Antimicrobial resistance (AMR) describes the rising resistance of common human pathogenic and commensal microorganisms (i.e. bacteria, viruses and parasites) to widely used drugs. Antimicrobials are chemical agents that are able to selectively kill or inhibit the growth of microbes, with antibiotics being selective against bacteria. The vast majority of antibiotics used by humans come from naturally occurring compounds and are often produced by bacteria themselves.
Bacteria have evolved mechanisms to overcome the effects of antimicrobials in their environment, which is best described by the fast Darwinian evolution model: spontaneous mutations in one individual give it a survival advantage over the rest of the population, which are then passed on to the next generations.
Such adaptations can be transmitted to other bacteria by horizontal gene transfer, which allows whole bacterial colonies to quickly develop and spread resistance over a short period of time. However, the growing rise of bacterial resistance to drug treatment is a serious threat to global health security and risks modern medicine as we know it.
One Health approach
The use of antibiotics in the human, animal and environmental sectors is a fundamental factor in the rise of AMR. The discovery of the first widely used antibiotic – penicillin – together with the rapid rise of new generations of antibiotics, has resulted in doctors over-prescribing them in situations where antibiotics have not always been necessary. Another issue is the use of antibiotics in livestock, which is considered to be the primary cause of resistance developing in human pathogens. Additionally, the heavy use of antibiotics in livestock can also be highly detrimental to animal welfare. From an environmental perspective, the extensive use of antibiotics and their entry into the sewage system can have negative impacts on the environment.
Global factors such as climate change, air pollution, and water and soil contamination from heavy metals also puts a high selective pressure on bacteria to adapt and become resistant to these environmental stressors.
The One Health Initiative is an important framework for addressing several issues threatening health, such as AMR. The essence of the One Health approach in tackling AMR appropriately and effectively is that collaborative efforts and partnerships are necessary across the human health, veterinary medicine and environment sectors.
- Kliebsella pneumoniae – resistance to a last line of treatment (carbapenem antibiotics) has been reported in all regions of the world
- Escherichia coli – in many countries, the urinary tract infection in more than half of the patients doesn’t subside upon the treatment with fluoroquinolone antibiotics
- Neisseria gonorrhoea – quinolones (a class of antibiotics) are no longer recommended for the treatment because of ubiquitous high levels of resistance to them
- Enterobacteriaceae – infections caused by strains resistant to carbapenems can only be fought off by use of colistin – the last resort treatment. Resistance to the latter one has been also reported, meaning such infections are currently untreatable