Biology Laboratory report (Lab Report Sample)

Differentiating Staphylococcus from Streptococcus species Introduction Staphylococcus is a bunched-up grape-like bacterial strain with many different types ranging from pathogenic to nonpathogenic. These types of Gram-positive cocci reside in the human microbiome, such as the skin (Shore 2022) heavily. The three common species of Staphylococcus are staphylococcus aureus, staphylococcus saprophyticus, and staphylococcus epidermidis. They have a filament type of body and reside in moist microbiomes such as the nose or mouth (Shore 2022). Some kinds of streptococcus include S. pyogenes, S. equi, and E. faecalis is, a different type of streptococcus called an enterococcus. A simple, quick Catalase test can determine the difference between Staphylococcus and Streptococcus or Enterococcus. This test differentiates between the two Gram-positive cocci by looking for the presence of the enzyme catalase. This enzyme helps protect certain bacteria against toxic oxygen species, such as hydrogen peroxide, and turns them into a safer compound like water or oxygen (Chess 2022). These results in the bubbling reaction, which indicates a positive impact on the presence of catalase since the gas bubbling is the production of oxygen. The result with no response means that the strain does not possess the catalase enzyme. According to Figure #1, Staphylococcus is catalase-positive, while streptococcus or enterococcus are catalase-negative. To look for a Staphylococcus species specifically, a series of tests are conducted after a positive catalase test that can differentiate between the three common staphylococcus species, including S. aureus, S. epidermidis, and S. saprophyticus. The Blood Agar Plate looks at a microbe’s ability to break down red blood cells. A microbe that can on this media but cannot break down any red blood cell growth is observed with a halo-like effect known as Gama hemolysis. If a microbe can partially break down a red blood cell, such as the breakage of hemoglobin, then on the media, it will appear with a dull yellow-green color known as alpha hemolysis. If a microbe can break down a whole red blood cell, then on the media, an apparent halo effect will appear through the plate known as beta hemolysis (Shore 2022). In Figure #1, S. aureus is positive for beta hemolysis while S. epidermidis and S. saprophyticus are harmful to beta hemolysis but can be either Gama or alpha-hemolytic. Also tested on the Blood Agar Plate is the Novobiocin test. This test looks at the susceptibility to the antibiotic novobiocin to distinguish between S. epidermidis and S. saprophyticus. According to Figure #1, when S. aureus is ruled out, this test helps determine the difference between the two-strain type by their reaction to Novobiocin. S. saprophyticus is resistant, shown on the media where no change has occurred, and the antibiotic is ineffective against this strain of Staphylococcus. S. epidermidis is susceptible to novobiocin shown on the media where a zone of inhibition is formed, and the antibiotic is effective against this strain. If S. aureus was considered, this strain is also susceptible to novobiocin. The mannitol salt agar is also a test used to help differentiate between bacterial staphylococcus strains. This pink, see-through media is both selective and differential when identifying different Staphylococcus species. This culture is demanding. After all, it has high salt levels that select for the growth of staphylococcus species only and differential because it uses the fermentation of mannitol to help distinguish between different strains (Shore 2021). Phenol red is used as an indicator of mannitol fermentation if the color changes on the media. If the media did not change color and there is no visible growth, it has inhibited Staphylococcus strains. In Figure #4, S. aureus is positive for mannitol growth by showing growth and changing the media’s color from pink to yellow. S. epidermidis is negative; therefore, it can grow on the media, but it cannot ferment the mannitol, so the media remains pink. S. saprophyticus can be either one depending on the batch used. To look for a Streptococcus or Enterococcus species, a series of tests are conducted after a negative catalase test to differentiate between the three common streptococcus or enterococcus species, including S. pyogenes, S. equi, and E. faecalis. This type of bacterium is distinguished between categorization groupings called Land field grouping (Chess 2022). For example, S. pyogenes is the only species in group A., S. equi is of many streptococci that belongs in Group C, and E. faecalis is one of many Enterococcus species that is included in Group D. Some do not have Lancefield grouping like Veridian grouping that are placed in a separate categorization altogether based on various distinction in characteristics. Once again, Blood Agar Plate is used to evaluate the effects of beta hemolysis, but this time it is used