2.3 AMR, AMU and AMC – what are the differences?

Surveillance of AMR can track changes in bacterial resistance patterns over time in order to inform treatment strategies at a local level, policy decisions at a national level, and global strategy to mitigate the risk of resistant infections and the associated morbidity and mortality in the human, animal and agricultural sectors.

Antimicrobial use (AMU) and antimicrobial consumption (AMC) monitoring are important complementary activities to One Health AMR surveillance (IACG, 2018). It should be noted that AMU and AMC are two closely related concepts, with the terminology often used inconsistently.

Antimicrobial use, or AMU, refers to data on the antimicrobials taken by individual patients (humans or animals). Data are collected at patient level, which allows for a more comprehensive set of data to be gathered, such as information on indication, treatment regimen, route of administration and patient characteristics. In general, the collection of data on antimicrobial use requires more resources but provides additional information on prescribing practices, which is important for guiding antimicrobial stewardship activities.

AMU data centres on monitoring antibiotic use, typically using a metric involving a measured mass of antimicrobials, e.g. milligram (mg), gram (g) or kilogram (kg) of antimicrobials used in the human or animal sector. A raw total of ‘kg of antibiotics’ is therefore a simple and widely used AMU metric, usually with information regarding the indication (e.g. prophylaxis, treatment, etc).

Antimicrobial consumption, or AMC, is defined in terms of the ‘sale’ of antimicrobial medicines. This ‘sale’ of antimicrobials is captured by way of national-level estimates of the quantities of antimicrobials imported and manufactured (and then sold to distributors) in a country. These estimates of antimicrobial ‘sale’ data are mainly derived from import, sales or reimbursement databases. Such data are usually more accessible and can serve as a proxy for the actual use of antibiotics, for which data collection is often more laborious.

AMC data is typically expressed in terms of a defined daily dose (DDD) (WHO, 2020). For all medicines, a WHO resource [Tip: hold Ctrl and click a link to open it in a new tab. (Hide tip)] is maintained that describes what is the expected dosing of that medicine for a 70 kg adult human – this is the defined daily dose. The AMC metrics may then further adjust the DDD quantity by dividing by numbers of individuals and/or periods of time to allow comparisons of consumption levels between populations of different sizes.

An example of a system which captures this type of AMC data in human health is the European Surveillance of Antimicrobial Consumption Network (ESAC-Net). ESAC-Net is a European Centre for Disease Control (ECDC) program which monitors AMC in human health and helps generate the evidence base necessary to promote AMR interventions at both local and national levels. ESAC-Net performs this using The European Surveillance System (TESSy) to collect data on the consumption of antimicrobials intended for systemic use and their related costs in EU/EEA/EFTA countries. The platform collects data in the community and hospital sectors at product level on:

• antibacterials for systemic use
• antimycotics for systemic use
• antimycobacterials
• antivirals for systemic use.

The resulting data are expressed as a number of DDD per 1000 inhabitants per day. AMC DDD data then permit comparisons to be made across local, national and global settings on trends in antimicrobial consumption over time, providing evidence of the impact of educational or regulatory interventions. See the Fundamentals of data for AMR module for more information, specifically the section on ‘drug utilisation methodology’.

An example of a system that captures data on antimicrobials for use in animals is the system designed and used by the OIE. Annually, the OIE invites its members to submit data on the quantities of antimicrobial agents intended for use in animals, using a specifically designed tool. While some countries have advanced systems in place to report sales data at the prescribers’ level, most countries are only able to report sales data at wholesalers’ level and/or import data as declared by custom authorities.

The data collected on quantities of antimicrobial agents used in animals in a country is analysed at OIE central level alongside the corresponding biomass of the animals present in country according to international databases held by the OIE and the FAO, (mg – quantity of antimicrobials used/kg – animal biomass). This allows for comparisons across OIE regions, and for trends in usage of antimicrobials over time to be understood. Section 8.1 discusses the OIE tool in further detail (OIE, 2020).