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Updated: May 23, 2026
Measuring Bacterial Load and Immune Responses in Mice Infected with Listeria monocytogenes
Published on: August 9, 2011
Validation of direct plating of a stool sample as a method for Listeria monocytogenes detection
Grzegorz Madajczak1, Jolanta Szych, Bożena Wójcik
1Department of Bacteriology, National Institute of Public Health, Warsaw, Poland. gmadajczak@pzh.gov.pl
Abstract:
The aim of current studies was to validate the direct plating of a stool sample for Listeria monocytogenes detection, using selective medium Palcam agar with Palcam selective supplement. Validation was performed using stool samples collected from healthy humans inoculated with Listeria sp. strains. Stool samples were frozen to determine the influence of freezing on method robustness. The presented research defines the Listeria monocytogenes limit of detection (LOD) as 10(3) cfu/g of stools for fresh and frozen samples. Repeatability and reproducibility of the method has been confirmed using statistical methods. We show the effectiveness of direct plating of stool samples on Palcam agar with Palcam selective supplement collected for Listeria monocytogenes detection. This method could be useful for this pathogen detection in stool samples collected from patients with diarrhoea.
Insights
Directly plating stool samples on Palcam agar effectively detects Listeria monocytogenes. This validated method is robust for both fresh and frozen samples, offering a reliable diagnostic tool for clinical use.
Area of Science:
- Microbiology
- Food Safety
- Clinical Diagnostics
Background:
- Listeria monocytogenes is a significant foodborne pathogen causing listeriosis.
- Accurate and rapid detection methods are crucial for public health.
- Current diagnostic methods may require optimization for clinical stool samples.
Purpose of the Study:
- To validate the direct plating method for Listeria monocytogenes detection in human stool samples.
- To assess the performance of Palcam agar with selective supplement for this purpose.
- To determine the method's robustness, including the impact of sample freezing.
Main Methods:
- Direct plating of human stool samples on Palcam agar with Palcam selective supplement.
- Inoculation of samples with known strains of Listeria sp.
- Validation using fresh and frozen stool samples.
- Determination of the limit of detection (LOD).
- Statistical analysis for repeatability and reproducibility.
Main Results:
- The limit of detection (LOD) for Listeria monocytogenes was established at 10^3 CFU/g for both fresh and frozen stool samples.
- The direct plating method demonstrated high repeatability and reproducibility.
- Palcam agar with selective supplement proved effective for Listeria monocytogenes isolation.
Conclusions:
- Direct plating on Palcam agar is an effective and validated method for Listeria monocytogenes detection in stool.
- The method is robust and reliable, even with frozen samples.
- This technique offers a valuable tool for diagnosing Listeria monocytogenes infections in patients.
