Question

Please respond to the following questions in your own words.

1. What is aseptic technique and why is it important in microbiology?
2. Using the video above, please describe the steps required to inoculate a petri plate using a liquid culture.
3. Please describe the shape and arrangement of the following bacteria: staphylococci, streptococci, and streptobacilli.

Answer 1

Aseptic technique means using practices and procedures to prevent contamination from pathogens. It involves applying the strictest rules to minimize the risk of infection.To protect patients from harmful bacteria and other pathogens during medical procedures, healthcare providers use aseptic technique. Microbiologists use aseptic technique for a variety of procedures such as transferring cultures, inoculating media, isolation of pure cultures, and for performing microbiological tests. Proper aseptic technique prevents contamination of cultures from foreign bacteria inherent in the environment.

Staphylococci:The cocci are arranged in grape-like clusters formed by irregular cell divisions in three plains.

Streptococci :The cocci are arranged in chains, as the cells divide in one plane.

Streptobacilli :The bacilli are arranged in chains, as the cells divide in one plane.

Label a Petri dish:

Petri dishes are labelled on the bottom rather than on the lid. Write close to the edge of the bottom of the plate to preserve area to observe the plate after it has incubated. Labels usually include the organism name, type of agar, date, and the plater's name or initials. Using sterile cotton swabs, remove any visible water on the agar in the plate or around the inner rim of the petri plate. Observe the plate and mentally divide it into three sectors. The plate will then be turned clockwise (if you are right handed) with the agar side up. The second sector will then be at the top for streaking and then the plate is turned again so that the third sector can be streaked.

Sterilize the Transfer Loop before Obtaining a Specimen:

To streak a specimen from a culture tube, metal transfer loops are first sterilized by flaming the wire loop held in the light blue area of a Bunsen burner just above the tip of inner flame of the flame until it is red-hot. If a hot incinerator is available, the loop may be sterilized by holding it inside the incinerator for 5 to 7 seconds. Once sterile, the loop is allowed to cool by holding it still. Do not wave it around to cool it or blow on it. When manipulating bacteria, transfer loops are usually held like a pencil. If plastic disposable loops are being utilized, they are removed from the packaging to avoid contamination and after being used, are discarded into an appropriate container. A new loop is recommended for each sector of an isolation streak plate.

Open the culture tube and collect a sample of specimen using the sterile loop

Isolation can be obtained from any of a variety of specimens. This protocol describes the use of a mixed broth culture, where the culture contains several different bacterial species or strains. The specimen streaked on a plate could come in a variety of forms, such as solid samples, liquid samples, and cotton or foam swabs. Material containing possibly infectious agents should be handled appropriately in the lab using bio safety procedure.
Remove the test tube cap. It is recommended that the cap be kept in your right hand (the hand holding the sterile loop). Curl the little finger of your right hand around the cap to hold it or hold it between the little finger and third finger from the back. Modern test tube caps extend over the top of the test tube, keeping the rim of the test tube sterile while the rim of the cap has not been exposed to the bacteria. The cap can also be placed on the disinfected table, if the test tube is held at an angle so that air contamination does not fall down into the tube. Insert the loop into the culture tube and remove a loopful of broth. Replace the cap of the test tube and put it back into the test tube rack.

Streak the Plate:

The lid of the agar plate has to be opened just sufficiently enough to streak the plate with the inoculation loop. Minimize the amount of agar and the length of time the agar is exposed to the environment during the streak process.

Three Sector Streak (t streak):

1. Sterilize the wire loop.
2. Cool the loop by touching it on the edge of the sterile agar plate.
3. Dip the loop into the broth culture containing the mixture of bacteria.
4. Lift the lid of the plate just enough to insert the loop. Drag the loop over the surface of the top one-third of the plate back and forth in a "zig-zag" formation.
5. The loop has picked up thousands of bacteria which are spread out over the surface of the agar.
6. Sterilize the loop in the flame.
7. Turn the plate 90 degrees and drag the loop through the area you have just streaked two to three times and continue to drag the loop in a "zig-zag" formation in the remaining half of the plate without touching that area again.
8. Sterilize the loop in the flame.
9. Turn the plate 90 degrees. Repeat the procedure. Drag the loop two to three times through the area you just streaked, and fill in the remaining area of the plate (zig-zag formation), being very careful not to touch any of the areas you previously streaked.
10. Incubate the plate for 24 hours. If you streaked correctly, you will see isolated colonies in the third sector. The heaviest growth will be in the first sector. There will be less growth and some isolated colonies in the second sector. The third area should have the least growth with isolated colonies.

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