Stuart Transport Medium: Usage and Laboratory Methods

Stuart Transport Medium is designed for the collection and transportation of specimens such as Neisseria species, Streptococcus pneumoniae, and Salmonella species. This medium creates a favorable environment for specimen viability through the reduction of oxygen and pH stabilization. This guide outlines its formulation, preparation, and usage.

Medium Composition (per Liter):

• Sodium Glycerophosphate: 10.0 g
• Cysteine Hydrochloride: 0.5 g
• Sodium Thioglycolate: 0.5 g
• Calcium Chloride: 0.1 g
• Agar: 5.0 g

pH: 7.4 ± 0.2 at 25°C

Principle

Stuart Transport Medium contains:

• Sodium thioglycolate and cysteine hydrochloride as reducing agents to lower oxygen levels, creating a relatively anaerobic environment.
• Sodium glycerophosphate as a pH buffer to stabilize the medium’s pH.
• Calcium chloride to balance osmotic pressure and maintain bacterial cell integrity.
• Agar as a solidifying agent.

Preparation and Methodology

Preparation:

1. Weigh 16.1 g of the medium and dissolve in 1,000 ml of distilled water.
2. Dispense into test tubes.
3. Sterilize at 121°C for 15 minutes, then cool immediately in cold water.

Testing Procedure:

1. Prepare quality control bacterial suspensions.
2. Dip sterile swabs into bacterial suspensions containing 100–1,000 CFU.
3. Insert the swabs into the transport medium.
4. Incubate at room temperature for 48 hours.
5. Remove the swabs and streak them onto blood agar plates.
6. Record the results after incubation.

Observation and Results

Precautions

1. This medium is only part of bacterial identification; additional confirmatory tests are required.
2. Strict aseptic techniques must be observed.
3. Used medium should be sterilized before disposal.
4. Store prepared media at recommended conditions and do not use after expiration.