Predatory bacteria as living antibiotics-where are we now?

Antibiotics have revolutionized modern medicine, but their effectiveness is threatened by the spread of multi- drugresistant bacteria for which there is no available treatment [1-3]. Antimicrobial resistance (AMR), often driven by unnecessary antibiotic use, is a serious, global health and economic threat [4-7]. Of particular concern is the declining antibiotic pipeline with limited antibiotics in development (in both number and diversity) to meet current and anticipated patient demands [8-11]. Moreover, scientific and economic challenges have contributed to many large global pharmaceu Antimicrobial resistance (AMR) is a global health and economic crisis. With too few antibiotics in development to meet current and anticipated needs, there is a critical need for new therapies to treat Gram- negative infections. One potential approach is the use of living predatory bacteria, such as Bdellovibrio bacteriovorus (small Gram- negative bacteria that naturally invade and kill Gram- negative pathogens of humans, animals and plants). Moving toward the use of Bdellovibrio as a 'living antibiotic' demands the investigation and characterization of these bacterial predators in biologically relevant systems. We review the fundamental science supporting the feasibility of predatory bacteria as alternatives to antibiotics.