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|Prompt=A microbiologist has been given a number of unknown clinical samples and is attempting to visualize the organisms by gram stain.  Which of the following organisms will he be unable to visualize with this method?
|Prompt=A microbiologist has been given a number of unknown clinical samples and is attempting to visualize the organisms by gram stain.  Which of the following organisms will he be unable to visualize with this method?
|Explanation=[[Legionella pneumophila]] is a primarily intracellular organism which gram stains poorly.  The stain of choice for Legionella is a silver stain.  Legionella infections cause atypical pneumonia and are associated with aerosols from contaminated water, such as certain air conditioning systems.  Legionella infection can cause the very severe [[Legionaire's disease]] in older individuals.  A more mild manifestation of Legionella infection is [[Pontiac fever]].  The treatment of choice for legionella infections is a macrolide (e.g. erythromycin).
|Explanation=[[Legionella pneumophila]] is a primarily intracellular organism which gram stains poorly.  The stain of choice for Legionella is a silver stain.  Legionella infections cause atypical pneumonia and are associated with aerosols from contaminated water, such as certain air conditioning systems.  Legionella infection can cause the very severe [[Legionaire's disease]] in older individuals.  A more mild manifestation of Legionella infection is [[Pontiac fever]].  The treatment of choice for legionella infections is a macrolide (e.g. erythromycin).
'''Educational Objective:''' Legionella pneumophila is a primarily intracellular organism which gram stains poorly.  The stain of choice for Legionella is a silver stain.
'''References:'''
First Aid 2014 page 121
|AnswerA=Streptococcus pyogenes
|AnswerA=Streptococcus pyogenes
|AnswerAExp='''Incorrect:''' Streptococcus pyogenes is a gram positive coccus.
|AnswerAExp=Streptococcus pyogenes is a gram positive coccus.
|AnswerB=Haemophilus influenzae
|AnswerB=Haemophilus influenzae
|AnswerBExp='''Incorrect:''' Haemophilus influenzae is a gram negative rod.
|AnswerBExp=Haemophilus influenzae is a gram negative rod.
|AnswerC=Bacteriodes fragilis
|AnswerC=Bacteriodes fragilis
|AnswerCExp='''Incorrect:'''  Bacteriodes fragilis is a gram negative rod.
|AnswerCExp=Bacteriodes fragilis is a gram negative rod.
|AnswerD=Legionella pneumophila
|AnswerD=Legionella pneumophila
|AnswerDExp='''Correct:''' Legionella pneumophila is a primarily intracellular organism which gram stains poorly.  The stain of choice for Legionella is a silver stain.
|AnswerDExp=Legionella pneumophila is a primarily intracellular organism which gram stains poorly.  The stain of choice for Legionella is a silver stain.
|AnswerE=Corynebacterium diptheria
|AnswerE=Corynebacterium diptheria
|AnswerEExp='''Incorrect:''' [[Corynebacterium diptheria]] is a gram positive rod.
|AnswerEExp=[[Corynebacterium diptheria]] is a gram positive rod.
|EducationalObjectives=Legionella pneumophila is a primarily intracellular organism which gram stains poorly.  The stain of choice for Legionella is a silver stain.
|References=First Aid 2014 page 121
|RightAnswer=D
|RightAnswer=D
|WBRKeyword=Bacteria, Microbiology, Legionella, Gram stain, Stain,
|WBRKeyword=Bacteria, Microbiology, Legionella, Gram stain, Stain,
|Approved=Yes
|Approved=Yes
}}
}}

Revision as of 23:50, 14 March 2014
Author PageAuthor::William J Gibson
Exam Type ExamType::USMLE Step 1
Main Category MainCategory::Microbiology, MainCategory::Pathology
Sub Category SubCategory::General Principles, SubCategory::Infectious Disease
Prompt Prompt::A microbiologist has been given a number of unknown clinical samples and is attempting to visualize the organisms by gram stain. Which of the following organisms will he be unable to visualize with this method?
Answer A AnswerA::Streptococcus pyogenes
Answer A Explanation AnswerAExp::Streptococcus pyogenes is a gram positive coccus.
Answer B AnswerB::Haemophilus influenzae
Answer B Explanation AnswerBExp::Haemophilus influenzae is a gram negative rod.
Answer C AnswerC::Bacteriodes fragilis
Answer C Explanation AnswerCExp::Bacteriodes fragilis is a gram negative rod.
Answer D AnswerD::Legionella pneumophila
Answer D Explanation AnswerDExp::Legionella pneumophila is a primarily intracellular organism which gram stains poorly. The stain of choice for Legionella is a silver stain.
Answer E AnswerE::Corynebacterium diptheria
Answer E Explanation [[AnswerEExp::Corynebacterium diptheria is a gram positive rod.]]
Right Answer RightAnswer::D
Explanation [[Explanation::Legionella pneumophila is a primarily intracellular organism which gram stains poorly. The stain of choice for Legionella is a silver stain. Legionella infections cause atypical pneumonia and are associated with aerosols from contaminated water, such as certain air conditioning systems. Legionella infection can cause the very severe Legionaire's disease in older individuals. A more mild manifestation of Legionella infection is Pontiac fever. The treatment of choice for legionella infections is a macrolide (e.g. erythromycin).

Educational Objective: Legionella pneumophila is a primarily intracellular organism which gram stains poorly. The stain of choice for Legionella is a silver stain.
References: First Aid 2014 page 121]]

Approved Approved::Yes
Keyword WBRKeyword::Bacteria, WBRKeyword::Microbiology, WBRKeyword::Legionella, WBRKeyword::Gram stain, WBRKeyword::Stain
Linked Question Linked::
Order in Linked Questions LinkedOrder::
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