WBR0053

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::'''Incorrect:''' Streptococcus pyogenes is a gram positive coccus.
Answer B	AnswerB::Haemophilus influenzae
Answer B Explanation	AnswerBExp::'''Incorrect:''' Haemophilus influenzae is a gram negative rod.
Answer C	AnswerC::Bacteriodes fragilis
Answer C Explanation	AnswerCExp::'''Incorrect:''' Bacteriodes fragilis is a gram negative rod.
Answer D	AnswerD::Legionella pneumophila
Answer D Explanation	AnswerDExp::'''Correct:''' 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::Incorrect: 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 Educational Objective: References: ]]
Approved	Approved::Yes
Keyword	WBRKeyword::Bacteria, WBRKeyword::Microbiology, WBRKeyword::Legionella, WBRKeyword::Gram stain, WBRKeyword::Stain
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