to differentiate the streptococcus and enterococcus grouping. According to Figure #1, Group A, which is S. pyogenes, and Group C, which is S. equi, are found to be beta-hemolytic where an apparent halo-like effect is seen on the media. E. faecalis and the Veridian Group are hostile to beta-hemolytic and can be either an alpha or Gama hemolysis (Shore 2021). To separate the Beta hemolytic further, the Bacitracin tests helps separate S. pyogenes Group A from non-group A. Group A is made up of only S. pyogenes, and this test is positive, see in Figure #1 for this strain, due to its susceptibility to bacitracin that creates a zone of inhibition. Group C or S. equi can inhibit the antibiotic bacitracin where no zone of inhibition occurs. SXT or trimethoprim antibiotics are used to separate Group B from Group C if Group B needs to be differentiated. Group B is susceptible to SXT and will create a zone of inhibition, while Group C or S. equi inhibits the growth. Next is differentiating between Group D E. faecalis and the Veridian Group. The Bile Esculin Test helps determine if a microbe can break down the bile salts contained in the slant and change the color of the pitch from tan to black. According to Figure#1, Group D E. faecalis has a positive result that allows it to grow on the slant media. However, the Veridian Group will not grow on this media because it cannot break down the bile. Enterococcus have adapted to live in harsh environments, such as the gastrointestinal tract, where it can withstand the effect of bile in the human microbiome (Chess 2021).  This study aimed to differentiate the different types of Gram-positive cocci bacterium from Staphylococcus to streptococcus or enterococcus. For this study, we observed two unknown bacteria. One strain, Unknown X, was identified as a staphylococcus bacterium. Another strain, Unknown Y, was another strain identified as a streptococcus or enterococcus bacterium. Figure #1 allowed for identifying these unknown strains through various distinct characteristics from a series of tests. Methods Catalase Test Procedures Students took a slide and added a couple of drops of hydrogen peroxide onto the slide. A toothpick inoculated an Unknown X sample and mixed the hydrogen peroxide on the decline. They then recorded their data based on the observed reaction. After recording data, they set up a new drop and repeated the procedure with Unknown Y. Label Unknown media. Unknown X bacterium was a staphylococcus species, and Unknown Y bacterium was a streptococcus species. Staphylococcus Tests Procedure Students inoculated two agar plates, Mannitol Salt Agar Plate and Blood Agar Plate. Inoculate only one blood agar plate with the Unknown X staphylococcus bacterium. Using a cotton swab, streak the unknown X bacterium on mannitol salt agar plate and blood agar plate with unknown Staphylococcus. A lawn should be in the middle, and enough room is given to the edges of the blood agar plate, so the effect of hemolysis is noticed in the media for results. The blood agar plate should have a novobiocin disc in the center of the inoculated strain. Use an aseptic technique to take out the novobiocin disk with tweezers. Fig 6: Streaking of the Bacteria on Mannitol Salt Agar Plate. Streptococcus Tests Procedure Students inoculated two media, Blood Agar Plate and Bile Esculin Slant. Inoculate the remaining blood agar plate with Unknown Y streptococcus or enterococcus bacterium. Streak the unknown Y bacterium on Blood Agar Plate using a cotton swab. Bunsen Burners were not used due to limited timing. Like Staphylococcus, the lawn must be in the middle to observe the effect of hemolysis and place both the Bacitracin and SXT discs onto the plate using tweezers. These discs should be placed far from each other to monitor the development of susceptibility. Inoculate the Bile Slant using the fishtail technique with the cotton swab. Label each media and hand in for incubation was 24 hours at 7 degrees Celsius and incubation for two weeks at 4 degrees Celsius. right22860000Results 7524756842760Figure 1. Dichotomous Key of Staphylococcus and Streptococcus species tests 00Figure 1. Dichotomous Key of Staphylococcus and Streptococcus species tests Figure#1 shows the key characteristics that distinguish different species of both staphylococcus and streptococcus bacterium. This was used to identify the two Unknown strains. Fig 2 A For the Mannitol Salt Agar Plate, Figure #2A showed a negative result for mannitol fermentation because no color change had occurred but indicated a positive outcome for a staphylococcus strain observed by the growth on the media. -314325125920500 -242508228455300Figure #4 compares the results from the Unknown X staphylococcus bacterium with three other staphylococcus species. The data collected for the Unknown X staphylococcus bacterium is listed under Figure #2. Figure #5 compares the results from the Unknown Y streptococcus or enterococcus bacterium with three other streptococcus ...