Globally, antibiotic-resistant bacteria are becoming more and more of a problem in health care. To be able to stop more resistance from developing, it is important to know where and how antibiotic resistance in bacteria comes from.
In a recent study from Uppsala University, they found that even low concentrations of antibiotics can cause bacteria to become resistant.
In this study, which was published in Nature Communications, the researchers looked into how long-term exposure to low levels of antibiotics leads to the development of bacterial resistance to antibiotics.
When taking antibiotics, a large percentage of the dose is excreted in the urine in an unmodified, active state, which can subsequently enter waterways, lakes, and soil through the waste.
As a result, modest quantities of antibiotics may be present in these environments. Meat production and aquaculture are two industries where substantial quantities of antibiotics are used, with modest doses added to animal feed to speed up the animals’ growth.
This exposes the bacteria in their intestines to low quantities of antibiotics over an extended period of time, and these germs can later infect humans via food, for example.
The researchers reveal in their work that low concentrations of antibiotics also play a significant role in the development of resistance. The study found that bacteria exposed to modest doses of antibiotics developed resistance to antibiotic levels thousands of times higher than the original level to which the bacteria were exposed.
It was also discovered that the resistance-causing changes in bacterial DNA are of a different type than those observed in bacteria exposed to high concentrations.
During the experiment, the bacteria acquired several mutations. Each of these produced low resistance, but when combined, they produced extremely high resistance.
Furthermore, the alterations occurred primarily in genes not previously thought to be typical resistance genes, implying that the number of genes capable of driving resistance development has been considerably underestimated.
“The results are interesting because they show that the very low antibiotic concentrations present in many environments, too, can lead to a high degree of resistance and contribute to the problem of resistance,” added Professor Dan I Andersson, who headed the study.
Source: 10.1038/s41467-018-04059-1
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