ACTA VETERINARIA ET ZOOTECHNICA SINICA ›› 2019, Vol. 50 ›› Issue (6): 1284-1291.doi: 10.11843/j.issn.0366-6964.2019.06.019

• BASIC VETERINARY MEDICINE • Previous Articles     Next Articles

Regulative Mechanisms of CpxR on the Colistin Susceptibility of Salmonella enterica Serovar Typhimurium through the Colistin Resistance-related Genes pmrB and phoQ

ZHAI Yajun1, LIANG Jun2, WEI Dandan1, SUN Huarun1, PAN Yushan1, WU Hua1, LIU Jianhua1, HU Gongzheng1*   

  1. 1. College of Animal Science and Veterinary Medicine, Henan Agricultural University, Zhengzhou 450002, China;
    2. Zhengzhou Animal Husbandry Bureau, Zhengzhou 450052, China
  • Received:2018-12-10 Online:2019-06-23 Published:2019-06-23

Abstract: To investigate the mechanisms of CpxR regulate the colistin susceptibility of Salmonella enterica serovar Typhimurium (Salmonella Typhimurium). The cpxR-pmrB or cpxR-phoQ co-expressed genes were acquired by overlapping PCR. The pmrB and phoQ single overexpressed strains and cpxR-pmrB or cpxR-phoQ co-expressed strains were constructed in this paper. The minimal inhibitory concentrations (MICs) of colistin for the above strains were measured by the 2-fold serial broth microdilution method. Growth curves were generated by OD600 nm of strains in LB medium and colistin time-kill assay were carried out with survival rate of strains after incubated with different concentrations of colistin. The results showed that the MIC of cpxR overexpressed strain JSΔΔ/pR was dramatically decreased by 93.75% compared with JS which was consistent with the previous study. The MICs for pmrB and phoQ single overexpressed strains JSΔΔ/pB and JSΔΔ/pQ were increased by 300% compared with JS. However, the MICs for cpxR-pmrB or cpxR-phoQ co-expressed strains JSΔΔ/pRB and JSΔΔ/pRQ were decreased by 50% and 75%, respectively. Furthermore, the growth curves showed that unlike the low growth rate of JSΔΔ/pR, the growth rate of JSΔΔ/pB, JSΔΔ/pQ, JSΔΔ/pRB and JSΔΔ/pRQ were slightly lower than JSΔΔ/pHisA. Colistin time-kill assay showed that JSΔΔ/pB and JSΔΔ/pQ was more susceptible than JSΔΔ/pRB and JSΔΔ/pRQ when incubated with increasing concentrations of colistin. In conclusion, the results indicated that CpxR was able to regulate the colistin susceptibility of Salmonella Typhimurium through colistin resistance-related genes pmrB and phoQ.

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