Thermo Scientific™ Oxoid™ Selenite Cystine Broth Base (copy)

Thermo Scientific™ Oxoid™ Selenite Broth Base (Lactose) is an enriched culture medium specifically designed for the isolation of Salmonella spp. from faeces and food products. It is used in conjunction with sodium biselenite to selectively inhibit non-target organisms while promoting the growth of Salmonella. This broth is an essential tool in clinical, food, and environmental microbiology.

Key Features

1. Selective Medium:
   • Contains sodium biselenite (added separately) for selective inhibition of non-Salmonella species.
   • Proteus and Pseudomonas spp. are resistant to selenite's effects but do not interfere due to their inability to ferment lactose.
2. Lactose Addition:
   • Prevents pH increase during incubation, maintaining the selective activity of the medium.
3. Versatile Applications:
   • Effective for isolating Salmonella from faecal samples, food, sewage, and river water.
4. Enhanced Selectivity at Higher Temperatures:
   • Incubation at 43°C improves isolation of Salmonella paratyphi B and other salmonellae in samples with high bacterial loads.

Typical Composition (g/L)

Preparation Instructions

1. Sodium Biselenite Solution:
   • Dissolve 4 g of sodium biselenite in 1 L of distilled water.
2. Broth Base:
   • Add 19 g of Selenite Broth Base to the sodium biselenite solution.
   • Warm gently to dissolve and mix well.
3. Sterilization:
   • Sterilize in a boiling water bath or free-flowing steam for 10 minutes.
   • DO NOT AUTOCLAVE, as heat-sensitive components may degrade.

Usage Recommendations

1. Inoculate with the specimen supernatant after separating debris to avoid nullifying selective properties.
2. Incubate at 35°C for 18-24 hours.
3. For high bacterial loads, subculture after 6 hours and again after 18 hours to minimize overgrowth of non-target organisms.
4. Subculture onto selective Enterobacteriaceae agar plates for further isolation.

Storage and Shelf Life

• Dehydrated Medium: Store at 10-30°C in a dry environment.
• Prepared Medium: Store at 2-8°C, protected from light.
• Use before the expiry date on the label.

Appearance

Quality Control

Precautions

1. Toxicity of Sodium Biselenite:
   • Handle with care; toxic by inhalation or ingestion.
   • Avoid exposure during preparation.
2. Prepared Medium Stability:
   • Discard if reduced selenite appears as a red precipitate.
3. Incubation Guidelines:
   • Do not incubate longer than 24 hours, as the selective effect diminishes after 6-12 hours.
   • Take subcultures from the upper third of the broth column.

Applications

• Clinical Microbiology:
  • Isolation of Salmonella from faecal and urine samples.
• Food Microbiology:
  • Detection of Salmonella in contaminated food products.
• Environmental Microbiology:
  • Isolation of Salmonella from sewage and water samples.

Selenite Broth Base (Lactose) is a reliable medium for isolating Salmonella spp. while minimizing interference from non-target organisms. Let me know if you need further assistance!

References

1. Robertson, D. S. F. (1970). Lancet, i. 518-519.
2. Klett, A. (1900). Zeitschrift für Hygiene und Infektion, 33, 137-160.
3. Guth, F. (1916). Zentralblatt für Bakteriologie I. Orig., 77, 487-496.
4. Leifson, E. (1936). American Journal of Hygiene, 24, 423-432.
5. Weiss, K. F., Ayres, J. C., & Kraft, A. A. (1965). Journal of Bacteriology, 90, 857-862.
6. Rose, M. J., Enriki, N. K., & Alford, J. A. (1971). Journal of Food Science, 36, 590-593.
7. Fagerberg, D. J., & Avens, J. S. (1976). Journal of Milk Food Technology, 39, 628-646.
8. Harvey, R. W. S., & Scott, T. (1953). Mon. Bull. Ministry of Health & PHLS, 12, 149-150.
9. Harvey, R. W. S., & Price, T. H. (1979). Journal of Applied Bacteriology, 46, 27-56.
10. Chattopadhyay, W., & Pilford, J. N. (1976). Medical Laboratory Sciences, 33, 191-194.