Gambino, M. | Search bioRxiv

bioRxiv2025

Characterization of a virulent bacteriophage consortium targeting Enterobacteriaceae from inflamed preterm gut mucosa

Preterm infants have a high risk of intestinal inflammation which can progress to necrotizing enterocolitis (NEC). The gut microbial colonization commencing at birth is essential for proper intestinal maturation, but this process is often disrupted in preterm infants, leading to dysbiosis and increased risk of developing NEC. Bacteriophages (phages), viruses that specifically infect bacteria, are an important constituent of the gut microbiome and protects the gut epithelium against invading bacteria. This study aimed to isolate and characterize phages for use as a preventive measure against NEC-associated bacteria. We initially cultured Enterobacteriaceae from ileal mucosa of preterm piglets that exhibited severe NEC-like pathology. We then screened 23 donor fecal samples for inhibition of bacterial growth and isolated a collection of unique phages to use further. The phages were characterized by whole genome sequencing, host receptor binding determination, and immune cell activation in vitro. The final phage collection consisted of ten virulent phages within five genera, representing myovirus, podovirus and siphovirus morphologies. All phages in the collection induced expression of both pro-and anti-inflammatory genes in co-culture with macrophage-like THP-1 cells, but to different extents than Escherichia coli. Ultimately, we selected one phage for a high-dose oral administration to newborn piglets and assessed its infectivity and presence in different gut segments. This intervention did not result in any direct side effects, while both infective phages and signatures of phage DNA were detected in the intestinal content and mucosa. Having characterized a set of rationally selected virulent phages, we support the advancement of phage therapy as a potential protection against NEC.

microbiology↗

bioRxiv2024

Protection against necrotizing enterocolitis by fecal filtrate transfer requires an active donor virome

Necrotizing enterocolitis (NEC) remains a frequent catastrophic disease in preterm infants, but fecal filtrate transfer (FFT) has been identified as a promising prophylactic therapy in preclinical studies. This study examined the importance of the FFT virome viability on gut colonization and NEC occurrence. We established an ultraviolet irradiation-based viral inactivation protocol and demonstrated total loss of infectivity of a viral mock community. Using this protocol, we inactivated an aliquot of sterile-filtered donor feces and compared the response in preterm piglets subjected to experimental NEC induction. Gut pathology and barrier properties were assessed, and bacterial and viral compositions were determined by 16S rRNA amplicon and viral metagenomics sequencing, respectively. Native FFT decreased NEC severity and proinflammatory cytokines, but inactivated FFT (iFFT) completely abolished these effects. Mild side effects in the form of diarrhea manifested earlier in recipients of native FFT than iFFT or controls. A distinct gut colonization pattern of increased viral heterogeneity increased bacterial homogeneity and reduction in pathobionts like Clostridium perfringens and Escherichia was observed in the group receiving native FFT, but not in the iFFT group. The present study uncovered a clear distinction between active and inactivated transferred viromes in the ability to modulate gut colonization after preterm birth and decrease NEC. FFT efficacy is potentially driven by active bacteriophages targeting pathogenic bacteria.

microbiology↗