Efficacy of phage therapy in preclinical models of bacterial infection: a systematic review and meta-analysis

Background Antimicrobial resistance of bacterial pathogens is an increasing clinical problem and alternative approaches to antibiotic chemotherapy are needed. One of these approaches is the use of lytic bacterial viruses known as phage therapy. We aimed to assess the efficacy of phage therapy in preclinical animal models of bacterial infection. Methods In this systematic review and meta-analysis, MEDLINE/Ovid, Embase/Ovid, CINAHL/EbscoHOST, Web of Science/Wiley, Cochrane Central Register of Controlled Trials, Cochrane Database of Systematic Reviews, and Google Scholar were searched from inception to Sept 30, 2021. Studies assessing phage efficacy in animal models were included. Only studies that assessed the efficacy of phage therapy in treating established bacterial infections in terms of survival and bacterial abundance or density were included. Studies reporting only in-vitro or ex-vivo results and those with incomplete information were excluded. Risk-of-bias assessment was performed using the Systematic Review Centre for Laboratory Animal Experimentation tool. The main endpoints were animal survival and tissue bacterial burden, which were reported using pooled odds ratios (ORs) and mean differences with random-effects models. The I-2 measure and its 95% CI were also calculated. This study is registered with PROSPERO, CRD42022311309. Findings Of the 5084 references screened, 124 studies fulfilled the selection criteria. Risk of bias was high for 70 (56%) of the 124 included studies; therefore, only studies classified as having a low-to-moderate risk of bias were considered for quantitative data synthesis (n=32). Phage therapy was associated with significantly improved survival at 24 h in systemic infection models (OR 0 center dot 08 [95% CI 0 center dot 03 to 0 center dot 20]; I-2=55% [95% CI 8 to 77]), skin infection (OR 0 center dot 08 [0 center dot 04 to 0 center dot 19]; I-2 = 0% [0 to 79]), and pneumonia models (OR 0 center dot 13 [0 center dot 06 to 0 center dot 31]; I-2=0% [0 to 68]) when compared with placebo. Animals with skin infections (mean difference -2 center dot 66 [95% CI -3 center dot 17 to -2 center dot 16]; I-2 = 95% [90 to 96]) and those with pneumonia (mean difference -3 center dot 35 [-6 center dot 00 to -0 center dot 69]; I-2 = 99% [98 to 99]) treated with phage therapy had significantly lower tissue bacterial loads at 5 +/- 2 days of follow-up compared with placebo. Interpretation Phage therapy significantly improved animal survival and reduced organ bacterial loads compared with placebo in preclinical animal models. However, high heterogeneity was observed in some comparisons. More evidence is needed to identify the factors influencing phage therapy performance to improve future clinical application. Funding Swiss National Foundation and Swiss Heart Foundation. Copyright (c) 2022 The Author(s). Published by Elsevier Ltd. This is an Open Access article under the CC BY-NC-ND 4.0 license.