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Unidentified Listeria-like bacteria isolated from cheese
N Rijpens1, G Vlaemynck, R Rossau
1Agricultural Research Centre, Department for Animal Product Quality, Melle, Belgium. n.rijpens@clo.fgov.be
Letters in Applied Microbiology
|November 13, 1998
Summary
Unidentified Listeria-like bacteria were found in cheese, challenging standard detection methods. Further analysis revealed they are distinct from known Listeria species but closely related.
Area of Science:
- Food microbiology
- Bacterial taxonomy
- Molecular diagnostics
Background:
- Routine cheese analysis for Listeria monocytogenes identified unusual Listeria-like bacteria.
- These isolates lacked a key phenotypic characteristic for Listeria species confirmation.
- Standard diagnostic assays (VIDAS, PCR, DNA probes) failed to identify them as Listeria.
Purpose of the Study:
- To investigate the homogeneity of the unidentified Listeria-like bacterial group.
- To determine the taxonomic relationship of these isolates to known Listeria species.
Main Methods:
- Repetitive sequence-based PCR (rep-PCR) for genetic fingerprinting.
- Pulsed-field gel electrophoresis (PFGE) for genomic profiling.
- 16S rRNA gene sequencing for phylogenetic analysis.
Main Results:
- rep-PCR and PFGE demonstrated homogeneity within the unidentified bacterial group.
- 16S rRNA gene sequence analysis showed 94% homology to established Listeria species.
- This homology suggests a closer relationship to Listeria than to other genera like Brochothrix.
Conclusions:
- The unidentified bacteria represent a distinct group closely related to, but not conforming to, the current definition of Listeria species.
- Current diagnostic methods may need refinement to encompass these novel Listeria-like organisms.
- Further research is needed to fully characterize and classify these bacteria.