Antibiotic Medium No. 10 | Seed Agar for Polymyxin AssaysSeed 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 assay of polymyxin B and colistin (polymyxin E) using the cylinder-plate (cup-plate) diffusion method. It is officially designated as “Medium K” in major international pharmacopoeias and regulatory standards, including:
USP <81>
European Pharmacopoeia 2.7.2
Japanese Pharmacopoeia (JP 17)
WHO guidelines
This medium uniquely contains manganese chloride (Mn²⁺), which is essential for the growth, sensitivity, and diffusion response of the required test organism Bordetella bronchiseptica. The presence of Mn²⁺ enables the formation of large, sharp, and highly reproducible inhibition zones, a defining characteristic of polymyxin antibiotics.
Ausamics 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⁺, critical 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 assay of:
Polymyxin B sulfate
Colistin sulfate (polymyxin E)
Cylinder-plate diffusion assays for polymyxin-containing pharmaceutical products
Quality-control testing of:
Topical polymyxin formulations
Ophthalmic preparations
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.
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 sterilization)
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
Sterilize by autoclaving at 121 °C for 15 minutes
Cool to 48–50 °C
Inoculate with a standardized 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
Why Buy Antibiotic Medium No. 10 from Ausamics?
Ausamics is an Australian life-science supplier specialising in compendial microbiological culture media, offering:
Pharmacopoeial-grade formulations
Consistent batch quality and documentation
Competitive alternatives to global brands
Reliable supply with international shipping
