RESTORING SENSITIVIT

Rendering environmental pathogens sensitive to antibiotics prior to infection

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 Obiettivo del progetto (Objective)

'Antibiotic resistance of pathogens is an accelerating problem and there is an urgent need for new antimicrobial agents. Pharmaceutical companies face numerous obstacles in developing new antibiotics, and therefore a method that will re-sensitize pathogens to well-established antibiotics harbors key advantages. We propose a system that restores antibiotic efficiency by reversing resistance of pathogens. The system utilizes bacteriophages, which possess engineering capabilities and are excellent, protected delivery vehicles. Unlike bacteriophage therapy, the proposed system does not rely on the ability of the phages to kill pathogens, but instead, to deliver genetic constructs to nosocomial pathogens rendering them sensitive to antibiotics prior to host infection. Pathogen-specific phages will be engineered with genes conferring sensitivity to an antibiotic of choice in a dominant fashion and small RNAs that target preferred resistance genes. Including a resistance marker to tellurite, a compound toxic to bacteria, will be used to generate a selective pressure, enriching for pathogens that harbor the phages. Genetic systems and molecular biology techniques will be used to maintain the phage in the pathogens and to ensure their transfer only as a complete unit, thus enhancing efficiency and providing safety measures. The proposed system may be used to render the pathogens susceptible to multiple antibiotics in a single construct. This will dramatically reduces evolvement of simultaneous resistance against multiple antibiotics. Extended treatment with the tellurite and the engineered phage will significantly enrich for antibiotic-treatable pathogens in nosocomial infections and in vast contrast to antibiotics and phage therapy, will change the nosocomial infections more susceptible to the proposed treatment. Moreover, the approach evades phage usage in the patient thus overcoming toxicity issues and neutralization of the phage by the spleen and the immune system.'

Introduzione (Teaser)

European researchers tested a novel approach for rendering drug-resistant bacteria sensitive to antibiotics.

Descrizione progetto (Article)

Antibiotic resistance constitutes a new medical challenge that often prohibits good therapeutic outcome. The design of new antibiotics has proven more difficult than initially envisaged and novel solutions are urgently required.

Scientists of the EU-funded 'Rendering environmental pathogens sensitive to antibiotics prior to infection' (RESTORING SENSITIVIT) project proposed the use of genetically engineered bacterial viruses (bacteriophages) to confer antibiotic sensitivity. Considering that most antibiotic-resistant bacterial strains emerge from mutations in target proteins, reintroduction of the wild-type forms of these proteins through bacteriophages should sensitise bacteria to antibiotics.

Two of these genes, rspL and gyrA, responsible for sensitivity to streptomycin and quinolones, were successfully used to confer multiple drug sensitivity in the pathogens. Additionally, the consortium exploited RNAi technology to generate bacteriophages that upon infection silenced the expression of antibiotic resistance genes in bacteria.

The major challenge faced by the RESTORING SENSITIVIT researchers was to select for the genetically manipulated bacteria. To achieve this, they introduced the tellurite resistance gene alongside their drug sensitivity cassette. Subsequent application of the drug tellurite enriched antibiotic-sensitive pathogens in nosocomial infections.

To counteract the great selective pressure imposed by antibiotics, the scientific team introduced an alternative backup system. They took advantage of a natural bacterial system for maintaining extrachromosomal elements, the toxin-antitoxin system. Incorporation of this system enhanced the effectiveness of the engineered bacteriophages as the pathogens maintained the phage-introduced DNA construct to survive.

RESTORING SENSITIVIT combined these features to generate one construct with sensitising DNA elements, ex vivo selection markers and a plasmid maintenance system. Exploiting the inherent capacity of bacteriophages to infect bacteria along with genetic engineering constitutes a novel approach to resolve antibiotic-resistant bacteria.