Adhesion is the first crucial step
The Relationship between Virulence and Transport of Listeria
monocytogenes in Saturated Sand Columns
By Trent Graham, Fabiola Quiroa, Lana Stump, Brian Grina & Dr. Abu-Lail
The School of Mechanical and Materials Engineering, REU Program: Introduction to Multiscale Engineering
in the pathogenesis of L. monocytogenes (1).
Goals
Introduction
•Listeria monocytogenes is a Gram positive, intracellular, food-borne
pathogens that may cause life-threatening infections in elderly or
immunocompromized individuals and can also result in the abortion of
fetuses .
•Strains of L. monocytogenes express a wide
range of virulence factors. Virulence can be
estimated by LD50values. LD50 represents the
lethal bacterial dose required to kill 50%
of mice in an in vivo bioassay.
Quantify the collision efficiencies of the seven strains
Correlate L. monocytogenes retention in sand to the varying
pathogenicity of the isolates
  7.53  10  1.6999  10  ln LD50#
Increasingly virulent strains of L. monocytogenes demonstrate
higher adherence to sand during advective transport.
•L. monocytogenes are soil microbes and their mobility through sand is
considered to play a vital role in their dispersal. Their abilities to transfer
in soil can be evaluated by their collision efficiency, a measurement of
the retention of the bacteria during transport in saturated porous media.
Our results indicate that the collision efficiency and the LD50 of
each strain are logarithmically correlated according to:
8
Hypothesis
Not applied routinely due to
highly demanding cost and labor
Conclusion
Results
Break Through Curves were analyzed at steady state with Yao model
filtration equation to calculate the collision efficiency to plot
against the strain’s LD50 value.
7
Such correlation indicates that collision efficiency could
potentially be used as a design criterion to distinguish
between virulent and nonpathogenetic L. monocytogenes
strains.
Stronger adhesion of non-virulent strains to inert surfaces
modeled by sand suggests these strains have an innate
advantage to their persistence within soil.
15313 Break Through Curve
Materials and Methods
1.0
Steady State
Value
0.8
e26
e25
e24
e23
e22
e21
e20
e19
e18
e17
e16
e15
C/Co
•Five L. monocytogenes strains
were grown for 12 hours at 250C
and 150 RPM in 5 mL brain heart
infusion broth (BHIB) and then
subcultered to 125 mL BHIB and
grown at the same conditions for
12 hours.
LD-50
LD-50 vs Strain
0
2
4
6
8
10
12
14
16
Pore Volumes
 3 1   

C
 exp 
L
Co
2
d
c


Strain
EGDE Growth Curve
Absorbance (600nm)
T. Graham was supported by the National Science
Foundation’s REU program under grant number
NSF: EEC 1157094
0.0
Increasingly Virulent
•The cells were isolated at the late
exponential phase of their growth.
•Cells were pumped through the
packed sand column at a speed of
1.16 m/day and their absorbances
were measured at 600nm every 16
seconds.
Acknowledgments
0.4
0.2
15313 19118 19115 1002 EGDe
•The culture was centrifuged at
5100 RPM for 10 minutes and
washed to resuspended the cells in
deionized water to an absorbance
of 0.5 A600 .
0.6
0.8
0.6
Mark Lawrence for providing bacterial strains
Asma Eskhan and Pinar Gordesli for their instruction
Kostyukova lab for providing a centrifuge
WSU startup funds for financial support of L. Stump and B. Grina
Collision Efficiency vs LD50
Late
Exponential
Phase
0.4
0.2
0.0
0
5
10
15
20
25
Time (hrs)
Experimental
Schematic
Peristaltic
Pump
Fraction
Collector
Column
filled with sand
4.6e-6
4.4e-6
4.2e-6
4.0e-6
3.8e-6
3.6e-6
3.4e-6
3.2e-6
3.0e-6
2.8e-6
2.6e-6
1e+6
Collision Efficiency
for 15313
References
1. Vazquez-Boland JA, Kuhn M, Berche P, et al. Listeria
Pathogenesis and Molecular Virulence Determinants.
Clinical Microbiology Reviews 2001 Jul;14(3):584–640.
1e+7
1e+8
1e+9
1e+10 1e+11
LD50
Greater Virulence