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Measuring Bacterial Load and Immune Responses in Mice Infected with Listeria monocytogenes
Published on: August 9, 2011
Rapid method for the isolation of Listeria monocytogenes from experimentally infected mice
Abstract:
Listeria monocytogenes was successfully isolated from experimentally infected mice by placing homogenized tissues in phosphate-buffered saline (PBS), trypsin, peptone, or pepsin followed by incubation at 37 C for 24 hr. A larger number of Listeria isolates were recovered from the trypsin or PBS splenic homogenate suspensions incubated at 37 C for 2 hr than from the other diluent suspensions. Holding infected tissues at 4 C for at least 3 months did not increase the efficiency of Listeria isolation. Listeria L-forms were not isolated from mice injected with the bacterial form. The in vitro viability of Listeria L-forms suspended in PBS or PBS splenic homogenate was greatly reduced when held at 4 C.
Insights
Researchers found that isolating Listeria monocytogenes from infected mouse tissues was most effective using trypsin or phosphate-buffered saline (PBS) suspensions. Longer incubation or cold storage did not improve Listeria recovery rates.
Area of Science:
- Microbiology
- Infectious Diseases
- Animal Models
Background:
- Listeria monocytogenes is a significant foodborne pathogen.
- Accurate isolation methods are crucial for diagnosing listeriosis.
- Understanding optimal conditions for Listeria recovery from host tissues is essential.
Purpose of the Study:
- To evaluate different diluents and incubation conditions for isolating Listeria monocytogenes from experimentally infected mouse tissues.
- To assess the impact of cold storage on Listeria isolation efficiency.
- To investigate the recovery of Listeria L-forms.
Main Methods:
- Homogenized mouse tissues were suspended in various diluents: phosphate-buffered saline (PBS), trypsin, peptone, or pepsin.
- Incubation was performed at 37°C for 24 hours or 2 hours.
- Tissue samples were also stored at 4°C for extended periods (≥3 months).
- Listeria L-forms were tested for viability in PBS and PBS splenic homogenate at 4°C.
Main Results:
- Listeria monocytogenes was successfully isolated using all tested diluents.
- Trypsin or PBS splenic homogenate suspensions incubated for 2 hours at 37°C yielded a higher number of Listeria isolates.
- Cold storage (4°C for ≥3 months) did not enhance Listeria isolation efficiency.
- Listeria L-forms were not recovered from mice infected with the bacterial form.
- In vitro viability of Listeria L-forms in PBS or PBS splenic homogenate was significantly reduced at 4°C.
Conclusions:
- Short-term incubation (2 hours) at 37°C with trypsin or PBS is an effective method for isolating Listeria monocytogenes from infected mouse tissues.
- Extended cold storage is not beneficial for Listeria isolation from these samples.
- Listeria L-forms may not be readily recoverable under these experimental conditions, and their viability is compromised at low temperatures.
