PAST PAPER Qs

Question 1

Which bacteria causes sore throat?
- Staphylococcus aureus
- Haemophilus spp
- Streptococcus pyogenes
- Mycoplasma pneumoniae

Answer 1

Streptococcus pyogenes

Question 2

Streptococcus pyogenes produces which infection?

Answer 2

Streptococcal sore throat

Question 3

Which bacteria causes Scarlet fever?

Answer 3

Streptococcus pyogenes

Question 4

Infection caused by Group B Streptococci are most common in which age group?
- Newborns
- Children aged 8 to 12
- Young adults
- All of them

Answer 4

Newborns

Question 5

A 5 year old girl has a sore throat. She is febrile and has a scant exudate on one tonsillar pillar. The most sensitive way to detect whether this infection is due to group A streptococci is:
- Throat Culture
- Strep group A antigen detection
- Strep M protein antigen detection
- Gram stain
- ASO titer

Answer 5

Strep group A antigen detection

Question 6

What diseases are associated with group B streptococci/S. agalactiae?

Answer 6

• Sepsis
• Meningitis in neonates (some women have vaginal colonisation and infect the baby through vaginal delivery)
• Soft tissue
• Endocarditis infections in adults

Question 7

A 2-day-old premature baby boy born to a 22-year-old woman developed pneumonia. The mother showed symptoms of UTI after the delivery. A blood specimen was taken from the baby for lab diagnosis. Beta-hemolytic colonies appeared on the culture plate after 24 hours. Which is the causative pathogen?

Answer 7

Streptococcus agalactiae

Question 8

The patient is a 2-week-old infant who was well until 2 days ago, when she stopped feeding and became irritable. She now has a fever of 38 degrees, developed a petechial rash all over her body and is very difficult to arouse. A blood culture and spinal tap were done. Gram stain showed gram +ve cocci in chains. Culture revealed beta hemolytic colonies. Which is the causative organism?

Answer 8

Streptococcus pyogenes

Question 9

What is Scarlet fever?

Answer 9

Erythrogenic toxin-mediated disease that develops in association of Streptococcus pyogenes and is characterised by a course, erythematous, blanching rash; a strawberry tongue; petechial lesions in skin creases (Pastia sign)

Question 10

How is rheumatic fever diagnosed?

Answer 10

Using the modified Jones criteria, which require two major criteria (carditis, migratory polyarthritis, subcutaneous nodules, erythema marginatum, chorea) or one major plus two minor criteria (previous history of acute rheumatic fever, elevated CRP, ASO titer)

Question 11

What is rheumatic fever?

Answer 11

An immunologic disease caused by cross-reactivity of S.pyogenes M protein and antigens of joint and heart tissue.

Clinically it presents 2-3 weeks following S.pyogenes pharyngitis (strep throat) and manifests with fever, migratory arthritis, chorea (rapid purposeless movements), carditis (new onset murmur), subcutaneous nodules and erythema marginatum (rash with pale enters and red margins)

Question 12

Why is it always important to treat Streptococcus impetigo?

Answer 12

Glomerulonephritis may develop secondary to untreated Streptococcus impetigo

Question 13

What complication only arises from Streptococcus pharyngitis and not Streptococcus impetigo?

Answer 13

Rheumatic fever

Explanation: it only develops after streptococcus pharyngitis infections

Question 14

How does S.pyogenes pharyngitis usually present and why must it be treated with antibiotics?

Answer 14

• High fevers
• Pharyngeal erythema
• Swollen tonsils with exudates
• Tender cervical lymph nodes

It should be treated with penicillin or a cephalosporin because untreated infections may result in rheumatic fever

Question 15

What is Exotoxin B?

Answer 15

A protease that rapidly destroys tissue and is produced in large amounts by the strains of S.pyogenes, the so-called “flesh-eating” streptococci that cause necrotising fasciitis

Question 16

What is Necrotising fasciitis and how is it treated?

Answer 16

A very serious subcutaneous infection that spreads rapidly along fascial plane and occurs typically after trauma of the skin. It can be either polymicrobial or monomicrobial (classically S.pyogenes). Treat with aggressive surgical debridement (including amputation) and antibiotics active against the likely pathogens. (If group A streptococcus, use penicillin and clindamycin. Clindamycin is added because it helps to inhibit toxin production)

Question 17

Which Exotoxin is often associated with Streptococcal toxic shock syndrome?

Answer 17

Exotoxin A

Question 18

What virulence factor causes beta-hemolysis?

Answer 18

Streptolysin O and S

Explanation:
- Antistreptolysin O (ASO) antibodies are important in the diagnosis of rheumatic fever
- Streptolysin S is oxygen stable and is not immunogenic

Question 19

What is M protein?

Answer 19

Antiphagocytic virulence factor of S.pyogenes.

Explanation:
Specific types of M protein are associated with pharyngitis/acute rheumatic fever, cellulitis/acute glomerulonephritis and necrotising fasciitis. The body makes antibodies against the M protein.