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  #1  
Old 05-06-2014
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Info Micro Question for Today

A 71-year-old man was admitted from his extended care facility because of recent aggravation of an exfoliative skin condition that has plagued him for several years. He had been receiving a variety of antibiotic regimens, including many topical preparations over the last year or two. He now has a temperature of 38.9 C (102 F). The skin of upper chest, extremities, and neck shows erythema with diffuse epidermal peeling and many pustular lesions. Cultures obtained from these lesions are reported back from the laboratory as yielding a gram-positive organism that is highly salt (NaCl) tolerant.
This organism is also most likely

(A) bacitracin sensitive
(B) bile soluble
(C) coagulase positive
(D) optochin sensitive
(E) novobiacin sensitive





ANSWER:
please someone kindly explain answer, the answer is C. but i have no explanation.
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Old 05-06-2014
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C..Staph. aureus, TSS
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Old 05-06-2014
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Staph aureus (coagulase +ve) causes Toxic Shock syndrome.
Desquamation is due to TSST-1 toxin (a super antigen)

You have to know that Staph. aureus is "SALT-TOLERANT".
This is mentioned in Kaplan, not in FA...........

And another hint would be that the condition persisted for several years
INSPITE of using many topical antibiotics. this may be due to Staph aureus
antibiotic resistance.....

Last edited by ICUdoc; 05-06-2014 at 08:58 AM.
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Old 05-11-2014
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Default

Quote:
Originally Posted by medstud. View Post
Staph aureus (coagulase +ve) causes Toxic Shock syndrome.
Desquamation is due to TSST-1 toxin (a super antigen)

You have to know that Staph. aureus is "SALT-TOLERANT".
This is mentioned in Kaplan, not in FA...........

And another hint would be that the condition persisted for several years
INSPITE of using many topical antibiotics. this may be due to Staph aureus
antibiotic resistance.....
EXACTLY, the salt tolerant part got me confused
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Old 05-12-2014
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You just need to know Staph aereus has exfoliative toxin to answer this question. I think it is not necessary to know staph aereus is nacl tolerant for usmle. If ıt was first aid would definitely add it
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Old 05-12-2014
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Quote:
Originally Posted by Barıs Olten View Post
You just need to know Staph aereus has exfoliative toxin to answer this question. I think it is not necessary to know staph aereus is nacl tolerant for usmle. If ıt was first aid would definitely add it
Yes.....you do need to know that staph aureus is Salt Tolerant to answer this question......

The answer could also very well be Streptococcal toxic shock syndrome(Strep pyogenes)......leading to the same clinical scenario.....
BUT its not salt tolerant...
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Quote:
Originally Posted by medstud. View Post
Yes.....you do need to know that staph aureus is Salt Tolerant to answer this question......

The answer could also very well be Streptococcal toxic shock syndrome(Strep pyogenes)......leading to the same clinical scenario.....
BUT its not salt tolerant...
i agree. i went with S. PYOGENES because the patient HAS A CHRONIC skin condition which it was likely secondarily infected,
so i went with bacitracin positive which is s.pyogenes. of course i read high salt tolerant and i was WTF??! i took it for granted, these tiny details makes a huge difference, so we have to pick up certain important clues from the vignette.

they mentioned in my live lectures that nowadays skin infections are almost equal etiology frequency when it comes to s.aureus and s.pyogenes incidence.

ALSO: scalded skin sx is very benign, only mild symptoms with the exfoliation and thats it, whereas strep has more marked symptoms.
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Last edited by drpisho; 05-12-2014 at 08:50 AM.
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Quote:
Originally Posted by medstud. View Post
Yes.....you do need to know that staph aureus is Salt Tolerant to answer this question......

The answer could also very well be Streptococcal toxic shock syndrome(Strep pyogenes)......leading to the same clinical scenario.....
BUT its not salt tolerant...
The answer cant be streptococcus pyogenes with this given question stem ı think. The question stem typically describes scalded skin syndrome of staph aereus. As far as i know strep pyogenes toxic shock syndrome doesnt ınvolve diffuse epidermal peeling.( I didnt read any micro book tho so i might be wrong but i speak clinically)
it seems like this patient has exfoliative exotoxin producing staph aereus.
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Quote:
Originally Posted by Barıs Olten View Post
The answer cant be streptococcus pyogenes with this given question stem ı think. The question stem typically describes scalded skin syndrome of staph aereus. As far as i know strep pyogenes toxic shock syndrome doesnt ınvolve diffuse epidermal peeling.( I didnt read any micro book tho so i might be wrong but i speak clinically)
it seems like this patient has exfoliative exotoxin producing staph aereus.
SSS is seen under age 5-6 year not elderly unless latter is immuno compromised.

2nd. This questions seems a typical kaplan question because only kaplan mentioned salt tolerant thing for s. aureus.

3rd this is TSS which can be seen in both S. aureus and S. pyogenes(although this typical case better fits S.pyogenes because of presence of previous skin infections) but salt tolerant thing distinguishes s. auerus vs s. pyogenes

Please correct me if am wrong.
Thank you.
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Quote:
Originally Posted by Redmoon View Post
SSS is seen under age 5-6 year not elderly unless latter is immuno compromised.

2nd. This questions seems a typical kaplan question because only kaplan mentioned salt tolerant thing for s. aureus.

3rd this is TSS which can be seen in both S. aureus and S. pyogenes(although this typical case better fits S.pyogenes because of presence of previous skin infections) but salt tolerant thing distinguishes s. auerus vs s. pyogenes

Please correct me if am wrong.
Thank you.
I am agree with you at all. TSS can be the diagnosis but doesnt it suppose to give Blood Pressure within the case? I havent read kaplan micro but i did uworld and i ve encountered TSS questions but all give BP and i think measured fever is lower than expected for TSS.
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Old 05-13-2014
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Quote:
Originally Posted by Barıs Olten View Post
I am agree with you at all. TSS can be the diagnosis but doesnt it suppose to give Blood Pressure within the case? I havent read kaplan micro but i did uworld and i ve encountered TSS questions but all give BP and i think measured fever is lower than expected for TSS.
IMHO,I Don't think so if given Low BP would make any difference to the correct answer here i.e C.
Besides, this question simply testing if one can identify bug based on given clue i.e salt tolerant, not if one can proper diagnose or not.
My 2 cents.
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