microbiology 3

For this assignment, the bacteria causing a leg wound infection must be isolated and identified. The clinician suspects that the cause could be the bacterial species, Staphylococcus aureus.

The following guideline outlines the major steps that you would take in order to diagnose this infection. This is sometime referred to as the “6 I’s” of labwork: Inoculation, Incubation, Isolation, Inspection, Information gathering, and Identification. Your job is to research each of these steps. In your powerpoint presentation, provide very specific details regarding what would be done for each step, paying very close attention to the fact that the clinician suspects Staphylococcus aureus.

Please follow this guideline for the preparation of your powerpoint presentation. In your presentation, you must use at least 2 scientific references.

General Procedure for the Isolation and Identification of Bacteria

1. Specimen Collection

a. Sample the site of infection

b. How is this done for a leg wound and how would the specimen be transported to the lab?

2. Inoculation

a. Culture media is the nutrient material used to grow microbes.

b. What type(s) of media would you use if Staphylococcus aureus was suspected and why?

c. Describe the procedure that would be used to ‘inoculate’ this media.

i. ‘inoculate’ means to introduce the specimen/bacteria to the culture media.

ii. How is this done, and what specific tools are used in the Microbiology lab to do this?

3. Incubation

a. The inoculated cultures are placed in an incubator.

b. Why is this done, and what is the temperature of the incubator?

4. Isolation

a. After the initial incubation period of about 24 hours, the culture is examined to determine how many different types of colonies are present. Each colony type must be ‘isolated’ to its own culture media in order to establish a “pure culture”.

i. What is a “pure culture”?

ii. What is the most commonly used method of isolation?

iii. What culture media would you use for this isolation if Staphylococcus aureus was suspected?

5. Inspection

a. Following the second incubation period of about 24 hours, the growth on the ‘pure culture’ is inspected macroscopically and microscopically

i. Macroscopic inspection involves a characterization of the colonies. What is the specific appearance of Staphylococcus aureus colonies?

ii. Microscopic inspection involves staining and viewing the bacterial cells under the microscope.

1. What specific staining procedure would be most valuable if Staphylococcus aureus was suspected?

2. What would be the results of this staining procedure for Staphylococcus aureus?

6. Information Gathering

a. Testing is done to determine the specific Genus and species of the organism that was isolated in the pure culture.

b. If Staphylococcus aureus was suspected, what specific biochemical tests would be key to diagnose that the organisms in the pure culture is Staphyococcus aureus?

7. Identification

a. Based on the results of the biochemical testing, an identification of the organism is made.

i. What would be the specific result for each biochemical test you set up if the organism is identified as Staphylococcus aureus?