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Comparative evaluation of desoxycholate citrate medium and xylose lysine desoxycholate medium in the isolation of
Abstract:
Studies of the relative efficacies of different modes of transport of fecal specimens intended for culture for the isolation of Shigellae have been carried out. When the delay between collection and culture was long, transportation in liquid nitrogen was slightly but not significantly better than transportation on ice. When the delay was short (10 hours or less) transportation at ambient temperature was as satisfactory as that on ice. A comparative study of the efficacies of three media for the isolation of Shigellae was also carried out. A total of 75 stool specimens containing Shigellae was studied. Isolation rates were highest with xylose lysine desoxycholate medium (XLD) and desoxycholate citrate medium (DCA). XLD was superior to DCA in that the Shigella colonies were clearly visible after overnight incubation, whereas use of DCA necessitated 48 hours of incubation. Also, colonial morphology on XLD was more specific. It is recommended that both XLD and DCA be employed, but if only one medium is to be used, XLD is the medium of choice.
Insights
For Shigella isolation, ambient temperature transport is effective for short delays (≤10 hours). Xylose lysine desoxycholate (XLD) medium is superior to desoxycholate citrate (DCA) medium for Shigella culture, offering faster and clearer results.
Area of Science:
- Clinical Microbiology
- Bacteriology
- Infectious Diseases
Background:
- Accurate isolation of Shigella is crucial for diagnosing bacillary dysentery.
- Optimizing transport and culture methods enhances diagnostic yield and patient management.
Purpose of the Study:
- To evaluate the efficacy of different fecal specimen transport methods for Shigella isolation.
- To compare the performance of various culture media for detecting Shigella.
Main Methods:
- Comparative analysis of specimen transport conditions: liquid nitrogen, ice, and ambient temperature.
- Assessment of three selective media: xylose lysine desoxycholate (XLD) and desoxycholate citrate (DCA) agar, among others.
- Inclusion of 75 stool specimens confirmed to contain Shigella.
Main Results:
- Short-delay transport (≤10 hours) at ambient temperature yielded results comparable to transport on ice.
- Liquid nitrogen transport showed minimal, non-significant improvement over ice for prolonged delays.
- Xylose lysine desoxycholate (XLD) and desoxycholate citrate (DCA) media demonstrated the highest Shigella isolation rates.
- XLD medium provided clearer colony visualization after overnight incubation compared to DCA, which required 48 hours.
Conclusions:
- Ambient temperature transport is a viable option for short-term fecal specimen preservation for Shigella culture.
- Xylose lysine desoxycholate (XLD) medium is the preferred choice for Shigella isolation due to its efficiency and specificity.
- Using both XLD and DCA media is recommended for maximum isolation, but XLD alone is sufficient if only one is available.