Staphylococcus aureus is responsible for difficult-to-treat bone and joint infections (BJIs). This is related to its ability to form biofilm and to be internalized and persist inside osteoblasts. Recently, bacteriophage therapy has emerged as a promising option to improve treatment of such infections, but data on its activity against the specific bacterial lifestyles presented above remain scarce. We evaluated the activity of a combination of three bacteriophages, recently used for compassionate treatment in France, against S. aureus HG001 in a model of staphylococcal biofilm and a model of osteoblasts infection, alone or in association with vancomycin or rifampin.

Up to 15% of patients infected by SARS-CoV-2 present severe forms requiring hospitalisation in intensive care units and which are associated with high mortality. The prevalence of bacterial infections in these patients is not well established and more data are needed to guide empiric antibiotic therapy and improve patient outcomes. In this prospective multicenter study, we assessed bacterial co-infections identified in culture from 99 French patients infected by SARS-Cov-2 and hospitalized in intensive care units. We concomitantly evaluated the value of the use of an innovative molecular diagnostic technologies, the BioFire® FilmArray® Pneumonia Panel plus (FA-pneumo) assay, to early identify these co-infections in these patients and the concordance with conventional culture. We showed that a bacterial co-infection was detected in 15% of patients based on conventional culture. S. aureus and H. influenzae were the most prevalent pathogens. The sensitivity of FA-pneumo compared to culture was 100%. Conversely, the specificity varied between 88.4 and 100% according to the pathogen and our results highlighted that 60.5% of bacterial targets reported using this assay were not recovered by culture; 76.9% of discordant results corresponded to bacteria belonging to commensal oral flora and/or reported with ≤ 10 ⁵ copies/mL of bacterial nucleic acids. Based on its excellent sensitivity, the FA-pneumo assay is useful to rule out bacterial co-infections in the context of severe SARS-CoV-2 infection and avoid the inappropriate prescription of antibiotics. However, positive tests should be interpreted carefully taking into consideration DNA bacterial load, all clinical and biological signs.

Phage-derived therapies comprise phage therapy and the use of phage-derived proteins as anti-bacterial therapy. Bacteriophages are natural viruses that target specific bacteria. They were proposed to be used to treat bacterial infections in the 1920s, before the discovery and widespread over-commercialized use of antibiotics. Phage therapy was totally abandoned in Western countries, whereas it is still used in Poland, Georgia and Russia. We review here the history of phage therapy by focusing on bone and joint infection, and on the development of phage therapy in France in this indication. We discuss the rationale of its use in bacterial infection and show the feasibility of phage therapy in the 2020s, based on several patients with complex bone and joint infection who recently received phages as compassionate therapy. Although the status of phage therapy remains to be clarified by health care authorities, obtaining pharmaceutical-grade therapeutic phages (i.e., following good manufacturing practice guidelines or being “GMP-like”) targeting bacterial species of concern is essential. Moreover, multidisciplinary clinical expertise has to determine what could be the relevant indications to perform clinical trials. Finally “phage therapy 2.0” has to integrate the following steps: (i) follow the status of phage therapy, that is not settled and defined; (ii) develop in each country a close relationship with the national health care authority; (iii) develop industrial–academic partnerships; (iv) create academic reference centers; (v) identify relevant clinical indications; (vi) use GMP/GMP-like phages with guaranteed quality bioproduction; (vii) start as salvage therapy; (vii) combine with antibiotics and adequate surgery; and (viii) perform clinical trials, to finally (ix) demonstrate in which clinical settings phage therapy provides benefit. Phage-derived proteins such as peptidoglycan hydrolases, polysaccharide depolymerases or lysins are enzymes that also have anti-biofilm activity. In contrast to phages, their development has to follow the classical process of medicinal products. Phage therapy and phage-derived products also have a huge potential to treat biofilm-associated bacterial diseases, and this is of crucial importance in the worldwide spread of antimicrobial resistance.

Background: Phage therapy a promising antimicrobial strategy to address antimicrobial resistance for infections caused by the major human pathogen Staphylococcus aureus. Development of therapeutic phages for human use should follow pharmaceutical standards, including selection of strictly lytic bacteriophages with high therapeutic potential and optimization of their production process. Results: Here, we describe three novel Silviavirus phages active against 82% of a large collection of strains (n = 150) representative of various methicillin-susceptible and -resistant S. aureus clones circulating worldwide. We also investigated the optimization of the efficiency and safety of phage amplification protocols. To do so, we selected a well-characterized bacterial strain in order to (i) maximize phage production yields, reaching phage titres of 10¹¹ PFU/mL in only 4 h; and (ii) facilitate phage purity while minimizing the risk of the presence of contaminants originating from the bacterial host; i.e., secreted virulence factors or induced temperate phages. Conclusions: In sum, we propose a quality-by-design approach for the amplification of broad-spectrum anti-S. aureus phages, facilitating the subsequent steps of the manufacturing process; namely, purification and quality control.

The worldwide emergence of highly resistant bacteria, such as carbapenemase-producing Enterobacteriaceae, is a major public health concern ([1][1]). Rapid detection of these highly resistant bacteria and distinction of carbapenemase production from other carbapenem resistance mechanisms, especially

Phage therapy is a highly promising approach to address the challenge that is presented by the global burden of antimicrobial resistance. Given the natural specificity of phages, phage susceptibility testing (PST) is a prerequisite for successful personalized therapy, allowing the selection of active phages from large and diverse collections. However, the issue of an easy-to-use and standardized technique remains. In this review, we describe the principles, advantages and drawbacks of two routinely used PST techniques: plaque and growth kinetic assays. These are labour-intensive and time-consuming methods that require automation of one or more steps, including preparation of test panels, incubation, reading and analysis of results. In addition to automation, there is an urgent need to establish a reference method to enable efficient of PST techniques selection of therapeutic phages. We discuss knowledge gaps and parameters that need to be investigated to work towards this goal.