Posted: July 5th, 2012 - 10:30am
Source: EFSA Journal 2012;10(6):2742 [64 pp.].

Abstract
Proposals to improve the harmonisation of monitoring and reporting of antimicrobial resistance in Salmonella, Campylobacter coli and jejuni, indicator Escherichia coli andEnterococcus from food producing animals and derived meat by the European Union Member States are presented. In establishing a list of combinations of bacterial species, food-producing animal populations and food products and in setting up priorities for the monitoring of antimicrobial resistance from a public health perspective, the potential exposure of the consumers has been considered as the first variable to be taken into account. As the prevalence of Salmonella is decreasing, monitoring of antimicrobial resistance should be enforced in indicator bacteria. The concept of a threshold is introduced for some animal populations and their derived meat (whose consumption is limited to certain Member States) to determine whether monitoring of antimicrobial resistance should be mandatory. Currently used phenotypic monitoring of antimicrobial resistance in bacterial isolates is to be retained but recommendations are given for broadening the harmonised panel of antimicrobials used for Salmonella,E. coli and Enterococcus spp. with the inclusion of substances that are either important for human health or that can provide clearer insight into the resistance mechanisms involved. The use of microdilution methods for testing is confirmed as the preferred option and this should be accompanied by the application of epidemiological cut off values for the interpretation of microbiological resistance. A two-step testing strategy has been devised to further characterise those isolates of E.coli and Salmonella spp. showing resistance to extended spectrum cephalosporins and carbapenems. Several analytical methods are suggested for monitoring of ESBL/AmpC-producing E.coli.Finally, full support is given to the collection and reporting of data at isolate level, in order to enable more in-depth analyses to be conducted, in particular on the occurrence of multi-resistance.
Summary
Provisions for monitoring of antimicrobial resistance in zoonotic and indicator bacteria in food producing animals and derived meat are laid down in Directive 2003/99/EC. In addition, Commission Decision 2007/407/EC, implementing Directive 2003/99/EC, lays down detailed and harmonised rules for the monitoring of antimicrobial resistance in Salmonella in poultry and pigs. The technical specifications of this Decision are applicable until the end of 2012. This legislative framework has been translated into practical recommendations in two technical specifications documents issued by the European Food Safety Authority in 2007 and 2008 and providing guidance on the harmonised monitoring of antimicrobial resistance in Salmonella, Campylobacter, indicator E. coli and enterococci in several food producing animal categories and derived meat. The implementation of these specifications by the European Union Member States has led to more harmonised and better comparable data on antimicrobial resistance; however, further enhancements are still required.
The European Food Safety Authority received a mandate from the European Commission to assess whether, in light of the experience accrued with the production of the European Union Summary Reports on Antimicrobial Resistance, the latest scientific opinions issued by European Food Safety Authority on the matter on antimicrobial resistance, and the efforts to increase the comparability between the findings from the food and animal sector with those gathered in the humans, there is need to revise existing specifications. This report includes a proposal for the revision of existing legislation and implementing guidance documents. The conclusions are partially built on the proposals and considerations from the recently issued scientific report on the analysis and reporting of data on antimicrobial resistance in the European Union Summary Report.
The evidence from the European Union Summary Reports on Antimicrobial Resistance has shown that guidance issued by the European Food Safety Authority has now mostly been followed by the Member States and has led to the production of more comparable data over the years. This is particularly true for the monitoring ofSalmonella and Campylobacter, whereas for the indicator bacteria data are available for a limited number of Member States with no sign of increase over the past years. With the prevalence of Salmonella becoming increasingly low, thanks to the success of the control measures in place in the European Union Member States, it becomes particularly relevant to use indicator bacteria for the monitoring of trends and occurrence of resistance. As a first measure, it is therefore recommended that monitoring of antimicrobial resistance in E. coli and in the two enterococcal species,Enterococcus faecium and E. faecalis should also become mandatory as it is already for Salmonella and Campylobacter in all major food-producing animal species and their derived meat.
In defining combinations of bacteria/animal/food to become subject to mandatory monitoring, the approach followed was to prioritise potential consumers’ exposure. Contrary to the previous recommendations and in order to obtain more informative and comparable results, sampling should no longer be stratified at the level of the different animal species (e.g. Gallus gallus, cattle, pigs) but should instead take into account the extremely diverse farming practices, including very different use of antimicrobials, that are in use in the different production types. Sampling should therefore be performed at the level of the different animal populations with the aim of collecting data that could be combined with those on exposure to antimicrobials. It is acknowledged that this approach would lead to an increase in the number of samples to be collected, and that this is a resource consuming activity for the Member States. In designing a sample scheme, therefore, special efforts have been made where possible to exploit samples that would be collected under other existing control programmes. Moreover, for those food-producing animal species and their derived fresh meat for which consumption is more specific to certain Member States (e.g. lamb, ducks, geese, goats) a threshold mechanism, calculated on the basis of the animals slaughtered, has been envisaged for the monitoring to become performed consistently in a given Member State. Similarly, for those animal production types that are not aimed at direct consumption and are characterised by lower antimicrobial resistance (e.g. dairy cows, laying hens) it is proposed to have less frequent samplings.
As regards the harmonised set of antimicrobial substances to be used for susceptibility testing, it is noted that the panels currently included in the technical specifications have been broadly used across the Member States and only minor revisions and additions are needed.
In particular, it is proposed to complement the existing panel of antimicrobials forSalmonella and E. coli with colistin and ceftazidime. Inclusion of the former is motivated by its recent and increased importance as a last resort treatment in human medicine; the latter is recommended, in addition to the already included cefotaxime, to improve the possibility of identifying isolates with resistance to extended-spectrum cephalosporins. In order to enhance the monitoring of extended-spectrum β-lactamase-producing bacteria it is also proposed to add a further step for those isolates that exhibit resistance to a third-generation cephalosporin. In these cases, isolates will be tested for resistance to cefoxitin, cefepime, meropenem and to synergy testing with ceftazidime + clavulanic acid and cefotaxime + clavulanic acid. In addition, a third panel of antimicrobial substances recommended (but not mandatory) for testing because of their relevance to public health is also proposed, comprising azithromycin, tigecycline and florfenicol.
As regards Campylobacter, no changes were deemed necessary to the currently recommended panel, whereas for Enterococcus faecium and Enterococcus faecalis it is proposed to complement the panel with the inclusion of the novel antimicrobial substances tigecycline and daptomycin given their importance for human health. In addition, it is proposed to include teicoplanin as a complement to vancomycin and thereby allow for deduction of the presumptive genotype of glycopeptide-resistant enterococci.
As regards the laboratory methodologies, it is confirmed that microdilution is the preferred method and that European Committee on Antimicrobial Susceptibility Testing epidemiological cut-off values should be used as interpretative criteria to define microbiological resistance. The concentration ranges to be used should ensure that both the epidemiological cut-off value and the clinical breakpoint are included so that comparability of results with human data is made possible. Also, in principle, the optimal concentration range should be tested for each substance although for some substances this could be reduced to a minimum range.
The monitoring of antimicrobial resistance in Shiga toxin/verotoxin-producing E.coli is not recommended as a priority. Several analytical methods are suggested for monitoring of extended-spectrum β-lactamase-producing E. coli, each of the methods having advantages and disadvantages. It is recommended that an experimental study the usefulness of these methods for monitoring purposes is carried out.
As regards the best format for the reporting of the data, the recommendations are the same as those from the technical specifications for the collection and reporting of data at isolate based level recently published.