MCQs on Gram Positive Cocci (Streptococcus pyogenes, Streptococcus pneumoniae, Staphylococcus aureus)

Gram-Positive Cocci (Streptococcus spp, Staphylococcus spp) -Multiple Choice Questions

1) A 2-day-old premature baby boy born to a 22-year-old woman developed pneumonia. The mother developed the symptoms of urinary tract infection after the delivery. A blood sample was collected from the newborn for laboratory testing, and within 24 hours, culture plates showed the growth of beta-hemolytic colonies.
Which of the following group B streptococci could be the possible pathogen that can be easily spread from the mother to the baby and cause pneumonia?
a) Streptococcus pyogenes 
b) Streptococcus agalactiae 
c) Enterococcus faecalis
d) Streptococcus bovis 

2) Which of the following bacteria is commonly isolated pathogen from infection pharyngitis?
a) Streptococcus pneumoniae
b) Staphylococcus aureus
c) Streptococcus pyogenes
d) Mycoplasma pneumoniae

3) A 4-year-old boy presented with an erythematous rash on his face and arms accompanied by reddeningof the skin, during the physical examination swollen lymph nodes around the infection were noted in the affected area, but no other symptoms were observed. A specimen was collected from the infected site, and the pathogen was identified as a gram-positive coccus.
What could be the possible diagnosis?
a) Glomerulonephritis
b) Erysipelas
c) Impetigo
d) Cellulitis

4) The possible pathogen for the above disease condition is.............................
a) Pseudomonas aeruginosa
b) Staphylococcus aureus 
c) Streptococcus agalactiae
d) Trichophyton rubrum

5) All of the following are the characteristics of Streptococcus pneumoniae, Except?
a) The colonies are diplococcus and encapsulated
b) Alpha hemolytic (greenish zone) colonies appear on blood agar
c) Found as normal flora in healthy individuals
d) It grows well in a high concentration of glucose media 

6) Which of the following bacteria is the common pathogen in otitis media?
a) Streptococcus pneumoniae 
b) Streptococcus agalactiae
c) Streptococcus pyogenes
d) Streptococcus intermedius

7) Which of the following cocci is a part of the normal flora of the mouth?
a) Streptococcus agalactiae
b) Staphylococcus saprophyticus
c) Staphylococcus epidermidis
d) Streptococcus mutans

8) What are the different infections caused by Group A Streptococcus spp
Select all the correct answers:
a) Pharyngitis
b) Impetigo
c) Scarlet fever
d) Meningitis

9) Which of the following bacteria are examples of Group D Streptococci?
a) Streptococcus mutans
b) Streptococcus bovis and Enterococcus faecalis
c) Streptococcus pyogenes and Enterococcus gallinarum
d) Streptococcus pneumoniae

10) Each of the following statements is correct about Enterococcus spp, Except?
a) They can grow in both aerobic and anaerobic conditions
b) Resistant to high salt concentrations
c) The morphological characteristics resemble that of S. pyogenes
d) The common cause of hospital-acquired infections

11) Name the cocci that are a part of the normal flora of human intestines? 
Select the correct answer: 
a) Enterococcus faecalis
b) Micrococcus luteus
c) Staphylococcus epidermidis
d) Streptococcus mutans

12) Which of the following is NOT the virulent factor, an important antigenic property of S. pyogenes?
a) M protein
b) Streptolysin
c) Streptokinase
d) Endotoxins

13) Which of the following pathogen is the main cause of endocarditis in individuals with heart disease?
a) Streptococcus intermedius
b) Enterococcus faecalis
c) Streptococcus suis
d) Micrococcus luteus

14) Which of the following antibiotics have been found to be most effective for the treatment of infections caused by Enterococcus faecalis?
a) Cephalosporin
b) Macrolide
c) Aminoglycoside with penicillin
d) Oral penicillin V with ampicillin

15) Which of the following bacteria have been found to be most resistant to the drug vancomycin?
a) Enterococcus faecium
b) Streptococcus pyogenes
c) Staphylococcus aureus
d) Lactobacillus acidophilus 

16) All of the following are the general characteristics of Micrococcus spp and Staphylococcus spp, Except?
a. On blood agar Micrococcus spp appear as smaller colonies than Staphylococcus spp
b. Micrococcus is ubiquitous in nature
c. Both are catalase-positive
d. Staphylococcus spp are more virulent than Micrococcus spp 
e. Both are capable of producing coagulase enzyme

