The Unknown Bacteria

9/12/08: Through the various tests that were ran in lab, we were able to discern quite a few things about our unknown. The first of which was that it is gram positive, since it was purple after the gram staining. This was supported further by the lack of growth on the EMB plate. It did, however, grow on the MSA plate, which indicates that it can grow in high salt concentrations. Furthermore, it ferments mannitol, since the color of the MSA agar changed. The unknown bacteria was also cocci-shaped and formed clusters.
As far as resistance goes, the unknown wasn't completely resistant to any of the antibiotics that we used. It was most resistant to streptomycin, having a region of inhibition only approximately 1/2 inch in diameter. It was least resistant to tetracycline and amoxicillan, which both had 1 inch diameter zones of inhibition. Penicillin caused a circle with a diameter of slightly less than 1 in without bacteria to form. While ampicillin resulted in approximately a 7/8 inch zone of inhibition. The negative control had no affect on the growth of the bacteria.
Based on these results, particularly the gram stain along with the shape of the individuals and clusters lead me to conclude our unknown bacteria to be a member of the staphylcocci group, probably one that makes itself at home on our salty skin. The unknown is very similar to, and possibly could be, S. aureus such as what we have worked with in lab, but lack of comparison to other staphylcocci bacteria makes this far from certain.

9/16/08: Looking at the Kirby-Bauer test plates again after several days, a new development has occured which strongly follows the theme of our microbiology class. At the last check, the region of inhibition was completely clear of bacterial colonies, this is no longer the case. All of the antibiotics, with the sole exception of tetracycline have individual colonies scattered all over the region where the bacteria had been unable to grow before. Amoxicillin had the most and largest colonies in this area. Ampicillin and penicillin, compared to amoxicillin, had slightly less colonies in number, but most were considerably smaller in size. Streptomycin had only a few resistant colonies but these were relatively larger in size.
-Jamie Maguire

My group has decided that our unknown bacteria would be similar to s. aureus because from both of the selective & differential media tests' we did last lab period. our unknown had the same pattern as s. aureus.
- B Burke

In my group we discovered that the unknown is very similar to s. aureus. We believe this because of the differential and selective media tests. We observed that the unknown had the same qualities as the s. aureus bacteria.
- Mackenzie Dorsett

After running some tests on our unknown bacteria in lab, we were able to make conclusions about the type of bacteria we had. The first test we ran was our gram staining and the unknown bacteria appeared purple. This would show us the bacteria is gram (+).
We also ran tests on an Eosine-Methylene Blue plate (EMB) and a Mannitol Salt Agar (MSA) plate. We noticed the unknown did not grow on the EMB plate but did grow readily on the MSA plate. We noticed this because of the unknown turned yellow. The S. aureus bacteria also turned yellow on the MSA plate. This shows our unknown can ferment mannitol and is able to live in salty conditions. On the EMB plate, our unknown did not show any growth, the S. aureus bacteria also did not show any growth.
Our unknown bacteria showed it was least resistant to tetracycline and amoxicillin. The bacteria showed most resistance to penicillin, neomycin and vancomycin. We judged this by the size of circles around the antibiotics ring. We also judged the antibiotics effectivness in killing bacteria as the antibiotic spread away from the antibiotic ring.
After these three tests we came to the conclusion our unknown bacteria is from the staphlococci group. Staphlococci bacteria qualities are consistent with the qualities we observed from our unknown.
CJ Gradoville and Alex Permann

After we ran our lab tests my group strongly believes that the unknown bacteria is S. aureus or something that is closely related to it. We got this result because in our MSA agar S. aureus grew and only things that can grow in high salt conditions will grow in the MSA agar also the unknown grew. In the EMB plate ecoli grew but the s. aureus and the unknown didn't grow. And since ecoli is gram negative we knew that our unknown must be gram positive. So we decided to do another streak plate and we took some of the unknown bacteria and some of the s. aureus to compare and they turned out the same so we know that the unknown must be s. aureus.
Molly O'Neill

in order to figure out the unknown group you have to look at the kirby bour test and that will tell what the unknown is resistant or suseptible to. then you have to look at selective and differential media to show us what the unknown is most similar too. we noticed ours was most like s. aureus.
shelby pomerenke

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