MOF, Alm.del - 2015-16 - Bilag 641: Henvendelse af 23/9-16 fra Dansk Svineavl, vedrørende resistente bakterier og MRSA CC398

Miljø- og Fødevareudvalget 2015-16
MOF Alm.del Bilag 641
Offentligt

Clinical Infectious Diseases Advance Access published August 11, 2016

MRSA CC398 in humans and pigs in Norway: A “One Health” perspective on

introduction and transmission

Carl Andreas Grøntvedt

1,*

, Petter Elstrøm

2,*

, Marc Stegger

3,4

, Robert Leo Skov

, Paal

Skytt Andersen

3,4

, Kjersti Wik Larssen

, Anne Margrete Urdahl

, Øystein Angen

1,3

Vildershøj Bjørnholt

2,#

Jesper Larsen

, Solfrid Åmdal

, Siri Margrete Løtvedt

, Marianne Sunde

1,2,#

, Jørgen

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The Norwegian Institute of Public Health, P.O. Box 4404 Nydalen, N-0403 Oslo, Norway

Statens Serum Institut, 5 Artillerivej, DK-2300 Copenhagen S, Denmark

Pathogen Genomics Division, Translational Genomics Research Institute (TGen), Flagstaff,

86001 Arizona, USA

St. Olavs Hospital, The Norwegian Reference Laboratory for MRSA, P.O. Box 3250

Sluppen, N-7006 Trondheim, Norway

The Norwegian Food Safety Authority, P.O. Box 383, N-2381 Brumunddal, Norway

Corresponding author: Carl Andreas Grøntvedt, The Norwegian Veterinary Institute, P.O.

Box 750 Sentrum, N-0106 Oslo, Norway, Tel: 00 47 23 21 63 87, Email: carl-

[email protected]

America.

This is an Open Access article distributed under the terms of the Creative Commons Attribution-

NonCommercial-NoDerivs licence (http://creativecommons.org/licenses/by-nc-nd/4.0/), which

permits non-commercial reproduction and distribution of the work, in any medium, provided the

original work is not altered or transformed in any way, and that the work is properly cited. For

commercial re-use, contact [email protected].

The Norwegian Veterinary Institute, P.O. Box 750 Sentrum, N-0106 Oslo, Norway

MOF, Alm.del - 2015-16 - Bilag 641: Henvendelse af 23/9-16 fra Dansk Svineavl, vedrørende resistente bakterier og MRSA CC398

contributed equally to this work

Summary

CC398 into closed pig populations. Further, it demonstrates that

stringent control and

eradication measures were effective and prevented dissemination from pig farms to the

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general human population.

Abstract

Background

Emerging livestock-associated methicillin-resistant

Staphylococcus aureus

(LA-

MRSA) persist in livestock populations and represent a reservoir for transmission to humans.

Understanding the routes of introduction and further transmission is crucial to control this

threat to human health.

Methods

All notified cases of LA-MRSA (CC398) in humans and pigs in Norway between

2008 and 2014 were included. Data were collected during an extensive outbreak investigation,

including contact tracing and stringent surveillance. Whole-genome sequencing of isolates

from all human cases and pig farms was performed to support and expand the epidemiological

findings. The national strategy furthermore included a “search and destroy” policy at the pig

farm level.

Results

Three outbreak clusters were identified, including 26 pig farms, two slaughterhouses

and 36 humans. Primary introductions likely occurred by human transmission to three sow

The present study

provides strong and novel evidence that humans may introduce MRSA

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farms with secondary transmission to other pig farms mainly through animal trade and to a

lesser extent via humans or livestock trucks. All MRSA CC398 isolated from humans without

an epidemiological link to the outbreaks were genetically distinct from isolates within the

outbreak clusters indicating limited dissemination to the general population.

Conclusions

This study identified preventable routes of MRSA CC398 introduction and

These findings are essential for keeping pig populations MRSA-free and from a One Health

perspective to prevent pig farms from becoming reservoirs for MRSA transmission to

transmission: human occupational exposure, trade of pigs and livestock transport vehicles.

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humans.

MOF, Alm.del - 2015-16 - Bilag 641: Henvendelse af 23/9-16 fra Dansk Svineavl, vedrørende resistente bakterier og MRSA CC398

Introduction

Staphylococcus aureus

is one of the main causes of nosocomial and community-acquired

infections, and methicillin-resistant

S. aureus

(MRSA) infections are associated with

exclusively a healthcare-associated problem, but since the late 1990s, the epidemiology has

further from the mid-2000s by emerging MRSA strains with a primary reservoir in livestock

[3, 4].

