Antibiotic Medium No. 5

Antibiotic Medium No. 5 (Streptomycin Base-Layer Agar)

Official Base Agar for Cylinder-Plate Antibiotic Assays
Catalog Number: AS-1118

Overview

Antibiotic Medium No. 5 is the official standardized base-layer agar used for the microbiological cylinder-plate assay of streptomycin and dihydrostreptomycin. It is designated as “Medium D (base)” 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 composition are specifically optimized to maximize streptomycin diffusion and to produce exceptionally large, clear, and reproducible inhibition zones when overlaid with seeded Antibiotic Medium No. 4 (or No. 8).

This medium is used exclusively as the base layer in official compendial streptomycin potency assays.

Applications

• Compendial base layer for streptomycin and dihydrostreptomycin potency assays

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

• Regulatory pharmaceutical quality-control testing

Key Features & Benefits

• Slightly alkaline pH (7.9) critical for maximum streptomycin diffusion

• Higher yeast extract level than standard base media for larger inhibition zones

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

• Official reference base 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 – 17.0 g

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

Preparation

• Suspend 31.5 g of dehydrated medium in 1 L purified water

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

• Sterilise by autoclaving at 121 °C for 15 minutes

• Cool to 60–65 °C

• Pour 20–25 mL into sterile 90–100 mm Petri dishes to form a uniform base layer
  (approximately 5–6 mm thick)

• Allow to solidify on a level surface

• Overlay with 4–6 mL of seeded Antibiotic Medium No. 4 (or No. 8) containing
  Klebsiella pneumoniae ATCC 10031 or Bacillus subtilis ATCC 6633

Storage & Stability

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

• Prepared base-layer plates: Store at 2–8 °C and use within 7 days

Mandatory Combination for Streptomycin Assay

• Base layer: Antibiotic Medium No. 5

• Seed layer: Antibiotic Medium No. 4 (or No. 8) + test organism

Intended Use

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

Quality & Compliance

• Official base-layer medium 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