Licensed To Kill: Engineering Enzymes to Counter Antibiotic Resistance

Courtesy Photo | Prophylactic activity of engineered EcN against P. aeruginosa infection. (a) Scheme for pre colonization of EcN in the GI tract followed by P. aeruginosa infection. (b) Colonization of EcN was assessed by fecal counting of bacteria as a function of time in animals that received different numbers of cells by oral gavage. (c) The level of P. aeruginosa was tracked over six days after giving 1010 cfu of the pathogen to each group of pretreated mice. (d) Total viable P. aeruginosa cell counts from fecal samples at day six post-infection. The data from two independent experiments are shown (n=5–10). * P<0.01(one-way ANOVA with Bonferroni correction for multiple comparisons). Data are presented in box plots with median as center line, 10 and 90 percent confidence limits, and minimum and maximum values. Graphics from Nature Communications.  

FORT BELVOIR, VA, UNITED STATES

08.22.2017

Courtesy Story

Defense Threat Reduction Agency's Chemical and Biological Technologies Department

Antibiotics are a cornerstone of modern medical treatments for bacterial infections. However, overuse can kill healthy flora in the intestinal tract, which can cause resistant bacterial strains. These resistant strains render normal medical treatments ineffective, putting civilians and warfighters at greater risk when exposed to bacterial illnesses.

An effort funded by the Defense Threat Reduction Agency’s Chemical and Biological Technologies Department and led by William Bentley, Ph.D., from the University of Maryland (UMD), is utilizing synthetic biology to engineer a probiotic to fight antibiotic resistant infections.

The use of probiotics, such as Escherichia coli Nissle 1917, boost host immune functions and protect intestinal barriers against pathogens. Probiotics may also stop the colonization of harmful bacteria in the intestinal tract. Several studies have demonstrated the ability to engineer probiotics for therapeutic use, such as site-specific expression and delivery of biomolecules to target bacterial or viral infections.

Bentley and his team built upon previous work by the National Center for Biotechnology Information (NCBI), in which researchers engineered E. coli to sense and kill Pseudomonas aeruginosa, a multi drug resistant (MDR) pathogen, in vitro. UMD researchers developed a probiotic strain that recently demonstrated efficacy against the pathogen. Utilizing this synthetic biology to engineer new therapeutics to fight MDR infections enhances the Department of Defense’s capability to protect warfighters from MDR pathogens, helping to ensure warfighter health and readiness.

The team has re-engineered the previous ‘sense-kill’ E. coli Nissle to include a gene encoding anti-biofilm enzyme. Referred to as EcN SED, this strain is activated only in the presence of P. aeruginosa. In the in vivo study, mice were administered EcN SED or the respective controls and exposed to the pathogen. P. aeruginosa gut colonization was evaluated at six days post-exposure.

Pretreatment with EcN SED resulted in 98 percent inhibition of P. aeruginosa infections compared with the controls (Figure 2). A low level of protection was observed in the other treatment groups, but the activity was not statistically significant.

A potential drawback to this approach is ensuring proper expression control. To address the concern, Bentley’s group developed a device that controls gene expression and cell behavior by electrically directing redox signaling. Using a simple cellular synthetic circuit regulates the transcription of the genetically modified bacteria by the products of the redox reaction. This could benefit warfighters by allowing MDR’s to be eliminated from the body before they can become deadly.

The bacterial response is quick, reversible and dependent on the amplitude and frequency of the electronic signals. In the future, Bentley envisions a system in which the engineered bacteria are placed in a capsule similar to endoscopy capsules used for videoing the gastrointestinal tract. The capsules will contain a semipermeable membrane allowing the release of the reaction products to treat the infection once detected. The reaction will be initiated remotely, allowing for electronically controlled expression, as well as encapsulating the bacteria to ensure elimination via the intestinal tract. This approach would increase warfighter readiness and protection by ensuring early therapeutic intervention against several MDR pathogens.

Avoiding antibiotic resistance is crucial to ensure the continued health of our civilians and warfighters. DTRA’s work controlling gene expression and cell behavior in EcN SED could play a vital role in protecting healthy intestinal flora and preventing the spread of antibiotic resistant bacteria.

POC: Mr. Dale Taylor; [e-mail]

• Date Taken: 08.22.2017
• Date Posted: 08.22.2017 14:33
• Story ID: 245600
• Location: FORT BELVOIR, VA, US