6  Background, data, material and methods

6.1 Demographics and denominator data

6.1.1 Humans

Official statistics on population in Sweden are provided by Statistics Sweden to the eHealth Agency. The number of people per age group and region in 2025 are provided in Table 6.1 and in total in Sweden from 2000-2025 in Table 6.2. These figures are used for calculation of antibiotic sales in humans.

Table 6.1. Denominator data (population in Sweden per region and age group) for calculation of antibiotic sales in humans, 2025. Data from the eHealth Agency. 
Region <1 years  1-4 years  5-19 years  20-44 years  45-64 years  65-84 years  ≥85 years  All age groups  0-6 years 
Blekinge  1 173  5 873  27 151  44 297  39 564  33 457  5 708  157 223  10 348 
Dalarna  2 342  11 030  49 327  79 586  69 577  64 701  9 983  286 546  19 679 
Gotland  414  2 060  9 969  16 421  15 360  14 558  2 189  60 971  3 681 
Gävleborg  2 247  10 530  48 192  80 078  71 357  62 818  9 336  284 558  18 986 
Halland  3 205  14 536  63 490  97 892  86 357  68 617  10 977  345 074  25 766 
Jämtland   1 149  5 094  22 965  38 985  32 268  28 295  4 083  132 839  9 219 
Jönköping  3 491  16 063  68 131  113 638  88 823  68 451  11 412  370 009  28 392 
Kalmar  2 050  9 585  41 370  67 629  60 839  55 864  9 015  246 352  16 847 
Kronoberg  1 863  8 752  36 959  62 529  48 425  38 262  6 561  203 351  15 359 
Norrbotten  1 983  9 212  39 282  74 162  61 062  54 537  8 382  248 620  16 133 
Skåne  13 663  61 094  257 293  461 136  348 477  248 477  38 486  1 428 626  107 788 
Stockholm  25 673  108 478  439 769  862 700  618 600  365 282  52 805  2 473 307  190 151 
Sörmland  2 640  12 154  55 549  85 913  74 163  61 887  9 236  301 542  21 846 
Uppsala  3 877  16 975  71 760  145 029  92 388  68 119  9 764  407 912  30 207 
Värmland  2 302  10 533  47 230  82 370  69 714  61 191  10 044  283 384  18 843 
Västerbotten  2 382  11 211  47 389  95 281  63 941  53 085  7 849  281 138  19 834 
Västernorrland  1 804  8 950  41 263  67 052  61 120  53 120  8 149  241 458  16 015 
Västmanland  2 554  11 727  50 096  85 496  68 617  53 786  8 882  281 158  20 796 
Västra Götaland  17 182  75 175  307 340  585 045  428 520  311 545  48 014  1 772 821  131 918 
Örebro  2 817  12 563  54 478  96 346  73 847  59 589  8 735  308 375  22 365 
Östergötland  4 261  19 082  82 747  151 641  113 478  87 302  13 935  472 446  33 715 
Sweden (total) 99 072  440 677  1 861 750  3 393 226  2 586 497  1 912 943  293 545  10 587 710  777 888 
Table 6.2. Denominator data (population in Sweden) for calculation of antibiotic sales in humans, 2000-2025. Data from the eHealth Agency.
Year  Population 
2000  8 861 426 
2001  8 882 792 
2002  8 909 128 
2003  8 940 788 
2004  8 975 670 
2005  9 011 392 
2006  9 047 752 
2007  9 113 257 
2008  9 182 927 
2009  9 256 347 
2010  9 340 682 
2011  9 415 570 
2012  9 482 855 
2013  9 555 893 
2014  9 644 864 
2015  9 747 355 
2016  9 851 017 
2017  9 995 153 
2018  10 120 242 
2019  10 230 185 
2020  10 327 589 
2021  10 379 295 
2022  10 452 326 
2023  10 521 556 
2024  10 551 707 
 2025  10 587 710  

6.1.2 Animals

Official statistics on agriculture in Sweden are provided by the Board of Agriculture. The Board of Agriculture maintains a statistical database accessible online (www.jordbruksverket.se). Annual figures on the number of animals are given in Table 6.3, on animals slaughtered in Table 6.4 and Table 6.5 and average herd size in Table 6.6. Readers are referred to the Board of Agriculture for further information.

