Antimicrobial resistance (AMR) happens when bacteria, viruses, fungi or parasites change so that the medicines used to treat them no longer work. One Health is the approach that tackles AMR across human health, animal health, food and the environment together, because resistant microbes and resistance genes move freely between them.
AMR is not only a hospital problem. Antibiotic use on farms, contaminated food, poor sanitation and hospital or pharmaceutical waste all play a part, which puts microbiologists, food safety professionals, vets, infection control teams and QA staff on the same side.
What AMR is, and how bacteria resist
Resistance is a property of the microbe, not the patient: a person does not become resistant, the bacteria they carry do. Resistance arises by mutation or by acquiring genes from other bacteria, and antimicrobial use then selects for resistant strains. Some bacteria are intrinsically resistant, for example Gram-negative bacteria to vancomycin, which cannot cross their outer membrane.
The main acquired mechanisms are:
- Enzymes that destroy the drug: beta-lactamases break the beta-lactam ring of penicillins and cephalosporins. Extended-spectrum beta-lactamases (ESBLs), such as CTX-M types, inactivate third-generation cephalosporins. Carbapenemases, such as KPC, NDM, OXA-48, VIM and IMP, also hydrolyse carbapenems, leaving few options.
- Efflux pumps: membrane proteins pump the drug out, sometimes affecting several classes at once.
- Target change: MRSA carries mecA, encoding an altered penicillin-binding protein (PBP2a), and DNA gyrase mutations reduce fluoroquinolone binding.
- Reduced permeability: Gram-negative bacteria can lose or alter outer membrane porins, slowing drug entry.
Resistance genes often sit on plasmids, transposons and integrons that move between bacteria by conjugation, transformation or transduction. The plasmid-borne colistin resistance gene mcr-1, first reported from China in 2015 in isolates from animals, meat and people, showed how quickly a gene can cross sectors.
How resistance spreads between sectors
- Humans: inappropriate prescribing, self-medication, weak infection control in hospitals, and travel.
- Animals: antibiotics used for treatment, prevention or, where still allowed, growth promotion in livestock, poultry and aquaculture.
- Food: resistant bacteria on raw meat, poultry, eggs, seafood and fresh produce, spread further by kitchen cross-contamination.
- Environment: untreated sewage, hospital and farm effluent, manure on fields and effluent from antibiotic manufacturing.
The One Health approach
One Health recognises that the health of people, animals and the environment is linked. For AMR, the Quadripartite organisations, WHO, the Food and Agriculture Organization (FAO), the World Organisation for Animal Health (WOAH, formerly OIE) and the UN Environment Programme (UNEP), coordinate global action.
In practice, it means shared surveillance data, joint investigations and policies that do not simply shift the problem from one sector to another. Restricting human antibiotic use while ignoring farm use will have limited effect.
Global and national frameworks
The WHO Global Action Plan on Antimicrobial Resistance, adopted by the World Health Assembly in 2015, has five objectives: improve awareness and understanding; strengthen surveillance and research; reduce infection through sanitation, hygiene and infection prevention; optimise antimicrobial use in human and animal health; and build the case for sustainable investment in new medicines, diagnostics and vaccines.
WHO launched GLASS, now the Global Antimicrobial Resistance and Use Surveillance System, in 2015 so countries can report standardised resistance and use data through their national systems.
The WHO AWaRe classification
AWaRe groups antibiotics into Access (first- or second-choice drugs with lower resistance potential, such as amoxicillin), Watch (higher resistance potential, for specific indications, such as ciprofloxacin and ceftriaxone) and Reserve (last-resort drugs for multidrug-resistant infections, such as colistin). Countries use it to monitor whether prescribing is shifting towards Access drugs.
India, Kerala and the GCC
India launched its National Action Plan on AMR (NAP-AMR) in 2017 with a One Health structure, and Kerala became the first state to publish its own plan, the Kerala Antimicrobial Resistance Strategic Action Plan (KARSAP), in 2018. GCC states have also developed national action plans aligned with the WHO plan. Targets and responsible agencies differ, so check the current plan with your national health, agriculture and environment authorities.
For food, the Codex Code of Practice to Minimize and Contain Foodborne Antimicrobial Resistance (CXC 61-2005, revised 2021) and the Guidelines on Integrated Monitoring and Surveillance of Foodborne AMR (CXG 94-2021) give authorities a common framework.
