Potassium Hydroxide String Test – Principle, Procedure, Uses and Result interpretation
Introduction The potassium hydroxide string test is a very simple, easy to perform and also inexpensive rapid test could be used in addition to the Gram staining for differentiate between Gram positive and negative isolates, where a Gram -negative cell wall are lyses when it’s mixed with a small volume of 3% KOH and releasing viscid chromosomal material from cell, makes the bacterial mixture suspension to become thick viscous or “stringy.” The positive string test indicates a gram negative organism. Hence the alternative name for the test is “String Test”. Some organism like Bacillus and Clostridium sp. appear Gram negative on staining resulting in possible misidentification because of they have lost some of the integrity of their cell wall. Purpose Distinguishing between Gram -negative and Gram -positive organisms Principle In the presence of 3% potassium hydroxide, the cell wall of Gram-negative is broken down. KOH easily dissolves the thin layer of cell walls (Peptidoglycan) o...