Bacteriology: streptococci: practice question

A Microbiology question in the style of the NEET PG paper. Answer it first, then read why the right option is right and why each of the others is wrong.

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Microbiology · Bacteriology: streptococci

Sample item

A throat swab culture grows Gram-positive cocci in chains with a wide zone of clear (beta) haemolysis on blood agar. The organism is sensitive to bacitracin and PYR positive. Which organism is this?

Original practice item, not a recalled exam question. Nothing here is recorded.

The answer and the reasoning

A. Streptococcus pyogenes (Group A)

Group A streptococcus is beta-haemolytic, bacitracin-sensitive and PYR positive. It causes pharyngitis, skin infection, and the non-suppurative sequelae rheumatic fever and post-streptococcal glomerulonephritis. Group B is bacitracin-resistant and hippurate positive. Enterococcus is PYR positive but bacitracin-resistant and non-beta-haemolytic.

Option by option

  • A. Streptococcus pyogenes (Group A) (correct)

    Correct. This combination identifies Group A streptococcus.

  • B. Enterococcus faecalis

    Enterococcus grows in 6.5% sodium chloride and is not usually beta-haemolytic.

  • C. Streptococcus pneumoniae

    Pneumococcus is alpha-haemolytic and optochin sensitive.

  • D. Streptococcus agalactiae (Group B)

    Group B streptococcus is bacitracin resistant, hippurate positive and CAMP positive.

Source note: Original NextPrep sample item — pending expert review. This item is original practice material awaiting independent expert review, so confirm important facts in a standard textbook.

More Microbiology questions

Questions about this Microbiology question

What is the answer to this Microbiology question?

The best answer is A, Streptococcus pyogenes (Group A). Group A streptococcus is beta-haemolytic, bacitracin-sensitive and PYR positive.

Why is "Enterococcus faecalis" not the answer?

Enterococcus grows in 6.5% sodium chloride and is not usually beta-haemolytic.

Why is "Streptococcus pneumoniae" not the answer?

Pneumococcus is alpha-haemolytic and optochin sensitive.

Why is "Streptococcus agalactiae (Group B)" not the answer?

Group B streptococcus is bacitracin resistant, hippurate positive and CAMP positive.

What concept does this question test?

It tests Bacteriology: streptococci in Microbiology. It causes pharyngitis, skin infection, and the non-suppurative sequelae rheumatic fever and post-streptococcal glomerulonephritis. Group B is bacitracin-resistant and hippurate positive. Enterococcus is PYR positive but bacitracin-resistant and non-beta-haemolytic.

How hard is this question?

We tag it as an application question: it asks you to use a fact on a patient or a finding. The tag is our own editorial judgement, not an official difficulty rating, so read the reason for every option, not only the answer.

How should I study Bacteriology: streptococci?

Make a one-line identity card for each organism: shape and stain, defining test, toxin, disease and drug. Then use the flashcards and the other Microbiology questions on this site to test what stuck.

Is this a real NEET PG question?

No. It is an original practice item (editorial status: sample, version 1). NextPrep does not publish recalled or leaked questions, and independent faculty review of this item has not been completed yet, so confirm important facts in a standard textbook.