17) Which of the following bacteria is Not is a part of the normal human microbiota?
a. Streptococcus agalactiae
b. Staphylococcus aureus
c. Streptococcus pyogens (A)
d. Enterococcus faecalis
e. Staphylococcus saprophyticus

18) Viridans Streptococci are all, Except?
a. Most of them show alpha hemolysis on sheep blood agar
b. Found as the most common pathogen in dental caries
c. Not groupable according to Lancefield serology
d. All of the pathogens are catalase negative
e. Found only in the oral cavities as commensals    

19) A 30-year-old individual experiencing symptoms suggestive of a urinary tract infection provided a urine sample to a local healthcare center. She reported discomfort, frequent urination, and observed the presence of blood in her urine.
Which of the following pathogen is less frequently isolated from the UTIs sample?
a. Streptococcus mutans
b. E.coli
c. Staphylococcus aureus
d. Streptococcus agalactiae

20) All of the following statements regarding coagulase-negative Staphylococcus spp (CONS) are true, Except?
a. S. epidermidis and S. saprophyticus are coagulase-negative
b. Infection with S. epidermidis are mainly hospital-acquired
c. S. saprophyticus is a normal flora of humans skin surface
d. Both are common pathogens in urinary tract infections

21) Majority of strains of Staphylococci are highly resistant to which of the following antibiotics?
a) Cephalosporins
b) Clotrimazole
c) Amphotericin
d) Penicillin

22) Name the constituent found in the cell wall of gram-positive cocci?
a) Lipopolysaccharide
b) Teichoic acid
c) Mycolic acid
d) Endotoxins

23) Which of the following bacteria is also called the gamma or nonhemolytic streptococci?
a) Streptococcus faecalis
b) Streptococcus pyogenes
c) Streptococcus agalactiae
d) None of the above

24) Which of the following statements is Not true about the hemolysins produced by Streptococci?
a) Produce streptolysin O and S
b)An important virulence factor
c)Commonly produced by S. agalactiae
d) Observed around the colonies on blood agar 

25) A pus specimen cultured in blood agar, is incubated at 37-degree Celcius for 24 hours. 
Select all the possible laboratory results from the options below:
a) Gram-positive cocci shaped bacteria may be observed
b) Gram-positive bacteria in chains may be identified
c) Pink rods/bacilli bacteria may be isolated and identified
d) None of the above

26) Which of the following is the common method for identification of Streptococcus pneumoniae?
a. Coagulase test
b. Optochin sensitivity test
c. Urease test
d. Indole test


Multiple Choice Answers and Explanation:
1-b) Streptococcus agalactiae also known as Group B streptococci infection is high in pregnant women. a) Streptococcus pyogenes is Group A streptococcus, d) Streptococcus bovis is a Group D streptococcus, c) Enterococcus faecalis formerly classified as Group D streptococci. 

2-c) Streptococcus pyogenes, a Group A streptococcus

3-c) Impetigo, it is a common and contagious skin infection caused by bacteria, most commonly Staphylococcus aureus or Streptococcus pyogenes (group A streptococcus).

4-b) Staphylococcus aureus, impetigo is a common and contagious skin infection caused by bacteria, most commonly S. aureus.

5-d) It grows well in a high concentration of glucose media 

6-a) Streptococcus pneumoniae, Otitis media is an infection or inflammation of the middle ear, which is the space located behind the eardrum. It is a common condition found in children.

7-d) Streptococcus mutans
8- a), b) & c) 
9-b) Streptococcus bovis and Enterococcus faecalis
10-c) The morphological characteristics resemble that of S. pyogenes 
11-a) Enterococcus faecalis 
12-d) Endotoxins 
13-b) Enterococcus faecalis 
14-c) Aminoglycoside with penicillin 
15-a) Enterococcus faecium 

16-e) Both are capable of producing coagulase enzyme. Only S. aureus is coagulase positive and the test distinguishes from other cocci microorganisms.

17- c) Streptococcus pyogens (A)
18- e) Found only in the oral cavities as commensals
19- a) S. mutans
20- c) S. saprophyticus is a normal flora of humans skin surface
21- d)Penicillins
22- b) Teichoic acid
23- a)Streptococcus faecalis
24- c)Commonly produced by S. agalactiae
25- a), b) and c)
26- Pneumococci are sensitive to optochin and will show a zone of inhibition around the disc.


  1. Are these questions from a book? if so, could you please share your reference? thanks!

    1. Thank you for the question. I usually take references from Bailey & Scott's diagnostic Microbiology book.


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