A novel lytic Seuratvirus phage CABI-SEA 2301 with broad host range against multidrug-resistant avian pathogenic Escherichia coli.

Abstract

Multidrug-resistant avian pathogenic Escherichia coli (MDR-APEC) causes high mortality in newborn chickens, leading to significant economic losses for poultry industry worldwide. The present study proposes an effective alternative strategy to control APEC infections by using bacteriophage specific to MDR-APEC. Lytic phage CABI-SEA 2301 isolated from a chicken faecal sample collected at a commercial poultry farm using the double layer agar overlay technique was classified as a novel species in the genus Seuratvirus, subfamily Queuovirinae. Genome sequencing unveiled that the selected phage consisted of a double-stranded DNA molecule with 61,452 base pairs and a GC content of 38 %, with no toxins, virulence, and antimicrobial resistance. Phage CABI-SEA 2301 demonstrated a broad host range, lysing 68 % of 50 MDR-APEC clinical isolates obtained from E. coli lesions at poultry farms. A high adsorption rate to the host was exhibited with 77 % within 10 min. One-step growth analysis showed that phage CABI-SEA 2301 had a latent period of 30 min with a burst size of 522 PFU/cell. Phage-infected MDR-APEC isolate CABI-SEA 2349 at the lowest multiplicity of infection of 0.01 showed a significant decrease in the bacterial growth after 4 h post-infection. Scanning electron microscopy further confirmed abnormal cellular morphology after treatment. Moreover, phage CABI-SEA 2301 could effectively inhibit the bacterial biofilm formation. Interestingly, the phage survived in mimic simulated chicken gastrointestinal conditions (96.67 ± 4.71 %) and revealed good stability under temperature between -80-50 ˚C and pH 4-12. The findings highlight the potential of the phage CABI-SEA 2301 as a biocontrol agent against MDR-APEC in the commercial farms.