These nanorobot-like microorganisms are viruses called bacteriophages as they only infect and lyse bacteria. Bacteriophages were discovered in 1915 by Frederick Twort in England, and by Félix d’Herelle in 1917 in France who first applied the discovery to human healthcare to treat infections.
Félix d’Herelle was working at the Pasteur Institute, studying the effect of dysentery on children. Dysentery is an infectious disease caused by the bacteria Shigella inducing diarrhea, which was often deadly at that time. Soon, he found the presence of a microorganism able to kill bacteria in the stool of children. This microorganism was interestingly always found in patients in recovery. He then isolated this microorganism and called them bacteriophages. He used the bacteriophage culture to treat and cure several children in a critical stage.
From then on, phage therapy was applied to treat infections before the discovery of antibiotics. Unfortunately, antibiotics are chemical compounds that can be studied easily, and phages, which are biological, present a riskier alternative. Phages can interact with human membranes, reach the blood vessels, and interact with non-targeted tissue. But until now, there is no proof that they can cause side effects in our body.
Furthermore, a phage infects a specific bacterial species. Phages of interest must be selected and mixed into a cocktail to have a maximum effect, but these cocktails are often unstable and therefore phages are not always kept active. Because of that, the effect of phage treatment is reduced.