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Profiling a Pathogen
There are many challenges to identifying
the guilty from among the innocent
• Natural populations of Vp are made up mostly of
harmless bacteria.
• Pathogens are nearly never detected in the environment
even during outbreaks.
• In order to determine whether pathogens are present,
you have to be able to recognize the pathogens.
• We have both native and invasive pathogens to worry
about (e.g. serotypes O3:K6, and west coast O4:K12)
How can you tell if there are pathogens present
abundance of a species
≠
abundance of pathogens
Most useful diagnostic tools are based on
unique traits or genetic material: virulence
factors must be confirmed in animal model for
infection (or in human subjects)
Vibrio cholerae (Vc):
Cholera toxin
(encoded in a virus that
infected some strains and
became part of its genome)
[email protected] u
Vibrio vulnificus (Vv) : No trait or gene content that is yet diagnostic
Vibrio parahaemolyticus (Vp): Traits/genes associated
with but not diagnostic of virulence potential
• Hemolysis: tdh/trh
• Caveat: not required for virulence
M. N ishibuchi
• Cytotoxicity and Enterotoxicity:
T3SS1 and T3SS2
• Caveats: all strains have T3SS1,
not all strains that have T3SS2 are
known pathogenic, nonpathogenic strains can be more
cytotoxic than clinical strains
• Serotyping (O:K) and Phylogeny
(relatedness)? e.g. Pandemic Vp
(O3:K6) and west coast ST36
(O4:K12/KUT)
RSC Publishing
Challenges and questions we face:
 Can we determine the abundance of pathogenic
strains from among the background of harmless
strains?
 Are tdh/trh sufficient for predicting pathogenic
potential or would other traits/genes be useful?
 How can we better predict and forecast public health
risks?
 What conditions allow pathogens to thrive as
residents?
By learning to better identify pathogenic strains, we can
develop targeted surveillance and also learn what conditions
promote their abundance in oysters
Phylogeny
(Family tree)
2010-2011
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ORF8
td h
trh
W : Wound
*: from MA
:sequenced
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Few clinical strains
from 2010-2011 are of
documented
sequence types
Pandemic
O3:K6
O4:K12
Cape Cod
endemic clade
Pacific
How can you tell if a strain is a pathogen
• Presence of pathogen associated markers
doesn’t mean a strain is pathogenic
• The standard for virulence requires an animal
model for infection
• Current models are insufficient
Alternative invertebrate model for
virulence of Vibrio parahaemolyticus
Incubate at 37C
for 6 hrs.
Incubate at 28C
for the duration of
the assay
Observe: mobility
(chemotaxis towards
attractant)
Velocity
Virulence of strains in nematode model
Acknowledgements
Lab Members and
previous students:
Jeff Sun
Evan DaSilva
Randi Foxall
Ash Marcinkiewicz
Caroline Ward
Avery Normandin
Saba Ilyas
Kylie Webber
Matt Gerding
Rachel Donner
Anna Tyzik
Megan Striplin
Jong Yu
Crystal Ellis
NH State Public Health Lab
Jenny Mahoney
MA Public Health Lab
Funding:
USDA, NHAES