The Two-Component System CpxRA Affects Antibiotic Susceptibility and Biofilm Formation in Avian Pathogenic Escherichia coli

SIMPLE SUMMARY: Avian pathogenic Escherichia coli (APEC) is the main pathogen of colibacillosis and impedes the development of the poultry industry. It is of great significance to study the mechanism of drug resistance in APEC. In this study, we investigated the role of the two-component system CpxRA in APEC. The results showed that cpxRA was involved in bacterial biofilm formation, antibiotic susceptibility, and transcription levels of efflux pump emrKY. Our data suggest that the two-component system cpxRA is indeed involved in APEC resistance. ABSTRACT: Avian pathogenic Escherichia coli (APEC) is one of the common extraintestinal infectious disease pathogens in chickens, geese, and other birds. It can cause a variety of infections, and even the death of poultry, causing enormous economic losses. However, the misuse and abuse of antibiotics in the poultry industry have led to the development of drug resistance in the gut microbes, posing a challenge for the treatment of APEC infections. It has been reported that the CpxRA two-component system has an effect on bacterial drug resistance, but the specific regulatory mechanism remains unclear. In this study, the regulatory mechanism of CpxRA on APEC biofilm formation and EmrKY efflux pump was investigated. The cpxRA knockout strain of E. coli APEC40 was constructed, and the molecular regulatory mechanism of CpxR on biofilms and efflux pump-coding genes were identified by biofilm formation assays, drug susceptibility test, real-time reverse transcription quantitative PCR, and electrophoretic mobility shift assay (EMSA). The results indicated that CpxR can directly bind to the promoter region of emrKY and negatively regulate the sensitivity of bacteria to ofloxacin and erythromycin. These results confirm the important regulatory role of the CpxRA two-component system under antibiotic stress in APEC.