efe-epaBy Noemí G. Gómez Madrid

Antibiotics are the first line of defense when it comes to fighting infections, but they are not selective and so kill off bacteria indiscriminately. Now, a group of scientists has managed to develop a new kind of antibiotic that can be programmed to tackle only the bad bacteria.

This new antibiotic, whose makers have dubbed a "programmable genetic bomb," also counteracts the build up of resistance; a global problem that the World Health Organization considers will cause some 10 million deaths in 2050.

The drug, which has been tested on living things, has been outlined in Nature Biotechnology magazine by researchers from the Technical University of Madrid (UPM) and Paris' Pasteur Institute.

One of the main drawbacks of antibiotics is that they attack almost all the bacteria in the body indiscriminately, which means they also get rid of ones that are beneficial. This process has led to the creation of multi-resistant bacteria, the UPM said in a statement.

And so there is a need to conduct research into intelligent drugs, Alfonso Rodríguez-Patón, a professor at the department of artificial intelligence at the UPM who is involved in the process, told Efe.

"This research opens a new line in the design and development of custom-made antibiotics, that is, selective ones to attack only the bad bacteria and programmable because they can be designed to attack one type of bacteria or another," the researcher said.

In the same way that probiotics are being developed to regulate gut microbiota, "we have designed programmable 'sentinel bacteria' capable of detecting and killing only the dangerous bacteria without affecting the good bacteria," Rodríguez-Patón added.

And for that, the research team has created something called a "programmable genetic bomb": a protein that is toxic just to bad bacteria.

The toxin travels to the sentinel bacteria and is programmed to activate and kill off only the bad bacteria that it recognizes, whether it is virulent or resistant to antibiotics.

"We can explain it as if it were a grenade, that it's an explosive device with a ring. The grenade only goes off if you pull out the ring and our toxin only goes off if it encounters a bad or resistant bacteria," Rodríguez-Patón said.

"We have programmed sentinel bacteria to prevent the genetic bombing of neighboring bacteria," Rodríguez-Patón added of the process, called "conjugation."

Bacteria have "hairs" that work like syringes, uniting sentinel bacteria with neighboring ones and antibiotics are transmitted via these hairs.

If the "genetic bomb" gets into a bad bacteria it will detect certain molecular signals, such as virulence or resistance to antibiotics, which will activate and kill the bacteria. If the antibiotic gets into a good bacteria, it will not react.

This mechanism of selective antibiotic activation can be programed to fight different resistant bacteria thanks to a molecule called intein, for which the Pasteur Institute has requested a patent.

The effectiveness of these antibiotics has been tested on living organisms, including zebra fish and crustaceans infected with the aquatic bacterium of cholera.

"We've succeeded in having our antibiotic get rid of the virulent and antibiotic-resistant cholera in infected zebra fish and that the rest of the bacteria present in the fish have not been affected and survive," the UPM researcher said.

This is significant, according to Rodríguez-Patón, as cholera affects over one million people every year and in serious cases can lead to death.

In order for these new antibiotics to become a reality, the next step is to test them on mice, Rodríguez-Patón said, adding that although it was too soon to be sure, they could be used to treat multi-resistant bacterial infections in human beings if they pass.

The development was possible thanks to engineers, physicians and microbiologists and is part of the European project Plaswires, headed by Rodríguez-Patón. EFE-EPA