China Animal Husbandry and Veterinary Medicine ›› 2020, Vol. 47 ›› Issue (8): 2603-2614.doi: 10.16431/j.cnki.1671-7236.2020.08.030

• Basic Veterinary Medicine • Previous Articles     Next Articles

Study on Antibacterial Effect of Antimicrobial Peptide NZ2114 Against Streptococcus dysgalactiae Isolated from Bovine Mastitis

ZHANG Qingjuan1,2,3,4, MA Xuanxuan3,4, TENG Da3,4, YANG Na3,4, WANG Xiumin3,4, MAO Ruoyu3,4, HAO Ya3,4, SHAN Yuxue1,2,3,4, LIU He3,4, FAN Huan2, WANG Jianhua3,4   

  1. 1. College of Life Sciences, Tianjin Normal University, Tianjin 300387, China;
    2. Tianjin Animal Science and Veterinary Research Institute, Tianjin 300381, China;
    3. Gene Engineering Laboratory, Feed Research Institute, Chinese Academy of Agricultural Sciences, Beijing 100081, China;
    4. Key Laboratory of Feed Biotechnology, Ministry of Agriculture and Rural Affairs, Beijing 100081, China
  • Received:2020-02-27 Online:2020-08-20 Published:2020-08-15

Abstract: In order to investigate the bactericidal effect and mechanism of Plectasin-derived peptide NZ2114 against Streptococcus dysgalactiae (S.dysgalactiae) isolated from bovine mastitis,the drug resistance and minimum inhibitory concentration (MIC) were tested by broth dilution method,the MIC and the bactericidal kinetics curve in tryptic soy broth (TSB) and ultra-high temperature instantaneous sterilization (UHT) environment were determined for evaluating the antibacterial properties of NZ2114,the morphological changes of S.dysgalactiae treated with NZ2114 were observed by scanning electron microscope (SEM),transmission electron microscope (TEM) and flow cytometer.The effects of NZ2114 on the genomic DNA were further analyzed by gel retardation,fluorescence spectrum and circular dichroism spectrum.The results showed that all S.dysgalactiae were resistant to ofloxacin and tetracycline,but the clinical isolates showed more antibiotic resistance,the values of MIC were only 0.11 to 0.45 μmol/L.NZ2114 had bacteriostatic activity in TSB and UHT milk medium,and reduced the number of S.dysgalactiae colonies by 3 orders of magnitude in a short time (0.5 to 3 h).The results of SEM,TEM and flow cytometer showed that NZ2114 could cause the leakage of S.dysgalactiae content and kill the bacteria.Gel retardation analysis,fluorescence and circular dichroism all showed that NZ2114 could bind to the genomic DNA and destroy DNA.The above results showed that antibacterial peptide NZ2114 had strong bactericidal activity against S.dysgalactiae isolated from bovine mastitis,it could directly affect the genomic DNA and change its secondary structure after destroying the cell membrane.Therefore,antimicrobial peptide NZ2114 was a promising alternative antibiotic for the treatment of mastitis caused by S.dysgalactiae.

Key words: bovine mastitis; Streptococcus dysgalactiae; antimicrobial peptide NZ2114; antibacterial activity; mode of action

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