Antimicrobial resistance patterns and biofilms resurgence ability of Escherichia coli associated with commercial layer chicken farms in Sri Lanka

This study aims to understand antimicrobial resistance (AMR) associated with planktonic and biofilm-forming bacteria in Sri Lankan chicken industry. Planktonic or biofilm-forming Escherichia coli were isolated from different sources in layer chicken farms and their AMR profiles were determined. Minimum inhibitory concentrations (MICs) of selected antibiotics were quantified against planktonic E. coli isolated from water. Minimum biofilm inhibitory/eradication concentrations (MBIC/MBEC) of tetracycline were determined for biofilm E. coli. Faecal E. coli demonstrated highest resistance to tetracycline (64 % of isolates). Biofilm-derived planktonic E. coli showed greater resistance to antibiotics than planktonic E. coli (75 % vs 62.5 %). The MBIC and MBEC of tetracycline in E. coli biofilm phenotype were significantly greater than MIC of planktonic phenotype of the same isolate (P < 0.05). This study highlights the importance of eliminating biofilms in chicken industry as biofilm-forming bacteria isolated from drinkers demonstrated a significantly greater AMR and can act as a source of AMR dissemination.