In brief, the number of dairy cows and pigs has decreased notably over the last three decades, but herd size has increased. During the same period, the number of beef cows has increased, as well as the number of chickens slaughtered.

Estimates of the number of dogs and cats are available from the Board of Agriculture for 2006 and 2012, and in studies by the company Novus in 2017, 2020, 2024 and 2026. In 2012, the numbers of dogs and cats in Sweden were estimated to 784 000 and 1 159 000, respectively. The corresponding figures for 2026 were 951 000 and 1 582 000.

Table 6.3. Number of livestock and horses (in thousands) 1980-2025. From the statistical database of the Swedish Board of Agriculture.
Animal category/species 1980 1985 1990 1995 2000 2005 2010 2015 2020 2021 2022 2023 2024 2025
Dairy cows 656 646 576 482 428 393 348 338 303 302 297 296 289.433 293
Beef cows 71 59 75 157 167 177 197 184 207 210 213 210 200.213 196
Other cattle >1 year 614 570 544 596 589 527 513 487 480 476 482 480 476.818 475
Calves <1 year 595 563 524 542 500 509 479 466 462 465 458 459 443.835 436
Cattle, total 1935 1837 1718 1777 1684 1605 1537 1475 1453 1453 1449 1444 1410.299 1400
Ewes and rams 161 173 162 195 198 222 273 289 263 272 264 264 240.739 240
Lambs 231 252 244 266 234 249 292 306 238 252 245 222 213.801 206
Sheep, total 392 425 406 462 432 471 565 595 501 523 510 486 454.54 446
Boars and sows 290 260 230 245 206 188 156 142 131 129 127 113 117.658 114
Fattening pigs >20 kg 1254 1127 1025 1300 1146 1085 937 830 869 845 895 852 860.979 870
Piglets <20kg 1170 1113 1009 769 566 539 427 384 368 376 371 339 359.048 349
Pigs, total 2714 2500 2264 2313 1918 1811 1520 1356 1368 1351 1393 1304 1337.685 1333
Laying hens 5937 6548 6392 6100 5670 5065 6061 7571 8403 6363 7919 7717 8043.862 7953
Chickens reared for laying 2636 2159 2176 1812 1654 1697 1647 1842 2420 2390 1722 2700 2557.336 2532
Hens for egg-production, total 8573 8708 8568 7912 7324 6762 7707 9413 10823 8753 9641 10417 10601.198 10485
Horses – – – – – – 363 – – – – – – –
Table 6.4. Number of animals slaughtered (in thousands) at slaughterhouses, 1980-2025. From the statistical database of the Swedish Board of Agriculture
Animal category/species 1980 1985 1990 1995 2000 2005 2010 2015 2020 2021 2022 2023 2024 2025
Cattle >1 year 574 584 523 502 490 433 425 406 420 400 401 410.45 414.82 375.46
Calves <1 year 130 152 70 30 39 33 27 22 13 11 11 10.97 9.95 7.26
Cattle, total 704 736 593 532 529 466 453 428 434 412 412 421.42 424.77 382.72
Sheep 302 328 280 189 202 206 255 256 240 227 227 228.72 201.19 185.77
Pigs 4153 4283 3653 3743 3251 3160 2936 2560 2623 2651 2672 2571.35 2579.13 2598.95
Broilers 40466 36410 38577 61313 68617 73458 78507 95974 110335 115629 112852 109379.89 111467.06 114061.42
Turkeys – – – – – – 495 475 521 528 533 525.83 477.13 445.89
Table 6.5. Quantity of livestock slaughtered (in 1000 tonnes) at slaughterhouses, 1995-2025. From the statistical database of the Swedish Board of Agriculture.
Animal category/species 1995 2000 2005 2010 2015 2020 2021 2022 2023 2024 2025
Cattle >1 year 140 145 131 134 130 139 134 133 136.41 137.89 127
Calves <1 year 3 4 5 4 3 2 2 2 1.75 1.62 1
Total, cattle 143 150 136 138 133 141 136 135 138 139.52 128
Sheep 3 4 4 5 5 5 5 5 4.73 4.17 4
Pigs 309 277 275 264 234 247 253 254 243.44 245.69 250
Broilers 74 90 99 114 140 167 179 172 171.7 181.16 184
Turkeys 1 3 4 3 4 5 5 5 4.73 4.26 4
Table 6.6. Average number of animals per holding 1995-2024. From the statistical database of the Swedish Board of Agriculture.
Animal category/species 1995 2000 2005 2010 2015 2020 2021 2022 2023 2024 2025
Dairy cows 27.2 33.7 46 61.9 81.5 98.3 102 106 110.477009345794 112.971506635441 118
Beef cows 9.2 12 13.8 16.2 17.7 20.6 21 22 21.4502649816551 21.1039316960051 21
Ewes and rams 19.5 24.8 29.2 31.7 31.8 33.2 32 32 31.7638070027674 31.0550825593395 31
Boars and sows 31 63 156 156 186 185 173 175 156.380027739251 153.599216710183 189
Fattening pigs 157 294 471 664 845 945 942 951 990.463953488372 968.48031496063 1011

