Antibiotic Medium No. 3 (Turbidimetric Assay Broth)
Official Liquid Medium for Turbidimetric (Photometric) Antibiotic Assays
Catalog Number: AS‑1110
 
Overview
Antibiotic Medium No. 3 is the official standardized liquid medium used for the cultivation of assay organisms and for the turbidimetric (photometric) microbiological assay of antibiotics. It is designated as “Medium C” in all major global regulatory and pharmacopeial standards, including:
FDA 21 CFR 436.102
USP <81>
European Pharmacopoeia 2.7.2
British Pharmacopoeia
Japanese Pharmacopoeia (JP 17)
WHO
ISO 20776‑2
Its balanced nutrient composition supports rapid, uniform, and heavy growth of standard assay organisms such as Staphylococcus aureus, Bacillus subtilis, Klebsiella pneumoniae, and Kocuria rhizophila. This ensures accurate, sensitive, and reproducible antibiotic potency determination using the tube‑turbidimetric method.
Ausamics Antibiotic Medium No. 3 is manufactured to deliver minimal batch‑to‑batch variation, consistent growth kinetics, and full compendial performance for regulated pharmaceutical QC laboratories.
 
Applications
Turbidimetric (photometric) antibiotic potency assays
Preparation of dense inoculum suspensions for cylinder‑plate assays
Growth and maintenance of test organisms for USP/EP/JP antibiotic bioassays
Pharmaceutical quality‑control laboratories using compendial methods
 
Key Features & Benefits
Internationally harmonized formulation (USP / EP / BP / JP / WHO)
Produces dense, uniform growth within 3–5 hours at 37 °C
Highly consistent growth response with minimal batch variability
Reference broth for all regulatory turbidimetric antibiotic assays
Supports a wide range of assay organisms
 
Composition (per litre)
Beef Extract – 1.5 g
Yeast Extract – 3.0 g
Peptone (meat or casein) – 6.0 g
D‑Glucose – 1.0 g Final pH: 7.0 ± 0.1 at 25 °C (after sterilization)
 
Preparation
Dissolve 11.5 g of dehydrated medium in 1 L purified water
Mix thoroughly until completely dissolved
Dispense into tubes or flasks as required
Autoclave at 121 °C for 15 minutes
Cool to room temperature before use
 
Storage & Stability
Dehydrated medium: Store below 30 °C in a cool, dry place
Prepared broth: Store at 2–8 °C
Shelf life (prepared broth): Use within 1 month
 
Standard Test Organisms (Examples)
Staphylococcus aureus ATCC 6538P
Bacillus subtilis ATCC 6633
Klebsiella pneumoniae subsp. pneumoniae ATCC 10031
Kocuria rhizophila ATCC 9341
 
Intended Use
For pharmaceutical quality‑control and compendial antibiotic assay applications only. Not for clinical diagnostic, food, or veterinary use.