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 2014, the monitoring of antibiotic resistance was harmonized in the EU, which made the comparison between countries easier. In alternate years the bacteria are isolated from caecal samples of slaughtered broilers and pigs, and from time to time from faecal samples of slaughtered cattle. 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) or from different slaughter batches (in the case of pigs and broilers).