Streptococcus Questions and Answers

Q: Which Gram-positive cocci are commonly associated with pneumonia?

The Gram-positive cocci associated with pneumonia are Streptococcus pneumoniae.S. pneumoniae, the pneumococcus, appears as Gram-positive lanceolate diplococci and is the most common cause of community-acquired lobar pneumonia.The other options fail on the Gram reaction or the shape. Neisseria are Gram-negative diplococci, and Vibrio are Gram-negative curved rods. Klebsiella pneumoniae does cause pneumonia, but it is a Gram-negative bacillus, not a coccus, so it does not fit the question.

Q: Which of the following cross-reacts with cell wall carbohydrate of Streptococcus pyogenes?

Correct answer: Cardiac valvesThe group A carbohydrate of the cell wall shares antigenic determinants with glycoproteins of the cardiac valves, so antibody raised against the organism attacks the valve tissue as well. This is the molecular mimicry that produces the valvular damage of rheumatic heart disease. The M protein cross-reacts with a different tissue, the myocardium.

Q: Which of the following microorganism causes lesions in the form of abscesses?

Correct answer: Staphylococcus aureusThe walled-off abscess is the characteristic staphylococcal lesion: coagulase clots the surrounding plasma into a fibrin barrier that keeps phagocytes and antibiotics out while the organism multiplies inside. Streptococcal infection spreads diffusely instead, through tissue planes, because streptokinase and hyaluronidase break down exactly the barriers that staphylococci build.

Q: Which of the following test indicates the susceptibility to streptococcal pyrogenic exotoxin?

Correct answer: Dick testThe Dick test injects a small dose of streptococcal pyrogenic (erythrogenic) exotoxin intradermally: a local erythematous reaction shows that the person lacks neutralising antibody and is therefore susceptible to scarlet fever. The Schick test is its diphtheria counterpart, and the ASO test measures antibody to streptolysin O rather than susceptibility to the toxin.

Q: Which of the following is NOT a typical infection caused by Group A Streptococcus?

Correct answer: MeningitisMeningitis is not a typical group A streptococcal infection; it is caused chiefly by S. pneumoniae, Neisseria meningitidis and, in the newborn, group B streptococcus. The other three are all group A diseases: pharyngitis, impetigo, and scarlet fever, which is pharyngitis together with the rash produced by the pyrogenic exotoxin.

Q: Which of the following is NOT the virulent factor, an important antigenic property of S. pyogenes?

Correct answer: EndotoxinsEndotoxin is lipopolysaccharide, a component of the gram-negative outer membrane, and S. pyogenes is gram-positive and has none. Its virulence rests on the M protein, which resists phagocytosis and is the principal antigen; the streptolysins, which lyse cells; and enzymes such as streptokinase and hyaluronidase, which spread the infection through tissue.

Q: Scarlet fever is similar to the pharyngitis in all respects.

Correct answer: FalseScarlet fever is streptococcal pharyngitis plus the effects of the pyrogenic exotoxin: a diffuse erythematous rash sparing the area around the mouth, a strawberry tongue, and subsequent desquamation. It occurs only when the infecting strain carries the toxin gene and the patient lacks neutralising antibody, which is what the Dick test detects.

Q: Puerperal fever is a streptococcal infection of the _____________

Correct answer: uterusPuerperal fever is streptococcal infection of the endometrium following childbirth, spreading from there to the bloodstream. It was the great killer of maternity wards until Semmelweis showed that hand disinfection prevented it, and it remains the historical demonstration that the organism is carried on the hands of attendants rather than arising within the patient.

Q: The possible pathogen for the above disease condition is..................

Correct answer: Staphylococcus aureusImpetigo is caused by S. aureus and by S. pyogenes, and S. aureus is now the commoner of the two in most settings, producing the bullous form as well as the crusted one. Both are gram-positive cocci, which is as far as the microscopy in the case takes you; culture and coagulase testing separate them.

Which Gram-positive cocci are commonly associated with pneumonia?

A.Neisseria
B.Vibrio
C.Streptococcus pneumoniae
D.Klebsiella

Exam Year(s)

RSMSSB - 2025, RSMSSB Lab Technician - 2025,

Answer: C

The Gram-positive cocci associated with pneumonia are Streptococcus pneumoniae.

S. pneumoniae, the pneumococcus, appears as Gram-positive lanceolate diplococci and is the most common cause of community-acquired lobar pneumonia.

The other options fail on the Gram reaction or the shape. Neisseria are Gram-negative diplococci, and Vibrio are Gram-negative curved rods. Klebsiella pneumoniae does cause pneumonia, but it is a Gram-negative bacillus, not a coccus, so it does not fit the question.

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Which of the following cross-reacts with cell wall carbohydrate of Streptococcus pyogenes?

