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Can disinfectants promote antibiotic resistance?
Yes, say researchers – who suspect that disinfectants used in food production may in fact be exacerbating a global public health problem.
According to figures published by the journal Nature, 73 per cent of the world’s antibiotics are used in the production of domestic animals.
They are used primarily for preventive purposes because these animals are kept in confined and unhygienic conditions, but are also administered to promote growth.
The result is that bacteria are becoming increasingly resistant to essential and life-saving antibiotics.
The message comes from researcher Gunhild Hageskal at SINTEF. Together with her colleagues, including Anne Tøndervik, she is currently working in the field of antibiotic resistance, which is currently regarded as one of the biggest threats to global public health.
“We know that resistant microbes can be transmitted from animals to humans via our food and the environment. This interaction is recognised as part of a ‘One Health perspective', acknowledging that all things are interconnected and that the battle to combat resistance must be fought at all levels,” Hageskal says.
A reduction in the use of antibiotics alone is no longer sufficient to combat the global increase in resistant microbes. According to researchers, preventive approaches must be introduced in order to inhibit transmission, with a particular focus on the livestock sector.
Norwegian food is safest
Together with Iceland, Norway can boast at being clearly among the best in the world when it comes to limiting its use of antibiotics in the livestock sector.
It is prohibited in the Norwegian sector to use antibiotics to promote growth or prevent disease. However, you don’t have to look any further than Denmark to find that it is common practice for pigs and other animals to be administered with antibiotics in their feed. According to the researchers, the situation is worse by far in Asia and South America.
As consumers, we should bear this in mind when we buy Argentinian beef, Danish bacon, or Spanish ham. Meat is of course incorporated into a variety of processed products, and even if the label says that the country of origin is Norway, this doesn’t necessarily mean that the animal was reared in Norway.
Resistant microbes, including bacteria and fungi, recognise no national borders. We are currently seeing an increase in infections that are difficult to treat in Norwegian hospitals today.
In 2019, 1.3 million people died because treatment did not work due to antibiotic resistance. Additionally, five million people died from related complications, according to a study published in the scientific journal The Lancet.
Disinfection holds the key
We continue to find unwanted microbes in the Norwegian food production sector. This is why disinfection procedures are a very important part of the production process.
The use of disinfection is crucial to disease prevention and the control of microbial threats in many fields, such as medicine, agriculture, aquaculture, food production, drinking water, and cleaning sectors, as well as personal hygiene.
“The problem is simply that the use of disinfectants can itself cause bacteria to develop resistance to antibiotics,” Anne Tøndervik says.
Some bacteria are even resilient enough to ward off the very agents that are designed to destroy them. These can then reproduce, enabling their descendants to inherit their resistance. Resistance may also develop naturally as a result of genetic mutation.
“We have seen indications that disinfectants can promote resistance and possibly also so-called cross-resistance, which enables bacteria to resist the threats of both antibiotics and disinfectants,” Hageskal says.
It is well known that disinfectants that contain quaternary ammonium compounds, one of the three most common active substances used for disinfection, are able to promote antibiotic resistance.
It is this problem that SINTEF is currently addressing as part of the DisinfectAMR project. Together with research partners at NTNU, SINTEF is looking into the effectiveness of agents used to disinfect poultry and salmon production lines, and whether these may have unwanted side effects in terms of contributing to antibiotic resistance.
In order to compare condition status in Norway with the situation overseas, researchers are working together with the University of Lasi in Romania, where scientists are taking samples from the premises of a local poultry producer.
A major evaluation / Bacteria in the factory
To date, researchers have been focusing on what are known as slaughterhouse processing lines. These conceal many nooks and crannies that are difficult to keep clean, even when premises are washed down and disinfected on a daily basis.
“This is where biofilms are created. Biofilms form thin, slimy layers of microbes that in some cases can be difficult to spot with the naked eye. Biofilms are another piece in the puzzle. They represent the natural habitat of bacteria and are well-known for acting as the cradle of resistance development,” Anne Tøndervik says.
The reason is that bacteria are better protected in the biofilm and can survive disinfection. It is easier for them to exchange genetic elements when many bacteria gather in one place. Biofilm is also involved in 80 per cent of all human infections.
The researchers have collected bacteria from a number of surfaces in poultry and salmon processing lines. To date, they have established a ‘clan assemblage’ of approximately 1,000 bacterial isolates, which are now being studied in detail in laboratories at SINTEF and NTNU. These bacteria are being identified and tested with a number of different disinfectants currently in use in the same processing lines.
“We’re also studying the variety of bacteria in the biofilms in the processing lines – the so-called microbiome – both before and after disinfection in order to see how the disinfection process impacts on bacterial communities across the slaughterhouse,” Hageskal explains.
Resistance can enter the cycle
In the next stage of the project, the genomes in the microbiome will be mapped and analysed. This will give the researchers a clearer picture of which resistance genes are present.
Even if the researchers succeed in destroying a bacterium, the genes that carry the resistance may still be intact and can be transmitted in residual raw materials and wastewater. This is how the snowball keeps on rolling.
“For this reason, it’s important to acquire as much knowledge as possible about how we can remove unwanted bacteria from the production process most effectively,” Hageskal says.
Reference:
Antimicrobial Resistance Collaborators. Global burden of bacterial antimicrobial resistance in 2019: a systematic analysis, The Lancet, vol. 399, 2022. DOI: 10.1016/S0140-6736(21)02724-0
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