RESUMEN
BACKGROUND: Bacteriophage (phage) therapy is a promising alternative antimicrobial approach which has the potential to transform the way we treat bacterial infections. The antibiotic resistance crisis is driving renewed interest in phage therapy. There are currently no licenced phage therapy medicinal products and phage therapy is used in small but growing patient numbers on an unlicensed basis. OBJECTIVES: This article provides guidelines on the assessment of patient suitability for unlicensed phage therapy for clinicians in the United Kingdom. SOURCES: This article builds on Health Improvement Scotland's recommendation for the consideration of phage therapy in difficult-to-treat infection and the experience of the author group who have collectively assessed the suitability of 30 patients for phage therapy. CONTENT: In the UK, unlicensed medicines, including phages, may be considered to meet special clinical needs. The use of unlicensed medicines is governed by national legislation and local NHS Trust policies. Phages can be used in any NHS Trust and decisions about suitability should be made via existing local clinical management pathways. This article sets out guidelines to support local clinical teams in the assessment of patient suitability for phage therapy. Clinical and microbiological considerations are presented, including allergy and pregnancy.
RESUMEN
Antimicrobial resistance (AMR) is a major problem globally. The main bacterial organisms associated with urinary tract infection (UTI) associated sepsis are E. coli and Klebsiella along with Enterobacter species. These all have AMR strains known as ESBL (Extended Spectrum Beta-Lactamase), which are featured on the WHO priority pathogens list as "critical" for research. Bacteriophages (phages), as viruses that can infect and kill bacteria, could provide an effective tool to tackle these AMR strains. There is currently no "gold standard" for developing a phage cocktail. Here we describe a novel approach to develop an effective phage cocktail against a set of ESBL-producing E. coli and Klebsiella largely isolated from patients in United Kingdom hospitals. By comparing different measures of phage efficacy, we show which are the most robust, and suggest an efficient screening cascade that could be used to develop phage cocktails to target other AMR bacterial species. A target panel of 38 ESBL-producing clinical strains isolated from urine samples was collated and used to test phage efficacy. After an initial screening of 68 phages, six were identified and tested against these 38 strains to determine their clinical coverage and killing efficiency. To achieve this, we assessed four different methods to assess phage virulence across these bacterial isolates. These were the Direct Spot Test (DST), the Efficiency of Plating (EOP) assay, the planktonic killing assay (PKA) and the biofilm assay. The final ESBL cocktail of six phages could effectively kill 23/38 strains (61%), for Klebsiella 13/19 (68%) and for E. coli 10/19 (53%) based on the PKA data. The ESBL E. coli collection had six isolates from the prevalent UTI-associated ST131 sequence type, five of which were targeted effectively by the final cocktail. Of the four methods used to assess phage virulence, the data suggests that PKAs are as effective as the much more time-consuming EOPs and data for the two assays correlates well. This suggests that planktonic killing is a good proxy to determine which phages should be used in a cocktail. This assay when combined with the virulence index also allows "phage synergy" to inform cocktail design.
