3种天然产物联合抗生素对肺炎克雷伯氏菌的协同抗菌作用

Synergistic antibacterial effects of three natural products combined with antibiotics on Klebsiella pneumoniae

为筛选出联合抗生素对肺炎克雷伯氏菌(Klebsiella pneumoniae)具有协同抗菌作用的天然产物,采用药敏纸片法测定肺炎克雷伯氏菌对8种抗生素的耐药性,采用微量肉汤稀释法测定抗生素和3种天然产物的最小抑菌浓度,应用棋盘法分别测定花青素和咖啡酸与抗生素联用对肺炎克雷伯氏菌的抗菌活性,并通过生长曲线评估咖啡酸与抗生素联用的协同抑菌作用。结果表明:肺炎克雷伯氏菌对8种抗生素均耐药,抗生素的MIC值为16~>512μg/mL。花青素和咖啡酸具有较好的抗菌活性,MIC值分别为25μg/mL和1875μg/mL,肉桂醛无抗菌作用,MIC>250μg/mL;花青素与头孢他啶和克林霉素联用对肺炎克雷伯氏菌具有协同抗菌作用,2种抗生素的MIC值降低了4倍,咖啡酸与8种抗生素存在协同作用,抗生素的MIC值降低了8~>4096倍。抗生素与咖啡酸联用的协同抗菌效果优于其与花青素的组合,且咖啡酸与磺胺甲恶唑和氯霉素联合使用能持续抑菌至少24 h。本研究首次报道了咖啡酸与抗生素联用对多重耐药肺炎克雷伯氏菌具有显著协同抗菌作用,表明联合疗法是消减细菌耐药性的一种有效策略。

This study screened out the natural products that have synergistic antibacterial effects on strain Klebsiella pneumoniae when combined with antibiotics.The K-B method was used to determine the drug resistance of strain K.pneumoniae to eight types of antibiotics.The broth dilution method was used to determine minimal inhibitory concentrations(MICs)of antibiotics and three types of natural products.Checkerboard method was used to determine the synergistic antibacterial activities of antibiotics in combination with anthocyanins or caffeic acid against strain K.pneumoniae.The synergistic bacteriostatic effect of the combination of caffeic acid(CA)and antibiotics was evaluated by time-dependent killing curve.The results showed that:The strain K.pneumoniae was resistant to eight types of antibiotics,and completely resistant to sulfamethoxazole(SMZ),clindamycin,chloramphenicol(CHL)and tetracycline;The MICs of antibiotics ranged from 16μg/mL to>512μg/mL;The MICs of anthocyanins and CA were 25μg/mL and 1875μg/mL respectively,which exhibited great antibacterial activities on strain K.pneumoniae,and the MIC of cinnamaldehyde was>250μg/mL,which had no antibacterial effect against strain K.pneumoniae,and anthocyanins enhanced the susceptibility of strain K.pneumoniae to ceftazidime and CHL by reducing 4-fold of the MICs of two antibiotics;CA synergistically enhanced strain K.pneumoniae susceptibility to 8 kinds of antibiotics,and the MICs of antibiotics decreased by 8~>4096 times;It is obvious that the synergistic effect of the combination of caffeic acid with antibiotics is better than that of anthocyanins in combination with antibiotics,and furthermore,CA in combination with SMZ or CHL could inhibit bacteria for at least 24 h.This study for the first time reported that the combination of CA with antibiotics had a significant synergistic antibacterial effect on multidrug resistant strain K.pneumoniae,and showed that combination therapy was an effective strategy to reduce the drug resistance of pathogens.