6.2 Materials and methods, sales of antibiotics

6.2.2 The ATC classification system and defined daily doses (DDD)

Since 1988, the Anatomical Therapeutic Chemical (ATC) and ATCvet classification systems recommended by the WHO are used in Sweden for national drug statistics. For drugs sold for use in humans and to facilitate drug utilisation studies from a medical point of view, the measure defined daily dose (DDD) is used as a unit of comparison in drug statistics. The DDD for a drug is established on the basis of the assumed average dose per day for the drug given to adults for its main indication. If possible, the DDD is given as the amount of active substance. The DDDs are usually equal for all dosage forms of a preparation. The statistical data systems of the Swedish eHealth Agency are upgraded annually according to the recommendations made by the WHO Collaborating Centre for Drug Statistics Methodology in Oslo, Norway. Sales figures are presented as number of DDDs per 1 000 inhabitants per day, which gives an estimate of the proportion of the population daily exposed to a particular drug. This number is a rough estimate and should be interpreted with caution.

All data on the number of DDDs in this report are displayed in the 2025 version of the ATC/DDD index, available at www.whocc.no/atc_ddd_index.

6.2.3 Antibiotic sales in humans

Sales statistics on medications have been monitored and compiled since 1975, initially by the National Corporation of Swedish Pharmacies. The sales are registered as number of DDDs, cash value and number of packages. Outpatient care data include information on the sales of prescribed drugs from all Swedish pharmacies by the prescription survey, running since 1974. The statistical material was until 1995 based on samples of dispensed prescriptions. From 1996, all prescriptions dispensed by pharmacies are included. From 1999, individually packed doses of drugs dispensed e.g. to the elderly are also included in the survey. Recorded data are trade name, quantity, patient fee, total cost, sex and year of birth of the patient. Data can be expressed as DDD per 1 000 inhabitants per day or number of prescriptions per 1 000 inhabitants per year. Inpatient care data include drugs delivered by all hospital pharmacies to the hospital departments (see the section “Completeness of data” below). The sales are expressed as cash value, number of packages and number of defined daily doses.

Following the de-monopolisation of the pharmacy market in Sweden in July 2009, the responsibility for collection of drug statistics was transferred to the core infrastructure supplier for all pharmacies, Apotekens Service. In January 2014, the activities in the state-owned company Apotekens Service were transferred to the Swedish eHealth Agency. The Swedish eHealth Agency aims to contribute to improved health care, improved public health and better caring by pursuing development of a national e-health infrastructure. The agency is also responsible for Sweden’s national drug statistics.

