Identifying an Unknown Microbial Organism
The purpose of identifying an unknown microbial agent is so that the five “I’s” of Microbiology, which are, Inoculation, Incubation, Isolation, Inspection and Identification can be practiced. Providing an unknown microbial agent tests the ability of ones skill of the above techniques and to accurately obtain the correct results and compare these results to biochemical test results that are already established. (Forrest & Elliott, 2012, p.111)
Test used include the Gram Stain, the Streak Plate and Biochemical test such as the MR-VP, SIM, Phenylalanine Deaminase, Simmon’s Citrate along with the Carbohydrate Fermentation and Urease tests.
Biochemical Test of Importance
Several Biochemical test were performed, however, only three will be three will be discussed due to these test being the most significant in the identification of the microbial agent. These test helped narrow down the options of which organism the results matched with. The tests, which will be further dissected, are the SIM, Simmon’s Citrate and the Urease tests.
First, the SIM test consisted of Sulfur, Indole, and Motility; however, the focus will be narrowed to the Sulfur portion of the test only due to it being the most significant. Two methods used in this portion of testing were direct testing on the specimen and culture/Isolation. During the SIM testing, aseptic technique was cautiously used. An inoculation needle was used to obtain culture. Afterwards, the needle was taken and stabbed into the SIM media. The media was then stored at 37 degrees Celsius for 24-48 hours. (Forrest & Elliott, 2012, p.114)
The Sulfur portion of the SIM test consisted of the enzymes Thiosulfate reductase and Cysteine desulfurase. Sodium thiosulfate and Cysteine are the substrates involved. The media indicator is iron or Ferrous Ammonium Sulfate. A positive result for Sulfur production is a black precipitate called Ferrous sulfide and a negative result would be no change in the media. (Forrest & Elliott, 2012, p. 114)
The next test used to help narrow down the unknown organism was the Simmon’s Citrate test. The method used for this particular test was also direct testing on the specimen and culture/isolation. Aseptic technique was used in this process as usual and the materials needed for this test was the unknown culture, an inoculating loop and of course the Citrate. After inoculation, this media was also incubated at 37 degrees Celsius for 24-48 hours.
The Simmon’s Citrate enzymes are Citrate Permease or Citrase. The substrate involved is called Citrate also. Simmon’s Citrate has an indicator called Bromthymol Blue, which indicates an increase in pH. Forrest Green indicates it being neutral, yellow indicates an acidic environment and Prussian Blue indicates a basic environment. A positive result will yield a Prussian blue color and a negative result will produce a Forrest Green. (Forrest & Elliott,...