Biofilm-forming capability of Salmonella isolates sourced from poultry production and farm environments in Great Britain

<b>Introduction.</b> Poultry and poultry products are commonly implicated in human salmonellosis, making effective <i>Salmonella</i> control in the poultry and allied industries an important public health priority. Several factors have been identified which contribute to <i>Salmonella</i> survival and persistence in the environment, including biofilm formation.<b>Gap Statement</b>. Biofilm-forming capability in <i>Salmonella</i> has previously been under-studied in environmental isolates sourced from some commercial poultry production environments, such as poultry feed mills, hatcheries and duck farms.<b>Aim</b>. This study assessed the biofilm-forming capabilities of 96 <i>Salmonella</i> isolates from the environments of commercial poultry premises in Great Britain: feed mills, hatcheries, chicken farms, turkey farms and duck farms.<b>Methodology.</b> A crystal violet microtitre plate biofilm assay was used at environmentally relevant temperatures of 20 °C and 25 °C under aerobic conditions. Analysis of correlations between the biofilm-forming capability and serovar of isolates, assay conditions and origin was undertaken.<b>Results.</b> Ninety-five of the 96 <i>Salmonella</i> isolates formed biofilms. The influence of incubation temperature varied between isolates but increased significantly after an extended incubation period of 72 h. Isolates originating from different types of commercial poultry environments showed significant differences in biofilm-forming capability. However, as different serovars predominated in the isolate panels from each poultry environment, the influences of serovar versus origin could not be differentiated. The influence on biofilm formation of sample type and/or surface material of origin was not statistically significant. Inter-serovar variation was observed with nine serovars also demonstrating intra-serovar variation, consistent with biofilm-forming capability being strain dependent.<b>Conclusion.</b> This study demonstrates that most <i>Salmonella</i> isolated from poultry environments have strong or moderate biofilm-forming capabilities in microtitre plate assays.