6.2.4 Completeness of data reported to the Swedish eHealth Agency

In Sweden, pharmacies are required by law to report sales statistics to the Swedish eHealth Agency. Concerns have been raised that after the re-regulation of the pharmacy market, the statistics on sales of medical products to hospitals in Sweden is less complete than before. After the re-regulation, regions can choose to manage drug supplies to hospitals independently. If so, the regions are not required to report data to the national database. However, to the best of our knowledge, all regions are currently reporting data to the Swedish eHealth Agency.

6.2.5 Data sources and inclusion criteria

Data on sales of antibiotics in outpatient and inpatient care as well as population data were obtained from the Swedish eHealth Agency during the period of February to March of 2026. For the overall statistics, the data include all antibacterial products marketed in Sweden in the ATC class J01. The data on sales of antibiotics for humans include all sales, even if the antibacterial (J01) is prescribed by a veterinarian. Throughout this report, methenamine is excluded in all displays of J01 as a group. Measures used are defined daily dose per 1 000 inhabitants per day (DDD/1 000 inhabitants per day) and prescriptions per 1 000 inhabitants per year. Every purchase of a drug prescribed in outpatient care is also recorded in the Prescribed Drug Register, maintained by the Swedish National Board of Health and Welfare. This register provides the opportunity to link each prescription to an individual, which makes it possible to study the actual number of individuals or the fraction of the population treated with a specific drug. Thus, some of the data are presented as treated inhabitants per 1 000 total inhabitants per year. Data on the age-adjusted average body weight of the population in Sweden were obtained in 2016 from Statistics Sweden, the agency responsible for official statistics in Sweden. Antibiotic sales to inpatient care are measured in DDD per 1 000 inhabitants per day. The number of DDDs is obtained from the Swedish eHealth Agency.

For antibiotics sold in Sweden on a special license, information regarding strength and package size may be incomplete, preventing proper DDD calculation. Therefore, when data is obtained from the Swedish eHealth Agency in DDD, these products sold on special license are not properly included and usage of certain antibiotics could be underestimated. For most antibiotic classes, this difference is negligible. However, for some antibiotic substances, such as several cephalosporins, this underestimation has a notable effect on data represented in DDD.

6.2.6 Trend analysis

In the report, some general regression models were executed in Chapter 1 - Sales of antibiotics in humans. Time was used as explanatory variable and the outcome was the sales of antibiotics, adjusted for population size in Sweden, data on population provided by the eHealth Agency. The analyses were executed on a basis of a negative binomial distribution.

6.2.7 The Swedish Prescribed Drug Register

Since July 2005, the National Board of Health and Welfare supplies an individual based register on all drugs prescribed and dispensed in outpatient care. The register includes information on the number of individuals treated with at least one course of antibiotics during a specific period, i.e. number of treated inhabitants per 1 000 total inhabitants per year (Inhabitants/1 000/year). It is also possible to follow the number of purchases per person.

6.2.8 Definitions of DDD 2025

Table 6.7. DDD for all antibiotic substances (J01) registered in Sweden in 2025. 

6.3 Material and methods, resistance in bacteria from animals

6.3.1 Isolation and identification of bacteria

Antibiotic resistance as notifiable diseases

ESBL

ESBLAA, ESBLM and ESBLCARBA-producing Escherichia coli were isolated by culture on MacConkey agar (Oxoid) with cefotaxime (1 mg/L) (MacC ctx) and MacConkey agar (Oxoid) with meropenem (0.12 mg/L) (MacC mp) with prior enrichment in buffered peptone water (BPW).

Intestinal samples: In short, 1 g of intestinal content was diluted in 9 ml BPW and incubated at 37°C overnight. From the BPW solution, 10 µl was spread each on a plate of MacC ctx and MacC mp. The plates were incubated overnight at 44°C (MacC ctx) or 37°C (MacC mp). From MacC ctx, up to three lactose positive colonies with morphology typical for E. coli were sub-cultured on MacC ctx and then sub-cultured again on horse-blood agar (5% v/v), after which the isolate was tested for production of tryptophanase (indole). One isolate per sample was selected for susceptibility tests and further tested for ESBL production. Isolates suspected to be Enterobacterales species on MacC mp were sub-cultured on MacConkey agar and then sub-cultured again on horse blood agar. These isolates were species-identified by MALDI-TOF MS and if positive for any Enterobacterales species, the isolate would be tested for antibiotic susceptibility and ESBL production.

