Exposing Salmonella Senftenberg and Escherichia coli Strains Isolated from Poultry Farms to Formaldehyde and Lingonberry Extract at Low Concentrations

Abstract

European Union (EU) countries strive to improve the quality and safety of food of animal origin. Food production depends on a good microbiological quality of fodder. However, feed can be a reservoir or vector of pathogenic microorganisms, including Salmonella or Escherichia coli bacteria. Salmonella spp. and E. coli are the two most important food-borne pathogens of public health concern. Contamination with these pathogens, mainly in the poultry sector, can lead to serious food-borne diseases. Both microorganisms can form biofilms on abiotic and biotic surfaces. The cells that form biofilms are less sensitive to disinfectants, which in turn makes it difficult to eliminate them from various surfaces. Because the usage of formaldehyde in animal feed is prohibited in European countries, the replacement of this antibacterial with natural plant products seems very promising. This study aimed to assess the inhibitory effectiveness of Vaccinium vitis-idaea extract against biofilm produced by model Salmonella enterica and E. coli strains. We found that formaldehyde could effectively kill both species of bacterial cells in biofilm, while the lingonberry extract showed some antibiofilm effect on S. enterica serovar Senftenberg. In conclusion, finding natural plant products that are effective against biofilms formed by Gram-negative bacteria is still challenging.

Keywords: Escherichia coli; Salmonella sv. Senftenberg; Vaccinium vitis-idaea; biofilm eradication; formaldehyde; inhibition.

Figure 1

Graph showing the optical density (OD) of biofilm formation by Salmonella Senftenberg and E. coli strains.

Figure 2

The viability of S. Senftenberg strains in biofilms after the application of formaldehyde at the concentrations of 0.02% (A) and 0.2% (B) for 1 and 15 min. Statistically significant results (p ≤ 0.05) of the tested samples compared with the control samples are marked with an asterisk (*); statistically significant differences (p ≤ 0.05) between samples treated with formaldehyde for 1 min and 15 min were noted with a hashtag (#). The experiment was repeated three times.

Figure 3

The viability of E. coli strains in biofilms after the application of formaldehyde at the concentrations of 0.02% (A) and 0.2% (B) for 1 and 15 min. Statistically significant results (p ≤ 0.05) of the tested samples compared with the control samples are marked with an asterisk (*); statistically significant differences (p ≤ 0.05) between samples treated with formaldehyde for 1 min and 15 min were noted with a hashtag (#). The experiment was repeated three times.

Figure 4

Antibiofilm properties of V. vitis-idaea extract in biofilms formed by S. Senftenberg 131 and 132 (A) and E. coli WW01 and CJ01 (B) strains. Statistically significant results (p ≤ 0.05) of the tested samples compared with the control samples are marked with an asterisk (*).