Alfahemolüüsiga

Alfahemolüüsiga, also known as alpha hemolysis, is a type of hemolysis observed in bacterial cultures on blood agar. It is characterized by the partial lysis of red blood cells surrounding the bacterial colonies. This partial lysis results in a greenish discoloration of the agar medium. The green appearance is due to the oxidation of hemoglobin to methemoglobin. Bacteria that exhibit alpha hemolysis typically produce enzymes such as hemolysins that degrade the cell membrane of red blood cells, but not completely. This partial breakdown allows some of the hemoglobin to remain in the area and undergo oxidation.

Common bacteria that demonstrate alpha hemolysis include many strains of *Streptococcus pneumoniae*, *Streptococcus viridans*, and some *Enterococcus* species. The presence or absence of alpha hemolysis is an important characteristic used in the laboratory identification and differentiation of bacterial species. For instance, the ability of *Streptococcus pneumoniae* to cause alpha hemolysis is a key diagnostic feature. While often associated with normal flora, some alpha-hemolytic streptococci can be opportunistic pathogens. The phenomenon is distinct from beta hemolysis, which involves complete lysis of red blood cells and a clear zone, and gamma hemolysis, which shows no lysis. Understanding alpha hemolysis aids in the microbiological diagnosis of infections and the study of bacterial pathogenicity.