Meat samples: In short, 25 g of surface meat was homogenised in 225 ml BPW and incubated at 37°C overnight. From the BPW overnight culture, 10 µl per agar plate was spread on MacC ctx and MacC mp and incubated overnight at 44°C (MacC ctx) or 37°C (MacC mp). From MacC ctx, up to three lactose positive colonies with morphology typical for E. coli were sub-cultured on MacC ctx and then sub-cultured again on horse blood agar (5% v/v), after which the isolate was tested for production of tryptophanase (indole). One isolate per sample was selected for susceptibility tests and further tested for ESBL production. E. coli-like colonies on MacC mp were sub-cultured on MacConkeyagar, and if they were lactose-positive, they were sub-cultured on horse blood agar. Lactose-positive isolates were species-identified by MALDI-TOF MS. Only E. coli was selected for susceptibility tests and tests for ESBL production.

Clinical isolates from cats, dogs and horses were submitted to the Dept. of Animal Health and Antimicrobial Strategies, SVA, as bacterial strains. Isolates were species-identified by MALDI-TOF MS.

MRSA and MRSP

Clinical isolates were species-identified by MALDI-TOF MS and tested for presence of mecA and mecC with PCR (see below, Genotyping). Isolates were susceptibility-tested using microdilution (see below, Susceptibility testing).

Isolation of MRSA from healthy pigs in the EU-harmonised baseline study was performed according to the protocol from the EURL-AR.

Zoonotic pathogens

Salmonella

Salmonella was isolated and identified at the Dept. of Microbiology, SVA or at regional laboratories in accordance with standard procedures. All samples within official control programmes are cultured according to the procedures detailed by the MSRV (ISO 6579-1:2017). Confirmatory identification and serotyping were performed according to the procedures of White-Kauffmann-Le Minor. For certain isolates, the serovar was verified by whole genome sequencing.

Campylobacter

Campylobacter coli from pigs were isolated and identified at the Dept. of Animal Health and Antimicrobial Strategies, SVA. Samples were cultured directly on modified Charcoal Cefoperazone Deoycholate agar (mCCDA) and Butzler selective agar according to Campylobacter EURL-protocol for isolation, identification and storage of Campylobacter jejuni and Campylobacter coli for the EU monitoring of antimicrobial resistance. The plates were incubated at 41.5°C in a microaerophilic environment for 48h. Identification was based on colony morphology and all isolates were species-identified by MALDI-TOF MS. Selection of colonies was equally distributed between the selective agars.

Clinical isolates from animals

Clinical isolates were isolated and identified with accredited methodology following standard procedures at SVA.

Mycoplasma bovis was cultured from PCR positive samples and species-identified with MALDI-TOF and/or genome sequencing.

Indicator bacteria

Escherichia coli

After the initial dilution in BPW and incubation (see screening for ESBL above), 10 µL was spread on MacConkey agar and incubated overnight at 44°C.

Up to three lactose-positive colonies with morphology typical for E. coli were sub-cultured on horse blood agar (5% v/v), after which the isolates were tested for production of tryptophanase (indole). Only lactose- and indole-positive isolates with typical morphology were selected for susceptibility tests.

6.3.2 Susceptibility testing

Microdilution

At SVA, fast-growing aerobic bacteria, Campylobacter and bacteria from fish are tested for antibiotic susceptibility with accredited methodology using dilution methods in cation-adjusted Mueller-Hinton broth (CAMHB) (Difco). Tests are performed following the standards for microdilution of the Clinical and Laboratory Standards Institute (Clinical and Laboratory Standards Institute (CLSI) 2024b). The microdilution panels used are produced by Thermo SCIENTIFIC Trek diagnostics systems (Sensititre) and for Brachyspira spp. the panels are produced by Merlin, Bruker. Different panels are used depending on the bacterial species tested and the purpose of the investigation (monitoring or clinical diagnostics). Minimum inhibitory concentration (MIC) is recorded as the lowest concentration of an antibiotic that inhibits bacterial growth.

