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Comparison of Antibody-Direct Epifluorescent Filter Technique with the Most Probable Number Procedure for Rapid Enumeration of Listeria in Fresh Vegetables
Comparison of Antibody-Direct Epifluorescent Filter Technique with the Most Probable Number Procedure for Rapid Enumeration of Listeria in Fresh Vegetables
- Source :
- Journal of AOAC INTERNATIONAL. 80:1208-1214
- Publication Year :
- 1997
- Publisher :
- Oxford University Press (OUP), 1997.
-
Abstract
- The antibody-direct epifluorescent filter (Ab-DEFT) technique was evaluated as a rapid alternative to the most probable number (MPN) method for enumeration of artificially inoculated Listeria monocytogenes in ready-to-eat packaged salads and other fresh vegetables. Ab-DEFT was performed by homogenization of food in mesh-lined Stomacher bags, followed by prefiltration of homogenate through a 5 μm pore nylon filter, and passage of filtrate through a 0.4 μm pore black polycarbonate filter to collect and concentrate Listeria cells. After cells were stained with a fluorochrome-labeled polyclonal antibody to Listeria, the filter surface was examined by epifluorescence microscopy, and fluorescent cells were counted. A 3-tube MPN procedure was performed by successive enrichments of homogenized foods in Listeria enrichment and Fraser broths, followed by selective plating. Ab-DEFT provided quantitative determinations of Listeria cells that correlated with plate counts and MPN estimates in a linear response over a range of cell concentrations from 10 to 107 colony forming units (CFU)/mL. Microbial backgrounds as high as 108 CFU/mL did not affect performance of Ab-DEFT. In contrast to the MPN method, which required 5 days to perform, quantitation by Ab-DEFT could be completed in less than 1 h. Despite cross-reactivities demonstrated by the polyclonal fluorescent antibody, the potential of Ab-DEFT as a rapid alternative to MPN for microbial cell enumeration was evident.
- Subjects :
- Pharmacology
Colony-forming unit
Chromatography
medicine.diagnostic_test
Biology
medicine.disease_cause
Immunofluorescence
biology.organism_classification
Analytical Chemistry
Listeria monocytogenes
Most probable number
medicine
Enumeration
Listeria
Fluorescence microscope
Environmental Chemistry
Agronomy and Crop Science
Bacteria
Food Science
Subjects
Details
- ISSN :
- 19447922 and 10603271
- Volume :
- 80
- Database :
- OpenAIRE
- Journal :
- Journal of AOAC INTERNATIONAL
- Accession number :
- edsair.doi...........2497bc75b658a8f37a3d6255acb54d33
- Full Text :
- https://doi.org/10.1093/jaoac/80.6.1208