Points to Ponder for NEET-PG, FMGE & NEXT
- BCYE agar is a selective medium for isolating Legionella pneumophila.
- Legionnaires’ disease presents with atypical pneumonia symptoms.
- BCYE medium contains essential nutrients and may include antibiotics for selectivity.
- MacConkey agar differentiates lactose-fermenting from non-fermenting Gram-negative bacteria.
- Baird-Parker agar is selective for coagulase-positive staphylococci.
- Sabouraud’s agar is used for isolating fungi.
Buffered Charcoal Yeast Extract (BCYE) Medium
- BCYE agar is a selective culture medium specifically designed for the isolation and growth of Legionella pneumophila, the bacterium responsible for Legionnaires’ disease.
Legionella:
- Gram-negative bacteria: Short, pleomorphic (variable shape) bacilli.
- Fastidious: Requires specific growth conditions.
- Non-spore forming: Does not produce dormant spores.
- Aerobic: Requires oxygen for growth.
Legionnaires’ Disease:
- Atypical pneumonia: Causes symptoms different from typical bacterial pneumonia.
- Symptoms:
- Cough
- Chest pain
- High fever
- Diarrhea
- Confusion
- Relative bradycardia (slow heart rate)
- Hyponatremia (low sodium in blood)
- Types:
- Pontiac fever: Self-limiting flu-like illness with no pneumonia.
- Legionnaires’ disease: More severe form with pneumonia.
- Nosocomial Legionnaires’ disease: Onset within 10 days of hospital discharge.
- Case fatality rate: 15-20%
BCYE Medium Components:
- Selective: Contains charcoal to absorb inhibitory substances from clinical specimens, allowing Legionella growth while suppressing other bacteria.
- Nutritive: Contains yeast extract for essential nutrients, L-cysteine for growth stimulation, alpha-ketoglutarate for intermediary metabolism, and iron for essential functions.
Comparison with Other Media:
- McConkey Agar: Indicator medium for differentiating lactose-fermenting and non-fermenting Gram-negative bacteria. Not selective for Legionella.
- Baird-Parker Agar: Selective medium for coagulase-positive staphylococci from food samples. Not for Legionella.
- Sabouraud’s Agar: Selective medium for fungal isolation. Not for Legionella.
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