Salmonella-specific phages from captive bearded dragons (Pogona vitticeps) : Temperate traits and temperature-dependent variability in inhibition across isolates

AIMS: Zoonotic infections with Salmonella spp. transmitted from reptiles to humans are an increasing concern due to the growing number of documented cases and the close contact between humans and reptiles. Reptiles, such as bearded dragons (Pogona vitticeps), frequently carry Salmonella enterica asymptomatically as part of their intestinal microbiota.Given the rise of antibiotic-resistant Salmonella strains in reptiles, bacteriophages (phages) may provide a targeted and sustainable alternative for preventing reptile-to-human transmission. METHODS AND RESULTS: Seventeen phages were isolated from ten of eighteen faecal samples collected from bearded dragons. Seven of these phages were selected for further analyses. Host range assays on 41 S. enterica and nine non-Salmonella isolates revealed a narrow spectrum: phages infected up to 63.4% of Salmonella isolates and lysed one non-Salmonella strain. Planktonic killing assays at 25 °C and 37 °C showed pronounced bacterial growth reduction, with 8 of 12 significant inhibitions observed at 37 °C. Phage cocktails generally showed stronger inhibition than individual phages. Electron microscopy and whole-genome sequencing identified six Myovirus-like and one Siphovirus-like phage, all temperate with integrase or transposase genes despite lytic activity. CONCLUSIONS: This study expands knowledge of S. enterica-specific phages from reptiles, detailing host specificity, morphology and genomic features. While in vitro results are promising, in vivo efficacy may be influenced by host physiology, immunity and microbiome interactions. The predominance of temperate phages may limit direct therapeutic use, though low lysogeny rates in related phages and genetic engineering advances may enable future applications.