Optimized, one-step, recovery-enrichment broth for enhanced detection of Listeria monocytogenes in pasteurized milk and hot dogs

Stephen J. Knabel

Research output: Contribution to journalArticle

5 Citations (Scopus)

Abstract

A one-step, recovery-enrichment broth, optimized Penn State University (oPSU) broth, was developed to consistently detect low levels of injured and uninjured Listeria monocytogenes cells in ready-to-eat foods. The oPSU broth contains special selective agents that inhibit growth of background flora without inhibiting recovery of injured Listeria cells. After recovery in the anaerobic section of oPSU broth, Listeria cells migrated to the surface, forming a black zone. This migration separated viable from nonviable cells and the food matrix, thereby reducing inhibitors that prevent detection by molecular methods. The high Listeria-to-background ratio in the black zone resulted in consistent detection of low levels of L. monocytogenes in pasteurized foods by both cultural and molecular methods, and greatly reduced both false-negative and false-positive results. oPSU broth does not require transfer to a secondary enrichment broth, making it less laborious and less subject to external contamination than 2-step enrichment protocols. Addition of 159mM D-serine prevented germination of Bacillus spores, but not the growth of vegetative cells. Replacement of D-serine with 12 mg/L acriflavin inhibited growth of vegetative cells of Bacillus spp. without inhibiting recovery of injured Listeria cells. oPSU broth may allow consistent detection of low levels of injured and uninjured cells of L. monocytogenes in pasteurized foods containing various background microflora.

Original languageEnglish (US)
Pages (from-to)501-504
Number of pages4
JournalJournal of AOAC International
Volume85
Issue number2
StatePublished - Mar 2002

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Listeria
hot dogs
pasteurized milk
Listeria monocytogenes
milk
Milk
Dogs
Recovery
food
Bacilli
vegetative cells
Serine
cells
Food
serine
Cells
Bacillus
spore
inhibitor
ready-to-eat foods

All Science Journal Classification (ASJC) codes

  • Food Science
  • Analytical Chemistry

Cite this

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Optimized, one-step, recovery-enrichment broth for enhanced detection of Listeria monocytogenes in pasteurized milk and hot dogs. / Knabel, Stephen J.

In: Journal of AOAC International, Vol. 85, No. 2, 03.2002, p. 501-504.

Research output: Contribution to journalArticle

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