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Imaging InlC Secretion to Investigate Cellular Infection by the Bacterial Pathogen Listeria monocytogenes
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Imaging InlC Secretion to Investigate Cellular Infection by the Bacterial Pathogen Listeria monocytogenes

Published on: September 19, 2013

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Listeria monocytogenes in Raw Milk: Detection, Incidence, and Pathogenicity

J Lovett1, D W Francis1, J M Hunt1

  • 1Division of Microbiology, Food and Drug Administration, 1090 Tusculum Avenue, Cincinnati, Ohio 45226.

Journal of Food Protection
|April 11, 2019
PubMed

Insights

Listeria monocytogenes contamination in raw milk varies by US region, with Massachusetts showing higher rates. Most isolated Listeria monocytogenes strains were found to be pathogenic in mice.

Area of Science:

  • Food safety
  • Microbiology
  • Veterinary public health

Background:

  • Raw milk consumption poses potential health risks due to microbial contamination.
  • Listeria monocytogenes is a significant foodborne pathogen of concern in dairy products.

Purpose of the Study:

  • To assess the incidence of Listeria monocytogenes in raw milk across different US regions.
  • To evaluate an isolation method for detecting Listeria species in raw milk.
  • To determine the pathogenicity of isolated Listeria strains.

Main Methods:

  • Raw milk samples were collected from three distinct areas in the United States.
  • An isolation method was employed to detect and quantify Listeria species.
  • Pathogenicity testing was performed on isolated Listeria monocytogenes and other Listeria species using adult mice.

Main Results:

  • Overall incidence of Listeria monocytogenes in raw milk was 4.2%, with regional variations (0% in California to 7% in Massachusetts).
  • The highest incidence of L. monocytogenes was observed in Massachusetts (12%) during March 1985.
  • In the same sampling period, the incidence of all Listeria species reached 26% in Massachusetts.
  • Out of 27 L. monocytogenes isolates, 25 (92.6%) were pathogenic in mice.
  • One of three Listeria ivanovii isolates was pathogenic; other Listeria species isolates were not pathogenic.

Conclusions:

  • Raw milk represents a potential source of pathogenic Listeria monocytogenes, with geographical variations in contamination levels.
  • The evaluated isolation method is effective for detecting Listeria in raw milk.
  • A significant proportion of Listeria monocytogenes strains found in raw milk possess pathogenic potential.

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