USMLE FREE QUIZ

Let’s discuss gram staining. There are five basic steps in gram staining. What is done to specimens in the first step?
- In the first step of gram staining, specimens are fixed to the slide by heat.

What is the second step in gram staining?
- Specimens are dyed with a basic stain, such as crystal violet
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Now, when would a Streptococcus Group A pyogenes infection be suspected? Name three clinical circumstances:

- First, a skin infection that also has erythema and edema.

- Second, an oropharyngeal infection where you see exudates on the tonsils.

- And third, worrisome symptoms after infections such as these have resolved including (please name 5, and please pause):
---- hematuria,
---- migratory arthritis,
---- subcutaneous nodules,
---- carditis,
---- erythema marginatum.
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How does necrotizing fasciitis from Streptococcus Group A usually begin?
- It usually begins as a very small or trivial-appearing skin infection.
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In addition, what two palpatory findings are you likely to have in your Clinical Exam when the patient has Scarlet Fever or Scarlatina due to Streptococcus Group A or Strep pyogenes?
- Palpable adenopathy and splenomegaly.
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What two serious conditions may develop in the patient after the Streptococcus Group A infection has completely resolved and there is actually no Strep Group A organism infecting the patient at all?
- First, post-streptococcal acute glomerulonephritis. Second, post-streptococcal acute rheumatic fever.

How does Clostridium tetani typically appear under the microscope?
- As rods that are shaped like tennis rackets; singly, in pairs or in chains

How does Clostridium tetani appear in culture and in what medium?
-Transparent villus colonies on serum agar under anaerobic conditions

What two groups of patients are most subject to Clostridium tetani infections?
-First: patients with wounds.
-Second: neonates who have become infected at the umbilical stump.

What is the lab test profile for Clostridium tetani?
-Lab tests are not usually performed

What is another name for tetanus toxin?
-Tetinospasmin
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What is the quick and dirty rule for attempting to diagnose what bacteria is causing a pneumonia? Please pause.
- If the patient can easily produce a lot of sputum and when you gram stain the stputum you see a lot of gram positive cocci and you see a lot of white blood cells it’s almost certainly Streptococcus pneumonia.
And, if you don’t get a lot of sputum easily and it doesn’t gram stain positive cocci then heaven only knows which bacteria is causing the bacteria, and you should just cover with broad spectrum antibiotic.
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Now what does H flu secrete or synthesize that causes this broncho constriction?
- Histamine.
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What particular form of Clostridium tetani actually performs the initial contamination of the wound?
- The spores
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Alright, let’s look at our outpatient who has a community acquired pneumonia.
What are the three most likely bacteria to be involved in order of frequency? Include gram stain, aerobic status and shape.
- First – Streptococcus pneumonia, gram positive, aerobic, cocci
- Second – Haemophilus influenzae, gram negative, aerobic, rod
And a distant third, this is not common but when it does occur it can be rapidly fatal, even in the community acquired type of patient. Staphylococcus aureus, gram positive, aerobic, cocci
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Let’s name five viruses likely to cause viral pneumonia, and because frequency varies so much according to time of year, location, and age of the patient let’s put them in alphabetical order.
Please include the distinguishing association.
- First – and please pause – Adenovirus, and adenoviruses can run rampant in situations where people are crowded together for lengthy periods of time such as especially in the military.
- Second – Hantavirus,
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What organism is Rifadin derived from?
- The soil mold streptomyces.

And tuberculosis and leprosy are both caused by what type of bacteria?
- The Mycobacteria.

And the two respectively here are mycobacteria tuberculosis and mycobacteria leprae.
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Now when you suspect meningitis and you do a lumbar puncture if the meningitis is caused by Hemophilus influenzaee you would expect what appearance of the CSF as it comes out?
- You would expect it to be cloudy.