Antibiotic Medium No. 13

Antibiotic Medium No. 13

Official Liquid Medium for Yeast Inoculum Preparation in Polyene Antifungal Assays

Catalog Number: AS-1113

Overview

Antibiotic Medium No. 13 is the official liquid medium used for the preparation of standardized yeast inoculum and spore suspensions in the compendial cylinder-plate assay of nystatin and amphotericin B. It is designated as “Medium N” in USP <81>, European Pharmacopoeia 2.7.2, Japanese Pharmacopoeia (JP 17), and WHO guidelines.

The medium is based on the classic Sabouraud broth formulation, containing 2% glucose and a slightly acidic pH (5.6–5.8). This composition promotes rapid, heavy growth and excellent viability of yeast cells, ensuring consistent and reproducible preparation of inoculum for antifungal potency assays.

Key Features & Benefits

Classic Sabouraud formulation with 2% glucose

Slightly acidic pH (≈ 5.7) optimal for yeast growth and spore production

Internationally harmonised medium (USP / EP / JP / WHO)

Official reference broth for polyene antifungal assays

Ensures reproducible inoculum preparation for seeded assay media

Typical Applications

Compendial Antifungal Assays
Preparation of standardised yeast inoculum for nystatin potency testing

Preparation of inoculum for amphotericin B cylinder-plate assays

Pharmaceutical Quality Control
Growth and maintenance of assay organisms

Routine QC testing of polyene antifungal products

Microbiological Inoculum Preparation
Cultivation of Candida albicans ATCC 10231

Cultivation of Saccharomyces cerevisiae ATCC 9763

Principle of the Medium

Antibiotic Medium No. 13 provides a nutrient-rich, mildly acidic environment that supports rapid yeast proliferation and high spore viability. The resulting growth can be washed and diluted to obtain a standardised inoculum, which is then used to seed Antibiotic Medium No. 12 or other assay plates for polyene antifungal potency determination.

Typical Composition (per litre)

Peptone (meat or casein) – 10.0 g

D-Glucose (Dextrose) – 20.0 g

Final pH: 5.7 ± 0.1 at 25 °C (after sterilisation)

Preparation

Dissolve 10.0 g peptone and 20.0 g glucose in 1 L purified water

Mix thoroughly until completely dissolved

Dispense into tubes or flasks as required

Sterilise by autoclaving at 121 °C for 15 minutes

Cool to room temperature before use

Usage in Assay

Inoculate with a fresh culture of:

• Candida albicans ATCC 10231, or

• Saccharomyces cerevisiae ATCC 9763

Incubate at 30–35 °C for 24–48 hours

Harvest, wash, and dilute the growth to prepare a standardised spore or cell suspension

Use the suspension to seed Antibiotic Medium No. 12 or other validated assay media

Storage & Stability

Dehydrated components or prepared broth: Store at room temperature, protected from light

Prepared medium: Stable for up to 3 months at 2–8 °C

Intended Use

For pharmaceutical quality-control and official compendial antifungal assays only.
Not for clinical diagnostic, food, or veterinary use.

Quality & Compliance

Formulated to meet USP <81>, EP 2.7.2, JP 17, and WHO requirements

Manufactured under controlled conditions for batch-to-batch consistency

Suitable for regulated pharmaceutical microbiology laboratories

Customs & Trade Information

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