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The isolation of sucrose-fermenting Salmonella mbandaka
R L Reid1, R C Porter, H J Ball
1Department of Agriculture for Northern Ireland, Veterinary Sciences Division, Stormont, Belfast, UK.
Abstract:
During media trials to evaluate the use of Brilliant Green Agar for the primary recognition of Salmonella, strains presenting fermentation reactions were observed. All fermenting strains (84 out of 145) belonged to the serotype Salmonella mbandaka (58%), and the activity was expressed on three batches of Brilliant Green Agar and one of Xylose-Lysine Desoxycholate Agar. It was established using individual lactose and sucrose broth that the reaction in these media was due to sucrose fermentation. The most frequently isolated Salmonella in this laboratory during 1990 was S. mbandaka (61%) i.e. 65 of the 106 isolates during this period. Primary differentiation of Salmonella from other members of the family Enterobacteriaceae on media incorporating sucrose would have resulted in 36% of Salmonella isolates not being recognised. BGA and XLD agar therefore would not be suitable for primary isolation of Salmonella from clinical material with such a high percentage of the major isolate, S. mbandaka, having the ability to ferment sucrose.
Insights
Brilliant Green Agar and Xylose-Lysine Desoxycholate Agar are unsuitable for primary Salmonella isolation. Many Salmonella mbandaka strains ferment sucrose, leading to misidentification and reduced detection rates.
Area of Science:
- Microbiology
- Clinical Diagnostics
- Food Safety
Background:
- Brilliant Green Agar (BGA) and Xylose-Lysine Desoxycholate (XLD) agar are commonly used for primary Salmonella isolation.
- Accurate identification of Salmonella is crucial for public health and food safety.
Purpose of the Study:
- To evaluate the suitability of BGA and XLD agar for the primary recognition of Salmonella.
- To investigate fermentation reactions observed in Salmonella strains on these diagnostic media.
Main Methods:
- Media trials were conducted using Brilliant Green Agar and Xylose-Lysine Desoxycholate Agar.
- Fermentation reactions were analyzed using individual lactose and sucrose broth.
- Salmonella serotypes and isolation frequencies were documented.
Main Results:
- 84 out of 145 (58%) Salmonella strains exhibited fermentation reactions on BGA and XLD agar.
- The observed fermentation was attributed to sucrose fermentation in Salmonella mbandaka.
- Salmonella mbandaka was the most frequently isolated serotype (61% in 1990).
Conclusions:
- BGA and XLD agar are not suitable for primary Salmonella isolation due to sucrose fermentation by S. mbandaka.
- A significant percentage (36%) of Salmonella isolates could be missed using these media.
- Alternative diagnostic approaches are needed for reliable Salmonella detection in clinical settings.