QseBC is involved in the biofilm formation and antibiotic resistance in isolated from bovine mastitis.

BACKGROUND

Mastitis is one of the most common infectious diseases in dairy cattle and causes significant financial losses in the dairy industry worldwide. Antibiotic therapy has been used as the most effective strategy for clinical mastitis treatment. However, due to the extensive use of antibacterial agents, antimicrobial resistance (AMR) is considered to be one of the reasons for low cure rates in bovine mastitis. In addition, biofilms could protect bacteria by restricting antibiotic access and shielding the bacterial pathogen from mammary gland immune defences. The functional mechanisms of quorum sensing regulators B an d C (QseBC) have been well studied in model strains; however, whether QseBC regulates antibiotic susceptibility and biofilm formation in clinical strain has not been reported.

METHODS

In this study, we performed construction of the gene mutant, complementation of the mutant, antimicrobial susceptibility testing, antibacterial activity assays, biofilm formation assays, real-time reverse transcription PCR (RT-PCR) experiments and electrophoretic mobility shift assays (EMSAs) to investigate the role of in regulating biofilm formation and antibiotic susceptibility in the clinical strain ECDCM2.

RESULTS

We reported that inactivation of QseBC led to a decrease in biofilm formation capacity and an increase in antibiotic susceptibility of an strain isolated from a dairy cow that suffered from mastitis. In addition, this study indicated that QseBC increased biofilm formation by upregulating the transcription of the biofilm-associated genes and and decreased antibiotic susceptibility by upregulating the transcription of the efflux-pump-associated genes , , , , and . We also performed EMSA assays, and the results showed that QseB can directly bind to the promoter.

CONCLUSIONS

The QseBC two-component system affects antibiotic sensitivity by regulating the transcription of efflux-pump-associated genes. Further, biofilm-formation-associated genes were also regulated by QseBC TCS in ECDCM2. Hence, this study might provide new clues to the prevention and treatment of infections caused by the clinical strains.