E. coli bacteria are found naturally in large quantities in our intestines. These bacteria do not normally cause disease, but there are several strains that can result in diarrhoea. In serious cases, they can also cause peritonitis and septicaemia.

The faeces of 128 Swedish infants were analysed in the studies underlying the thesis. The results show that 21% of E. coli strains in these infants ™ gut flora were resistant to at least one type of antibiotic. Even children who had never been given antibiotics had resistant bacterial strains in their intestines.

This is a growing problem, and it ™s serious even when ordinary harmless bacteria develop resistance, as these genes can be transferred to more harmful bacteria, says microbiologist Nahid Karami.

Many had thought that resistant bacteria would disappear if the use of antibiotics were to be reduced, but the thesis shows that E. coli strains carrying resistance genes are just as good at colonising the gut for long periods as sensitive strains.

Our research suggests that there ™s little cost to the bacteria from carrying a resistance gene, and this presumably means that this resistance will be retained for a long time by the bacteria in our gut flora even if we stop using antibiotics, says Karami.

Bacteria have a natural ability to absorb and transfer resistance genes to other bacteria. The study discovered two cases of such transfers between E. coli strains found simultaneously in a child ™s intestines. The first was in an infant who was treated with penicillin, and the second in an infant who was not treated with antibiotics.

Our results suggest that the transfer of resistance genes in the gut flora may be very common, which makes the resistance issue much more serious, as genes can easily be transferred from bacteria in the normal flora to more harmful bacteria, says Karami.

sahlgrenska.gu.se/

In addition, the method could be used one day in gene therapy. It may be possible to replace damaged proteins that cause severe diseases with genetically engineered proteins, and to control these proteins' activity levels in a precise manner by giving appropriate doses of the drug. Another potential future application is in agricultural genetic engineering. The method might make it possible, for example, to create genetically engineered plants in which the precise timing of fruit ripening would be controlled using a substance that increases the activity of proteins responsible for ripening. Moreover, numerous proteins are used in industrial processes, as biological sensors and in other applications. The possibility of controlling these applications “ strengthening or slowing the rate of protein activity in an immediate and reversible manner “ can be of great value.

Prof. Mordechai Liscovitch's research is supported by the Nella and Leon Benoziyo Center for Neurological Diseases; La Fondation Raphael et Regina Levy; and the Estate of Simon Pupko, Mexico. Prof. Liscovitch is the incumbent of the Harold L. Korda Professorial Chair of Biology.

The Weizmann Institute of Science in Rehovot, Israel, is one of the world's top-ranking multidisciplinary research institutions. Noted for its wide-ranging exploration of the natural and exact sciences, the Institute is home to 2,600 scientists, students, technicians, and supporting staff. Institute research efforts include the search for new ways of fighting disease and hunger, examining leading questions in mathematics and computer science, probing the physics of matter and the universe, creating novel materials, and developing new strategies for protecting the environment.

weizmann.ac.il/