Some adaptations from the CLSI standard are employed. For Pasteurella spp. the tests are made by dilution in CAMHB supplemented with 5-10% horse serum, followed by incubation in CO2 at 37°C for 16-18 hours. For testing of A. pleuropneumoniae, dilution in HTM broth was performed followed by incubation in CO2 at 37°C for 18-24 hours. Streptococcus spp. were tested using CAMHB supplemented with 5-10% horse serum followed by incubation at 35°C for 16-18 hours.

Susceptibility of C. jejuni and C. coli were tested according to the CLSI standard M45 Ed3 for fastidious bacteria (Clinical and Laboratory Standards Institute (CLSI) 2015).

Susceptibility of Brachyspira hyodysenteriae and B. pilosicoli was tested by a broth dilution method described by (Karlsson et al. 2003), in tissue culture trays with 48 wells per plate. The wells were filled with 0.5 ml of a suspension of bacteria (1x106-5x106 CFU/ml) in brain heart infusion broth (BHI) with 10% foetal calf serum and incubated in an anaerobic atmosphere at 37°C for four days on a shaker.

Bacteria from fish are tested for antibiotic susceptibility by broth microdilution adapted for aquatic bacteria according to (Clinical and Laboratory Standards Institute (CLSI) 2020a).

Phenotypic confirmatory tests for production of extended spectrum beta-lactamases (ESBLs) in Enterobacterales were performed with and without clavulanic acid in Sensititre EUVSEC2 microdilution panels and interpreted according to EUCAST.

Susceptibility of Mycoplasma bovis was tested with broth microdilution in Mycoplasma broth with Mycoplasma selective supplement-G (Oxoid). The inoculum density was 1x106-5x106 CFU/ml and the inoculum volume 100 µl per well and incubation was performed in CO2 at 37°C for 72 hours.

6.3.3 Genotyping

Suspected index isolates of MRSA and MRSP were confirmed by detection of the mecA or mecC genes, applying real-time PCR as described by Pichon et al. (Pichon et al. 2012). Isolates of Enterobacterales with AmpC phenotypes were subjected to PCR, detecting genes encoding ESBLM(Perez-Perez and Hanson 2002) and ESBLA(Woodford et al. 2006; Fang et al. 2008). Isolates positive in PCR for ESBL-encoding genes, mecA, mecC, phenotypically confirmed as ESBLA or suspected of being ESBLCARBA were subjected to genome sequence analysis.

DNA was extracted from overnight cultures on horse blood agar using EZ1 DNA tissue kit (Qiagen, Halden, Germany), according to the recommendations of the manufacturer. DNA was sent to Clinical Genomics Stockholm, Science for Life Laboratory (Solna, Sweden) for library preparation and paired-end sequencing using Illumina technologies. Reads were trimmed with Fastp v1.1.0 (Chen 2025) and assembled with SKESA v2.4.0 (Souvorov et al. 2018). Assemblies were searched for potential contamination using Kraken2 with the MiniKraken database (Wood et al. 2019).

ESBL-encoding genes and point mutations conferring elevated MIC for third generation cephalosporins were determined using AMRFinder+ v4.2.5 with database version 2026-01-21.1 (Feldgarden et al. 2021) with the species-specific –organism option where applicable, and by using Staramr v0.11.0 (Bharat et al. 2022) with the ResFinder database from September 9th 2025 (Zankari et al. 2012) and the PointFinder database from November 5th 2025 (Zankari et al. 2017), all with the cutoff values ≥98% identity and ≥95% coverage. Spa-typing, a single locus sequence typing method using the polymorphic region X of the spa gene encoding Protein A, was performed on MRSA assemblies using SeqSphere+ v10.5.2 software (Ridom GmbH, Germany, https://spa.ridom.de). Sequence types (ST) were found in MRSA and MRSP assemblies using MLST (Seemann, n.d.) or given STs by submitting data to Public databases for molecular typing and microbial genome diversity (www.pubmlst.org) developed by Keith Jolley (Jolley et al. 2018), sited at the University of Oxford and funded by the Wellcome Trust.

