Streptococcus Questions and Answers

Q: Which of the following microbe does not belong to Group D enterococci group?

Correct answer: S. bovisS. bovis carries the group D antigen but is not an enterococcus: it fails to grow in 6.5 per cent salt and remains bile-aesculin positive, so it is distinguished from the true enterococci by the salt test. The distinction has clinical value, since S. bovis bacteraemia and endocarditis are associated with colonic carcinoma and prompt a search for one.

Q: A urine sample was taken from a 30 year old who had symptoms related with urinary tract infection, she complained of painful and frequent urination with blood in the urine. Which of the following pathogen is Not most commonly found in the urine sample?

Correct answer: Streptococcus mutansS. mutans is an oral organism and is not a urinary pathogen. The others are all found in urine cultures: E. coli overwhelmingly the commonest, S. aureus in catheterised or bacteraemic patients, and S. agalactiae particularly in pregnancy, where its presence in urine indicates heavy genital colonisation.

Q: A 2 days old premature baby boy born to a 22-year-old woman developed a pneumonia, the mother was healthy but after the premature delivery she showed the symptoms of urinary tract infection. The blood specimen was taken from the baby, beta hemolytic colonies was observed in the culture plate. Which could be the possible pathogen that might have transferred from the mother to the baby and caused infection?

Correct answer: Streptococcus agalactiaeGroup B streptococcus is carried in the maternal genital tract and is the leading cause of early onset neonatal sepsis and pneumonia, acquired as the baby passes through the birth canal. Prematurity is a recognised risk factor and maternal urinary tract infection points to heavy colonisation. The beta-haemolytic colonies are consistent, and screening in late pregnancy exists to prevent exactly this.

Q: Which of the following is a major virulence factor of Streptococcus pneumoniae?

Correct answer: polysaccharide capsuleThe pneumococcal capsule prevents phagocytosis and is the organism’s principal virulence factor: unencapsulated strains are avirulent. It is also the basis of prevention, since both the polysaccharide and the conjugate vaccines are directed against it, and of typing, there being more than ninety capsular serotypes. M protein and the streptolysins belong to S. pyogenes.

Q: Which of the following bacteria is Not is a part of the normal human microbiota?

Correct answer: Streptococcus pyogens (A)S. pyogenes is regarded as a pathogen rather than a commensal: asymptomatic throat carriage occurs, particularly in children, but it is not part of the established normal flora and its presence is significant. The other three are genuine commensals - S. aureus in the anterior nares, S. agalactiae in the genital and gastrointestinal tracts, E. faecalis in the bowel.

Q: Streptococus pyogenes comprises which Lancefield group?

Correct answer: AS. pyogenes carries the group A cell wall carbohydrate, which is what the Lancefield grouping detects and what gives it its everyday name of group A streptococcus. Group B is S. agalactiae, the neonatal pathogen, and group D covers the enterococci and S. bovis.

Q: Which of the following bacteria is most resistant to the drug vancomycin?

Correct answer: Enterococcus faeciumVancomycin resistance is far commoner in E. faecium than in E. faecalis, and vancomycin-resistant E. faecium is one of the principal hospital-acquired resistance problems. The resistance comes from van gene clusters that replace the terminal D-alanine of the cell wall precursor, so vancomycin can no longer bind.

Q: Which of the following bacteria causes otitis media?

Correct answer: Streptococcus pneumoniaeS. pneumoniae is the commonest bacterial cause of acute otitis media, as it is of sinusitis and community-acquired pneumonia - all infections spreading from nasopharyngeal carriage into an adjacent space. Conjugate vaccination has reduced the incidence of all three, which is indirect confirmation of the organism’s role.

Q: Antibiotics can easily reach the staphylococci.

Correct answer: FalseThe staphylococcal abscess is designed to keep them out. Coagulase converts fibrinogen to fibrin around the lesion, producing an avascular wall that antibiotics cannot cross in useful concentration, and the organisms inside are metabolically slow and correspondingly tolerant. This is why an abscess must be drained surgically and why antibiotic therapy alone so often fails.

21.

Which of the following microbe does not belong to Group D enterococci group?

A.S. faecalis
B.S. faecium
C.S. durans
D.S. bovis

Answer: D

Correct answer: S. bovis

S. bovis carries the group D antigen but is not an enterococcus: it fails to grow in 6.5 per cent salt and remains bile-aesculin positive, so it is distinguished from the true enterococci by the salt test. The distinction has clinical value, since S. bovis bacteraemia and endocarditis are associated with colonic carcinoma and prompt a search for one.

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22.

A urine sample was taken from a 30 year old who had symptoms related with urinary tract infection, she complained of painful and frequent urination with blood in the urine. Which of the following pathogen is Not most commonly found in the urine sample?

