The World Health Organization (WHO) last week updated its list of medically important antimicrobials for use in human medicine, adding new categories based on their importance in human medicine, antimicrobial resistance (AMR) risk, and the potential human health implications of non-human use.
The WHO says the updated list, developed in collaboration with the Food and Agriculture Organization, the United Nations Environmental Programme, and the World Organization for Animal Health, was created to guide international, national, and subnational antimicrobial stewardship efforts and is intended to serve as a reference point for national regulators, policymakers in ministries of health and agriculture, physicians, veterinarians, and food-animal producers.
"Because AMR develops and transfers within and among all sectors, minimizing the risk of emergence and transmission of AMR calls for a One Health approach," the WHO wrote. "To improve the responsible and prudent use of antimicrobial agents—and in particular medically important antimicrobial agents—it is thus essential to decrease their inappropriate use across sectors."
Among the new categories in the updated list is "authorized for use in humans only," which includes drug classes and individual antibiotics that have not been used in food-producing animals and should not be used in food-producing animals in the future. This group includes anti-pseudomonal penicillins; carbapanems; third-, fourth-, and fifth-generation cephalosporins with beta-lactamase inhibitors, sideraphor cephalosporins (cefiderocol), aminoglycosides (plazomicin), and drugs used solely to treat tuberculosis.
The medically important antimicrobials group, which includes drugs used both in humans and food-producing animals, is further divided into "highest priority critically important antimicrobials (HPCIA)," "critically important antimicrobials (CIA)," "highly important antimicrobials," and "important antimicrobials." Antimicrobials in this group were categorized using the WHO Essential Medicines List and AWaRE (Access, Watch, and Reserve) classification system.
Because AMR develops and transfers within and among all sectors, minimizing the risk of emergence and transmission of AMR calls for a One Health approach.
The criteria for inclusion in the first two medically important antimicrobial categories is whether the antimicrobial class is one of the limited available therapies or the sole available therapy to treat serious bacterial infections and if it's used to treat bacterial infections possibly transmitted from non-human sources (such as Salmonella and Escherichia coli). Among the classes categorized as HPCIA are third- and fourth-generation cephalosporins, quinolones, and polymyxins. The CIA category includes aminoglycosides and macrolides.
Another new category, "authorized for use in animals only," includes antimicrobials for which there is no substantial evidence that their use could result in resistance to medically important antimicrobials.
The ultimate aim of the document is to reduce or restrict the use of these drugs in non-human sectors in order to preserve their effectiveness. The WHO says the risk to human health is greatest if the antimicrobials listed as "authorized for use in humans only" are used in non-human sectors, with the risk and impact lessening progressively with use of agents from the other categories.
The WHO says that while use of medically important antimicrobials in food-producing animals is the greatest concern because they are main source of AMR risk to people, use in aquaculture, companion animals, plants, and crops may also pose a risk.