Cary-blair transport medium
- Cary-blairsemisolid transport medium is used to preserve the viability of entericpathogens in faeal specimens
- Salmonella, Shigella, Vibrioand Yersinia enterocolittica survivewell in cary-blair medium for at least 48 hours (several days for Salmonella, Shigella, Vibrio species)and Campylobacter species for up to 6hours.
- Carry- blair medium can be obtained in dehydratedform but it can be more economically prepared in the laboratory as follos
Composition of Cary-blair transport medium
- To make about 70 bottles:
- Sodiumthioglycollate………………….0.75 g
- di-sodiumhydrogen phosphate…………0.55g
- sodiumchloride…………………………2.5 g
- agar……………………………………..2.5g
- calciumchloride, 10 g/l(1% w/v)*…….4.5 ml
- distilledwater………………………….495 ml
Preparation procedure of Cary-blair transport medium:
- Dissolve the dry ingredients in the water by heating in a container of boiling water ( do not boil the medium)
- Allow the medium to cool to 50°C and then add 4.5 ml of the freshly prepared calcium chloride solution and mix well.
- Adjust the pH to 8.4 using 0.1 mol/I (N/10) sodium hydroxide.
- Dispense the medium in 7ml amounts in screw-cap bottles of 9 ml capacity (large size Bijou bottles)
- Sterilize by steaming (with caps loosened) for 15 minutes. When cool, tighten the bottle caps. Label the bottles.
- Date the medium and give it a batch number. Record the expiry date (6 month from the preparation date) on each bottle.
Quality control
- pH of medium: this should be within the range pH 8.3-8.5 at room temperature.
- Store in a cool dark place with the bottle tops screwed tightly
Use of Cary-blair transport medium:
- It is also a good transport medium for Yersinia pestis.
- Used to transport enteric bacteria (Salmonella, Shigella, Vibrio, Yersinia) from faecal specimen. *Immerse a swab of the faecal specimen in the medium, cutting off the swab stick to allow the bottle top be replaced tightly. Protect the swab from direct light and excessive heat.