Antimicrobial resistance is a growing threat to global health. In 2019, it caused over 1.27 million deaths worldwide – and it is projected that antimicrobial resistance (including bacterial resistance to antibiotics) could contribute to 10 million deaths per year by 2050 .
Antibiotics are used to treat bacterial infections such as urinary tract infections and pneumonia. However, their abuse and overuse have contributed to the emergence of bacteria that carry genes that allow them to resist the deadly effects of antibiotics. This leads to infections that are much more difficult to treat.
Antimicrobial resistance is mainly transmitted to humans via contaminated food or water. However, a recent study suggests that this is not the only way resistant bacteria can spread. Air pollution could also lead to the spread of antibiotic resistance, according to researchers from China and the UK.
This is the first study to comprehensively assess the link between increased antibiotic resistance and air pollution worldwide.
The exposure to air pollution
The review analyzed the results of previous studies examining patterns of airborne antibiotic resistance spread over nearly two decades. They looked at 12 research studies conducted in 116 countries – including the UK, US, China, India and Australia. These studies estimated the presence of antibiotic-resistant bacteria or genes in the atmosphere.
The study looked specifically at the most dangerous type of air pollution – PM2.5. This is fine dust with a diameter of 2.5 micrometers – about 3% of the diameter of a strand of human hair. PM2.5 is not visible to the naked eye and is easily inhaled.
The study found that antibiotic resistance increased with increasing levels of PM2.5 in the air. Every 10% increase in PM2.5 levels was associated with a 1.1% increase in antibiotic resistance worldwide and 43,654 deaths from antibiotic-resistant bacterial infections.
The study found that the highest levels of antibiotic resistance were seen in North Africa and West Asia. These areas also had the highest PM2.5 pollution. In comparison, Europe and North America – where PM2.5 levels were lowest on average – also had lower levels of antimicrobial resistance.
The study also reported that even a 1% increase in PM2.5 was associated with an increase in all regions Klebsiella pneumoniae Resistance to multiple antibiotics – including polymyxins, which are antibiotics of last resort. This bacterium typically spreads in hospitals and can cause pneumonia, meningitis, and urinary tract infections.
Although Klebsiella Not being airborne suggests that air pollution can also allow resistant bacteria to thrive and spread throughout the environment.
The study shows that there is a significant link between air pollution and antibiotic resistance. Although the authors did not provide any evidence of a causal relationship between the two factors, they found antibiotic resistance genes in the DNA of bacteria sequenced from air samples. This suggests that PM2.5 could facilitate airborne spread of antibiotic-resistant bacteria and genes.
spread of resistance
This isn’t the first study to show a link between air pollution and antibiotic resistance.
Air pollution has also been shown to be a risk factor for tuberculosis caused by the bacterium Mycobacterium tuberculosis. This bacterium has developed resistance to several antibiotics.
A study in Hong Kong also found a link between outdoor exposure to PM2.5 and tuberculosis. The study found that an increase in PM2.5 concentrations in winter was associated with a 3% increase in tuberculosis cases in the following spring and summer.
However, it is still unclear what underlying mechanisms might allow the spread of antimicrobial resistance in air pollution. It will be important for future studies to investigate this.
From this and other studies, we know that PM2.5 can harbor antibiotic-resistant bacteria or genes that can enter the human body through the airways when we breathe.
We also know from previous studies that antibiotic-resistant bacteria and their genes can be transmitted from person to person via airborne respiratory droplets. Respiratory droplets can be released when sneezing, coughing and even speaking. It’s also possible for a person who has breathed airborne antibiotic-resistant bacteria to pass it on to another person when they cough or sneeze.
Environmental changes caused by air pollution (e.g. increased temperature and humidity) can also facilitate resistant bacteria to thrive. But again, it will be important for researchers to conduct studies to investigate whether this is the case.
It will also be important for researchers to investigate the role of other factors (besides PM2.5) that may contribute to antibiotic resistance. For example, exposure to pollutants, the foods we eat, the use of antibiotics in animals, and environmental disasters.
While we may not know exactly how air pollution contributes to the spread of antibiotic resistance, the connection between the two is clear. Air pollution is also linked to a range of other health conditions – including cardiovascular disease, asthma, poorer lung function and a higher risk of depression.
Given the many harms air pollution is already doing to our health, this study only reinforces the case for urgently improving air quality and reducing pollution around the world.
Manal MohammedLecturer in Medical Microbiology, University of Westminster
This article was republished by The Conversation under a Creative Commons license. Read the original article.