You are working in a clinical laboratory in a hospital setting. You're handed a throat swab from a patient. You are told specifically that the physician is only interested in the presence and type of Gram positive cells. Identification isn't the main goal here-just a first step to work towards determining what Gram positive cells might be there. What might you do first to go about working towards this goal?
A) Perform a Gram stain.
B) Streak the sample for isolation on a tryptic soy agar general purpose medium plate.
C) Streak the sample for isolation on a medium that is selective for Gram positive cells.
D) Grow the microbes on the swab by inoculating a tryptic soy broth liquid medium tube.
E) Perform an acid-fast stain.

Question

Quizplus · Accepted Answer

The first step in identifying Gram positive cells is to perform a Gram stain. This will distinguish the cells by their cell wall structure and color them purple, indicating that they are Gram positive. This information can then be used to guide further testing and identification. Streaking the sample for isolation or growing the microbes on a medium can come later in the process once the initial identification has been made. Selecting a medium that is selective for Gram positive cells may be an option after the initial Gram stain, but it is not the best first step. Performing an acid-fast stain is not relevant in this situation as it is used to identify acid-fast bacteria such as Mycobacterium.

You Are Working in a Clinical Laboratory in a Hospital