Isolation, characterization and evaluation of a novel phage against Elizabethkingia anophelis.

The rise of multidrug-resistant Elizabethkingia anophelis (E. anophelis) presents a significant public health challenge. Here, we report the isolation, morphological and biological characterization, and genomic analysis of a novel lytic bacteriophage, XANYB1, targeting E. anophelis. XANYB1 was isolated from hospital wastewater in Xi’an, China, using a clinical strain as the host. Transmission electron microscopy revealed that XANYB1 belongs to the order Caudoviricetes, featuring icosahedral heads and long, non-contractile tails. Whole-genome sequencing showed very low similarity to known phages, confirming XANYB1 as a novel bacteriophage. The optimal multiplicity of infection (MOI) was determined, and one-step growth curve analysis indicated a latent period of 30 min and a lysis period of approximately 40 min. XANYB1 remained stable across a broad pH range (3–11), at temperatures up to 50 °C, and in the presence of up to 5% chloroform. Host range analysis showed that XANYB1 lysed 5 of 14 clinical E. anophelis isolates. In a mouse sepsis model, XANYB1 exhibited effective in vivo antimicrobial activity, highlighting its potential as a therapeutic candidate. These findings support the application of XANYB1 in phage therapy against multidrug-resistant E. anophelis infections.