer 21

• 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

Question 22

Clues to diagnosing Rheumatic fever

Answer 22

Sore throat or URI followed by joint pain, new murmur

Question 23

Tx of Rheumatic fever

Answer 23

Penicillin (often indefinitely for prevention of recurrent infection)

Question 24

Cardiac involvement of Rheumatic fever

Answer 24

Acute RF -> severe valve disease, heart failure

Later -> mitral stenosis (rarely aortic or tricuspid valves)

Question 25

Post-streptococcal GN

Answer 25

* 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)

Question 26

Strep agalactiae features

Answer 26

* 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

Question 27

Beta-hemolytic strep

Answer 27

* GAS (Strep pyogenes) * GBS (Strep agalactiae)

Question 28

Rapid Strep agalactiae test

Answer 28

Hippurate test

Question 29

Step pneumonia features

Answer 29

* "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

Question 31

Step pneumonia illnesses

Answer 31

* Lobar pneumonia * Meningitis * Ottitis media * Sinusitis

Question 32

Strep viridans features

Answer 32

* group of similar bacteria * No strep Lancefield grouping * Normal mouth flora

Question 33

Strep viridans illnesses

Answer 33

* Dental caries (Strep mutans) * Subacute endocarditis (Strep sanguis)

Question 34

Subacute endocarditis

Answer 34

* 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

Question 35

Dextran?

Answer 35

Strep viridans

Question 36

Types of enterococcus

Answer 36

* E. faecalis * E. faecium

Question 37

Features of Enterococcus

Answer 37

* normal colonic bacteria * Group D Strep (Lancefield Group D) * Resistant to penicillin * Vancomycin resistant Enterococcus (VRE) * dangerous hospital acquired infection

Question 38

Enterococcus illnesses

Answer 38

* UTIs * Endocarditis (rare) * VRE (Vancomycin Resistant Enterococcus) * dangerous hospital acquired infection

Question 39

Antibiotics for Enterococcus

Answer 39

* 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

Question 40

Enterococcus UTIs

Answer 40

* Often hospital acquired (associated with catheters) * Removal of catheter alone may cure infection * Urinalysis: negative for nitrites

Question 41

UTIs negative for nitrites

Answer 41

only 2 bacteria do this * Staph saprophyticus * Enterococcus

Question 42

Enterococcus Endocarditis

Answer 42

* 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

Question 43

Strep bovis features

Answer 43

normal colonic bacteria

Question 44

Strep bovis illnesses

Answer 44

* 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)