Simple micro question

[Unregistered1]

Hi,

I know this may seem like an easy question but the 'correct answer' that kaplan gave doesn't seem correct to me. Maybe there was a typo in the book. Please verify.

A 4 year old boy develops several honey crusted lesions behind his ears and on his face, The simplest test for the physician to determine the genus of bacteria responsible for this child's illness is the:

a.) Catalase test
b.) Coagulase test
c.) hemolysis pattern on blood agar
d.) growth of the organism in 6.5% sodium chloride
e.) polymerase chain reaction

[justjeatit]

impetigo

i think its staph so coagulase test

[justjeatit]

sorry its strep

group a strep

catalse test

[Unregistered1]

Well the answer in the book says this:

"Answer B: The easiest way to differentiate between Staphylococcus and Streptococcus is the catalase test. (choice A). This is important because they can have similar presentations. Coagulase (choice B) differentiares between members of the genus Staphylococcus. Hemolysis pattern (choice C) is inconclusive. Growth of organism in sodium chloride (choice D) can be useful for enterococcus. And PCR (choice E) is currently used to ID organisms that are difficult to culture."

But when I was doing this question my answer choice was A - the catalase test. My reasoning is that the GENUS Staphylococcus would be differentiated from Strep by the catalase test. But the SPECIES (ie. S. aureus) would be differentiated from S. epidermidis etc. by the coagulase test.

So catalase for genus and coagulase for species. So was kaplan wrong? Did it have a typo? Or am I still wrong and the answer is B?

HELP!

[taladega]

the answer is wrong, its a typo......i talked to the doc who wrote the book......the answer is right (coagulase), but the explanation is wrong.....the only way to tell the dif b/w staph and strep other than morphology for this question is the coagulase test since s.aureus is the only organism possessing this enzyme other than yersinia pestis

[taladega]

catalase is good for differentiating gram positives and negatives

[stateofequilibrium]

catalase is good for differentiating gram positives and negatives

eer, I'm fairly sure strep is catalase negative.

[MD777]

Pyoderma, also known as impetigo, often occurs around the mouth as honey crusted ulcers in younger children.

Catalase: diff. strep (-) or staphlo (+)

Coagulase: diff. species (s. epidermidis, s. aureus) under staphlo

Impetigo Impetigo is a highly contagious bacterial skin disease. Most of the 1.4 million Americans who develop impetigo are children. It's usually caused by either Streptococcus pyogenes or Staphylococcus aureus, two common bacteria. Any break in the integrity of the skin, such as a minor cut, scrape, etc., provides the opening for these bacteria to enter the skin and start the infection. Less commonly, impetigo may follow other skin problems, such as scabies, lice, fungal infections, or insect bites.

therefore, the answer should be Catalase to diff. either strep or staph...

finally, hope this helps...

more analysis welcome...

[taladega]

so sorry everyone......long story, but someone who has no idea what they are talking about posted as me......
as for the question, of course they are looking for the easiest way to differentiate between staph and strep, case describing classic impetigo, and the answer is definitely catalase (choice A) as staph is cat+ and strep is cat-