Drivers, sectors and actions
| Driver | Sector | Action |
|---|---|---|
| Unnecessary antibiotic prescribing | Human health | Stewardship programmes, guidelines, AWaRe-based monitoring |
| Antibiotics sold without prescription | Human health, pharmacy | Enforce prescription-only rules, public awareness |
| Hospital transmission | Human health | Hand hygiene, screening, isolation, environmental cleaning |
| Routine preventive or growth-promotion use | Animal health | Veterinary oversight, vaccination, farm biosecurity |
| Resistant bacteria on raw food | Food | Hygienic slaughter, thorough cooking, cross-contamination control |
| Untreated sewage and effluent | Environment | Wastewater treatment, controls on manufacturing discharge |
| Weak laboratory capacity | All sectors | Quality-assured AST, resistance detection, reporting to surveillance |
Stewardship and the role of laboratories
Antimicrobial stewardship means the right drug, dose, route and duration, and only when needed. Hospital programmes use prescribing guidelines, prospective audit and feedback, a review once culture results are available, de-escalation and IV-to-oral switch.
Laboratories make stewardship possible. They need quality-assured antimicrobial susceptibility testing to current CLSI or EUCAST standards, reliable ESBL and carbapenemase detection, selective reporting that steers prescribers to Access drugs, and cumulative antibiograms. Food and veterinary labs monitor indicator E. coli and pathogens such as Salmonella and Campylobacter.
Food businesses contribute through supplier approval, hygiene and cooking controls, and by asking suppliers about responsible antibiotic use on farms.
Worked example: a farm-to-hospital AMR investigation in Kerala
A district hospital laboratory in Kerala sees more community urinary tract infections caused by ESBL-producing E. coli than in previous quarters. The infection control team notes that several patients live near a cluster of broiler farms and chicken shops.
A district One Health team of health, animal husbandry, food safety and environment officers agrees a sampling plan:
- Patient isolates from the hospital laboratory, handled under its confidentiality rules.
- Faecal and litter samples from participating farms, with antibiotic use records.
- Retail chicken from local shops.
- Water from drains and a stream receiving farm and shop waste.
Isolates undergo AST, and a referral lab sequences a selection. Several human, chicken and farm isolates carry the same CTX-M gene on similar plasmids, although the bacterial strains differ.
The team is careful: shared genes show a connection between sectors but do not prove the direction of transmission. Actions follow anyway, because they reduce risk in every direction: veterinary review of farm antibiotic use, ending non-therapeutic use, better biosecurity and vaccination, handwashing facilities and hygiene training in chicken shops, proper waste disposal, stewardship for community UTI prescribing, and repeat sampling after six months.
Common mistakes
- Treating AMR as only a hospital or prescribing problem.
- Reporting resistance genes without phenotypic AST, or running AST without quality control.
- Using outdated breakpoints after CLSI or EUCAST revisions.
- Inferring the direction of transmission from gene similarity alone.
- Investigating one sector and ignoring the others.
Key takeaway: AMR arises in microbes, is selected by antimicrobial use and spreads between people, animals, food and the environment. Only a One Health response, with stewardship, infection prevention, quality-assured labs and shared surveillance, can slow it.
Frequently Asked Questions
What is the main cause of antimicrobial resistance?
Resistance develops naturally, but its rise is driven mainly by the misuse and overuse of antimicrobials in people, animals and agriculture, which selects for resistant microbes. Poor infection control, inadequate sanitation, contaminated food and environmental pollution then help resistant bacteria and their genes spread between people, animals and the environment.
What is One Health in AMR?
One Health is an approach that treats human, animal and environmental health as connected. For AMR, it means health, veterinary, agriculture, food and environment sectors share surveillance data, investigate together and coordinate action, because resistant bacteria and genes move between them. WHO, FAO, WOAH and UNEP promote it through their Quadripartite collaboration.
What is the difference between ESBL and carbapenemase?
Both are beta-lactamase enzymes. ESBLs break down penicillins and most cephalosporins, including third-generation drugs such as ceftriaxone, but usually not carbapenems. Carbapenemases can also break down carbapenems, which are often used to treat ESBL infections. Carbapenemase producers are therefore harder to treat and a high priority for detection and infection control.
How can food businesses help reduce AMR?
Food businesses can approve suppliers that use antibiotics responsibly, apply good hygiene and cooking controls, prevent cross-contamination between raw and ready-to-eat foods, and train staff in handwashing. These steps reduce the spread of resistant bacteria to consumers, alongside regulatory monitoring of foodborne resistance by the competent authority.
Next steps
To strengthen the infection prevention side of AMR control, explore our Infection Prevention and Control Essentials course. If genomic surveillance interests you, Bioinformatics and Genomics Essentials introduces the tools used to track resistance genes.
Related reading: next-generation sequencing explained, WHO 5 Moments for hand hygiene and foodborne pathogens: sources, symptoms and control. Want guidance on your next course? Speak to a counsellor.
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