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S3 Ross Micro - Lab Diagnosis
Sloma lecture 44
23
Microbiology
Professional
11/07/2009

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Cards

Term
What is a specific example when the timeliness of a specimen collection is important?
Definition
Smears for malaria diagnosis should be collected at different times during the day because parisitemia can be intermittent
Term
When should you NOT collect a microbial specimen from a patient.
Definition
You would not want to collect a sample from the patient AFTER antimicrobial therapy. Please don't make me explain this.
Term
Describe Blood Agar
Definition
A General Purpose agar that can isolate microbes based on if they somewhat break down the agar, completely break it down, or can't break it down at all (alpha, beta, gamma, respectively)
Term
Describe Chocolate Agar and an example of a microbe that loves it
Definition
Chocolate agar is like blood agar but all the RBCs are lysed. Bugs like Haemophilus and Neisseria thrive in this medium. Thayer-Martin = chocolate + antibiotics. It is used to detect N. gonorrhoeae
Term
You are working in a lab and need to use a medium that is selective for S. aureus, what would you choose?
Definition
Mannitol-salt agar has a high [salt] and inhibits most bugs. If S. aureus is present the agar turns from red to yellow.
Term
What organisms is MacConkey agar selective for? What carbs does it have? What microbes does it inhibit?
Definition
Selective for gram negative organisms. It only has Lactose. Inhibits gram (+) and hemophilus and neisseria. Lactose fermentation = red/pink.
Term
Describe EMB agar.
Definition
Eosin Methyylene Blue show lactose fermenters as blue-black, possibly with a metallic sheen.
Term
What is Bile esculin agar selective for? How is it determined visually?
Definition
Bile esculin agar is selective for Group D Strep and Enterococcus. These bugs convert esculin to exculitin which reacts with iron to produce a black precipitate.
Term
You suspect a patient of yours has Salmonella poisoning. What agar would you use? Why?
Definition

Hektoen enteric (HE) agar isolates enteric pathogens.

 

Fermenters = yellow-pink.

Non-fermenters = green or clear.

H2S-producers = black (salmonella)

Term
Your patient comes in complaining of Hot-tub rash and you suspect Pseudomonas aeruginosa. What agar would you place the culture on to confirm?
Definition
Cetramide agar will inhibit most other microbes and shows pseudomonas as blue-green or yellow-green colonies.
Term
Your patient presents with fatigue, mild fever and problems swallowing. You suspect Corynebacterium diphtheriae but you can only choose one agar to grow it on. What would you choose?
Definition
Tellurite agar/Cystine-tellurite agar is selective and differential for C.diphtheriae. The colonies are gray or black with a brown halo.
Term
A salesman comes to your office and he says he's got the "Optimus Prime" of agars. It can colonize different bugs showing up as different colors and can even differentiate MRSA and MSSA. You says, "Homie, that's not new. Its called..."
Definition
Chromogenic agar
Term
What are two biochemical tests that you can do for bacteria that can be run in minutes?
Definition
Catalase (Hydrogen peroxide to H2O + O2) and Oxidase (presence of Cytochrome C oxidase). Coagulase agglutination test is also rapid
Term
How is Thioglycollate used? How is it read?
Definition
Thioglycollate test allows various amounts of O2 to diffuse to different levels. Obligate aerobes grow at the top. Facultative anerobes grow throughout but more to the top. Aerotolerate anaerobes grow throughout. Strict anaerobes will not grow at the top.
Term
List some ways one can visualize microbes from a smear or sample.
Definition
Wet prep, stained prep, dark field, light field, phase contrast, fluorescence, electron microscopy.
Term
Why is an agglutination test useful?
Definition
It is fast and can be used even if the patient has been treated with antibiotics.
Term
What antibodies can be detected to...detect Hepatitis Virus or dimophic fungi?
Definition
IgG or IgM. These are very sensitive tests but M can only be detected from 7-10 days and G can only be detected 2-4 weeks later.
Term
In immuno assay what technique targets two different epitopes for measure and capture?
Definition
The sandwich technique
Term
Which type of test is considered to be objective but is still very useful?
Definition
Indirect Fluroescent antibody
Term
An old, labor-intensive, technically challenging method for detection of antibodies against specific pathogens?
Definition
Complement fixation
Term
THE go-to test for HIV
Definition
Western Blot
Term
What is the difference between Signal Amplification and Nucleic-Acid amplification?
Definition
With signal-amplification a single nucleic acid signal will produce a highly-amplified signal is proportional to the number of copies of the specific nucleic acid. Nucleic-acid amplification is simple PCR...I'm pretty sure. Someone correct me if I'm wrong.
Term
What sucks about PCR?
Definition
Besides the fact that you had to run a million of them in undergrad, they have licensing fees every time you use it.
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