Streptococci

Question 1

What are the characteristics of Streptococci?

Answer 1

Catalase Negative
Cocci in pairs/chains
Complex Media requirements
Prefers Anaerobic
Gram Positive Cocci

Question 2

Describe streptococci relative to staph when plated on agar?

Answer 2

Staph: white/cream opaque colonies in grape like clusters
Strep: clear colonies in chans or pairs

Question 3

What happens if you put in a drop of H2O2 on Staphylococci or Streptococci?

Answer 3

Staph: Catalase + -> bubbles of O2 formed
Strept: Catalase - -> no bubbles

Question 4

How are the subspecies of streptococci classified?

Answer 4

Hemolytic properties: B (complete hemolysis), A (incomplete hemolysis), Gamma(No hemolosys)

Question 5

What are hte key species of streptococci?

Answer 5

B-hemolytic: Strep Pyogenes (Group A), Strep Agalactiae (Group B)
Strep Viridans (alpha hemolytic)
Strep Pneumo (alpha hemolytic)

Question 6

What are the diseases caused by S.Pyogenes?

Answer 6

Acute Pharyngitis: self limiting; respiratory droplet transmission

Impetigo: mostly children; associated with trauma/insect bites; Pustules with yellow crust

Erysipelas:spreading erythema wiht well demarcated edge on face

Scarlet Fever

Necrotizing FAscitis

Toxic Shock Like syndrome

Puerperal SEpsis

Rheumatic Fever

Acute Glomerulonephritis

Question 7

What is scarlet fever?

Answer 7

Caused by erythrogenic exotoxin with complication of streptococcal pharyngitis

Rash of tiny red bumps on chest and abdomen with blanching on pressure => 12-48 hrs after fever

Spares the face
Sore throat
Fever
Strawberry Tongue
Desquamation as rash fades

Question 8

What causes necrotizing fascitis?

Answer 8

Strep infection that occurs deep in subcutaneous tissues and spreads along fascial planes leading ot destrcution of muscle and fat

Question 9

What is a key characteristic of a patient with necrotizing fascitis and how is it treated?

Answer 9

Pain is significantly disproportionate to how it looks

Surgery -> debride dead tissue

Question 10

What causes toxic shock like syndrome with S.pyogenes infections?

Answer 10

SPE toxins (similar to TSST-1 of staph aureus)

Question 11

What is puerperal sepsis?

Answer 11

Seen in women when they get sick following delivery/abortion

Question 12

how does puerperal sepsis occur?

Answer 12

Organisms in genital tract or OB personnel invade upper genital tract -> bacteremia, endometritis, necrotizing fascitis, streptococcal toxic shock syndrome

Question 13

What is Rheumatic Fever?

Answer 13

Nonsuppurative Inflammatory Disease 1-5 weeks after strep pharyngitis (can occur in pts sometimes if you dont treat for strep throat)

Characteristic cardiac lesions -> valvular damage-> possible future endocarditis

Question 14

How does strep cause acute glomerulonephritis?

Answer 14

Antigen from strep -> forms Ab-antigen complex with complement -> complex goes to glomeruli -> damage tissue-> glomerulonephritis

Question 15

What are the virulence factors of S.Pyogenes?

Answer 15

Capsules
Lipoteichoic Acid
Hemolysin(S: oxygen stable, non antigenic; O: oxygen labile, ASO Abs)
Streptokinase
Nucleauses

Question 16

What are SPE?

Answer 16

Streptococcal Pyrogenic Exotoxins (A, B , C)
Can act as superantigens to stimulate cytokine response -> shock/organ failure
Causes the rash in scarlet fever

Question 17

What is the M protein in S.Pyogenes?

Answer 17

Strains w/out M protein are AVIRULENT

Promote antiphagocytic characteristics by degrading Complement C3b and also adherence to epidermal cells

Question 18

How is S.pyogenes treated?

Answer 18

Penicllin/Ampicillin/Amoxacillin

Cephalosporin

Pt is allergic: use erythromycin (macrolide)

Question 19

What is GBS?

Answer 19

Group B Strep: Strep Agalactiae

Question 20

How does GBS infections occur?

Answer 20

Kids get it if mothers are carriers as it is normal flora in throat, vagina, GI tract

Question 21

What does GBS cause?

