Study on the Intervention Mechanism of Fuzheng Touxie Jiedu Huayu Formula on Multidrug-Resistant Klebsiella Pneumoniae Carrying KPC-2 Gene

LIU Tong; LI Yan; XU Hongri; ZHANG Luyao; WANG Baoyu; LIU Yan; LIU Fengyi

Abstract：Objective To investigate the intervention mechanism of Fuzheng Touxie Jiedu Huayu formula(FTJHF)on multidrug-resistant Klebsiella pneumoniae(MDR-KP)carrying the KPC-2 gene,and its synergistic effect and mechanism with ceftazidime.Methods The in vitro antibacterial activity of ceftazidime combined with FTJHF or drug-containing serum was evaluated by broth dilution method and Kirby-Bauer disk diffusion method.Bacterial growth curves and morphological damage were observed using a microplate reader and transmission electron microscopy(TEM).The effect of FTJHF on KPC-2 mRNA expression was detected by RT-qPCR.Results The minimum inhibitory concentration(MIC)of FTJHF alone was 0.5 g/mL,while the drug-containing serum(1×,2×,4×,8×)alone showed no antibacterial activity.However,all serum-ceftazidime combinations reduced the MIC of ceftazidime from 512 μg/mL to 256 μg/mL.Compared with ceftazidime alone,the inhibition zone diameters of 2×,4×,and 8×serum-ceftazidime groups significantly increased,with the 8×group showing the strongest effect(P<0.01).FTJHF directly inhibited bacterial growth,and its combination with ceftazidime further prolonged the lag phase of bacterial growth.TEM revealed that serum-ceftazidime combinations caused severe structural damage to bacteria in a dose-dependent manner.Notably,ceftazidime alone significantly upregulated KPC-2 expression(P<0.001),whereas 2×and 4×serum-ceftazidime combinations downregulated it,with the 4×group being most effective(P<0.001).Conclusion FTJHF synergizes with ceftazidime to inhibit MDR-KP,partially restoring bacterial susceptibility.The mechanism involves downregulation of KPC-2,disruption of bacterial metabolism,and enhancement of ceftazidime-induced structural damage.