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Livestock-associated MRSA (LA-MRSA) has now spread worldwide, especially in pig farms

where it is transmitted to humans mainly by occupational exposure [5-7]. In countries with a

low overall prevalence of MRSA in humans, like Denmark and the Netherlands, LA-MRSA

has greatly impacted the notification rate of MRSA in humans and is increasingly found in

people without livestock contact [8-10].

LA-MRSA in pig holdings in Europe most commonly belong to the clonal complex (CC) 398,

but the prevalence varies greatly among European countries, with up to 70% of all farms

positive in Denmark and the Netherlands [8, 11]. In contrast, several surveillance programs

conducted in Norway, including the 2008 EU baseline study and two more recent nationwide

population surveillance programs found either an absence or a very low prevalence of LA-

MRSA in pigs [12-14]. Trade in pigs has been identified as the major risk factor for inter-farm

transmission of LA-MRSA [15, 16], including transboundary transmission [17]. In the period

from 2000 to 2015, fewer than 80 live pigs were imported into the Norwegian commercial pig

population, most of these in two separate imports of 49 and 20 high-health breeding animals

from Finland and the Netherlands respectively [18]. In the latter the imported animals were

changed significantly with dissemination of community-associated MRSA (CA-MRSA) and

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increased morbidity, mortality and costs [1, 2]. For a long time, MRSA was almost

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tested and confirmed to be negative for MRSA. Thus, the Norwegian pig population is de

facto a “closed” production system.

The objective of the present study was to describe the first known introductions and

The study included all identified cases of MRSA CC398 in humans and pigs in Norway from

2008-2014.

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transmission of MRSA CC398 in pig herds and the subsequent spread to humans in Norway.

Materials and methods

MRSA investigations in pigs

MRSA in the Norwegian pig population was first investigated in an EU baseline study in

2008, which did not detect LA-MRSA [12]. In 2011 and 2012, anonymized prevalence

studies demonstrated MRSA CC398 in a few samples from a single slaughterhouse and a pig

Norwegian pig population initiated a public health risk assessment concerning the possible

impacts of an increasing prevalence of LA-MRSA in pigs. This prompted an investigation to

identify and control the transmission of MRSA CC398 to pig farms and humans. Norwegian

authorities implemented a strategy including a farm level “search and destroy” policy to

prevent the establishment of LA-MRSA in the Norwegian pig population. In 2014, a

nationwide surveillance program of all sow farms (n=986) was initiated to investigate the

prevalence of MRSA in the pig population [19].

The outbreak-related investigation collected epidemiological data from farmers by

questionnaires (Table S1 in Supplementary Appendix) and included both human and animal

contact tracing. Demographic information, farm characteristics, husbandry and production

herd [13, 14]. In early 2013, two independent identifiable findings of MRSA CC398 in the

MOF, Alm.del - 2015-16 - Bilag 641: Henvendelse af 23/9-16 fra Dansk Svineavl, vedrørende resistente bakterier og MRSA CC398

details were collected. In total, 74 pig farms and five slaughterhouses were included and

sampled in the outbreak investigation during 2013 and 2014 (Supplementary Appendix 1).

MRSA investigations in humans

Human MRSA infections have been notifiable to the Norwegian surveillance system for

communicable diseases (MSIS) since 1995 and MRSA carriage has been notifiable since

2005 [20]. Humans are investigated for MRSA based on clinical signs of infection, admission

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MRSA CC398 cases notified to MSIS were included.

Epidemiological data on all persons occupationally exposed to pigs in the current outbreaks

were collected (Table S2 in Supplementary Appendix). Household members were sampled if

they were patients in healthcare institutions, worked as healthcare personnel, or if a farm or

abattoir worker was found to be MRSA positive. MRSA screening samples from humans

were collected from the vestibulum nasi, throat, and skin lesions (if present). In total, 272

persons were included.

Bacteriological analyses

All samples from animals and environment were investigated for MRSA using the protocol

described by the European Food Safety Authority [22]. Human MRSA samples taken as part

of the outbreak investigation were analyzed at seven medical microbiological laboratories

using slightly different methodologies (Supplementary Appendix 2).

screening in healthcare facilities, contact tracing and outbreak investigations [21]. All human

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The national reference laboratory for MRSA confirmed presumptive MRSA isolates from

human, animal and environmental samples by PCR detection of the genes

mecA, spa

and PVL

using PCR protocols previously described [23, 24].

