Inactive luxS influence on biological characteristics of O1, O2 and O78 serotypes isolates in avian pathogenicity Escherichia coli

Abstract:

[Objective] LuxS/AI-2-type quorum sensing participates in regulation of bacterial biological properties by AI-2, which is synthesized by the enzymes LuxS (encoded by luxS). The aim of this study is to elucidate luxS effects on biological characteristics of different serotypes in Avian Pathogenic Escherichia coli (APEC).[Methods] The biological characteristics of 3 APEC strains, including APECO₁ (serotype O₁), DE17 (serotype O₂) and E940 (serotype O₇₈) and their luxS mutant strains were analysed by growth curve, biofilm-producing, rdar morphology, bacterial motility and sensitivity to antibiotics.[Results] luxS knockout, eliminating AI-2 formation, had no influence on bacterial growth, but significantly decreased biofilm-producing in E940 and APECO₁ (P<0.05), without effect on DE17. Results of rdar morphology indicate that the APECO₁ strain showed remarkable change in rdar morphology compared with luxS mutant, but no change in DE17 and E940. Moreover, deletion of luxS lead to decreasing the motility of APECO₁ and DE17, but no influence on E940 strain. The transcriptional levels of fliG and fliI were significantly decreased in APECO1, DE17 and E940 (P<0.05). Furthermore, results of drug-resistance indicate that luxS inactivation caused APECO₁ resistant to cefepime, amikacin, and sensitive to chloramphenicol. luxS inactivation also caused E940 strain sensitive to chloramphenicol, but no significant effect on drug-resistance of DE17 strain.[Conclusion] LuxS plays a significant role in regulation of biological properties in APEC.