A1 Medium (ATCC Medium No. 1)
CAT: AS-1101
 
Overview
A1 Medium, also known as ATCC Medium No. 1, is a highly enriched, non‑selective broth designed for the maximum recovery and luxuriant growth of fastidious and delicate microorganisms. It is particularly effective for clinical specimens with low bacterial counts. Widely used in microbiology laboratories, this medium supports the isolation of pathogenic Streptococcus, Neisseria, Haemophilus, and other demanding bacterial species. Its complex formulation provides essential amino acids, vitamins, and growth factors, ensuring growth even for stressed or injured cells.
 
Applications
Enrichment and isolation of fastidious pathogens from blood, cerebrospinal fluid, and other clinical samples
Primary recovery of Streptococcus pneumoniae, Neisseria meningitidis, Haemophilus influenzae, and Brucella spp.
Blood culture enrichment (often supplemented with SPS or other neutralizers)
Cultivation of microorganisms following antibiotic treatment or environmental stress
 
Key Features
Extremely nutrient‑rich formulation for maximum recovery rates
Supports rapid, dense growth of clinically important bacteria
Standard reference medium in ATCC and international protocols
Excellent performance with injured or slow‑growing organisms
 
Composition (per liter)
Trypticase Peptone (Pancreatic Digest of Casein) – 20.0 g
Yeast Extract – 5.0 g
Glucose – 5.0 g
Sodium Chloride (NaCl) – 5.0 g
L‑Cystine – 0.2 g
Sodium Sulfite (Na₂SO₃) – 0.1 g
Thiouracil – 0.01 g
Phenol Red (optional indicator) – 0.01 g
 
Final pH: 7.2 ± 0.2 at 25 °C
Preparation
Dissolve 35.31 g of dehydrated medium in 1 L purified water
Mix thoroughly and warm gently if needed until dissolved
Dispense into tubes or bottles as required
Autoclave at 121 °C for 15 minutes
Cool to room temperature before use
 
Storage
Dehydrated medium: Store below 30 °C, protected from moisture and light
Prepared broth: Store at 2–8 °C and use within 14 days
 
For laboratory and research use only. Not for diagnostic procedures without proper validation. Not for human or veterinary consumption.