Gross Colony Characteristics Used to Differentiate and Identify Presumptively Microorganisms
Microbiologist can easily identify or guess an isolate by observing the colony characteristics of the organisms that have been isolated. The descriptions that follow are commonly used to investigate colony characteristics. Many of the colony characteristics listed below may differ between species and strains of the same genus. Hemolysis On sheep blood agar , hemolysis observed in the medium immediately surrounding or underneath the colony is caused by bacterial enzymatic or toxin activity. Hemolysis (e.g. α, β, or no hemolysis with other colony characteristics) on sheep blood agar aids in presumptive identification, particularly of streptococci and enterococci. It is critical to decide whether true hemolysis is present or whether the discoloration of the medium is due to the organism’s growth on the plate. To visualize the hemolytic pattern, the colony is often removed with a loop. To decide if the organism is hemolytic, proper technique necessitates the passage of bright light thr...