Would removing bile salts from HE agar alter the mediumâs sensitivity or specificity? Explain your answer. ( See pages 8 and 9, âA Word About Experimental Design,â for assistance with these terms.)

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Jamar FerryLv2

30 Apr 2019

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(a) Some organisms are able to grow on the medium without hydrolyzing the esculin. Other organisms are able to hydrolyze esculin but darken only a portion of the medium. Are either of these types of organisms considered positive for this test? If yes, why? If no, under what circumstances would they be considered positive? EXPLAIN.

Extra information: Bile Esculin Azide agar testing S. pyogenes and E. faecalis

(b) Is darkening LESS THAN half the medium due to failure of sensitivity or specificity in this test system? EXPLAIN

Q1. Will the omission of the 7.5% NaCl in MSA medium affect its specificity or sensitivity? Explain.

Q2. Will the addition of only 1/10^th of mannitol in the MSA medium affect its specificity or sensitivity? Explain.

Q3. In clinical settings, Blood Agar plates are used to detect b-hemolysin producers. Suppose that after processing a patientâs sample, you saw growth on Blood Agar plate, but with no single colonies. Of the areas that showed growth, you observe full clearing of the blood cells. What conclusions would you draw about the presence of the b-hemolysin producers and a-hemolysin producers? Explain.

Q4. On EMB plates, colonies that would normally appear pink may turn into a metallic green shade if left sitting on the plate for multiple days. Explain why that is the case. Is this a specificity or sensitivity problem?

Q5. One of the features that separate E. coli from closely-related species are its ability to ferment lactose very efficiently. (A) If the lactose in the EMB plate is replaced with glucose, will it affect the specificity or sensitivity of the media?

(B) If the amount of lactose in EMB is reduced by 75%, will that impact the specificity or sensitivity of the medium?

coffeelouse766

Robert had always heard that eating cheese before bedtime causednightmares. He decided to use the scientific method to see if thiswas true. He formed a hypothesis; âDoes cheese cause nightmares?âHe recruited nine members of his family (parents, siblings, oneuncle, and three cousins) and asked them to participate for oneweek. He made the following conditions; participants either had toeat cheese before bedtime (the experimental group) or not eatcheese (control group). He provided each participant with anotebook and pencil to keep next to their bed, to record if theywoke in the middle of the night from a nightmare. After one week hefound that of the 9 participants four, including Robert, had hadnightmares during the week, all of them had eaten cheese theevening before.

Has Robert proved that cheese causesnightmares?

Critically evaluate Roberts experiment. Identify fourflaws in his experimental design. For eachmake a suggestion as to how his experimentcould be improved.