A direct plating method for monitoring the contamination of Listeria monocytogenes in silage

Jose Francisco Fernández-Garayzábal, M. Blanco, Jose A Vazquez-Boland, V Briones, J.A Garcia, C Delgado, M Domingo, J Marco, L Dominguez

Research output: Contribution to journalArticlepeer-review

Abstract

Twenty-two silage samples were analyzed for the presence of L. monocytogenes using five Listeria selective plating media, with and without previous selective enrichment step. L. monocytogenes was recovered from 3 samples by both procedures, but direct plating allowed the quantification of Listeria population. Two of these positive samples were implicated in outbreaks of listeriosis in sheep; the L. monocytogenes population in these samples was about 10(6) cells/g. The L. monocytogenes population in the other positive sample was 10(3) cells/g. Direct isolation of L. monocytogenes was only possible from LPM, PALCAM and LSAMm media. MOX and LSM media were not selective enough to allow direct Listeria isolation. In our hands, LSAMm was the most suitable plating medium for the direct isolation and specific quantification of L. monocytogenes from silage employing a red blood cells overlay technique.
Original languageEnglish
Pages (from-to)513-8
Number of pages6
JournalZoonoses and Public Health
Volume39
Issue number7
DOIs
Publication statusPublished - Sep 1992

Keywords

  • Animals
  • Colony Count, Microbial
  • Culture Media
  • Food Microbiology
  • Listeria monocytogenes/growth & development
  • Silage/microbiology

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