Spa-typing

was performed on all isolates

(http://www.seqnet.org/downloads.html). Multilocus sequence typing (MLST) was performed

on new

spa-types

as described by Enright et al [25].

phylogenetic analysis of MRSA CC398 from all pig farms and all human cases reported in

Norway, as well as selected MRSA CC398 isolates was performed (Supplementary Appendix

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Statistical analyses

The data were collected with the objective of prevention and control of transmission of

MRSA and not as a part of a planned scientific study. Stata Version 13 (Stata-Corp, College

Station, TX, USA) was used to calculate attack rates (AR) and odds ratio (OR) of MRSA

among persons distributed on occupational exposure and pig farms distributed on type of pig

production.

Results

Overview of MRSA CC398 in Norway

The first human case of MRSA CC398 was notified in March 2009, and by the end of 2014, a

total of 84 human cases had been reported, including human cases identified through outbreak

investigations (Figure 1).

3).

Whole-genome sequencing (WGS), detection of resistance and virulence markers, and

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The first traceable finding of LA-MRSA in pigs occurred in February 2013, and by the end of

2014, outbreak investigations and surveillance had identified MRSA CC398 in 26 pig farms

farms and persons in three clusters located in, or originating from, central eastern (outbreaks 1

environment and humans in these three clusters belonged to the following CC398 associated

spa

types: t034 in outbreak 1, t034 and t12359 in outbreak 2 and t011 in outbreak 3. The

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Supplementary Appendix 4). MRSA CC398 detected in samples from a slaughterhouse in the

anonymized survey of 2011 (NORM-VET 2011) was shown by WGS to be related to isolates

in outbreak 1 (Figure 3). Most pig farms in outbreak 1 regularly supplied this slaughterhouse.

A single pig isolate from the 2012 survey and 48 human isolates not epidemiologically linked

to the three outbreaks described were all genetically distinct from the isolates in the outbreak

clades (Figure 3 and Supplementary Appendix 4). Based on information reported to MSIS, 25

(52%) of the human cases not linked to the outbreak clusters had likely acquired MRSA

CC398 abroad.

Introductions of MRSA CC398 to the pig population

The index cases in the three outbreaks were identified through samples collected from a post-

mortem examination of a fattening pig in February 2013 (outbreak 1), clinical infection in a

farm worker in June 2013 (outbreak 2) and in a national surveillance program of sow farms in

June 2014 (outbreak 3). Contact tracing identified two primary case sow farms having

findings were further supported by WGS-based phylogenetic analysis (Figure 3 and

and 3) and south-western (outbreak 2) Norway (Figure 2). MRSA isolates from animals,

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(Table 1), two slaughterhouses and 36 humans (Table 2). Epidemiological data placed these

MOF, Alm.del - 2015-16 - Bilag 641: Henvendelse af 23/9-16 fra Dansk Svineavl, vedrørende resistente bakterier og MRSA CC398

supplied the index case farms in outbreaks 1 and 2. The index case farm in outbreak 3 was

considered the primary case farm. All primary case farms had farm workers and/or

consultants originating from other European countries. The use of foreign labor was common,

as 24/62 (39%) and 4/63 (6%) of sow and finishing pig farm workers respectively, were of

non-Norwegian nationality. The majority of foreign workers (25/28) were from Eastern

Europe, while the remaining three were from Denmark (n=2) or the Netherlands (n=1). None

of the farms investigated had imported pigs from abroad. WGS data from both human and pig

isolates in outbreaks 1 and 2 demonstrated a close genetic relationship with isolates identified

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in Denmark, whereas isolates from outbreak 3 showed genetic relatedness to MRSA CC398

t011 strains from several European countries, including Denmark (Figure 3).

Further transmission

The trade of pigs was identified as the main route of MRSA CC398 transmission from the

three primary case farms. This was considered the most likely route of transmission to 19

farms. In three farms, the most probable explanation for transmission was through the mutual

use of farm workers or veterinary practitioners.

One farm had two separate introductions of MRSA CC398 (t034 and t011) based on

epidemiological information supported by WGS data, and was involved in both outbreaks 2

and 3. The trade of pigs or contact through personnel was excluded as the route of re-

introduction to this farm. A livestock transport vehicle had on two occasions transported pigs

from a MRSA CC398 positive finishing farm to a slaughterhouse without subsequent

disinfection shortly before transporting pigs to the farm involved and was considered the most

likely transmission route.

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Pigs from MRSA CC398 positive farms were slaughtered at five different slaughterhouses in

southern Norway, and MRSA was detected in samples from pigs, personnel or the

environment in two of these (Figure 2).

