Dynamics of multidrug-resistant avian pathogenic E. coli biofilm formation on various surfaces and its dispersion with phage antibiotic synergism

Avian pathogenic Escherichia coli (APEC) infections are persistent threats to the poultry industry, causing substantial economic losses. This study evaluated the biofilm-forming potential of 32 multidrug-resistant APEC (MDR-APEC) isolates on three common poultry industry surfaces: polypropylene (PP), stainless steel (SS), and polyvinyl chloride (PVC). The results indicated that PVC had the highest biofilm formation rate (82%), followed by SS (79%) and PP (64%). Three isolates that showed moderate to strong biofilm formation across all surfaces were tested for minimum inhibitory and bactericidal concentrations (MICs and MBCs) of Gentamicin (GEN) and Ciprofloxacin (CIP) ranging from 2500 µg/ mL to 31.25 µg/ mL. These isolates exhibited resistance, requiring varying doses for a bactericidal effect. Sensitivity to the phages EscoΦA-06, EscoΦA-07, and EscoΦB-01 was confirmed by bacterial lysis assay. Bacterial killing assays revealed that a multiplicity of infection (MOI) of 100 was optimal for antimicrobial activity. Phage‒antibiotic synergy (PAS) tests revealed effective combinations for dispersing biofilms on all surfaces. Although PAS was predominant, some phage‒antibiotic antagonism (PAA) was observed with Ciprofloxacin combinations. Surface-specific analysis revealed that PP enabled the most efficient biofilm dispersal, whereas PVC proved challenging due to strong biofilm formation. This study offers critical insights into optimizing phage‒antibiotic combinations to combat biofilm-associated challenges in controlling MDR‒APECs infections in poultry. Understanding the synergistic and antagonistic interactions between phages, antibiotics, and surface materials can offer a promising avenue for developing effective antimicrobial strategies for poultry management.