Antibiotic Medium No. 4

Antibiotic Medium No. 4 (Streptomycin Seed Agar)

Official Seed Agar for Cylinder-Plate Antibiotic Assays
Catalog Number: AS-1117

Overview

Antibiotic Medium No. 4 is the official standardized seed agar used for the microbiological cylinder-plate assay of streptomycin, dihydrostreptomycin, and related aminoglycoside antibiotics. It is designated as “Medium D” in USP <81>, European Pharmacopoeia 2.7.2, Japanese Pharmacopoeia (JP 17), and WHO guidelines.

The slightly alkaline pH (7.8–8.0) and enriched yeast-beef formulation are specifically optimized to produce large, sharp, and highly reproducible inhibition zones with the test organism Klebsiella pneumoniae ATCC 10031 (or Bacillus subtilis ATCC 6633 in validated alternative methods).

This medium is essential for accurate and compliant streptomycin potency determination in regulated pharmaceutical quality-control laboratories.

Applications

• Compendial potency assay of streptomycin sulfate and dihydrostreptomycin

• Cylinder-plate diffusion assay of streptomycin-containing pharmaceutical products

• Regulatory quality-control testing of parenteral and oral streptomycin preparations

Key Features & Benefits

• Slightly alkaline pH (7.9) critical for streptomycin diffusion and zone clarity

• Higher yeast extract content than Antibiotic Media No. 1–3 for enhanced sensitivity

• Internationally harmonized formulation (USP / EP / JP / WHO)

• Official reference seed agar for all compendial streptomycin assays

Composition (per litre)

• Beef Extract – 1.5 g

• Yeast Extract – 6.0 g

• Peptone (meat or casein) – 6.0 g

• D-Glucose – 1.0 g

• Agar – 15.0 g

Final pH: 7.9 ± 0.1 at 25 °C (after sterilisation; strictly controlled)

Preparation

• Suspend 29.5 g of dehydrated medium in 1 L purified water

• Heat with frequent agitation and boil for 1–2 minutes until fully dissolved

• Sterilise by autoclaving at 121 °C for 15 minutes

• Cool to 48–50 °C

• Inoculate with a standardized suspension of Klebsiella pneumoniae subsp. pneumoniae ATCC 10031
  (or Bacillus subtilis ATCC 6633 where validated)

• Pour 4–6 mL of seeded agar over a pre-prepared base layer
  (typically Antibiotic Medium No. 1 or No. 2)

Storage & Stability

• Dehydrated medium: Store below 30 °C in a cool, dry place

• Prepared seeded plates: Use within 24 hours

• If required, store seeded plates at 2–8 °C for short periods

Critical Note

The final pH must be 7.9 ± 0.1.
Deviation from this range significantly reduces inhibition zone size and compromises assay accuracy.

Intended Use

For pharmaceutical quality-control and official compendial streptomycin assay applications only.
Not for clinical diagnostic, food, or veterinary use.

Quality & Compliance

• Official seed agar for streptomycin cylinder-plate assays

• Complies with USP <81>, EP 2.7.2, JP 17, and WHO requirements

• Manufactured under controlled conditions for batch-to-batch consistency

• COA, SDS, and TDS available upon request

Customs & Trade Information

HS / AHECC Code: 3821.00.00
Prepared culture media for development or maintenance of microorganisms