Differential sensitivity of Staphylo coccus epidermidis and Escherichici coli to lysozyme

Abstract

Lysozyme is a natural host defence mechanism in the human body that destroys the cell walls of bacteria, and interferes with the toxic and destructive activity of endotoxins found in the lipopolysaccharide layer of the cell wall of gram-negative bacteria. Disc sensitivity methods currently in use in microbiology manuals, to measure lysozyme sensitivity of gram-positive bacteria, show small zones of inhibition or fail to show zones of inhibition indicating ambiguous sensitivity responses, and gram-negative bacteria lack zones of inhibition indicating resistance to the enzyme. This paper demonstrates a standard dilution and confluent plate procedure that clearly shows the enhanced sensitivity of gram-positive bacteria to lysozyme, and the moderate sensitivity of gram-negative bacteria to this enzyme.