Micro - Streptococcus spp

Question 1

what is the gram stain & morphology of strep spp?

Answer 1

Gram pos cocci in chains/pairs

Question 2

what test differentiates strep & staph?

Answer 2

catalase test
- staph = POS
- strep = NEG

Question 3

group A strep is also known as ?

Answer 3

strep pyogenes

Question 4

what strep spp are beta hemolytic?

Answer 4

strep pyogenes (Grp A)
strep agalactiae (Grp B)

Question 5

strep pyogenes commonly causes what disease(s)?

Answer 5

• streptococcal pharyngitis aka STREP THROAT –> scarlet fever or rheumatic fever
• necrotizing fasciitis
• toxic shock syndr. via pyrogenic exotoxins

Question 6

types of hemolysis seen with Strep spp?

Answer 6

• β-hemolysis → complete clearing
• α-hemolysis → green/partial
• γ-hemolysis → none

Question 7

key ID features of Strep pyogenes (grp A)

Answer 7

• B hemolytic
• Bacitracin SENSITIVE
• PYR pos
• Lancefield grp A

Question 8

what post infection complications are caused due to Grp A strep infection?

Answer 8

• Rheumatic fever
• Post streptococcal glomerulonephritis

Question 9

Key features of Strep. agalactiae (Grp B)

Answer 9

• beta hemolytic
• bacitracin RESistant
• CAMP Pos
• Hippurate POS
• Lancefield Grp B

Question 10

clinical manifestations/disease assc of Strep agalactiae ?

Answer 10

• NEONATAL meningitis/sepsis

Question 11

what strep spp are alpha hemolytic?

Answer 11

1. Strep pneumoniae
2. Viridans grp Strep

Question 12

key ID characteristics of Strep pneumoniae ?

Answer 12

• alpha hemolytic
• LANCET shape dipplococci
• Optochin SENSITIVE
• bile soluble
• encapsulated

Question 13

what diseases are caused by Strep. pneumoniae?

Answer 13

• meningitis
• pneumonia
• otitis media

Question 14

key ID features of Viridans streptococci

Answer 14

• alpa hemolytic
• Optochin RESISTANT
• bile INSOLUBLE
• normal oral flora

Question 15

common gamma hemolytic streptococci?

Answer 15

Enterococcus (E. faecalis & E. faecium)

Question 16

key ID features/characteristics of Enterococcus spp?

Answer 16

• gamma hemolytic
• bile esculin POS
• growth in 6.5% NaCl
• PYR pos

Question 17

How do Enterococcus spp differ from Group D strep (non-enterococci)?

Answer 17

Enterococcus → grows in 6.5% NaCl

Non-enterococcal Group D → does NOT

Question 18

Clinical importance of Enterococcus spp?

Answer 18

• UTIs
• Endocarditis
• Wound infections
• VRE (vancomycin resistance)

Question 19

which test differentiates S. pyogenes & S. agalactiae ?

Answer 19

• Bacitracin –> Grp A = S ; Grp B = R
• PYR –> Grp A = Pos ; Grp B = Neg
• CAMP –> Grp A = NEG ; Grp B = Pos

Question 20

which test identifies Enterococcus spp?

Answer 20

• bile esculin
• growth in 6.5% NaCl
• PYR

Question 21

A throat culture from a 9-year-old with fever and sore throat grows Gram-positive cocci in chains. Colonies are beta-hemolytic on blood agar. The organism is bacitracin sensitive and PYR positive.

Which organism is most likely?

A. Streptococcus agalactiae
B. Streptococcus pyogenes
C. Viridans streptococcus
D. Enterococcus faecalis

Answer 21

B. Strep pyogenes

Question 22

Two weeks after a skin infection, a patient presents with dark urine, edema, and hypertension. Prior culture showed beta-hemolytic streptococci.

Which complication is most consistent with this presentation?

A. Toxic shock syndrome
B. Rheumatic fever
C. Post-streptococcal glomerulonephritis
D. Scarlet fever

Answer 22

✅ Correct Answer: C – Post-streptococcal glomerulonephritis

Why:

Immune-complex mediated

Occurs after skin or throat infection

Associated with Group A strep

Question 23

A newborn develops sepsis and meningitis within 24 hours of birth. Vaginal culture from the mother grows beta-hemolytic streptococci that are bacitracin resistant, CAMP positive, and hippurate positive.

Which organism is the cause?

A. Streptococcus pyogenes
B. Streptococcus agalactiae
C. Enterococcus faecium
D. Viridans streptococcus

Answer 23

B. Strep agalactiae –> think of micro rotation @ University; on urine bench we were on the lookout for grp B strep esp in child bearing women

Question 24

CSF culture from a patient with meningitis shows alpha-hemolytic colonies. Gram stain reveals lancet-shaped diplococci. The isolate is optochin sensitive and bile soluble.

What is the organism?

A. Viridans streptococcus
B. Enterococcus faecalis
C. Streptococcus pneumoniae
D. Streptococcus agalactiae

Answer 24

C. strep pneumo –> lancet shape, hemolysis, & optochin test are key identifiers

Question 25

A urine culture grows gamma-hemolytic Gram-positive cocci. The organism is bile esculin positive, PYR positive, and grows in 6.5% NaCl. Which organism is most likely? A. Streptococcus bovis B. Viridans streptococcus C. Enterococcus faecalis D. Streptococcus pneumoniae

Answer 25

✅ Correct Answer: C – Enterococcus faecalis Why: Bile esculin + 6.5% NaCl growth PYR + Classic Enterococcus profile

Question 26

A bile esculin-positive organism fails to grow in 6.5% NaCl. What does this result indicate? A. Enterococcus species B. Viridans streptococcus C. Non-enterococcal Group D streptococcus D. Group B streptococcus

Answer 26

✅ Correct Answer: C – Non-enterococcal Group D streptococcus Why: Group D ≠ always Enterococcus NaCl growth differentiates

Question 27

A beta-hemolytic streptococcus is bacitracin resistant but PYR positive. What is the correct interpretation? A. S. agalactiae B. S. pyogenes C. Enterococcus species D. Viridans streptococcus

Answer 27

✅ Correct Answer: B – S. pyogenes Why: PYR positivity overrides bacitracin Bacitracin alone is screening, not definitive

Question 28

Two isolates are both alpha-hemolytic. One is optochin sensitive, the other optochin resistant. Why is optochin testing necessary? A. To determine Lancefield group B. To differentiate S. pneumoniae from viridans strep C. To detect capsule formation D. To confirm beta-hemolysis

Answer 28

✅ Correct Answer: B Why: Both are alpha-hemolytic Only pneumococcus is optochin sensitive