6.3.4 Quality assurance system

Laboratories performing antibiotic susceptibility testing at SVA are accredited according to ISO/IEC 17025:2017 by the Swedish Board for Accreditation and Conformity Assessment (SWEDAC) to perform antibiotic susceptibility tests with microdilution methods. The Dept. of Microbiology is accredited for isolation and identification of animal pathogens and of Salmonella according to the same standard. The Dept. of Animal Health and Antimicrobial Strategies is accredited for isolation of E. coli in the monitoring programme, both ESBL-producing and indicator E. coli.

For susceptibility tests of zoonotic, pathogenic and indicator bacteria, Escherichia coli ATCC 25922, Enterococcus faecalis ATCC 29212, Staphylococcus aureus CCUG 15915 (analogue to ATCC 29213), Actinobacillus pleuropneumoniae ATCC 27090, Trueperella pyogenes CCUG 13230, Acinetobacter baumannii 2012-70-100-69 - EURL 69 (used for control of higher concentrations of cephalosporins and carbapenems), Aeromonas salmonicida subsp. salmonicida CCUG 2116 (analogue to ATCC 14174), Flavobacterium psycrophilum CCUG 35200 (analogue to ATCC 49418), Mycoplasma bovis Donetta PG45T ATCC 25523T and Campylobacter jejuni CCUG 11284 (analogue to Campylobacter jejuni ATCC 33560) were included as quality controls. When testing animal pathogens, relevant control strains were included and evaluated at least once weekly. For testing of Brachyspira, the B. hyodysenteriae type strain B78T ATCC 27164T was used for quality control.

The Dept. of Animal Health and Antimicrobial Strategies participates yearly in two proficiency tests for antibiotic susceptibility testing, one for isolation and antibiotic susceptibility testing and one comparative test for antibiotic susceptibility testing. These are arranged by the European Union Reference Laboratory - Antimicrobial Resistance and as a national ring trial. We also participate in the DTU genomic proficiency test once a year. Likewise, the Dept. of Microbiology participates in proficiency tests concerning isolation and identification of Salmonella and general clinical veterinary bacteriology and susceptibility tests.

6.3.5 Data handling

Records such as source of cultured sample, identification results, antibiotic susceptibility etcetera were registered in a laboratory information management (LIM) system at SVA.

6.3.6 Cut-off values for resistance

For interpretation of MICs from susceptibility testing of zoonotic bacteria (Salmonella and Campylobacter) and indicator bacteria (Escherichia coli and enterococci), epidemiological cut-off values (ECOFFs) issued by EUCAST or values suggested by the European Food Safety Authority are used. For some antibiotics, values based on MIC distributions obtained in Svarm are used.

ECOFFs are used when available also for clinical isolates from animals. When ECOFFs are not available, or the range of concentrations tested precludes use of a recommended value, values based on MIC distributions obtained in Svarm are used, but clinical breakpoints issued by CLSI (Clinical and Laboratory Standards Institute (CLSI) 2024a) or epidemiological cut-offs (ECVs) issued by CLSI (Clinical and Laboratory Standards Institute (CLSI) 2020b) are also taken into consideration.

ECOFFs and ECVs classify isolates with acquired reduced susceptibility as non-wild type. In Svarm, non wild-type isolates are called resistant. This classification is relevant for monitoring purposes, but it should be understood that resistance defined in this manner does not always imply clinical resistance.

6.4 Svarm 2000-2025

The number of isolates of different matrices reported in Svarm since 2000 is available as
Supplementary material on the SVA web page.