A patient comes to see you, complaining of a very sore throat. When you examine

Question

A patient comes to see you, complaining of a very sore throat. When you examine her, you find that she has a fever of 39-degree Celsius, and you observe that her throat is extremely red, with pus on her tonsils. You swab the pus and make a slide, which you then send to the clinical lab for Gram staining. The lab sends back a report in which it is noted that the slide has many long chains of round cells that have stained purple in color. you inform the patient that the result of the gram stain indicate to you that the bacteria in her throat are ____ in shape, and have a ____ cell wall

1) round; thin

2) cylindrical; thick

3) round; thick

4) spiral; thick

5) cylindrical; thin

Explanation / Answer

Answer. 3) Round ; thick

The pus swap on Gram’s staining was observed as long chain of round cells and were stained purple. That means it’s a gram positive bacteria which have thick cell wall due to the presence of several layers of peptidoglycan with low lipid content.

Thus, it retains the primary stain (crystal violet) of Gram staining protocol and appears purple under microscope. Whereas gram negative bacteria have comparatively thin cell wall with one layer of peptidoglycan and high lipid content, which dissolves when treated with alcohol (after crystal violet + mordant) and gets stained red with counter stain safranin.

Certainly, this microorganism is Streptococcus pyogenes which predominantly causes throat infections.

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