Monitoring antimicrobial resistance involves sampling bacteria to test their response to different antibiotics. These samples can be taken from healthy animals, i.e. at the slaughterhouse or in meat, or from sick animals, in which case the samples are taken by the vets treating the animals. Only the monitoring of antimicrobial resistance in healthy animals and in meat is harmonised at European level. Several countries, including France, also monitor antimicrobial resistance in sick animals. In France, ANSES is responsible for both monitoring systems. "The systems are complementary," explains Jean-Yves Madec, scientific director for antimicrobial resistance at ANSES. "It’s important to compare the results of each one. Sick animals may be undergoing antibiotic treatment while healthy animals are not, so we can expect to find different levels of antimicrobial resistance between the two animal groups."
Complementary surveillance systems
This comparison was made in a study published in the journal Microorganisms. The study monitored the antimicrobial resistance of Escherichia coli bacteria in four European countries, with particular emphasis on France and Germany. The study highlighted differences in resistance levels, not only between antibiotic types and animal species, but also between countries and their surveillance contexts. The differences in resistance levels between countries can be explained in part by the different ways antibiotics are used. Scientists have shown that trends may differ when comparing surveillance data from healthy and sick animals. For example, resistance to one antibiotic, nalidixic acid, is tending to increase in bacteria from sick chickens but to decrease in healthy chickens, in both France and Germany. This could reflect the fact that pathogenic Escherichia coli strains come into more frequent contact with the antibiotic, thus favouring the development of resistance.
Proposal for a new European network
These results show the need for data relating to both healthy and sick animals. In another publication, ANSES scientists and their colleagues from various European institutes call for a European Antimicrobial Resistance Surveillance network in veterinary medicine (EARS-Vet). Their paper sets out the basics of this network, detailing the possible objectives. It also points out that a network of this type is a realistic possibility, since it could draw upon data gathered by national and European antimicrobial resistance surveillance systems, for both animal and human health. Nevertheless, harmonisation is necessary, given the differences in the criteria and species currently monitored by individual countries.
Other bacteria could also be monitored
Monitoring for antimicrobial resistance could also be improved by expanding it to include other bacteria. Currently, the only bacteria that are monitored regularly are those that can be transmitted from animals to humans, such as Salmonella or Campylobacter, or that are considered to provide a good indicator of the general level of antimicrobial resistance, such as Escherichia coli. However, other bacteria could also benefit from this type of monitoring, such as those responsible for diseases causing significant livestock losses and requiring the use of medication. In a paper published in Frontiers in Veterinary Science, ANSES scientists showed that the national surveillance network Vigimyc, which records cases of mycoplasma infections in ruminants, could be linked to the monitoring of antimicrobial resistance for this group of bacteria. Scientists were able to detect trends in the antimicrobial resistance of the different mycoplasma species collected through the Vigimyc network. However, the implementation of large-scale surveillance would also require harmonisation of monitoring methods and the criteria for interpreting results.