Methicillin-Resistant Staphylococcus aureus in Children Living with Industrial Hog Operation Workers Bayesian Network Risk Models Jacqueline MacDonald Gibson, Associate Professor Department of Environmental Sciences and Engineering Gillings School of Global Public Health University of North Carolina at Chapel Hill November 1, 2018
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Methicillin-Resistant Staphylococcus aureus in Children Living with Industrial Hog Operation Workers
Bayesian Network Risk Models
Jacqueline MacDonald Gibson, Associate ProfessorDepartment of Environmental Sciences and Engineering
Gillings School of Global Public HealthUniversity of North Carolina at Chapel Hill
November 1, 2018
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Outline
• Introduction Antibiotic use in livestock Prior evidence of risk to humans
• MethodsData set from eastern North Carolina—high-intensity hog farmingBayesian network learning algorithmsModel evaluation and selection
• Results Insights on risk factors Bayesian network model accuracy
• Conclusions: interventions to decrease risk
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Modern Livestock Production: Breeding Ground for Antibiotic Resistance?
71% of domestic antibiotic use is for livestock production —mostly subtherapeuticSOURCES: Wendy Nicole, Env. Health Perspectives, 2015; FDA, 2015
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Use of Medically Important Antibiotics for Livestock Is Increasing
0.E+00
2.E+06
4.E+06
6.E+06
8.E+06
1.E+07
1.E+07
2008 2009 2010 2011 2012 2013 2014 2015 2016
Kg
Use
d in
Liv
esto
ck
YearSOURCE: FDA, 2015, Antimicrobials Sold or Distributed for Use in Food-Producing Animals
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Staphylococcus aureus Bacteria Can Transmit from Hogs to Humans
• S. aureus can acquire antibiotic resistance in hogs
• Resistant strains can pass to humans
• Example: methicillin-resistant S. aureus (MRSA)
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First Documented Case of MRSA Transmission from Hogs in 2004
• 6-month-old Dutch infant
• Parents also colonized
• Remained colonized for months despite aggressive treatment
• Source traced to hogs on the family’s farm
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Mounting Evidence of Hog-to-Human Transmission Since 2004
SOURCE: George, Stewart, and MacDonald Gibson, in review, Environmental Health Perspectives.
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Farm
Wor
kers
(Con
vent
iona
l)
Farm
Wor
kers
(Alte
rnat
ive)
Slau
ghte
rhou
seW
orke
rs
HH
Mem
bers
(Con
vent
iona
l)
HH
Mem
bers
(Alte
rnat
ive)
Com
mun
ityM
embe
rs
Vete
rinar
ians
Hea
lthca
reW
orke
rs
Hos
pita
l Pat
ient
s
% P
ositi
ve fo
r MR
SA
Percentage of Human Subjects Colonized with Hog-Associated MRSA
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Prevalence of Human S. aureus Infections Resistant to Methicillin is High
Prevalence of invasive S. aureus infections resistant to methicillin
How much does animal use of antibiotics contribute?
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Objective
• Characterize risk factors for MRSA transmission to hog workers’ children
• Build a predictive model to assess potential interventions
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Methods
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Data from Hog Workers in Eastern North Carolina (NC)
• 198 children living with hog workers
• MRSA colonization tested via nasal swabs
• Questionnaires administered to adult household members
Eastern NC has among highest industrial hog operation densities in world.
SOURCE: Wing et al., 2000.
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Questionnaire Included 98 Potential Explanatory VariablesParent MRSA
Recent hospitalization
Daycare
Age, gender, race
Education
Race
Handwashing
Household pet
Jobs
Workplace hygiene . . .
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Previously Published Analysis Found Only Four of 98 Items Influenced Risk
“The other IHO work activities and factors evaluated . . . were null or non-interpretable due to insufficient numbers.”
Factor Prevalence RatioTake work clothing home
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Use disinfectant 6Work with nursery pigs
2.2
Handle dead pigs 3.2
Risk Factors Identified by Log-Binomial Regression
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We Tested 17 BayesiaLab Algorithms to Build Predictive Model, Gain Insights