Swab Case

The following tests according to the lab manual were performed: gram stain, fermentation tubes, methyl red, vogues proskauer, sulfur, indole, motility and growing it up on MacConkey agar. The gram stain was performed incorrectly the first time. This is because the decolorizer was not on the bacterium slide for long enough, giving a false outcome.

4. Using a cotton swab, evenly spread the bacteria on the agar of each plate, making sure to open the lids as little as possible.

I identified Citrobacter freundii, the gram negative rod, by running a series of tests. I began with the Phenol Red Lactose tests, which tests if the organism contains various enzymes that determine if it can ferment lactose. The broth turned yellow after it was incubated, indicating that the lactose was fermented to acid, and there was also gas present in the Durham tube. Since the Phenol Red Lactose Test was positive, I then ran the Phenol Red Sucrose test, which tests if the bacteria contain different enzymes that determine if sucrose can be fermented. After incubation, the broth was yellow, indicating that sugar was fermented to acid, and there was also gas present in the Durham tube. Next, I ran the Sulfide Production, Indole Formation, Motility test, but I was only testing for Hydrogen Sulfide Production to differentiate between the organisms Citrobacter freundii and Enterobacter aerogenes. This test detects if the organisms can metabolize sulfur into hydrogen sulfide, which is revealed by the formation of ferrous sulfide that causes blackening around the growth. The test also reveals if the organism can break tryptophan into indole or migrate away from initial stab area. After incubation, the agar slant was completely black, indicating that the organism produces hydrogen sulfide and is motile proving that it was Citrobacter

This test is used to detect if the bacteria contains any deoxyribonuclease activity. Because no color change was observed from blue to clear my unknown bacteria displayed a negative result.

The patient stated suffering several ear infections during her childhood. As a result, she states she has developed occasional ringing in her ears, but she reports that it does not distract her hearing.

Next I performed a KOH test to further confirm that my organism was a Gram-negative species. For the KOH test, I added 3 drops of 10% potassium hydroxide (KOH) to a small drop of distilled water onto a clean microscope slide, transferred a visible clump of organism to the KOH solution using my inoculating loop. I than mixed the cells into the solution using small, circular motions for 60 seconds and then lifted up the loop to look for what appears to be a “stringing” affect which means it’s confirmed that it is gram- negative species. Next, I created a streak plate using nutrient agar so that I could see pure culture of my organism. I aseptically obtained a loop full of my organism and gently inoculated one quarter of the nutrient agar plate by running the loop back and forth across the surface. I then flame sterilized the inoculating loop, allowing it to cool for 10 seconds, and then streaked the organism from quadrant I into quadrant II using a zigzag motion technique. I repeated those steps streaking from quadrant II to quadrant III and then streaking from quadrant III to quadrant IV. Once completed, I put the streak plate in the incubator at 37° for 24-48 hours. 48 hours later, I check my streak plate and it had a lot of growth on it. I was able to determine that the organism was definitely an off white color, opaque. The IV quadrant was the quadrant that best

The enzyme urease breaks urea down into NH3 and CO2. An orange broth containing urea is used for this test and needs to be inoculated with the gram negative bacteria. A pink color in the medium indicates a urease-positive organism, an orange or yellow is negative.

To perform this test, a tube of broth rich with glucose is acquired. In this tube is phenol red, a pH indicator. Initially, the tube appeared pink in color, indicating a normal pH level. Next, a sample of unknown #44 is introduced into this medium using the aseptic technique, and this is allowed to sit for several days. If the organism is able to ferment glucose, the pH in the medium would decrease and cause the phenol red to exhibit a yellow color. In addition to the straw color, gas can also be produced and trapped inside the Durham tube placed in the medium. This production of acid and gas is a direct result of the fermentation of glucose, as seen with unknown

I used an inoculating needle to stab the SIM test tube and then incubated it at 37 degrees Celsius for 24 hours. The SIM test was used to test whether an organism has the ability to reduce sulfur to hydrogen sulfide. Iron salts in the media reacts with the hydrogen sulfide to form a black precipitate called ferric sulfide. If sulfur can be reduced than a black color will be seen in the tube. This test also sees if an organism is and indole producer. Indole producers are bacteria that produce the enzyme trytophanase which can hydrolyze tryptophan to pyruvate, ammonia and indole. To test for indole production,

The patient tells me he started noticing symptoms on Sunday, August 16th. He said he started noticing some blisters along the left side of his face as well as his left ear started hurting and as he would scratch at it, he would see blood and discharge coming from it. He says that he typically does use Q-tips after the shower, but he does not think that he traumatized his ear. He has never had anything like this happen before. He has not really noticed any itching, but there is some discomfort. He describes it more of a discomfort, than a true pain. He has not had any fevers, chills, or body aches. There have been no

In this experiment an agar diffusion test (Bauer-Kirby Test) will be conducted to determine if a sample of S. aureus is susceptible to any of the five antibiotic discs that were used in this experiment. To begin, with a sharpie divide the outside of the TSA plate into five sections. Once the TSA plate has been divided, inoculate the TSA plate by dipping a sterile swab into the liquid culture of S. aureus bacteria. Swab the entire plate making sure to cover the entire surface of the plate with the bacteria. Next, rotate the plate sixty degrees and swab the entire TSA plate again making sure to cover the entire surface of the plate including the edges of the plate. Next, using aseptic technique sterilize a set of tweezer using alcohol. Using

The patient is a 67-year-old female who tells me this past Thursday, she was at a training session and felt somewhat dizzy. She describes this as several times feeling like she almost lost her balance. She had no falls. She has no spinning sensations associated with this. She did not feel lightheaded. Saturday, she states she started noticing that her ears were blocked. She started taking pseudoephedrine every four to six hours. She had no cold symptoms, no runny nose, no postnasal drip, no allergies known. She has not had any recent flights, etc. Nothing really has changed. Sunday night, her ears continued to be blocked and she went to an urgent care in Exeter. She was told she had fluid behind her

Incubate the bacteria for about 24 hours and then begin testing. If hydrogen sulfide is present, it will react with the sodium thiosulfate in the medium and the indicator, ferric ammonium citrate, to produce ferrous sulfide which falls out of solution as a blackish precipitate. The presence of hydrogen sulfide typically means that the bacteria produces the enzyme cysteine desulfanase which breaks up the cysteine in the medium into hydrogen sulfide. A positive result will turn the medium black. If the result is negative then the medium will stay semi-clear.

With the results of the Starch Hydrolysis Test I preceded to the final test which is the Citrate Test. Using aseptic technique, I streaked the organism onto the surface of the Simmons’ citrate slant and let it incubate overnight at 37°C. The Citrate Test determines if the organism is able to

2. Making the smear: Place a small drop of blood near an end of a slide. Bring the edge of another slide in contact with the drop and allow the drop to bank evenly behind the spreader. The angle between the two slides has to be 30-40 degrees. Now, push to the left in a smooth, quick motion. The smear should cover about half the slide.