What characterizes beta hemolysis?

Beta hemolysis is characterized by the complete lysis of red blood cells. This occurs when certain bacteria, such as Group A Streptococcus (Streptococcus pyogenes), produce hemolysins that break down the hemoglobin within red blood cells, resulting in a clear zone surrounding the bacterial colonies on blood agar. This clear zone is indicative of the complete destruction of red blood cells in that area.

While options that mention partial lysis or no lysis describe alpha hemolysis and gamma hemolysis, respectively, they do not apply to beta hemolysis. Alpha hemolysis results in partial lysis, leading to a greenish discoloration due to the reduction of hemoglobin to methemoglobin. Gamma hemolysis indicates the absence of hemolysis, with no change in the appearance of the blood agar. Thus, the hallmark of beta hemolysis is the clear zone indicating total lysis, confirming this option as the accurate representation of the phenomenon.