A.Cardiac valves
B.Synovial fluid
C.Myocardium
D.Vascular intima

Answer: A

Correct answer: Cardiac valves

The group A carbohydrate of the cell wall shares antigenic determinants with glycoproteins of the cardiac valves, so antibody raised against the organism attacks the valve tissue as well. This is the molecular mimicry that produces the valvular damage of rheumatic heart disease. The M protein cross-reacts with a different tissue, the myocardium.

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Which of the following microorganism causes lesions in the form of abscesses?

A.Staphylococcus aureus
B.Streptococcus pyogenes
C.Streptococcus pneumoniae
D.Clostridium perfringens

Answer: A

Correct answer: Staphylococcus aureus

The walled-off abscess is the characteristic staphylococcal lesion: coagulase clots the surrounding plasma into a fibrin barrier that keeps phagocytes and antibiotics out while the organism multiplies inside. Streptococcal infection spreads diffusely instead, through tissue planes, because streptokinase and hyaluronidase break down exactly the barriers that staphylococci build.

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All of the following are the characteristics of Streptococcus pneumoniae, EXCEPT?

A.The colonies are diplococcus and encapsulated
B.Alpha hemolytic colonies appear in blood culture media
C.It is present as normal flora in healthy individuals
D.It grows well in a high concentration of glucose media

Answer: D

Correct answer: It grows well in a high concentration of glucose media

Pneumococci are fastidious and are inhibited rather than favoured by a high glucose concentration, because the acid produced from fermenting it lowers the pH below what the organism tolerates. The other three are all correct: it is a capsulated diplococcus, it is alpha-haemolytic on blood agar, and it is carried in the nasopharynx of healthy people.

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Which of the following test indicates the susceptibility to streptococcal pyrogenic exotoxin?

A.Schick test
B.Dick test
C.ASO test
D.Precipitation test

Answer: B

Correct answer: Dick test

The Dick test injects a small dose of streptococcal pyrogenic (erythrogenic) exotoxin intradermally: a local erythematous reaction shows that the person lacks neutralising antibody and is therefore susceptible to scarlet fever. The Schick test is its diphtheria counterpart, and the ASO test measures antibody to streptolysin O rather than susceptibility to the toxin.

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Which of the following is NOT a typical infection caused by Group A Streptococcus?

A.Pharyngitis
B.Impetigo
C.Scarlet fever
D.Meningitis

Answer: A

Correct answer: Meningitis

Meningitis is not a typical group A streptococcal infection; it is caused chiefly by S. pneumoniae, Neisseria meningitidis and, in the newborn, group B streptococcus. The other three are all group A diseases: pharyngitis, impetigo, and scarlet fever, which is pharyngitis together with the rash produced by the pyrogenic exotoxin.

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Which of the following is NOT the virulent factor, an important antigenic property of S. pyogenes?

A.Endotoxins
B.Streptolysin
C.Streptokinase
D.M protein

Answer: A

Correct answer: Endotoxins

Endotoxin is lipopolysaccharide, a component of the gram-negative outer membrane, and S. pyogenes is gram-positive and has none. Its virulence rests on the M protein, which resists phagocytosis and is the principal antigen; the streptolysins, which lyse cells; and enzymes such as streptokinase and hyaluronidase, which spread the infection through tissue.

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Scarlet fever is similar to the pharyngitis in all respects.

A.True
B.False

Answer: B

Correct answer: False

Scarlet fever is streptococcal pharyngitis plus the effects of the pyrogenic exotoxin: a diffuse erythematous rash sparing the area around the mouth, a strawberry tongue, and subsequent desquamation. It occurs only when the infecting strain carries the toxin gene and the patient lacks neutralising antibody, which is what the Dick test detects.

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Puerperal fever is a streptococcal infection of the _____________

A.kidney
B.skin
C.uterus
D.heart

Answer: C

Correct answer: uterus

Puerperal fever is streptococcal infection of the endometrium following childbirth, spreading from there to the bloodstream. It was the great killer of maternity wards until Semmelweis showed that hand disinfection prevented it, and it remains the historical demonstration that the organism is carried on the hands of attendants rather than arising within the patient.

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10.

The possible pathogen for the above disease condition is..................

A.Pseudomonas aeruginosa
B.Staphylococcus aureus
C.Streptococcus agalactiae
D.Trichophyton rubrum

Answer: B

Correct answer: Staphylococcus aureus

Impetigo is caused by S. aureus and by S. pyogenes, and S. aureus is now the commoner of the two in most settings, producing the bullous form as well as the crusted one. Both are gram-positive cocci, which is as far as the microscopy in the case takes you; culture and coagulase testing separate them.

Discuss in Forum

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