Rational Design of Frontline Institutional Phage Cocktail for the Treatment of Nosocomial Enterobacter cloacae Complex Infections

Abstract Phage therapy is a promising strategy to treat antimicrobial-resistant infections. Currently, phage therapy applications span personalised treatments that are tailored for a given patient’s infection, through to the use of pre-established cocktails of virulent phages against clinically relevant pathogens. However, both approaches face challenges, with personalised phage therapy being time-consuming and requiring a phage match to a patient’s infection, while phage cocktails may not be effective against a patient’s specific strain. The Alfred Hospital in Melbourne, Australia has reported an ongoing outbreak of infections by the Enterobacter cloacae complex (ECC), a group of emerging multidrug-resistant pathogens responsible for considerable morbidity and mortality. Utilising the hospital’s strain collection, built over the last decade, we established an initial three-phage product with 54% ECC coverage that effectively reduced bacterial loads (>99%) in septicaemic mice. We then iteratively improved this product by enhancing phage killing efficiency using phage training and expanded host range through targeted phage isolation against low-coverage ECC strains. This iterative optimisation led to the creation of the product Entelli-02 , containing five well characterised virulent phages that target clinical ECC strains through distinct bacterial cell surface receptors. Importantly, Entelli-02 exhibits broad host coverage (99%) and efficacy (92%) against The Alfred Hospital’s ECC strain collection ( n = 156). We produced this as a therapeutic-grade product, verified and endotoxin unit compliant, ready for use. This approach integrated academic phage research with clinical insights to produce the phage product Entelli-02 as an institution-specific phage cocktail with frontline efficacy and on-demand availability. SUMMARY In brief We developed a phage product containing five phages with frontline potential to address infections caused by multidrug-resistant Enterobacter cloacae complex.