Hypervirulent community-associated MRSA clones such as Staphylococcus aureus (S. aureus) USA300 drive rapidly progressive necrotizing pneumonia with high morbidity and limited therapeutic options. Bacteriophage K (phage K) is a well-characterized lytic phage active against S. aureus, but its efficacy is limited by restricted host range and the emergence of bacterial resistance. Here, we subjected phage K to experimental evolution on S. aureus USA300 to select an adapted variant with enhanced bactericidal properties. Wild-type phage K and the evolved derivative, designated phage KJ25, were compared using growth inhibition assays, time-kill kinetics, genomic differences and transcriptomic analyses of the bacterial response to infection. Efficacy was evaluated in an in vitro A549 lung epithelial cell infection model and ex vivo murine precision-cut lung slices (PCLS).Phage KJ25 exhibited significantly improved killing of USA300, achieving faster bacterial reduction and sustained suppression of regrowth. Genomic analysis identified a function-impairing mutation in gene gp102, encoding a predicted DNA-binding protein implicated in transcriptional regulation. RNA sequencing revealed that KJ25 infection of USA300 induced a slower and less disruptive host transcriptional takeover than wild-type phage K. Importantly, in both A549 cells and PCLS model, phage KJ25 markedly reduced bacterial burden while preserving lung tissue integrity, supporting its therapeutic potential.Collectively, these findings highlight the value of experimental evolution for tailoring therapeutic phages and support phage adaptation as a promising strategy for developing interventions against multidrug-resistant S. aureus.
Swanti Schapp, P. Seibold, Yasmina Reisser et al.· Emerging Microbes and Infect...· 0 citations
Biomaterial‐associated infections (BAIs) and insufficient early cellular response remain critical challenges for orthopedic implants. We introduce a comprehensive study that bridges current knowledge gaps by examining an early‐stage antimicrobial effect on the clinically relevant alloy Ti–6Al–4V. It combines pathogenic strains with parallel osteoblast assays and tilted‐view SEM analysis to obtain a qualitative understanding of the adhesion mechanisms. Detailed physicochemical characterization revealed a progressive increase in nanoscale roughness and oxide layer thickness, accompanied by selective Al/V depletion and pronounced hydrophilization. To evaluate biological responses, we used standardized in vitro models with Staphylococcus aureus, Staphylococcus epidermidis, and Escherichia coli. Bacterial adhesion was quantified by SYTO9 staining, a GFP‐expressing strain as a viability control, and SEM imaging. Nanostructured (Rq ≤ 40 nm) surfaces significantly reduced early bacterial attachment compared to polished nanoflat controls. In parallel, osteoblast‐like SaOs‐2 cells showed stable adhesion and spreading, confirmed by phalloidin/DAPI staining and LDH cytotoxicity assay. Together, these results demonstrate that NaOH‐etched Ti–6Al–4V surfaces can impair early microbial adhesion based on physical action and preserve osteoblast compatibility. By integrating advanced materials characterization with microbiological and cell biological assays, we provide a framework for topography‐driven surface design toward infection‐resistant orthopedic implants that support favorable early osteoblast–surface interactions.
Sadaf Khalatbarizamanpoor, Adrian G. Nowotnick, Stephanie Lippmann et al.· Small Science· 0 citations