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Additional Test Results:
- Other tests that were run resulted in that the organism is catalase negative and susceptible to the antibiotic/biochemical bacitracin.

Catalase Test:
- The catalase test is used to differentiate staphylococci which is catalase-positive from streptococci which is catalase-negative. In catalase, there is an enzyme that is formed by bacteria that respire by using oxygen and that protects them from the toxic by-products of oxygen metabolism (Michigan State University 2021). A catalase positive bacteria will form bubbles whereas a catalase negative bacteria will not form any bubbles when hydrogen peroxide is added to it. This type of test tells us if the bacteria may be anaerobes or aerobes or even facultative in either of these states (Hartline 2022 Jan 15).

- Since the test result was catalase negative, we can conclude that Streptococcus pyogenes is a facultative anaerobe. This type of anaerobe is able to make its own ATP by aerobic respiration if oxygen is present, but is also able to alter itself to fermentation if there is no oxygen present.

Bacitracin Susceptibility Test:
- The bacitracin susceptibility test is a differential test that is used to differentiate between organisms that are sensitive to the antibiotic bacitracin and those which are not. Bacitracin can be defined as a peptide antibiotic that is created by Bacillus subtilis, and it prevents cell wall synthesis along with interrupting the cell membrane (Taxos A 2021).

- This particular test is genuinely used to identify the difference between the beta-hemolytic streptococci: Streptococcus agalactiae which is bacitracin resistant and Streptococcus pyogenes which is bacitracin sensitive (Taxos A 2021).

- Since the test resulted in the susceptibility to the antibiotic/biochemical bacitracin, we can conclude that the beta-hemolytic streptococci was resistant to the bacitracin.

Resources

Hartline R. 2022 Jan 15. 18: Catalase Test. Biology LibreTexts. [accessed 2023 Feb 8]. https://bio.libretexts.org/Courses/West_Hills_College_-_Lemoore/Microbiology_Laboratory_Manual/18%3A_Catalase_Test.

Michigan State University. 2021. Catalase Test - Virtual Interactive Bacteriology Laboratory. learnchmmsuedu. [accessed 2023 Feb 8]. https://learn.chm.msu.edu/vibl/content/catalase.html.

Tankeshwar A. 2017 May 10. Catalase test: principle, uses, procedure and results -. Microbeonlinecom. [accessed 2023 Feb 9]. https://microbeonline.com/catalase-test-principle-uses-procedure-results/.

Taxos A | Summary of Biochemical Tests | Additional Info | Molb 2021 | College of Agriculture and Natural Sciences. wwwuwyoedu. [accessed 2023 Feb 9]. https://www.uwyo.edu/molb2021/additional_info/summ_biochem/taxos_a.html.

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Gram Staining Information:
- A gram stain can be performed by using aseptic technique and placing a loopful of water on a slide and then mixing a colony of bacteria with the water on the slide. Next, it is vital to heat fix the slide and allow it to cool. Then, stain the slide with Crystal Violet for one minute and then rinsing the slide with water. After that, add iodine on the slide for one minute and then rinse with water. Next, decolorize the slide for 3 seconds with Gram Stain decolorizer and then rinse with water. Then, counterstain the slide with Safranin for 30 seconds and then rinse with water. Finally, insert the slide between Bibulous paper in order to dry the slide. Furthermore, a microscope can be used to observe the bacteria (Chamberlain and Cox 1997).

Results from Gram Stain Test:
- The gram stain came back as a Gram-positive cocci. Gram positive bacteria will appear purple under a microscope.

Typical Shape & Arrangement Under the Light Microscopy:
- Streptococci grow in long chains and can be described as spherical or oval like. These cocci also measure between 0.5 and 2 μm in diameter (Hossain 2014). Also the bacteria on the slide will appear purple while the background appears pink which indicates that the bacteria is positive while the background in negative. Additionally, positive purple bacteria will have thick cell walls (Nunez 2019).

References

Chamberlain N, Cox B. 1997. Instructions: Gram Stain. wwwatsuedu. [accessed 2023 Feb 8]. https://www.atsu.edu/faculty/chamberlain/Website/lab/idlab/gramst.htm.

Hossain Z. 2014. Streptococcus - an overview | ScienceDirect Topics. wwwsciencedirectcom. [accessed 2023 Feb 8]. https://www.sciencedirect.com/topics/immunology-and-microbiology/streptococcus.

Nunez K. 2019 Dec 18. Gram-Positive Bacteria Overview, Interpreting Test Results. Healthline. [accessed 2023 Feb 8]. https://www.healthline.com/health/gram-positive.

Todar K. 2012. Streptococcus pyogenes and streptococcal disease. Textbookofbacteriologynet. [accessed 2023 Feb 8]. http://textbookofbacteriology.net/streptococcus.html.

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Blood Agar Information:
- Blood agar is made out of sheep's blood, is filled with nutrients, and is a differential media. The differential media allows multiple types of bacteria to grow, but each organism's ability to lyse red blood cells will be presented differently which can present the microbiologist with clues in order to identify what kind of bacteria is growing (Prinzi and Rohde 2020).

