Why should blood agar plates for throat cultures be incubated both aerobically and anaerobically?

Incubating blood agar plates for throat cultures both aerobically and anaerobically is essential because some bacteria, particularly certain species of Streptococcus, may exhibit different growth patterns under varying oxygen conditions. Specifically, some Streptococci may not produce beta-hemolysis — the complete lysis of red blood cells around bacterial colonies, which is an important identification characteristic for these bacteria — when exposed to aerobic environments.

By incubating under both conditions, it ensures a comprehensive evaluation of microbial growth and hemolytic activity. This is critical in clinical diagnostics, as it allows for accurate identification of Streptococcus species that may be responsible for throat infections. The dynamics of oxygen presence can significantly influence the expression of hemolytic activity, making dual incubation a pivotal practice in bacteriology.