In total, 48 of 74 farms sampled during outbreak investigations were identified as MRSA

negative. Twelve farms were sampled as they had supplied pigs to MRSA CC398 positive

the 51 farms that had received pigs from MRSA CC398 positive farms, 32 were MRSA

negative. Of these 32 farms, 14 had received pigs from farms in which MRSA CC398 had

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had changed suppliers and had washed and disinfected the premises before the change of

supplying herd.

Three were identified through notification to MSIS, and subsequently linked to the outbreaks

by epidemiological data, supported by WGS results (Figure 3 and Supplementary Appendix

4). All 36 persons had direct and regular contact with positive pigs (Table 2). No differences

in the MRSA prevalence between different types of occupational exposure were observed.

Discussion

The present study encompasses all identified cases of MRSA CC398 in humans and pigs in

Norway, between 2008 and 2014. All the traceable detections of MRSA CC398 in pig farms

and slaughterhouses clustered in three separate outbreaks. Furthermore, 43% (36/84) of all

human MRSA CC398 cases in the period were related to these outbreaks. The study strongly

suggests that the outbreaks were caused by human introduction of MRSA. Phylogenetic

Of the 36 human cases included in the outbreaks, 33 were detected through contact tracing.

most likely only been recently introduced, 12 had been only sporadically supplied, and six

farms, and four farms had contact through MRSA CC398 positive veterinary practitioners. Of

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analysis revealed that the introduced MRSA strains were closely related to strains isolated in

other European countries. The isolates from the primary case farms in outbreaks 1 and 2

showed close genetic relatedness to MRSA CC398 isolates from Denmark, and persons linked

to the two farms had known contact with pig farms in Denmark. Further, the primary case

farm in outbreak 3 involved farm workers from abroad, although without confirmed livestock

contact outside Norway.

To our knowledge, the present study is the first to describe the importance of the human

introduction of MRSA CC398 to livestock populations. Since there is virtually no import of

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important route of introduction into the Norwegian pig population. Our findings are therefore

highly relevant for the future prevention of LA-MRSA introduction to pig populations, at both

the national level and farm level.

Based on other studies, the trade of pigs has been shown to be the predominant route of

transmission of MRSA CC398 among pigs [15, 16], including transboundary transmission

[17]. Domestic trade in pigs was found to be the main route of inter-farm transmission of

MRSA after primary introductions, indicating that limiting the number of farms connected

through trade is important in preventing MRSA transmission. In addition, we found humans

and in one case a livestock truck to be the most likely explanation for MRSA transmission to

farms not connected through the trade of pigs. These transmission routes may further

constitute routes of dissemination to other segments of the animal population.

Our results show that 32 of 51 pig farms which had purchased pigs from MRSA positive

suppliers were found to be MRSA negative at the time of sampling. This may be explained by

the supplying farms not being MRSA positive at the time of delivering the animals or that

management practices and hygiene routines prevented MRSA from becoming established in

live pigs to Norway, human transmission of LA-MRSA should be regarded as the most

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the recipient farms, the latter being the most likely explanation in at least six farms. This

indicates that changing to a supplier with a MRSA negative herd (all in – all out) combined

with good routines for washing and disinfecting facilities may be effective measures to

prevent MRSA establishment on finishing pig farms. These findings are supported by results

from the Norwegian control strategy for LA-MRSA in the pig population, and may be

relevant also for pig farms in other countries [26].

Other studies have identified direct contact, and to a lesser extent indirect contact to positive

animals as a major risk factor for MRSA CC398 in humans [5, 27, 28]. In addition, an

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farms has been described from areas with a high density of pig herds [8, 9, 29]. In the present

study, we did not observe the transmission of MRSA CC398 from the outbreaks to the general

public. This may be partly explained by the relatively short exposure times, as all pigs on

MRSA CC398 positive farms were slaughtered and the holding facilities thoroughly washed

and disinfected.

