Azide Dextrose Broth

Updated: 2026-09-11

Overview

Azide Dextrose Broth is a specialized microbiological growth medium formulated for the selective cultivation of enterococci and related gram-positive bacteria. Its composition includes sodium azide (NaN₃), which suppresses gram-negative organisms, and dextrose as an energy source. Developed for standardized testing protocols, it is widely adopted in regulatory and industrial microbiological analyses. The medium is particularly valued for its role in water quality assessment, where it aids in detecting fecal contamination through enterococcal enumeration. Its selectivity and reliability have also made it a staple in food safety laboratories and clinical diagnostics for identifying pathogenic gram-positive cocci.

Physical and Chemical Properties

Azide Dextrose Broth typically presents as a clear to lightly colored liquid with a neutral pH (6.8–7.2). The sodium azide concentration (0.04–0.06%) provides selective inhibition, while peptones and dextrose support microbial growth. The medium is sterilized by autoclaving and remains stable for months when stored properly. Key chemical interactions include the azide ion's disruption of cytochrome oxidase in gram-negative bacteria, rendering them non-viable. Dextrose fermentation by target organisms often produces visible turbidity and gas formation, serving as growth indicators. The medium's formulation may vary slightly between manufacturers but maintains consistent performance across commercial batches.

Main Applications

Primary applications focus on environmental and public health testing, especially water analysis per ISO 7899-2 and EPA Method 1600. Laboratories use it to confirm fecal contamination in drinking water, recreational water bodies, and wastewater systems. The broth's selectivity makes it indispensable for differentiating enterococci from other waterborne bacteria. In food microbiology, it assists in detecting sanitary quality indicators in dairy products, processed foods, and beverages. Clinical labs employ modified versions for urinary tract infection diagnostics. Industrial users include pharmaceutical manufacturers monitoring microbial contamination in non-sterile products.

Safety and Storage

Sodium azide requires strict handling precautions: use personal protective equipment (PPE) including nitrile gloves and safety goggles. Avoid acid contact, which may produce toxic hydrazoic acid vapor. Spills should be neutralized with sodium nitrite solution before cleanup. Unopened bottles remain stable for 12–24 months at room temperature when protected from light. Prepared media should be used within 48 hours if stored at 2–8°C. Discard any broth showing precipitation or unusual coloration. Always follow institutional biosafety protocols when culturing potential pathogens.

B2B Procurement Guide

Industrial buyers should prioritize suppliers with ISO 13485 or ISO 9001 certification for consistent quality. Key specifications include lot-to-lot performance validation with ATCC reference strains (e.g., Enterococcus faecalis ATCC 29212) and certificate of analysis for each batch. Bulk purchases (50+ liters) commonly reduce unit costs by 15–30%. Consider ready-to-use sterile bottles versus powdered formulations based on lab throughput. Some manufacturers offer custom modifications like pH adjustment or additional indicators for specific applications. Lead times typically range 1–3 weeks for specialized orders.