A report giving an overview of antimicrobial use and resistance in Denmark has been published by Statens Serum Institute and the National Food Institute.

The Danish Integrated Antimicrobial Resistance Monitoring and Research Program (DANMAP) monitors the use of antimicrobials in humans and animals in Denmark, and the occurrence of antimicrobial-resistant bacteria in animals, people, and foods.

The annual report summarizes results of susceptibility testing of isolates from hospitals, general and veterinary practice, food industry laboratories and the Danish Veterinary and Food Administration.

Pig, cattle and poultry sector

There has been a decreasing trend in the use of antimicrobials in animals since 2013 with 100 tons used in 2018. Three-quarters of all veterinary prescribed antimicrobials are used in the pig sector. Using tetracyclines and colistin in pigs has reduced significantly but the use of macrolides and aminoglycosides has risen.

Overall use for cattle has fluctuated between 12 and 13 tons over the past five years. In 2018, more than two-thirds were to treat cattle older than one year. Antimicrobial use in poultry is low at 1,326 kg but it has more than doubled in the aquaculture industry due to the warm 2018 summer.

“Antimicrobial resistance is a global problem, as resistance in one country can create problems beyond its borders e.g., through the export of food and travel. Therefore, in order to tackle the resistance problem, international measures are needed alongside the effective Danish measures,” said Helle Korsgaard, a senior academic officer from the National Food Institute.

In Denmark, antimicrobials are generally not recommended for the treatment of diarrhea in humans including salmonellosis and campylobacteriosis. If needed, patients should be treated with macrolides such as azithromycin and erythromycin. Campylobacteriosis is the top cause of bacterial gastroenteritis with an estimated 40-60,000 foodborne infections per year. A total of 4,546 lab-confirmed cases were reported last year.

Around one-third of Campylobacter infections are travel-associated. The most common source of domestically acquired cases in poultry meat. Cattle are also important and transmission happens through meat, unpasteurized milk, the environment, and direct contact.

Salmonella and Campylobacter data

The level of azithromycin resistance in Salmonella Typhimurium isolates from humans was less than 1 percent, and 5 percent in Danish pork. No erythromycin resistance was found in Campylobacter jejuni isolates from animals or human patients.

Resistance to quinolones remained the most common in Campylobacter jejuni from broilers, cattle, and humans. Around one-third of isolates of animal origin and domestically acquired human cases were resistant to ciprofloxacin, whereas 83 percent of travel-associated human isolates were ciprofloxacin-resistant.

Tetracycline resistance in Campylobacter jejuni from broilers increased significantly from 2017 to 2018 and this coincided with a rise among the human isolates of domestic origin. Resistance to tetracycline and ciprofloxacin also increased in isolates from broilers.

Salmonella Typhimurium and Salmonella Derby were the most prevalent serotypes isolated from Danish pigs and pork. About two-thirds of the Salmonella Typhimurium isolates were monophasic and a similar pattern was observed among the human Salmonella Typhimurium isolates. There were high levels of resistance to tetracycline, ampicillin, and sulphonamide. About half of all Salmonella isolated from Danish pigs and pork were Salmonella Derby, where lower levels of resistance were observed.

Among human cases, resistance to fluoroquinolones remained high among Salmonella Typhimurium isolates from travel versus isolates from cases acquired in Denmark. Resistance to third-generation cephalosporins and carbapenems was very low in Salmonella Typhimurium from human cases and not found in Salmonella isolates from Danish pigs and pork.

E. coli findings

Prominent changes in resistance in indicator E. coli from food-producing animals were a reduction in multidrug-resistance in isolates from broilers and pigs and an increase in fully susceptible isolates from pigs compared to previous years.

The imported chicken meat was more likely to contain E. coli producing extended-spectrum beta-lactamases (ESBLs) and AmpC beta-lactamases (AmpCs) than Danish broilers and broiler meat.

Methods found at least one ESBL- or AmpC-producing bacterium in 15 percent of the packs of Danish-produced chicken meat and 46 percent of imported chicken included in the study.

“Chicken meat sold in Denmark does not appear to be a major source of bloodstream infections in humans, which are caused by ESBL- or AmpC-producing E. coli bacteria,” said Professor Rene Hendriksen from the National Food Institute.

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