Public health surveillance data from Norway show that more than one third of all notified

human MRSA cases have acquired MRSA abroad [12, 30]. An increased prevalence of

MRSA on Norwegian pig farms could change this epidemiological situation by constituting a

new domestic reservoir for MRSA, leading to an increase of the total public health burden of

MRSA. Such a development has been described in Denmark, where the rapid spread of

MRSA CC398 in the pig population has led this to be the dominant clone found in humans

[8]. The rapid increase of MRSA CC398 in humans in other low endemic countries and the

results from the present study, highlights the importance of control measures to prevent the

introduction and further transmission of MRSA CC398 in pig populations. The present

Norwegian control strategy includes targeted screening of personnel before working in pig

herds, annual national surveillance of the pig population and contact tracing with eradication

increased incidence rate of MRSA CC398 in the general public without contact with pig

MOF, Alm.del - 2015-16 - Bilag 641: Henvendelse af 23/9-16 fra Dansk Svineavl, vedrørende resistente bakterier og MRSA CC398

measures, resembling a “search and destroy” strategy. The preliminary results of testing in

herds following the implementation of MRSA eradication measures show that this has largely

been an effective strategy [26].

Some of the data described here were collected in order to control outbreaks and, although

extensive, were not fully comprehensive. Only household contacts of MRSA CC398-positive

the detection of further spread. The WGS analysis was compared to available sequences

primarily from Denmark, thus the relatedness to isolates from other countries was explored to

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the active surveillance programs in the pig population together with mandatory notification of

all human MRSA diagnoses, giving a near-complete description of MRSA CC398 in Norway.

In conclusion, this study confirms that the trade of pigs and occupational exposure are the

major risk factors for transmission of MRSA CC398 between humans and pigs. However, the

primary introductions leading to the three outbreak clusters cannot be explained by the trade

of animals. In these cases, both the epidemiological and the WGS data indicate that these

introductions were the result of human-to-animal transmission. In addition, further

transmission likely occurred via humans and livestock transport vehicles to farms not

connected to MRSA CC398 positive farms through the trade of live animals. These findings

have important implications for risk management to prevent the dissemination of MRSA

CC398 among farms. In Norway, we believe that the prevention of human introduction of

LA-MRSA is of the utmost importance for the current ambitious strategy to control LA-

MRSA to prove feasible and successful in the longer term.

a lesser extent. The major strengths of the study are the extensive outbreak investigations and

occupationally exposed humans were screened, thus bias may have been introduced regarding

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Contributors

Outbreak investigations (PE, MS, AMU, JVB, SÅ, SML), data collection (CAG, PE, MS,

AMU, JVB, SÅ, SML, JL, KWL, ØA), data analysis and interpretation (CAG, PE, MS,

MSt). CAG and PE contributed equally as shared first authors with the primary responsibility

authors. All authors contributed to revising the manuscript and approved the final version.

Acknowledgments

of writing and revising the manuscript. MS and JVB contributed equally as shared senior

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AMU, JVB, KWL, RLS, JL, PSA, MSt, ØA), preparing tables and figures (PE, CAG and

We would like to acknowledge the dedicated efforts of Bjørn Lium (DVM, Dr.Sci.) in the

outbreak investigation and Berit Tafjord Heier (DVM, PhD) for preparing the maps. We thank

the Norwegian Food Safety Authority, Public Health Officers, the Norwegian Pig Health

Service and the people involved from the pig production sector for their contributions and

cooperation in the outbreak investigations. The following laboratories provided samples and

data: the Norwegian Veterinary Institute (Oslo, Norway), St. Olav Hospital (Trondheim,

Norway), Stavanger University Hospital (Stavanger, Norway), Fürst Medical Laboratory

(Oslo, Norway), Vestre Viken Hospital Trust (Drammen, Norway), Sørlandet Hospital HF

(Kristiansand, Norway), Akershus University Hospital (Lørenskog, Norway), Vestfold

Hospital Trust (Tønsberg, Norway), Sykehuset Innlandet Trust (Lillehammer, Norway) and

Statens Serum Institute (Copenhagen, Denmark).

Funding

This work was supported by the Norwegian Food Safety Authority; the Norwegian Veterinary

Institute; The Norwegian Institute of Public Health; Statens Serum Institut and St. Olavs

Hospital. The funders of the study had no role in study design, data collection, data analysis

MOF, Alm.del - 2015-16 - Bilag 641: Henvendelse af 23/9-16 fra Dansk Svineavl, vedrørende resistente bakterier og MRSA CC398

and interpretation, or writing of the report. The corresponding author had full access to all the

data in the study and had final responsibility for the decision to submit for publication.

Conflicts of interest

JL reports grants from the National Institute of Allergy and Infectious Diseases (Grant/Award

Number 1R01AI101371-01A1), outside the submitted work. MSt has a patent (13/379,499)

with royalties.

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ESCMID Conference on methicillin-resistant

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ipt

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MOF, Alm.del - 2015-16 - Bilag 641: Henvendelse af 23/9-16 fra Dansk Svineavl, vedrørende resistente bakterier og MRSA CC398

Figure Legends:

Figure 1.