A.Staphylococcus aureus
B.E.coli
C.Streptococcus mutans
D.Streptococcus agalactiae

Answer: C

Correct answer: Streptococcus mutans

S. mutans is an oral organism and is not a urinary pathogen. The others are all found in urine cultures: E. coli overwhelmingly the commonest, S. aureus in catheterised or bacteraemic patients, and S. agalactiae particularly in pregnancy, where its presence in urine indicates heavy genital colonisation.

Discuss in Forum

23.

A 2 days old premature baby boy born to a 22-year-old woman developed a pneumonia, the mother was healthy but after the premature delivery she showed the symptoms of urinary tract infection. The blood specimen was taken from the baby, beta hemolytic colonies was observed in the culture plate. Which could be the possible pathogen that might have transferred from the mother to the baby and caused infection?

A.Streptococcus pyogenes
B.Streptococcus agalactiae
C.Enterococcus faecalis
D.Streptococcus bovis

Answer: B

Correct answer: Streptococcus agalactiae

Group B streptococcus is carried in the maternal genital tract and is the leading cause of early onset neonatal sepsis and pneumonia, acquired as the baby passes through the birth canal. Prematurity is a recognised risk factor and maternal urinary tract infection points to heavy colonisation. The beta-haemolytic colonies are consistent, and screening in late pregnancy exists to prevent exactly this.

Discuss in Forum

24.

All of the following statement regarding coagulase negative Staphylococcus spp (CONS) are true, Except?

A.S. epidermidis and S. saprophyticus are coagulase negative staphylococci
B.Infection with S. epidermidis are usually hospital acquired
C.S. saprophyticus is normal flora of humans skin surface
D.Both are common pathogens in urinary tract infections

Answer: C

Correct answer: S. saprophyticus is normal flora of humans skin surface

S. saprophyticus belongs to the genitourinary flora rather than being a general skin commensal; it is S. epidermidis that colonises skin everywhere. The distinction matters clinically, because S. saprophyticus in a urine culture from a young woman is a genuine pathogen while S. epidermidis in a blood culture is more often a contaminant.

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25.

Which of the following is a major virulence factor of Streptococcus pneumoniae?

A.polysaccharide capsule
B.M protein
C.streptolysin O
D.streptolysin S

Answer: A

Correct answer: polysaccharide capsule

The pneumococcal capsule prevents phagocytosis and is the organism’s principal virulence factor: unencapsulated strains are avirulent. It is also the basis of prevention, since both the polysaccharide and the conjugate vaccines are directed against it, and of typing, there being more than ninety capsular serotypes. M protein and the streptolysins belong to S. pyogenes.

Discuss in Forum

26.

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

Answer: C

Correct answer: Streptococcus pyogens (A)

S. pyogenes is regarded as a pathogen rather than a commensal: asymptomatic throat carriage occurs, particularly in children, but it is not part of the established normal flora and its presence is significant. The other three are genuine commensals - S. aureus in the anterior nares, S. agalactiae in the genital and gastrointestinal tracts, E. faecalis in the bowel.

Discuss in Forum

27.

Streptococus pyogenes comprises which Lancefield group?

Answer: A

Correct answer: A

S. pyogenes carries the group A cell wall carbohydrate, which is what the Lancefield grouping detects and what gives it its everyday name of group A streptococcus. Group B is S. agalactiae, the neonatal pathogen, and group D covers the enterococci and S. bovis.

Discuss in Forum

28.

Which of the following bacteria is most resistant to the drug vancomycin?

A.Enterococcus faecium
B.Streptococcus pyogenes
C.Staphylococcus aureus
D.Lactobacillus acidophilus

Answer: A

Correct answer: Enterococcus faecium

Vancomycin resistance is far commoner in E. faecium than in E. faecalis, and vancomycin-resistant E. faecium is one of the principal hospital-acquired resistance problems. The resistance comes from van gene clusters that replace the terminal D-alanine of the cell wall precursor, so vancomycin can no longer bind.

Discuss in Forum

29.

Which of the following bacteria causes otitis media?

A.Streptococcus pneumoniae
B.Streptococcus agalactiae
C.Streptococcus pyogenes
D.Streptococcus intermedius

Answer: A

Correct answer: Streptococcus pneumoniae

S. pneumoniae is the commonest bacterial cause of acute otitis media, as it is of sinusitis and community-acquired pneumonia - all infections spreading from nasopharyngeal carriage into an adjacent space. Conjugate vaccination has reduced the incidence of all three, which is indirect confirmation of the organism’s role.

Discuss in Forum

30.

Antibiotics can easily reach the staphylococci.

A.True
B.False

Answer: B

Correct answer: False

The staphylococcal abscess is designed to keep them out. Coagulase converts fibrinogen to fibrin around the lesion, producing an avascular wall that antibiotics cannot cross in useful concentration, and the organisms inside are metabolically slow and correspondingly tolerant. This is why an abscess must be drained surgically and why antibiotic therapy alone so often fails.

Discuss in Forum

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