DISSERTATION PROPOSAL:
Antibiotic-resistant Staphylococcus
aureus: Investigation of a poultry
reservoir
Department of Occupational & Environmental Health
Sept.10, 2010
Abby L. H. Maples, MPH
Introduction

Background
 Significance





Goals
Specific Aims
Limitations of Current Literature & Research
Research Design & Methods
Strengths & Limitations
Background

Staphylococcus aureus
 Signs
& symptoms
 Methicillin-resistant S. aureus (MRSA)
 Hospital


94,000 infections (Klevens, 2007)
18,000 deaths (Klevens, 2007)
 Community
1% of US population colonized
(Graham, 2006; Kuehnert, 2006;
Shorr, 2007)

 Livestock
http://www.medicinenet.com/mrsa_infection/page2.htm
Antibiotic-resistant S. aureus & Animals


S. aureus can cause infection in animals
(Baptiste, 2005; De Neeling, 2007; JuhaszKaszanyitzky, 2007; Khanna, 2008; Smith, 2009;
Van Loo, 2007; Weese, 2005; Weese, 2006)
Role of humans


Role of animals



Transient carriers or reservoirs?
Endemic?
Swine herds studied
Livestock-associated MRSA increasing
Antibiotic-resistant S. aureus in
Environmental Samples

Airborne transmission
 Colonization

role?
Previous airborne transmission studies
(Gibbs, 2004; Gibbs, 2006)


Surface contamination
Meat contamination
(De Boer, 2009;
Hanson, in press)
http://www.takepart.com/news/tag/anti-factory-farming
Goals

Long-term goal
 Understand
ecology & epidemiology of antibioticresistant (AbR)S. aureus

Objective
 Characterize

ecology & epidemiology of AbR S. aureus
Central hypothesis
 Workers
in close proximity to poultry are at risk of
occupational exposure to AbR S. aureus
 Farmers in contact with poultry will be colonized with
MRSA
Specific Aims
1.
2.
3.
Establish the prevalence & molecular
characteristics of AbR S. aureus on poultry farms
Establish the prevalence & molecular
characteristics of AbR S. aureus in poultry
processing facilities
Determine risk factors for presence of AbR S.
aureus on farms or processing facilities
Limitations of Current Literature



S. aureus is rapidly changing
Previous studies in chickens did not include workers
Epidemiologic studies in poultry have not been
conducted in U.S.
http://www.sciencedaily.com/releases/2009/03/090316120846.htm
Preliminary Studies


Prevalence of MRSA in Iowa & Illinois swine
18 swine farms in Iowa & Illinois (Smith, 2009)
9
each – confined animal feeding operations (CAFOs)
& antibiotic-free systems

5/18 (27.7%) farms positive for MRSA
 All


CAFOs (55.5%, 5/9)
Prevalence in swine 43/428 (10.0%)
Prevalence in humans 29/89 (32.6%)
 Humans
working at CAFOs (45.3%, 29/64)
Research Design & Methods

Farm Description
 Broilers,
layers, and turkeys
 Estimate 40% (± 5.0%) prevalence in poultry
 95%
confidence interval, 80% power = 600 animals
 20 animals from 30 farms (10 each)
 Convenience Sample
 Estimate
 Goal
1-2 employees per farm
to enroll 60 humans
http://newshopper.sulekha.com/turkey-farm_photo_1063248.htm
Research Design & Methods Continued

Sample Collection
 IRB
& IACUC Approved
 Humans
 Nasal
& throat Swabs
 Comparison, non-exposed group
 Poultry
 Choanal

(palatine) cleft & cloaca swabs
Air Sample Collection
 6-stage
Andersen Viable Cascade Impactor
Research Design & Methods Continued

Processing Facility Sample Collection
 Estimate
25% prevalence in processing facilities
 Surface & worker swabs of facility

Occupational Exposure Questionnaire
 Animal
exposure in last year
 Demographic & behavioral questions

Farm Owner/Manager Questionnaire
 Farm-specific
questions
Research Design & Methods Continued

Bacterial Growth
 6.5%

Staph enrichment broth, CNA & CHROMagar
Microbiology
 Gram
stain, catalase, coagulase, S. aureus latex
agglutination assay
 MRSA confirmed by penicillin binding protein presence
Diagnostic Schematic
Research Design & Methods Continued

Molecular Typing
 Spa
typing
 PVL PCR
 Multilocus sequence typing (MLST)
 Pulsed-Field Gel Electrophoresis (PFGE)

Antibiotic Resistance Testing
 Broth
dilution (CLSI standards)
 Tested for susceptibility
Research Design & Methods Continued

Data and Statistical Analysis
 Double-entry
 Excel,
into databases
Access, and Teleform Verifier
 Unique
specimen numbers
 Multivariate modeling of risk factors (SAS)
 Logistic
regression
 Cochran-Armitage trend test
Strengths & Limitations
Strengths




First study of S. aureus in
live poultry & workers in US
Well qualified &
experienced team
Collaboration with ISU
Iowa is a national leader in
eggs and turkey production
Limitations




Convenience, single-time
samples (not
representative)
Pilot study
Limited geography
Limited farmer enrollment
Impact & Benefit to Field




Assess infectious disease risks
Provide recommendations for preventative measures
Establish prevalence and dominant molecular types
of S. aureus in poultry
Create potential implementations to prevent spread
of S. aureus in rural Iowa
Three Publishable Paper Topics




Literature review of poultry diseases
Antibiotic resistant Staphylococcus aureus:
Investigation into a poultry reservoir
Staphylococcus aureus in environmental samples and
humans: Two poultry production facilities in Iowa(?)
Airborne Staphylococcus aureus in (10) poultry
barns (?)
**Open for discussion
Project Timeline



Oct 2010 – Sept 2011: Farm Sampling
Dec 2010 – June 2012: Molecular analysis &
antibiotic resistance testing
June – Sept 2012: Finish analysis & draft manuscript
Oct-Dec
2010
Jan-March
2011
April-June
2011
July-Sept
2011
Oct-Dec
2011
Jan-March
2012
April-June
2012
July-Sept
2012
Farm Sampling
Molecular analysis & antibiotic resistance testing
Finish analysis &
draft manuscript
Questions, Comments, or Concerns?
http://ehsmanager.blogspot.com/2009/05/bacteria-create-aquatic-superbugs-in.html
Reference:
www.Slideshare.com