Avian pathogenic Escherichia coli (APEC) is responsible for colibacillosis in poultry. E. coli can form biofilms, which facilitate horizontal gene transfer and contribute to the dissemination of antimicrobial resistance. This study aimed to assess the biofilm formation ability of APEC and the influence of temperature variations on this property.
Thirty-four APECs were isolated from diseased chickens (n = 27) and turkeys (n = 7). Biofilm production was assessed according to Laconi et al. (2023). Bacterial suspensions were incubated in microplates at 37°C and 42°C for 24 hours. The analysis was conducted in two biological replicates, each comprising three technical replicates. The optical density (O.D.) of samples (O.D.S) was calculated as the mean of the absorbance of replicates and compared with the mean O.D. of negative control (O.D.NC). The APECs were classified into four classes: non-(O.D.S ≤ O.D.NC); weak (O.D.NC < O.D.S ≤ 2 × O.D.NC); moderate (2 × O.D.NC < O.D.S ≤ 4 × O.D.NC); and strong (O.D.S > 4 × O.D.NC) biofilm producers.
At 37°C, 70.6% (24/34) of APECs were weak biofilm producers, 20.6% (7/34) were moderate, and 8.8% (3/34) were strong, with none classified as non-biofilm producers. The two different temperatures appear to have no significant effect on t APEC's biofilm formation ability, although eight and three isolates exhibited reduced and enhanced biofilm formation ability, respectively, at 42°C compared to 37°C. A similar distribution of biofilm classes was observed between isolates from chickens and turkeys.
Despite being primarily weak biofilm producers, all isolates demonstrated the ability to form biofilms, potentially facilitating the exchange of resistance genes. Future investigations should focus on elucidating the genetic background underlying APEC biofilm-forming ability.
Acknowledgments: This study was co-funded by European Union Project 101136346
Laconi, A., Tolosi, R., Apostolakos, I., Piccirillo, A. (2023). Biofilm formation ability of ESBL/pAmpC-producing Escherichia coli isolated from the broiler production pyramid. Antibiotics, 12(1). https://doi.org/10.3390/antibiotics12010155
