Differentiation of gram-positive and gram-negative bacteria and yeasts using a modification of the "string" test.

Solutions of potassium hydroxide and sodium hydroxide with concentrations between 0.5% and 4% were found to produce mucoid and sticky suspensions when added in drops, using a bacteriological loop, to smears of 609 strains of gram-negative bacteria on glass slides. A total of 461 strains of gram-positive bacteria and yeasts did not produce any mucoid or "string" formation when treated with the same solutions. It was concluded that this modified test could aid in differentiating gram-positive from gram-negative organisms.