Strep

Question 1

What is the morphological difference between Strep and Staph?

Answer 1

Streptococci form chains; staphylococci form “graph clusters”

Question 2

What is the catalase test difference between Strep and Staph?

Answer 2

Streptococci are catalase negative (they will NOT bubble); staphylococcus are catalase positive

Question 3

What is the species of Group A Strep?

Answer 3

S. pyogenes

Question 4

What are the β-hemolytic Strep species and how do you distinguish them?

Answer 4

S. pyogenes and S. agalactiae, and GAS is bacitracin sensitive

Question 5

What are the α-hemolytic Strep species and how do you distinguish them?

Answer 5

S. pneumoniae and Viridans, and S. pneumoniae is optochin-sensitive and has pearly colonies due to its capsule and Quellun (+)

Question 6

What are the γ-hemolytic Strep species and how do you distinguish them?

Answer 6

Enterococcus and non-Enterococcus species; both are bile scullion (+) but Enterococcus grows in salt media

Question 7

What does hyalorunate do in S. pyogenes?

Answer 7

It forms a protective capsule to help protect it from the immune system

Question 8

What are the functions of the M-protein?

Answer 8

(1) Binds complement, (2) anti-opsonization; autoantibodies can form to M-proteins

Question 9

What are the two invasion factors of Strep?

Answer 9

Hyaluronidase breaks down ECM and Streptokinase activates plasmin, dissolving the blood clots to release bacteria

Question 10

What are the two major toxins from Strep?

Answer 10

Streptolysin O lyse erythrocytes and pyrogenic agents like erythrogenic toxin cause scarlet fever; superantigens overactivate T cells

Question 11

What is a suppurative infection?

Answer 11

A pus-producing infection

Question 12

What are some common suppurative infections caused by GAS?

Answer 12

Erysipelas (outermost layer, dermis); cellulitis (middle layer, dermis/sub-cu); necrotizing fasciitis; impetigo (crusty red sores around the nose)

Question 13

What are some of the classic signs of scarlet fever?

Answer 13

Desquamating sandpaper rash, circumoral pallor, strawberry tongue, fever

Question 14

What are some of the signs and causes of streptococcal toxic shock syndrome?

Answer 14

Hypotension, end organ damage; thought to be caused by superantigen activation

Question 15

What are the organ systems usually affected by acute rheumatic fever?

Answer 15

Skin, joints, heart, brain

Question 16

What are three of the five criteria for ARF?

Answer 16

Pancarditis, polyarthritis, subcutaneous nodules, erythema marginatum, Sydenham chorea

Question 17

What is the common renal complication of GAS infection?

Answer 17

Post-streptococcal glomerulonephritis (PSGN), which is caused by antibody complex deposition

Question 18

What are the four categories of β-lactams?

Answer 18

Penicillins, cephalosporins, carbapenams, and monobactams

Question 19

What is the mechanism of β-lactams?

Answer 19

They block the active site of the penicillin binding protein, so the bacterial cell wall cannot form

Question 20

What are the two main paths to β-lactam resistance?

Answer 20

β-lactamases and modifications of the PBPs

Question 21

What are the two types of resistance development?

Answer 21

Inducible resistance and plasmid transfer

Question 22

What is the most common adverse effect of β-lactam drugs?

Answer 22

GI adverse effects

Question 23

How is bacterial pharyngitis distinguished from viral?

Answer 23

Viral pharyngitis also has coryza, conjunctivitis, and a cough

Question 24

What are the two major diagnostic tests for strep?

Answer 24

Bacterial culture of pharyngeal swab (24-48 hours); strep rapid antigen detection test (10 min; follow-up culture if negative)

Question 25

Name the five Centor criteria (and the one extra).

Answer 25

Fever >38°C, tender anterior cervical LNs, tonsillar swelling, lack of a cough, age 3-14; -1 for age 45; test with RADT for 2+

Question 26

What is the treatment for GAS pharyngitis?

Answer 26

Penicillin (or azithromycin/clindamycin if allergic)