Phage Inhibition of ESBL-Producing E. coli

Five phages (JEP1, 4, 6, 7, and 8) were reported in our previous study to inhibit ESBL-producing E. coli isolates from chicken carcasses (18 (link)). All cesium chloride (CsCl)-purified phages (≥10¹⁰ plaque forming units per milliliter [PFU/mL]) were used in this experiment. ESBL-producing E. coli strains E20, E41, E55, and E59 belonging to phylogroups A, B1, B2, and D, respectively, were isolated from retail raw chicken in our previous study (18 (link)) and routinely cultured at 37°C in Luria Bertani (LB) medium (Difco, NJ, USA). Campylobacter was cultured at 42°C in Mueller-Hinton (MH) medium (Oxoid, Hampshire, UK) under microaerobic conditions (5% O₂, 10% CO₂, 85% N₂). All bacterial strains were stored at −80°C in LB or MH broth with 15% glycerol. The sodium chloride-magnesium sulfate (SM) buffer (100 mM NaCl, 8 mM MgSO₄·7H₂O, and 50 mM Tris·HCl, pH 7.5) was used as the phage buffer.