GPC Small Group

Question 1

1. Discuss the strengths and weaknesses of a rapid strep test v. a culture in diagnosing pharyngitis.

Answer 1

rapid strep test (uses latex agglutination) is very quick and easy to do; it is only 90-95% sensitive compared to throat culture; negative rapid test results are confirmed by culture before withholding treatment

Question 2

2. Describe the 3 types of hemolytic patterns produced by the aerobic streptococci.

Answer 2

alpha- colony surrounded by zone of partially destroyed erythrocytes

beta- colonies of beta-hemolytic streptococci are surrounded by a clear zone in which few or no erythrocytes are visible

gamma-produces no visible change in the blood surrounding the colony (non hemolytic)

Question 3

3. Explain how group A beta-hemolytic strep is identified.

Answer 3

serologic tests: detection of Lancefield antigen using latex agglutination (definitive)

bacitracin test: inhibits growth of non group A strains

PYR test: disc with substrate for enzyme L-pyrroglutamyl-aminopeptidase, positive test yells cherry red color (strep A and d enterococci are PYR +)

Question 4

4. Identify the antibody most commonly found in patients with acute rheumatic fever.

Answer 4

streptozyme test screens for antibodies to streptococcal antigens (DNAse, streptokinase, streptomycin O and hyaluronidase) positive test require confirmation with more definitive tests such as antistreptolysin-O test

high titers of antibodies to stretolysin O are usually found in patients with rheumatic fever

Question 5

5. Explain why a Gram stain is not used to diagnose strep throat.

Answer 5

alpha-hemolytic Gram positive streptococci that are part of the normal microbiota cannot be distinguished from the pathogen, finding Gram positive cocci in chains does not give meaningful information

Question 6

6. LIst the two organisms that can cause toxic shock syndrome.

Answer 6

Staph aureus and Strep pyogenes (both are aerobic Gram-positive cocci)

Question 7

7. Explain how the staphylococci and streptococci are identified and the significance of the two enzymes, catalase and coagulase in the disease process.

Answer 7

Staph aureus will be catalase positive, catalase positive organisms will convert peroxide to water and O2 creating bubbles when a colony is placed on hydrogen peroxide; organisms that are able to break down reactive forms of oxygen that are toxic to bacteria

Staph can further be divided by a coagulase test, coagulase causes plasma to clot and this aids the organism in hiding from the immune system (Staph aureus is coag. positive, epidermidis and saphrophyticus are negative) positive test means a suspension of colony causes rabbit blood to coagulate

Question 8

What is the optochin test?

Answer 8

used to identify Streptococcus pneumoniae; if the optochin disk inhibits colony growth overnight, that means a positive test

Question 9

What are the two major items on your differential for pharyngitis and why is it important to differentiate?

Answer 9

major diagnosis are bacterial and viral causes, bacterial can and should be treated (reduce the risk of acute rheumatic fever and decrease suppurative complications), viral does not get treated

Question 10

What are findings that are suggestive of bacterial v. viral pharyngitis?

Answer 10

bacterial: sudden onset, fever, age 5-15, headache, nausea, red swollen tonsils covered with exudate, petechiae on the palate and tender anterior cervical nodes, scarlet fever-like rash
viral: conjunctivitis, coryza, cough, hoarseness, mouth ulcers and viral rash

note examination of the abdomen should be done because palpation of the spleen suggests a diagnosis of mononucleosis (giving a patient amoxicillin to a patient with mono commonly leads to a rash)

Question 11

When should you follow up a negative rapid strep test with a culture?

Answer 11

especially in patients 5-15yrs, current guidelines down play the need in adults

Question 12

What are recommendations for strep pharyngitis?

Answer 12

1st line penicillin or amoxicillin
2nd line for allergies: cephalosporin, clindamycin or macrocodes

additional testing if culture is negative for EBV, recommend analgesics, antipyretics and anti inflammatories

difficult cases may need tonsillectomy

Question 13

Child presents with right tonsil larger and pushed toward the midline, what is the most likely diagnosis?

Answer 13

peritonsillar access, ampilcillin/sulbactam should be used to cover strep as well as anaerobes, incision and drainage of abscess is often necessary

Question 14

Treatment with appropriate antibiotic within ____ days of strep throat will prevent ARF.

Answer 14

9days

Question 15

What is the mnemonic for the major Jones Criteria.

Answer 15

Joints (migratory polyarthritis)
O carditis (new murmur)
Nodules (subcutaneous)
Erythema marginatum (rash with red margin)
Sydenham's chorea (uncontrolled random movement)

Question 16

What are the major possible etiologies of a patient presenting to the ER with toxic shock syndrome?

Answer 16

toxigenic strain of S. aureus: usually due to mucosal colonization (often with tampon or small children of nasal packs)

TSS caused by Group A strep is far more serious usually originating from cellulitis or primary bacteremia

Question 17

What is the differential diagnosis for a patient presenting with shock of unknown etiology, what would you look for/ask?

Answer 17

look for plausible sources of infection (pyelonephritis, peritonitis, pneumonia

be suspicious of possible primary bacteremia: in a previously well younger patient: Nesseria meningitides, Staph aureus and Group A streptococci

TSS syndrome possible

Question 18

What are the toxins produced by Staph and Strep causing TSS?

Answer 18

Group A strep: streptococcal pyogenic exotoxin (SPE-A)
S. Aureus: Enterotoxin F (TSST-1)

they are super antigens activation huge numbers of circulating T lymphocytes resulting in massive release of cytokines

Question 19

What symptoms would you suspect from the infection source a Group A strep infection that was causing TSS?

Answer 19

often associated with necrotizing cellulitis, producing tissue destruction, severe local pain and tenderness and a characteristic grayish hue to the skin (if the infection extends down to the fascia, it is termed necrotizing fasciitis)

Question 20

How is TSS treated clinically.

Answer 20

IV resuscitation is the most critical aspect of therapy
source control needs to happen simultaneously

antibiotics effective against the infecting organism are important

supportive therapy may include ventilatory support, hemodyalisis, tx. with fresh frozen plasma or platelets if coagulopathy causes hemorrhage

Question 21

Why is the mortality of strep TSS so much higher than that caused by TSS?

Answer 21

both are include multi-organ failure due to toxins, the source of infection with strep is associated with more severe invasive disease such as necrotizing fasciitis or bacteremia and has a worse prognosis