Antibiotic Medium No. 10

Antibiotic Medium No. 10

Official Seed Agar for Polymyxin B & Colistin Cylinder-Plate Assays

Catalog Number: AS-1111

Overview

Antibiotic Medium No. 10 is a specialised seed agar formulated for the microbiological cylinder-plate (cup-plate) assay of polymyxin B and colistin (polymyxin E). It is designated as “Medium K” in USP <81>, European Pharmacopoeia 2.7.2, Japanese Pharmacopoeia (JP 17), and WHO guidelines.

The formulation uniquely contains manganese chloride (Mn²⁺), an essential component for the optimal growth, metabolic activity, and antibiotic sensitivity of the required test organism, Bordetella bronchiseptica. The presence of Mn²⁺ enables the formation of large, sharp, and highly reproducible inhibition zones, which are characteristic of polymyxin antibiotics.

Antibiotic Medium No. 10 is manufactured to deliver compendial performance, consistent organism response, and high assay reproducibility, making it suitable for regulated pharmaceutical quality-control laboratories.

Key Features & Benefits

Contains Mn²⁺ essential for Bordetella bronchiseptica sensitivity to polymyxins

Produces clear, wide, and highly reproducible inhibition zones

Globally harmonised formulation (USP / EP / JP / WHO)

Official reference seed medium for polymyxin assays

Optimised for consistent organism growth and antibiotic diffusion

Typical Applications

Official Compendial Assays
Potency assay of polymyxin B sulfate

Potency assay of colistin sulfate (polymyxin E)

Cylinder-Plate Diffusion Assays
Assay of polymyxin-containing pharmaceutical products

Pharmaceutical Quality Control
Testing of topical polymyxin formulations

Testing of ophthalmic polymyxin preparations

Testing of parenteral polymyxin products

Principle of the Medium

Antibiotic Medium No. 10 provides a nutrient-balanced agar matrix supplemented with manganese ions, which are required for optimal metabolic activity and antibiotic response of Bordetella bronchiseptica. This formulation ensures stable organism growth, controlled diffusion of polymyxins, and accurate, reproducible zone measurement in cylinder-plate assays.

Typical Composition (per litre)

Peptone (meat or casein) – 6.0 g

Beef Extract – 1.5 g

Yeast Extract – 3.0 g

D-Glucose – 1.0 g

Manganese Chloride (MnCl₂·4H₂O) – 0.097 g
(≈ 27 mg Mn²⁺)

Agar – 15.0 g

Final pH: 7.2 ± 0.1 at 25 °C (after sterilisation)

Preparation

Suspend 26.597 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 standardised suspension of Bordetella bronchiseptica ATCC 4617

Pour immediately as the seed layer in cylinder-plate assays

Required Test Organism

Bordetella bronchiseptica ATCC 4617

Equivalent strains: NCIMB 8344, NCTC 8344

Mandatory test organism for all official polymyxin assays

Storage & Stability

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

Prepared seeded plates:
Use immediately, or
Store at 2–8 °C and use within 24 hours

Intended Use

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

Quality & Compliance

Formulated to meet USP, EP, JP, and WHO requirements

Suitable for regulated pharmaceutical microbiology laboratories

Performance comparable to leading international reference media

Customs & Trade Information

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