This question has multiple parts, didn\'t know how to post them separately becau

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This question has multiple parts, didn't know how to post them separately because they rely on each other to answer the other questions.

11. What tests can you now perform to help identify the problem bacteria?

a. You decide to start with fermentation tests. You incubate your tubes for 24 hours. In both the PRB glucose tube and PRB lactose tube you see yellow broth and an air bubble in the Durham tube. What does this mean?

Summarize your results:

                 Glucose

Appearance             Result

               Lactose

Appearance            Result

Now that you know the fermenting capabilities of your bacteria, you decided to run the IMViC tests. The first test you try is the Citrate Utilization test.

a. When making the Simmon’s citrate media, you added glucose along with the citrate. Will your test yield accurate results if you use this media? Why or why not?

b. If you don’t add glucose to the Simmon’s citrate media, will your test results be accurate? Why or why not?

c. After running the test properly, you find that the media is a deep blue color and there is growth on the slant. What does this result mean?

d. Next, you perform the Indole test. You find out that your bacteria cannot degrade tryptophan. What does this tube look like?

e. You inoculate your bacteria into 2 MRVP tubes and incubate them for 72 hours. When you perform the methyl red test with one of the 2 MRVP tubes, the media retains a yellow color. What does this result mean? Give 2 possible explanation for this result!

i. Now you perform the Voges-Proskauer test using the second MRVP tube, and the media develops a rose color. What does this result mean and does this result help to interpret the result of the methyl red test? Give a detailed explanation!!!

Summarize your results:

Methyl Red

Appearance            Result

Voges-Proskauer

Appearance           Result

Indole

Appearance            Result

Citrate

Appearance             Result

12. Knowing all these different test results can you clearly identify the bacterium that is causing the infection? If not what additional test(s) would you do to identify the bacterium? Give a detailed explanation! (Hint: You can use your results from class to help answer this. You may need to do some extra searches outside of the book.)

You decide to perform the litmus test as your final test. You inoculate a tube containing litmus milk medium and incubate the tube for 24hrs. What would you expect to see when you look at the tube the next day? Give a detailed explanation!!!!!

14. Based on what you know so far, what antibiotic might you recommend? Why?

                 Glucose

Appearance             Result

               Lactose

Appearance            Result

Explanation / Answer

Phenol red in Phenol red broth is a pH indicator, which turns yellow in acids produces during glucose and lactose fermentation. The gas produced is trapped as a bubble. Thus it can ferment both glucose and lactose.

Glucose -
Appearance - yellow and bubble, Result - Positive

Lactose -
Appearance - yellow and bubble, Result - Positive

Simmon’s citrate media is used to test the utilization of citrate as the sole carbon sourse, a growth in the media in is indicated by a color change from green to blue.

a) If we use glucose, then citrate non-utilizors will also grow which will give a false positive result as we have seen in the preceding test, they can ferment glucose.

b) If we do not add glucose, we will be able to get an accurate result.

c) A blue test indicates citrate positive. It may be a colifirm.

d) Indole test is performed in presence of tryptophan in the medium (peptone water). The final product is indole which is detected by adding Kovac's Reagent, which will result a pink layer on the surface of the media. If it does not degrade tryptophan, then the color of the top will remain unchanged. As this is does not degrade tryptophan, it may be Klebsiella pneumoniae or enterobacter aerogens.

e) Positive methyl red test are indicated by the development of red color after the addition of methyl red reagent. Methyl red is a pH indicator which turns red below pH 4. This low pH will be prevalent if the microbe performs mixed acid fermentations. A no color change indicates a negative result, which indicates the bacterium may be Klebsiella pneumoniae or enterobacter aerogens.

i) The VP test uses alpha-naphthol and potassium hydroxide to test for the presence of acetoin, produced by Klebsiella spp, Enterobacter spp, Hafnia spp and Serratia spp. A rose color indicates VP positive (acetoin producer). It only substantiates the results of the MR test, as the question still remains the same, as both Klebsiella pneumoniae and enterobacter aerogens are positive for VP test.

12. The identification si still nor clear. As both Klebsiella pneumoniae and enterobacter aerogens are the possibility. To differentiate them, motility test can be used. Soft agar stabs of the two bacteria on Sulfite-Indole-Motility (SIM) agar will result spreading of the bacterium from the stab. Otherwise, hanging drop test can be used to view them directly under microscope. E. aerogens is motile and K. pneumoniae is not.

Based on the above results, carbapenems will be the best choice of antibiotics. Imipenem, doripenem and meropenem act against both E. aerogens and K. pneumoniae.

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