After being washed with alcohol, some bacteria remained blue or purple, while others did not retain the stain. The first group was dubbed "gram-positive," while the latter was designated "gram ...

Gram-positive bacteria: A group of bacteria that have a thick cell wall and retain the crystal violet stain used in the Gram staining procedure, making them appear purple under a microscope.

“Gram stains show whether the bacteria in urine samples are gram positive or negative by staining them purple or pink,” says Miyatsuka. “Only the most experienced technicians can make ...