BCYE

BCYE, or Buffered Charcoal Yeast Extract agar, is a selective and differential culture medium widely used in microbiology. Its primary purpose is to isolate and cultivate Legionella bacteria, a genus that includes the causative agent of Legionnaires' disease. The medium contains several key components that contribute to its effectiveness. Yeast extract provides essential nutrients for bacterial growth, while charcoal acts as a detoxifying agent, absorbing toxic substances that may be present in clinical or environmental samples, which can inhibit the growth of Legionella.

The buffering system, typically using potassium phosphate, helps maintain a stable pH, crucial for optimal Legionella growth. BCYE agar is often supplemented with specific growth factors, such as ferric pyrophosphate and L-cysteine, which are essential for the metabolic processes of Legionella. These supplements are vital because Legionella bacteria have unique nutritional requirements that are not met by standard growth media.

To enhance selectivity, BCYE agar is usually prepared in two forms: BCYE and BCYE/GVC. BCYE/GVC contains antibiotics like vancomycin, ceftazidime, and polymyxin B, which inhibit the growth of most other bacteria commonly found in mixed samples, allowing for the selective isolation of Legionella. The characteristic appearance of Legionella colonies on BCYE agar is typically gray, translucent, and often exhibit a bluish-green fluorescence under UV light, aiding in their presumptive identification.