Create DICHOTOMOUS KEY showing
Create DICHOTOMOUS KEY showing which selective media andbiochemical tests you would need if you were to test your unknownbacteria (SALMONELLA ENTERICA) in the lab and also, describe thedichotomous key of Salmonella Enterica in paragraph like in exampleshown below.
[[ Like this is example for Staphylococcus epidermis shown by myprofessor: You would say this. According to my unknown bacterium16S DNA sequence result from NCBI database, my unknown bacteriumwas identified to be Staphylococcus epidermidis. To identify andconfirm Staphylococcus epidermidis bacterium in lab traditionallyusing culture and media, I would first grow the bacterium innutrient broth, then using the grown culture, I would perform GramStaining, which should show me purple cells under microscopebecause this bacterium is gram-positive, then I will procced totesting for Catalase enzyme. This test would help me differentiateStaphylococcus from Streptococcus. The catalase test should bepositive. Then, I will test for coagulase enzyme to make sure it isnegative because coagulase positive would indicate my bacterium isStaph aureus. Then, I would test for oxidase enzyme to make sure itis negative. Positive oxidase enzyme would indicate my bacterium isMicrococcus. Then, I would perform Kirby-Baur assay usingnovobiocin antibiotic to test for the antibiotic sensitivity. Thelarger zone of inhibition means the bacterium is sensitive tonovobiocin, which indicates the the bacterium is Staphylococcusepidermidis.
The selective media we can use to ID Staphylococcus Epidermis isthe MSA (Mannitol Salt Agar).]]
Like wise in the same way, as above example for StaphylococcusEpidermis, 1) Create DICHOTOMOUS KEY showing which selective mediaand biochemical tests you would need if you were to test yourunknown bacteria (SALMONELLA ENTERICA) in the lab and 2)Describethe dichotomous key of Salmonella Enterica in paragraph like inexample shown.
Answer:
Solution
Identification and confirmation of Salmonellaenterica
1. Bacterial Culture
The bacteria was grown on nutrient agar media. Smooth whiteround glossy colonies were obtained.
2. Gram staining
Bacteria from one of the colonies from the nutrient agar platewas subjected to Gram staining. Pink colored (safranin stained) rodshaped cells were observed under the light microscope. Thisindicates that the bacteria is Gram-negative bacilli.
3. Biochemical tests to identify the Gram-negativebacilli
(a) Test for glucose fermentation
The result differentiates between glucose fermenters andnon-fermentors.
Result: Positive result indicates glucosefermentors.
(b) Oxidase test
Oxidase test results differentiate betweenEnterobacteriaceae family from other glucose fermentingbacteria.
Result: Negative, indicatesEnterobacteriaceae family.
Enterobacteriacea family commonly consists of Shigella,Salmonella, Yersinia, Morganella, Serratia, Edwardsiella, Proteus,Providencia.
(c) Methyl red test (MR)
This test differentiates between Serratia from the restin the group Enterobacteriaceae.
Result: MR positive, rules outSerratia.
(d) Motility test
This test rules out Shigella.
Result: Positive, indicates the bacteris is notShigella.
(e) Phenyalanine deaminase
This test differentiates between Proteus,Providentia, Morganella versusSalmonella, Yersinia, Edwardsiella.
Result: Negative, indicates either ofSalmonella, Yersinia or Edwardsiella.
(f) H2S test
This test eliminates Yersinia from Salmonella,Yersinia or Edwardsiella.
Result: Positive, indicates the bacteria iseither Salmonella or Edwardsiella
(g) Indole test
This test differentiates between Edwardsiella andSamonella.
Result: Negative indicates the bacteria isSalmonella sp.
Salmonella sp. can be divided into Salmonellabongori and Salmonella enterica.
To differentiate between the two we need to performmolecular serotyping using genomic isolation, PCR amplificationwith suitable primers, sequencing and database mining (alignmenttools).
The selective media that is used for Salmonella sp. :Xylose-Lysine-Deoxycholate agar produces black colonies (due toH2S) indicates Salmolella.
The Dichotomous Key
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