Modern hospitals and antibiotic treatments are not alone to blame for the emergence of drug-resistant strains of bacteria. A new study found that the emergence of some resistant bacteria was influenced by natural selection pressures.
Using analysis and sequencing technologies, scientists have created a graph of the evolution of the bacterium Enterococcus faecalis. It is a common bacterium that can develop antibiotic resistance. Another example of an antibiotic-resistant hospital infection is methicillin-resistant Staphylococcus aureus.
The results, published today in Nature Communications, show that this E. faecalis bacterium has the ability to adapt very quickly to selection pressures. For example, the use of chemicals in agriculture, as well as the development of new drugs that have caused the emergence of different strains of the same bacteria. Because of its widespread distribution, scientists suggest testing people for this type of bacteria on admission to the hospital in the same way as for other superbugs. The goal is to reduce the likelihood of developing and spreading infection in the healthcare system.
Enterococcus faecalis is a common bacterium found in most people in the intestinal tract and does not harm the host. However, when immunity is weakened and enters the bloodstream, it can cause serious complications.
Antibiotic-resistant strains of E. faecalis are more common in hospitals, and it was originally thought that the widespread use of antibiotics and other controls in modern hospitals led to the development of these strains.
In the new study, scientists from the Wellcome Sanger Institute, the University of Oslo and the University of Cambridge analyzed about 2,000 E. faecalis specimens from 1936 to the present. They used bloodstream isolates from patients and stool samples from animals and healthy people.
Using genome sequencing (including chromosomes and plasmids) using Oxford Nanopore technology, the team mapped the evolutionary path of the bacterium. In addition, they created a timeline and a map of the development of its various strains. Including those that are now recognized as resistant to antibiotics.
It turned out that resistant strains appeared earlier than scientists thought. This happened before the widespread use of antibiotics.
The researchers found that farming and early medical practices such as the use of arsenic and mercury influenced the evolution of certain strains. In addition to this, strains similar to the antibiotic-resistant variants that are now threatening hospitals have been found in wild birds. The study showed how successfully this type of bacteria adapts and easily transforms into new strains.