Biofilm-forming capability and drug resistance of extraintestinal pathogenic Escherichia coli isolated from diseased swine

Abstract:

[Background] Porcine extraintestinal pathogenic Escherichia coli (ExPEc), a pathogen seriously endangers the swine industry. However, few studies have reported the biofilm-forming capability and drug resistance of porcine ExPEc. [Objective] To study the relationship between the biofilm-forming capability and drug resistance of 3 ExPEc strains isolated from the diseased swine lung, and provide the reference to prevent and treat the porcine ExPEc disease in the perspective of anti-biofilm formation. [Methods] The optimal conditions and capability for biofilm formation of porcine ExPEc strains were examined using 96-well plate crystal violet staining combined with orthogonal experiments. The morphologic features of the biofilms produced by each strain were observed using a scanning electron microscopy. Biofilm-forming related genes carried by each strain were detected by PCR, as well as the minimum inhibitory concentration (MIC) of antibiotic to porcine ExPEc strains both in floating form and biofilm form were determined by micro-broth dilution method, respectively. [Results] The optimal film-forming conditions of 3 ExPEc strains were not consistent, but showed strong biofilm formation under their optimum conditions, and carried synchronously 10 kinds of biofilm-forming related genes (pgaA, pgaB, pgaC, pgaD, luxS, fimA, hipA, iha, flhC, flhD). Scanning electron microscopic observation showed that the strain SE-1 aggregated to form a flaky biofilm, while both SE-2 and SE-3 strains aggregated to form multi-layered biofilms, and there was obvious space between aggregates. The MIC values of some tested antibiotics to 3 strains growing in a biofilm were 2?32 times higher than those of corresponding planktonic bacteria, and the drug sensitivity changed from sensitivity to medium or resistance. [Conclusion] The result in the study provides a basis for the prevention and treatment of porcine ExPEc infection from the perspective of anti-biofilm formation.