Image of Serratia

Description:

This inoculated human blood agar culture plate cultivated colonial growth of Gram-negative, rod-shaped and facultatively anaerobic Serratia marcescens bacteria.

Note the hemolytic effect induced by the presence of the S. marcescens, which was indicated by the halo surrounding each of the bacterial colonies. In these lightened area, a lysis of red blood cells (RBCs) contained in the blood agar medium had taken place. In this case the hemolytic effect is termed beta-hemolysis (ß-hemolysis), whereupon, there is a complete lysis of the RBCs. Beta hemolysis is due to the bacterial production of hemolysins. There is another type of hemolytic reaction, which is known as alpha hemolysis (a-hemolysis), in which case there would be a greenish halo visible surrounding the bacterial colonies, and is sometimes referred to as incomplete, or partial hemolysis. Alpha hemolysis is brought on due to the bacterial production of peroxides.
Created: 1973