Notified cases of human MRSA involving CC398 in Norway, from the first case in March 2009 until

Figure 2.

Geographical distribution of (A) MRSA CC398 positive farms (circles), slaughterhouses (triangles),

and (B) MRSA CC398 positive farm or slaughterhouse workers in outbreak one (red), two (blue) and three

(yellow). In A, negative farms and slaughterhouses are indicated in green. Insert in A depicting Norway in

Europe with box highlighting focus area in A and B.

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Figure 3. Phylogenetic analysis for understanding diversity and spread of CC398 MRSA isolates in

Norway.

The phylogenetic relationship was inferred using maximum likelihood based on 4,854 SNPs in 271

isolates. The human-adapted (HuA) and livestock-associated (LA) clades are highlighted. Identified outbreaks in

relation to Norwegian livestock were identified and highlighted; Outbreak 1 (red), outbreak 2 (blue), and

outbreak 3 (yellow). Genotypic and epidemiological data are represented encircling the topology. Inner circle

represent Norwegian isolates (solid), Danish pig-production isolates (empty), and others (blank). Middle circle

represent the sample environment with livestock, meat and environmental samples (solid) and human isolates

(empty). Outer circle depicts the occurrence of specific fluoroquinolone-associated resistance mutations in

gyrA

(Ser84Leu) and

parC

(Ser80Tyr).

ipt

December 2014.

MOF, Alm.del - 2015-16 - Bilag 641: Henvendelse af 23/9-16 fra Dansk Svineavl, vedrørende resistente bakterier og MRSA CC398

Table 1:

MRSA outbreaks: The number and type of pig farms sampled and results from MRSA analysis.

Outbreak 1

Pos

AR(%)

Outbreak 2

Pos

AR(%)

Outbreak 3

Pos

AR(%)

Total

Sow farms

Finishing

pig farms

Total

(42

(47·4)

28*

(18·8)

(28·6)

(100·0)

(66·7)

(28·0)

(36·7)

(75·0)

(35·1)

ipt

Pos

AR(%)

Ref.

1.26

(95%

CI)

(0·50 –

3·57)

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(46·2)

(25·0)

Number of pig farms sampled (one farm included in both outbreak 2 and 3)

Number of pig farms found positive of MRSA (*one farm included in both outbreak 2 and 3)

Attack rate

Odds ratio

MOF, Alm.del - 2015-16 - Bilag 641: Henvendelse af 23/9-16 fra Dansk Svineavl, vedrørende resistente bakterier og MRSA CC398

Table 2:

Results of case tracing of persons, distributed by the type of known exposure to MRSA

Outbreak 1

Pos

AR(%)

Outbreak 2

Pos

AR(%)

Outbreak 3

Pos

AR(%)

Total

pig farm

Working in

finishing pig farm

Veterinary

practitioner

Working in

slaughterhouse

Household

members

Total

(14·3)

(20·0)

124

(8·06)

(25·0)

272

(13·2)

Working in sow

(52·6)

(7·7)

(25·0)

(17·2)

(11·8)

ipt

Pos

AR(%)

(22·6)

Ref.

0·63

0·89

0·36

(95%

CI)

(0·24 –

1·57)

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(18·2)

(25·0)

(0·16 –

3.17)

(0·14 –

0·86)

107

(8·4)

(5·9)

(0·0)

171

(15·2)

Number of humans sampled

Attack rate

Odds ratio

Number of humans found positive of MRSA

(9·3)

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Persons found positive with MRSA CC398 without known contact to pig herds in Norway

Persons found positive with MRSA CC398

spa-type

t034 in outbreak 1

Persons found positive with MRSA CC398

spa-type

t034 or t12359 in outbreak 2

Persons found positive with MRSA CC398

spa-type

t011 in outbreak 3

1 2 3 4 5 6 7 8 9 10 11 12 1 2 3 4 5 6 7 8 9 10 11 12 1 2 3 4 5 6 7 8 9 10 11 12 1 2 3 4 5 6 7 8 9 10 11 12 1 2 3 4 5 6 7 8 9 10 11 12 1 2 3 4 5 6 7 8 9 10 11 12

2009

2010

2011

2012

2013

2014

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MOF, Alm.del - 2015-16 - Bilag 641: Henvendelse af 23/9-16 fra Dansk Svineavl, vedrørende resistente bakterier og MRSA CC398

FQ-mutations

Origin

Country

HuA