Mixed Culture Identification Report

Identification of A Mixed Culture Unknown

An experiment such as this one serves the purpose of allowing us, the students, to apply what we already know about any organism and any laboratory procedure to the difficult task at hand. It is possible to identify a mixed culture by running familiar experiments on the unknown bacteria and taking information already known about specific bacteria and applying it to the results. This helps to slowly eliminate any bacteria that do not correspond with the results. I obtained tube number twelve to run various tests on. There are only two microorganisms, one is Gram positive and one is Gram negative, inside the test tube. The Gram positive possibilities are to be narrowed down from Bacillus cereus, Clostridium perfringens, Corynebacterium xerosis, Enterococcus faecalis, Streptococcus agalactaie, Staphylococcus aureus, and
I began using the streak plate technique by diving the medium into four quadrants with a wax penicil. Then I used the aseptic technique to transfer a small amount of bacteria with my inoculating loop to the first quadrant. Still using the loop, I streaked the bacteria across the quadrant making sure to remain in that quadrant. Then, I flamed the loop and used it to streak some bacteria from quadrant one to quadrant two. I kept on repeating this process until all four quadrants were streaked (exercise 8). I did the same thing on another identical TSA plate and incubated one under aerobic conditions at 37°C and the other under anaerobic conditions at 37°C. Next, I used Columbia colistin nalidixic acid agar (Columbia CNA) with 5% sheep blood as my medium. I used the same streak plate technique on this medium as I used on the TSA plates and incubated it at 37°C as well. Then, I used MacConkey agar as a medium to detect lactose fermentation, used the same streak plate technique with my bacteria, and incubated the plate at