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Microbiology: Current Research 2017 | Volume 1, Issue 2
Joint Conference
GLOBAL APPLIED MICROBIOLOGY CONFERENCE
MICROBIAL & BIOCHEMICAL RESEARCH AND TECHNOLOGIES
October 18-19, 2017
Toronto, Canada
International Congress on
&
Magnetic bead based immuno-detection of
Listeria monocytogenes
and
Listeria ivanovii
from infant
formula and leafy green vegetables using the Bio-Plex suspension array system
James B Day
US Food and Drug Administration, USA
L
isteriosis, a disease contracted via the consumption of
foods contaminated with pathogenic
Listeria
species, can
produce severe symptoms and high mortality in susceptible
people and animals. The development of molecular methods
and immuno-based techniques for detection of pathogenic
Listeria
in foods has been challenging due to the presence
of assay inhibiting food components. In this study, we
utilize a macrophage cell culture system for the isolation
and enrichment of
Listeria monocytogenes
and
Listeria
ivanovii
from infant formula and leafy green vegetables for
subsequent identificationusing theLuminexxMAP technique.
Macrophage monolayers were exposed to infant formula,
lettuce and celery contaminated with
L. monocytogenes
or
L. ivanovii
. Magnetic microspheres conjugated to Listeria
specific antibody were used to capture Listeria from infected
macrophages and then analyzed using the Bio-Plex 200
apparatus. As few as 10 CFU/mL or g of
L. monocytogenes
was detected in all foods tested. The detection limit for L.
ivanovii was 10 CFU/mL in infant formula and 100 CFU/g
in leafy greens. Microsphere bound
Listeria
obtained from
infected macrophage lysates could also be isolated on
selective media for subsequent confirmatory identification.
The method presumptively identifies
L. monocytogenes
and
L. ivanovii
from infant formula, lettuce and celery in less than
28 hours with confirmatory identification completed in less
than 48 hours. While FDA focuses its regulatory microbiology
methods on development of high throughput techniques,
this method is useful for the isolation of
L. monocytogenes
from food samples containing high levels of competitor
microorganisms that make it difficult to obtain discrete
colonies on plating agars.
Speaker Biography
James B Day is a Research Microbiologist at the U.S. Food and Drug Administration in
College Park, Maryland, where he is involved in developing detection methodologies
for bacterial pathogens in contaminated foods. He has developed techniques for rapid
identification of
Francisella tularensis, Salmonella enterica
and
Listeria monocytogenes
in various food matrices and recently established a novel macrophage-based assay for
enrichment of intracellular bacterial pathogens for enhanced identification. He earned
his PhD from the University of Miami School of Medicine (UM), where he worked on
bacterial pathogenesis of
Yersinia pestis
. At UM, he developed a widely used system
to measure virulence protein secretion and host cell translocation. He went on to
complete his Postdoctoral studies at Harvard Medical School, where he worked on
type III secretion mechanisms of
Salmonella enterica
as well as regulatory factors that
control virulence protein induction.
e:
james.day@fda.hhs.gov