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Measuring Bacterial Load and Immune Responses in Mice Infected with Listeria monocytogenes
Published on: August 9, 2011
Listeria monocytogenes isolation from human faecal specimens: experiments with the selective media, PALCAM and
1Department of Clinical Microbiology, Statens Seruminstitut, Copenhagen, Denmark.
Abstract:
The selective media PALCAM and L-PALCAMY were evaluated for their potential ability to detect Listeria monocytogenes in faeces. Recovery on PALCAM was almost total, and similar at 30 degrees C and 35 degrees C with or without CO2 incubation. Warm enrichment in L-PALCAMY was necessary in order to detect low numbers (< 10(2)/ml faeces). Faeces in excess of 0.25 ml/10 ml L-PALCAMY was inhibitory. The results point to L-PALCAMY and PALCAM as an epidemiological tool.
Insights
The PALCAM and L-PALCAMY selective media effectively detect Listeria monocytogenes in fecal samples. Optimal detection of low Listeria monocytogenes levels requires warm enrichment in L-PALCAMY media.
Area of Science:
- Microbiology
- Food Safety
- Veterinary Diagnostics
Background:
- Listeria monocytogenes is a significant foodborne pathogen.
- Accurate detection in fecal samples is crucial for epidemiological surveillance.
- Selective media are essential for isolating Listeria monocytogenes from complex matrices.
Purpose of the Study:
- To evaluate the efficacy of PALCAM and L-PALCAMY selective media for Listeria monocytogenes detection in feces.
- To determine optimal incubation conditions for Listeria monocytogenes recovery.
- To assess the impact of sample volume on media performance.
Main Methods:
- Comparative analysis of PALCAM and L-PALCAMY media.
- Testing various incubation temperatures (30°C and 35°C) and atmospheres (with/without CO2).
- Evaluation of warm enrichment protocols for L-PALCAMY.
- Assessment of inhibitory effects of excess fecal material.
Main Results:
- PALCAM media demonstrated high recovery rates for Listeria monocytogenes.
- Incubation temperature and CO2 atmosphere had minimal impact on PALCAM recovery.
- Warm enrichment in L-PALCAMY was essential for detecting low Listeria monocytogenes concentrations.
- Inhibitory effects were observed when fecal material exceeded 0.25 ml/10 ml of L-PALCAMY.
Conclusions:
- PALCAM and L-PALCAMY are valuable tools for Listeria monocytogenes epidemiological studies.
- Optimized protocols, including warm enrichment, enhance sensitivity for low-level detection.
- Careful consideration of sample-to-media ratio is necessary to avoid inhibition.
