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MRSA in the Swine Industry - Recent Developments - Dr. Peter Davies, University of Minnesota, from the 2014 Allen D. Leman Swine Conference, September 15-16, 2014, St. Paul, Minnesota, USA. More presentations at http://www.swinecast.com/2014-leman-swine-conference-material
Citation preview
MRSA in the US Swine Industry
Recent Developments
Peter Davies, Jisun Sun, My YangCollege of Veterinary Medicine
University of Minnesota
Outline
Background of ‘livestock associated’ MRSA?
State of play - 2013 Recent UMN research
US swine veterinarians (UMASH) US pig farms (NPB – pork check off)
Recent developments in Europe and USA
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Staphylococcus aureus
Common inhabitant of warm-blooded animals ‘Normal flora’ (20-30% of people)
Common opportunistic pathogen in humans Insignificant to fatal Broad clinical manifestations Skin and soft tissue infections Invasive: pneumonia, septicemia and death Bacteremia: 80% fatality rate prior to antibiotic era
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Holland – an issue emerges!
Very low MRSA prevalence Intensive screening and typing with sma1 PFGE ‘Search and destroy’ policy – isolation/decolonization
2004: 6mo girl screened before surgery for a congenital heart defect
MRSA isolate not typable with Sma1 PFGE
2 other screening isolates not typable by Sma1 PFGE All 3 ‘cases’ epidemiologically linked to pigs
Studies of MRSA prevalence in pigs, farmers and pork
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MRSA in animals – publication rate
0
2
4
6
8
10
12
70s 80s 90-95
96 97 98 99 00 01 02 03 04 05 06 07
Years
Cattle
Cat, Dog
Horse
Pig, Sheep
2010>50
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S. aureus subtyping methods
PFGE
MLST
SCCmec typing (I – XI)
Spa typing Ridom
egenomics
‘Livestock associated’
Sma1 Untypable
ST398 (CC398)
III, IV, V
t034, t011, t108……...
539, ………………..…..
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LA-MRSA: more than ST398 in pigs
ST9 (t899, t337) - Asia, Italy, Spain, USA ST5 (t002) - North America (US, Canada) ST1 - Denmark, USA, Switzerland, Italy ST72 - USA, Korea ST97 – Italy, Spain ST49 – Switzerland ……
LA-MRSA: more than ST398
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ST398t011, t108
t034, t567… >30 spa
typesST5t002
ST9t899t337
Not all ‘livestock associated’ MRSA are ST398
‘Animal independent’ ST398 clinical infections in NY city (Uhlemann et al, 2012)
Studied outpatient MRSA isolates, non-invasive MSSA cases, and bloodstream MSSA isolates
ST398 t571: 5% of non-invasive MSSA; 2.5% of MSSA bacteremias
“Clinically important clone that differs significantly at the genome level from its livestock associated counterpart”
Distinct ‘pig clade’ and ‘human clade’ of ST398 t571 Only reported ST398 infections in USA are t571
MSSA without known livestock contact
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ST398 MRSA exposure riskGenerally accepted facts (2013)
ST398 occur in livestock species in many countries
High MRSA exposure risk for people with direct animal contact 20-50% prevalence in farmers ~ 0.5 - 2% in general populations
Key questions Are they truly colonized? What is the consequent risk to health?
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ST398 MRSA public health risk Generally accepted facts (2013)
Elevated occupational risk of infection not well documented
Current evidence suggests low transmissibliity No reports of outbreaks
Current evidence suggests low virulence? Significantly less invasive disease in Europe Serious infections uncommon General lack of virulence determinants Few fatalities
ST398 bacteremia cases in Denmark (Petersen pers. Comm.)
Impact low ~1% of cases Only 6 MRSA
cases Trend concerning No animal contact
in bacteremia cases
Are they livestock associated?
and how?12
ST 398 1.2% of bacteremic S. aureus
cases in 2013
Studies of S. aureus
Pilot study of ecology of S. aureus on swine farms (NPB)
Longitudinal study of S. aureus and MRSA colonization and infection in swine veterinarians NIOSH (UMASH center) 68 swine veterinarians
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Study design
18 months longitudinal study to Dec. 2013 66 swine veterinarians across 15 states
Monthly nasal swabs Survey of pig exposure and events of injury/infection
One time quantitative study Direct enumeration of CFU in nasal swabs
Prevalence of SA and MRSA in vets
t034 (ST398) , t337 (ST9), t002 and t045 (ST5) most common types Correspond with the most common variants in US pigs.
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SA : 58.3% to 82.4% MRSA : 5.9% to 15.2%
Permanent of intermittent carriage?
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Colonization patterns ofPersistent Carriers
Intermittent carriers
Do permanent carriers harbor more SA?
41 volunteers at AASV 18 PC 23 IC
Nasal swab at meeting Time since pig contact Quantitative culture
Direct plating – without enrichment
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Do persistent carriers harbor more SA?
More PC were positive 15 of 18 (83%) PC 7 of 23 (30%)
PC had more SA ‘PC’ of S. aureus occurs in a subset of swine
vets who are frequently culture positive and carry higher numbers of organisms Importance of host factors?
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S. aureus prevalence in US swine herds
Samples processed from 31 farms (of 36) 20 nasal swabs from growing pigs Collected by vets in UMASH study (1 farm per
vet) Multiple states Data on farm, including antibiotic exposure
Spa typing, MLST typing results Antimicrobial resistance and enterotoxin
production to be conducted21
Prevalence by farm
One farm S. aureus negative Only 1 farm harbored MRSA (known
positive) MLST and spa types similar in pigs and vets Vet and pig data indicate relatively low
MRSA prevalence in the US swine industry
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**
* Size of circles : Prevalence (%)
Comparison of spa types detected in veterinarians and swine
82.7% 92.4%
82.7% 92.4%
t2330 t7160 t2876 t1255 t1250 t045 t856 t062
t1430 t1334t922 t363 t8314
t2196 t008t126 t6509t330 t338
t2330 t7160 t2876 t1255 t1250 t045 t856 t062
t1430 t1334t922 t363 t8314
t2196 t008t126 t6509t330 t338
t899 t2582
t306 t899t5838 t8314t2462 t1793
t11374t11241t5462
t899 t2582
t306 t899t5838 t8314t2462 t1793
t11374t11241t5462
Veterinarians
Veterinarians PigsPigs
82.7%
92.4%
Scaremongering?
Most data indicate the public health risk of S. aureus (incl. MRSA) in the pig reservoir is minimal
Indication of increases in some EU countries Changes in screening practices Combine clinical and non-clinical cases
Lack of significant clinical infections in occupationally exposed people
Steady drum beat of publications ‘talking up’ the risk
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Schinasi et al. Environmental Health 2014 13:54
Conclusion:Moderate densities of swine ….were associated with MRSA nasal carriage detected by PCR. This finding is supported by past evidence of associations between MRSA nasal carriage and contact with swine production.
Summary
Livestock associated MRSA remains a difficult public relations issue for the swine industry
Accumulating data point to much lower prevalence than in many EU countries Swine veterinarians Pig farms
Promises to be a case study in misinformation and biased inference in science
27