- Organisms that grow on this type of media can be read in three different ways: beta, alpha, or gamma hemolytic. Beta hemolytic organisms fully lyse red blood cells which leaves a portion of complete clearing underneath and surrounding the colonies. An alpha hemolytic organism only partly lyses red blood cells and the media appears a greenish color. Lastly, gamma hemolytic organisms do not lyse red blood cells and the media stays unaffected (Prinzi and Rohde 2020).

Results from Blood Agar Test:
- The blood agar plate came back as beta hemolytic, and its colonies were identified as S. pyogenes. Blood agar is an important media to use for testing for this bacteria because it enhances the growth of streptococci by using catalase (Spellerberg and Brandt 2016).

References

File:Agarplate redbloodcells edit.jpg. 2020 May 27. Wikipedia. [accessed 2023 Feb 8]. https://en.wikipedia.org/wiki/File:Agarplate_redbloodcells_edit.jpg.

Prinzi A, Rohde R. 2020 Sep 25. Why Differential & Selective Media Remain Invaluable Tools. ASMorg. [accessed 2023 Feb 8]. https://asm.org/Articles/2020/September/Why-Differential-Selective-Media-Are-Invaluable-To.

Spellerberg B, Brandt C. 2016 Feb 10. Laboratory Diagnosis of Streptococcus pyogenes (group A streptococci). Nihgov. [accessed 2023 Feb 8]. https://www.ncbi.nlm.nih.gov/books/NBK343617/.

Todar K. 2012. Streptococcus pyogenes and streptococcal disease. Textbookofbacteriologynet. [accessed 2023 Feb 8]. http://textbookofbacteriology.net/streptococcus.html.

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How It Works:

1. The pt.'s tonsils are swabbed at the back of their throat

2. The swab is sent to a microbiology lab and is plated to a blood agar plate

3. The blood agar plate is incubated aerobically at 35°C for 24 to 48 hours

4. A microbiologist examines the plate for bacteria that commonly causes pharyngitis

References

Throat culture. 2022 Dec 8. Wikipedia. [accessed 2023 Feb 9]. https://en.wikipedia.org/wiki/Throat_culture.

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What I Am looking forward to learning more about in microbiology

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What I Am looking forward to learning more about in microbiology

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- Given the details of this case study, I am looking forward to learning more about catalyze tests in microbiology. I have an interest in learning more about this because I want to know more about what bacteria are aerobes or anaerobes.

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How the Health Care Team Used the Test Results to Make a Diagnosis:
-  With the following test results of a false negative Rapid antigen detection test (RADT) for Group A Streptococcus (GAS), throat swab, beta hemolytic blood agar, Gram-positive cocci Gram stain, negative catalase, and resistance to bacitracin susceptibility, the health care team was able to make a diagnosis for the 28 year old male patient. This diagnosis concluded that that patient had Group A streptococcal pharyngitis (strep throat).

Treatments Prescribed:
- The pt. was prescribed penicillin because it is highly effective in killing off bacteria, especially Streptococcus pyogenes.

Outcome for Pt.:
- The final diagnosis of this pt. was Group A streptococcal pharyngitis, and this only could have been truly determined by having a throat culture performed. This is due to the fact that the rapid antigen test result was falsely negative. Overall though, the patient’s peritonsillar abscess was drained, and the patient was treated for 10 days with penicillin. His symptoms completely resolved with this course of treatment.

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(Patients & Visitors Albany, New York (NY), St. Peter’s Health Partners 2023)

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Patient Overview:
- Pt. is a 28 year old male

Signs & Symptoms Upon 1st Arrival to ED:
- Sore throat and fever
- No pus, but tonsillar swelling

Microbiology Tests Ordered:
1. Rapid antigen detection test (RADT) for Group A Streptococcus (GAS)

- This test is detecting if the pt. has antigens to strep A. Strep A is a certain type of bacteria that causes strep throat which affects the throat and tonsils. Strep throat can go away on its own, but sometimes antibiotics are needed to help treat it. Additionally, this type of test typically gives results in about 10-20 minutes (Strep A Test 2021).

- Test Result: negative

2. Throat Swab

- Due to the Rapid antigen detection test (RADT) for Group A Streptococcus (GAS) being negative, the doctor ordered a throat swab. This test is also looking for Strep A bacteria, but it yields more accurate results compared to the rapid test, and it takes about 24-48 hours for results (Strep A Test 2021).

- This test is still being cultured at this point. The pt. is informed with directions for symptomatic relief, is told to go back home, and is thought to have viral pharyngitis. Pharyngitis is an inflammation of the throat.

Signs & Symptoms For Day 2 of Coming Back to ED:
- Worsening sore throat
- Difficulty swallowing
- Pus is seen on the tonsils and the uvula is deviated towards one side of his throat

References

Patients & Visitors Albany, New York (NY), St. Peter’s Health Partners. 2023. wwwsphpcom. [accessed 2023 Feb 7]. https://www.sphp.com/for-patients/.

‌Strep A Test: MedlinePlus Lab Test Information. 2021 Nov 8. medlineplusgov. [accessed 2023 Feb 8]. https://medlineplus.gov/lab-tests/strep-a-test/.

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