Depression of biofilm formation and antibiotic resistance by sarA disruption in Staphylococcus epidermidis

AIM： To study the effects of disruption of sarA gene on biofilm formation and antibiotic resistance of Staphylococcus epidermidis （ S. epiderrnidis）. METHODS： In order to disrupt sarA gene, the double- crossover homologous recombination was applied in S. epiderrnidis RP62A, and tetracycline resistance gene （tet） was used as the selective marker which was amplified by PCR from the pBR322 and inserted into the locus between sarA upstream and downstream, resulting in pBT2ΔsarA. By electroporation, the plasmid pBT2ΔsarA was transformed into S. epiderrnidis. Gene transcription was detected by real-time reverse transcription-PCR （RT-PCR）. Determination of biofilm was performed in 96-well flat-bottomed culture plates, and antibiotic resistance was analyzed with test tube culture by spectrophotometry at 570 nm respectively. RESULTS： A sarA disrupted strain named S. epiderrnidis RP62AΔsarA was constructed, which was completely defective in biofilm formation, while the sarA complement strain RP62AΔsarA （pHPS9sarA） restored the biofilm formation phenotype. Additionally, the knockout of sarA resulted in decreased erythromycin and kanamycin resistance of S. epiderrnidis RP62A. Compared to the original strain, S. epiderrnidis RP62AΔsarA had an increase of the sensitivity to erythromycin at 200-400 μg/mL and kanamycin at 200-800 μg/mL respectively. CONCLUSION： The knockout of sarA can result in the defect in biofilm formation and the decreased erythromycin and kanamycin resistance in S. epiderrnidis RP62A.