The bacteriologist is staining the slides of a client diagnosed with scarlet fever and rheumatic fever. The slide identifies S. pyogenes and stains purple by crystal violet dye. The result would indicate:

Gram staining is a technique used to differentiate between Gram-positive and Gram-negative bacteria.

Explanation:

Gram stain color the bacteria either red or violet depending on whether they are Gram positive or Gram negative. Gram positive bacteria have thick cell wall containing peptidoglycan compared to Gram negative bacteria which have thin cell wall. Due to this Gram positive bacteria stains purple by crystal violet. So, slide containing S. pyogenes with purple violet indicates that it is a Gram positive bacteria.