Microbial Delivery of Antimicrobial Peptides for Protection Against Multidrug-Resistant Pathogens

Antibiotics are vital for all modern medicine but the recent era when bacteria killed only in exceptional cases may be coming to an end. There are over 2,000,000 infections resulting in 23,000 deaths from antibiotic-resistant bacteria (ARB) estimated in the US every year, and the trends of increasingly frequent multidrug-resistant pathogens are disconcerting. A strong argument can be made that unless we invest in new antimicrobial technologies, the threat of multi- or, worse, of pan-resistant bacteria may become massive, global and lethal.

Currently, intensive care unit patients, surgery patients, burn patients and cancer patients are at particular ARB infection risk. Whether treated surgically or with radiation or chemotherapy, these patients are more susceptible to infections than healthy individuals. Consequently these patients are routinely treated with antibiotics.

A perfect storm forms when these patients carry ARB or contract ARB during their hospital stay. Administered antibiotics clear the natural flora in the patient’s gastrointestinal (GI) tract, enabling the drug-resistant strains to dominate GI tract colonization. Higher bacterial counts combined with diminished host defenses result in difficult to treat infections and negative clinical outcomes.

In response to this challenge, we develop a new antimicrobial technology against ARB. We modify probiotic bacteria to express and secrete antimicrobial peptides (AMPs). We propose to use this technology to reduce ARB in patient GI tracts. The idea is rather simple: administer recombinant antimicrobial probiotics that compete against ARB and can lower the counts of drug-resistant strains in the gut. Lower counts of ARBs may then tip the balance in favor of patients. The GI tract is often the major reservoir for bacteria, including ARB, to colonize and then spread and infect via the fecal-oral route. If antimicrobial probiotics can safely reduce ARBs in the GI tract, we can envision therapeutic solutions that relieve some of the pressure exerted by ARB on humans.

In this presentation, we will discuss probiotic E. coli Nissle 1917 (EcN) engineered to deliver AMPs targeting vancomycin-resistant Enterococcus (VRE), an opportunistic pathogen that causes thousands of hospital-acquired infections and deaths each year.

We first demonstrate the ability of the probiotic to reduce VR E. faecium and E. faecalis counts in laboratory cultures. Modified EcN eliminates over 99% of VR E. faecium after one hour of co-culture.

We then test the efficacy of our probiotics in reducing intestinal pathogen counts in mice colonized with VRE via oral administration. Mice administered EcN producing AMPs on average exhibited a 10x reduction in E. faecium fecal counts compared to mice administered no probiotic.

Importantly, we demonstrate that this EcN probiotic platform can be readily modified to express alternative peptides targeting a variety of pathogens including Salmonella and uropathogenic E. coli.

Volzing et al., ACS Synth Biol. 2013; 2(11):643-50
Geldart et al., Appl Environ Microbiol. 2015; 81(11): 3889–3897.
Forkus et al., Sci Rep. 2017; 7: 40695.
Geldart et al., Pharmaceuticals (Basel). 2016; 9(4): 60.

Geldart and Kaznessis, Antimicrob Agents Chemother. 2017; AAC.02033-16