Answer 21

Early Onset Neonatal Disease: 1st week of life -> bacteremia, pneumonia, meningitis

Late Onset Neonatla Disase: 1 wk -3 mo -> bacteremia w/ meningitis

Pregnant Women: UTI, carrier

Question 22

Describe the pathogenesis of GBS

Answer 22

Maternal colonizaiton in vagina or rectum -> baby exposed during birht -> lacks protective maternal Ab -> can disseminate

Question 23

How do hospitals prevent perinatal GBS disease?

Answer 23

Women are cultured vaginally/rectally with swabs at 35-37 weeks gestation

If woman comes in with no prenatal history -> treat as if they are positive for GBS by starting Abx at delivery and then treating baby as well

Question 24

How do we treat S.Agalactiae/GBS?

Answer 24

Penicllin/Ampicillin + Gentamicin (enhance killing)

Prophylaxis: Culture + pregnant women -> penicllin/ampicillin to prevent neonatal disease

Peniciillin allergy: Clindamycin

Question 25

What are the characteristics of Strep Viridans?

Answer 25

Alpha/Gamma hemolytic
Causes dental caries
Bile REsistant
Optochin resistant
Adhere to fibrin platelet aggregates in damaged heart valves -> endocarditis

Normal flora in upper resp tract
Opportunistic pathogen

Question 26

What is S.Bovis?

Answer 26

Non-enterococcal group D streptococci

Question 27

What is the key fact about S.Bovis

Answer 27

Isolation of S.Bovis from blood is associated with colon carcinoma

Pt shoudl get worked up for this if positive for S.bovis

Question 28

What is the Strep Milleri Group?

Answer 28

Produce pinpoint colonies
Require CO2 for isolation
Butterscotch odor when cultured on agar plates

Question 29

Where are S.Milleri group found and what do they cause?

Answer 29

Commensals in mouth, oropharynx, GI , vagina

Cause deep seated pyogenic infections in cardiac, abdominal, skin, CNS tissues

Seen in brain abscesses

Question 30

What do nutritionally deficient strep require to grow on plates?

Answer 30

VitB6 deficient -> needs to be grown with organism producing VitB6 for them

Question 31

A 7-year-old child presents with a fever, pain in his ankles,
knees and wrist, and a new heart murmur. His mother said
that he complained of a “sore throat” last month, but the
symptoms resolved without taking him to the pediatrician. A
rapid screening test for strep throat is negative. His most
likely diagnosis is:
A. Toxic shock-like syndrome
B. Rheumatic fever
C. Scarlet fever
D. Puerperal fever
E. Acute glomerulonephritis

Answer 31

B

Question 32

What does strep pneumo cause?

Answer 32

Most common cause of meningitis
Pneumonia
Sinusitis
Otitis Media
Endocarditis, osteomyelitis, septic arthritis, etc

Question 33

What are the characteristics of Strep Pneumo?

Answer 33

Gram Positive Cocci: lancet shaped diplococci
Capsulated
Alpha Hemolytic
Catalase Negative
Bile Soluble
Optochin Sensitive
Many serotypes -> makes vaccination hard

Question 34

What are the virulence factors for S.Pneumo?

Answer 34

Pneumolysin: damage ciliated cells and activate alt complement path

SIgA Protease = prevent IgA binding of cells to mucus

Teichoic Acid/Peptidoglycan = activate complement alternative path -> inflammation -> C- reactive protein precipitation

Neuraminidase

Phosphorylcholine

Question 35

What can predispose someone to S.Pneumo?

Answer 35

Alcoholism
DM
Chronic lung, renal diseases
Malignancies

Question 36

What is S.pneumo the most common cause of?

Answer 36

Most common cause of bacterial meningitis in US

Highest rate of meningitis in children

Question 37

What are the treatment options for S.Penumo?

Answer 37

Penicillin if susceptible
Cefotaxime/Ceftriaxone if susceptible
*Breakpoints differ for meningeal and nonmeningeal cases

Alternatves: Macrolides (Erythromycin, Clarithromycin, Azithromycin) => MOST COMMON
Fluoroquinolones: Levofloxacin, Moxifloxacin