The antibiotic resistance in indicator bacteria that are a natural part of and commonly found in the gastrointestinal tract of healthy animals is seen to reflect the selection pressure caused by the use of antibiotics. Indicator bacteria can maintain a reservoir of resistance determinants (genes) and transfer these determinants to pathogenic bacteria under favourable conditions.
The FINRES-Vet monitoring programme analyses the antibioticl resistance of Escherichia coli isolated from the intestinal canal of food-producing animals (and up to 2013 also of Enterococcus faecalis and Enterococcus faecium). In alternate years the bacteria are isolated from caecal or faecal samples of broiler chickens, cattle, and pigs at slaughter. In 2014, the monitoring of antibiotic resistance was harmonized in the EU, which made the comparison between countries easier. The number of samples taken is proportional to the annual slaughter volume: slaughterhouses involved in the programme are responsible for approximately 90–100 % of the total slaughter volumes in Finland. Samples are taken from animals that originate from different holdings (in the case of cattle and pigs) or from different flocks (in the case of broiler chickens).