Antimicrobial activity of eugenol against carbapenem-resistant Klebsiella pneumoniae and its effect on biofilms.

A preliminary study found that eugenol expressed an antibacterial activity against Klebsiella pneumoniae. However, the mechanism of action of eugenol against K. pneumoniae still remains unexplored. The aim of this study was to gain further insight into the antibacterial effect of eugenol against carbapenem-resistant Klebsiella pneumoniae (CRKP) and possible mode of action. Here, minimum inhibitory concentration (MIC) of eugenol against CRKP strains was determined using the agar dilution method. Moreover, variations in intracellular ATP concentration, intracellular pH (pHin), membrane potential and membrane integrity were measured to evaluate the effect of eugenol on cell membrane. Besides, changes in cell structure and biofilm formation of CRKP as well as biofilm-associated cell damage were determined using field emission scanning electron microscope (FESEM), transmission electron microscope (TEM) and confocal laser scanning microscopy (CLSM). Finally, gene expression of biofilm-related biosynthesis was investigated. The results showed that MICs of eugenol against four tested CRKP were 0.2 mg/mL. Eugenol damaged the cell membrane of CRKP, as evidenced by decreased intracellular ATP concentration, reduced pHin and cell membrane hyperpolarization, coupled with enhanced membrane permeability. Furthermore, eugenol compromised cell structure and induced loss of intracellular components of CRKP. Additionally, eugenol inhibited biofilm formation and inactivated biofilm CRKP cells. Finally, eugenol presented strong inhibitory effects on biofilm formation and biofilm-associated gene expression, and inactivated CRKP cells growing in biofilms. These findings suggest that eugenol exhibits antimicrobial effect against CRKP strains and could be potentially used to control CRKP-related infections.

Qian W ，Sun Z ，Wang T ，Yang M ，Liu M ，Zhang J ，Li Y ... -  《-》

Antimicrobial and antibiofilm activities of paeoniflorin against carbapenem-resistant Klebsiella pneumoniae.

To evaluate the antimicrobial effect of paeoniflorin against carbapenem-resistant Klebsiella pneumoniae (CRKP). Minimum inhibitory concentration (MIC) of paeoniflorin against CRKP was determined by agar dilution method. Changes in intracellular ATP concentration, intracellular pH (pHin), cell membrane potential and membrane integrity were investigated to assess the influence of paeoniflorin on cell membrane damage. Additionally, alterations in cell structure of CRKP cells and cell damage within biofilms were examined. The results indicated that paeoniflorin was effective against CRKP at MIC of 1·2 mg ml-1 . Paeoniflorin destroyed the integrity of CRKP cell membrane, as was confirmed by decrease of intracellular ATP, pHin, membrane potential, as well as distinctive alteration in cell morphology, resulting in leakage of CRKP intracellular components. Moreover, paeoniflorin displayed a markedly inhibitory influence on biofilm formation of CRKP and inactivated CRKP cells within biofilms. Paeoniflorin shows promise as an effective antibiotic against CRKP with the potential to be an alternative therapeutic agent. This study provides information about the potential use of paeoniflorin to reduce the infection of CRKP in clinical practice and food production.

Qian W ，Zhang J ，Wang W ，Wang T ，Liu M ，Yang M ，Sun Z ，Li X ，Li Y ... -  《-》

Antimicrobial and antibiofilm activities of ursolic acid against carbapenem-resistant Klebsiella pneumoniae.

Qian W ，Wang W ，Zhang J ，Wang T ，Liu M ，Yang M ，Sun Z ，Li X ，Li Y ... -  《-》

A Study of the Virulence Traits of Carbapenem-Resistant Klebsiella pneumoniae Isolates in a Galleria mellonella Model.

Khalil MAF ，Hager R ，Abd-El Reheem F ，Mahmoud EE ，Samir T ，Moawad SS ，Hefzy EM ... -  《-》

Emergence of ceftazidime/avibactam resistance in carbapenem-resistant Klebsiella pneumoniae in China.

The aim was to investigate the activity of ceftazidime/avibactam (CAZ/AVI) against carbapenem-resistant Klebsiella pneumoniae (CRKP) and identify the resistance mechanisms before CAZ/AVI coming to Chinese market. Clinical CRKP isolates were continuously collected from 36 tertiary hospitals in China from 1 March 2017 to 31 July 2017. CAZ/AVI MICs were determined by agar dilution method. CAZ/AVI resistant isolates were submitted to whole genome sequencing. The copy number and relative expression of blaKPC were determined by quantitative PCR. A total of 872 CRKP isolates were collected, and MIC50 and MIC90 of CAZ/AVI were 4 and 8 mg/L. The resistant rate of CAZ/AVI was 3.7% (32/872). Among the resistant isolates, 53.1% (17/32) were metallo-β-lactamase-producing K. pneumoniae (MBL-KP), 40.6% (13/32) were Klebsiella pneumoniae carbapenemase (KPC)-producing K. pneumoniae (KPC-KP) and 6.3% (2/32) produced both MBL and KPC. One of the KPC-KP with high level CAZ/AVI resistance (>128 mg/L) harboured mutated blaKPC-2 (D179Y). In 12 wild-type blaKPC-2 isolates, the relative copy number and expression of blaKPC-2 gene were 2.5-fold and 2.7-fold higher than that in the CAZ/AVI MIC ≤0.5 mg/L group (p < 0.05), and when added avibactam at a fixed concentration of 8 mg/L, 91.7% (11/12) isolates could restore susceptibility. Resistance against CAZ/AVI in CRKP emerged before clinical use of CAZ/AVI in China, although most of the CRKP isolates maintained the susceptibility. MBL production, blaKPC-2 point mutation and high KPC expression played an important role in CAZ/AVI resistance.

Zhang P ，Shi Q ，Hu H ，Hong B ，Wu X ，Du X ，Akova M ，Yu Y ... -  《-》