Biochemical Unknown

Essay by amiee123loveCollege, UndergraduateA, November 2014

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Gram Positive Bacteria-

My biochemical unknown is a gram positive bacterium and stains purple, it also grew on the Phenyl Ethyl Agar (PEA) in which it confirms that organism is gram positive because on only gram positive grows on the PEA selective media. It is a staphylococcus like the majority the given gram positives so it will be difficult to distinguish them from each other. The broth had turbidity and sediment, as well as a smell. Catalase test was used to help eliminate some of the other bacteria, this organism tested positive for the catalase meaning that this organism has the catalase enzyme. Since all the gram positive bacteria all test positive for catalase, I have to analyze the chart and determine which tests distinguishes their different results.

The majorities of the gram positive bacteria are staphylococcus and test positive for catalase, which makes it a little harder to narrow down the different types of test to complete.

The coagulase was one of the first tests that I did to differentiate the bacteria, this organism tested negative for coagulase, and it does not have the coagulase enzyme. This left was a result for all of the gram positive bacteria except for the Staphylococcus Aureus, which is coagulase positive. The other testing I did was the growth on the Mannitol Salt Agar plate (MSA) I was surprised to see that my organism not only grows on the agar but also ferments mannitol because of the golden colonies and the bright yellowing of the agar. According to the chart the only positive organism that ferments mannitol would be S. aureus, this definitely confused a lot of things. Before that I stuck between Staphylococcus Epidermidis and Micrococcus leuteus based on the chart and test results. I later completed a Blood Agar plate to confirm if it could really maybe S. aureus, and it turns out that there was complete clearing around the colonies meaning that it was betta hemolysis, and that is correct according to the chart. From then on I did the Urea test to distinguish the difference between S. epidermidis and S. aureus; the result I got was negative meaning that this organism does not have the urease enzyme. S. aureus tested negative for urea. I also did a TSI test to check to see if that would help but it did not, I got an A/A meaning that all the sugars were fermented. Those were the results for S. epidermidis, but later completing the MRVP test I checked in to all the right results for S. aureus. This means the biochemical unknown is S. aureus, although the test results were inconclusive most of the answers were correct based on S. aureus standards.

S. aureus is important in medical care because of MRSA (Methicillin Resistant Staphylococcus Aureus) many doctors have carelessly given out antibiotics to patients who are suffering from a bacterial infection and the bacteria have become immune to the antibiotic. Over the years the staph bacteria has learned to overcome the antibiotic. If this isn't stopped sooner or later there will be many people dying because there aren't anymore antibiotic to help treat them because everything will become resistant. It is very difficult to create new antibiotics because of the time and money, but also because of the effectiveness, as well as the side effects. This should be taken seriously because if antibiotics are carelessly used then all bacteria will become resistant to antibiotics.

Gram Negative Bacteria-

My biochemical unknown organism stained red for the gram staining, which indicates that it is a gram negative. To confirm my test staining, I inoculated an Eosin Methylene Blue plate (EMB) where mainly gram negatives can grow on this selective media. The organism grew on the EMB and it confirms the gram negative testing. The morphological characteristics of this organism are its bacillus shape and strepto or chain like arrangement. The broth characteristics show sediment and turbidity, as well as vague smell. I also completed an oxidase test to help eliminate some of the biochemical tests. The oxidase test tests for the cytochrome- c oxidase enzyme, this organism tested positive (blue) which means this bacterium is an aerobic bacteria. After this result I was able to eliminate almost all of the other gram negative bacteria, but leaving only two left because of the positive result for oxidase. The two bacteria I was left with were Pseudomonas aeruginosa and Alcaligenes faecalis.

Since the only bacteria I have left were Pseudomonas aeruginosa and Alcaligenes faecalis, I had to figure out which of the following biochemical test can differentiate the two considering they have a lot of the same test results. I've concluded that the following tests can help me decide which bacteria is the unknown; the biochemical tests are Nitrate test, Urea test, gelatin test, OF- glucose test, and Glucose/ gas test. For the Urea test I had inoculate twice because the first time it was inoculated there was no result, where as the second there was a fuchsia pink result meaning that the organism has the urease enzyme and is therefore positive. Pseudomonas aeruginosa had the positive result, compared to Alcaligenes faecalis where it was a negative result. When I did the Glucose/ gas test there was some confusion, according to the chart both Pseudomonas aeruginosa and Alcaligenes faecalis should test negative. But Pseudomonas aeruginosa tested positive for the fermentation of glucose and negative for gas production, which is correct. Although I did not let this inconclusive result question my gram negative because most of all the other tests results matches the charts results for Pseudomonas aeruginosa and due to the limited of time I did not waste my time pondering what when wrong instead of continuing on with my other tests. In this case Pseudomonas aeruginosa tested positive for gelatinase enzyme, oxidative, and positive for both the nitrate and nitrite reductase.

Pseudomonas aeruginosa is extremely important in the medical field because of its increasing numbers of nosocomial infections. P. aeruginosa likes to attack individuals with weakened immune systems, such as people who are hospitalized or with AIDS. There are lots of patients in the hospitals that are on breathing machines, and P. aeruginosa is known for its respiratory infections such as pneumonia, once they are infected it can potentially have serious risks and life threatening conditions. The prevention of P. aeruginosa is important to patients and health care providers to keep everyone safe because it can keep patients in hospital longer than they need to be or even kill them.