Bugs: Streptococcus 1 β-hemolytic and Viridans Streptococci

Question 1

Describe the division of Gram Positive Cocci, based on biochemical tests and hemolysis

Answer 1

Catalase: 
Positive -- Staphylococcus 
coagulase: 
Postitive -- Staph aureus 
negative - Saprophyticus, epidermidis, lugdenesis 

Catalase Negative:
Streptococcus
Beta (Complete) hemolysis: Group A Strep (pyogens), Group B strep (agalactiae)
Alpha hemolysis + Postiive Optochin (Strep pneumo)
Alpha hemolysis + negative optochin (Viridans strep)

Question 2

What are the Beta Hemolytic Strep:

Answer 2

Group A strep – S. pyogens

Group B strep – S. agalactiae

Question 3

Group A strep:
- what is the human pathogenic speices:

• describe some of its virulence factors:

Answer 3

Strep Pyogenes

Virulence:
Capsule
Adherence factors: M protein, lipoteichoic acid, protein F
Toxins: Hemolysis (stretolysin O, streptolysin S)
Strep Pyrogenic Exotoxins (SpeA and SpeC antigens; which are superantigens)

Enzymes: DNAase, Hyaluronidase; streptokinase (degrades fibrin)

Question 4

What is M protein?
what does it do?
what is its most significant complication?

Answer 4

M protein – Virulence factor; adherence factor

• Binds Factor H ; inhibits activation of alternative complement system
• antibodies made against factor M also attack cardiac myosin and sarcolemma

= Rheumatic heart disease – occurs only after pharyngitis

Question 5

Group A strep:
Epi
WHere does it colonize
how is it transmitted

Answer 5

Humans are the only host

S. pyogens disease is very common in the US

Transient colonization of oropharynx and skin

Transmitted person to person via oral secretions or contact with skin lesions
Common in day cares (kids ages 4, 5)

Question 6

What are the classes of disease manifestations of S. pyogenes

Answer 6

Suppurative vs Non-Suppurative:

Question 7

What are the suppurative disease of Group A strep

Answer 7

Pharyngitis (aka Strep Throat)

Skin: Impetigo, Erysipelas, Necrotizing Fasciitis (strep gangrene)

Strep TSS:

Question 8

what are the clinical features of strep throat? how is it treated? how is it diagnosed?

what is its primary complication? What are the symptoms ?
what viruelnce factor is the cause?

Answer 8

Strep Throat: Fever, cervical LAD, Purulent exudates;
ABSENCE OF cough

Dx: Rapid Strep Test; Culture

Treatment: PCN, Macrolides, Clindamycin

Primary complication; Scarlett Fever
Sx: Strawberry tongue, punctate erythema, circum oral palor, capillary fragility (red skin folds); desquamation (painless skin peeling)

Caused by SpeA, SpeC extoxins

Question 9

What are the different GAS skin infections and how are they treated?

Answer 9

Impetigo:

• Topicals: bacitracin, mupirocin
• systemic: (Amox-clav), cephalexin

Erypsielas: (localized erythema, and edema)

Nec Fas: “pain out of proportion with findings;” Hemorrhagic bullae;
Treated surgically

Question 10

What are the non suppurative manifestations of GAS?
what do they occur after
how do you treat

Answer 10

Rheumatic fever— occurs only after pharyngitis
Treat: ASA, corticosterouds; treat the pharyngitis (PCN, macrolides); otherwise give PCN G monthly, PCN oral daily

Acute Glomerulonephritis – occurs after pharyngitis or skin infections;

Question 11

What is the main player of group B strep;

what are some virulence factors;

where does it colonize?
What is the primary concern?
what would be the manifestations?

how is this handled?

How is it treated in the neonate?

Answer 11

Strep agalactiae

Few virulence factors

Colonizes GI and female genital tracts

Concern: passing infection to child during delivery

Manifestations: neonatal sepsis, PNA, meningitis;

All pregnant women are screened for GBS prior to term
Treated with Amplicllin if positive

Neonatal disease: PCN,
Vanc/Clinda for PCN allergy;

Question 12

S. Anginosis Group (aka S. milleri)

• • what’s unique about the hemolysis
• • what does it typically manifest as?
• name of the species

Answer 12

Variable Hemolysis (Alpha, Beta, gamma)

Causes abscess

S. Angiosis, constellatus, intermedius

Question 13

Viridans Strep:

• Virulence factors?
• what is its hemolysis pattern?
• where does it colonize?
• name some of the 25 species
• what is the significance of S bovis?

how do you treat the group?

Answer 13

Few virulence

either gamma or alpha hemoylsis

Colonizes Mouth and other mucosal surfaces; not skin

S Anginosis group (abscess)
S mitis – endocarditis; some PCN resistance
S mutans – endocarditis;
S bovis – Endocarditis; typically associated with colonic neoplasia. Always follow up with colonoscopy

Treat: PCN
Mitis – Vancomycin