Abstract
The increasing incidence of tigecycline resistance undoubtedly constitutes a serious threat to global public health. The combination therapies had become the indispensable strategy against this threat. Herein, 11 clinical tigecycline-resistant Klebsiella pneumoniae which mainly has mutations in ramR, acrR, or macB were collected for tigecycline adjuvant screening. Interestingly, ML-7 hydrochloride (ML-7) dramatically potentiated tigecycline activity. We further picked up five analogs of ML-7 and evaluated their synergistic activities with tigecycline by using checkerboard assay. The results revealed that ML-7 showed certain synergy with tigecycline, while other analogs exerted attenuated synergistic effects among tigecycline-resistant isolates. Thus, ML-7 was selected for further investigation. The results from growth curves showed that ML-7 combined with tigecycline could completely inhibit the growth of bacteria, and the time-kill analysis revealed that the combination exhibited synergistic bactericidal activities for tigecycline-resistant isolates during 24 h. The ethidium bromide (EtBr) efflux assay demonstrated that ML-7 could inhibit the functions of efflux pump. Besides, ML-7 disrupted the proton motive force (PMF) via increasing ΔpH, which in turn lead to the inhibition of the functions of efflux pump, reduction of intracellular ATP levels, as well as accumulation of ROS. All of which promoted the death of bacteria. And further transcriptomic analysis revealed that genes related to the mechanism of ML-7 mainly enriched in ABC transporters. Taken together, these results revealed the potential of ML-7 as a novel tigecycline adjuvant to circumvent tigecycline-resistant Klebsiella pneumoniae.
Highlights
Antimicrobial resistance has become one of the greatest global public health challenges
To assess if ML-7 was capable of inhibiting the efflux pump, we explored the effect of ML-7 on the functions of efflux pump by using ethidium bromide (EtBr) as a fluorescent probe
Our findings indicated that ML-7 restored the susceptibility of tigecycline-resistant K. pneumoniae through two pathways: (1) ML-7 could inhibit the functions of efflux pump and lead to the accumulation of tigecycline in bacteria; (2) ML-7 increased DpH and resulted in perturbing the proton motive force (PMF), which subsequently inhibited the functions of efflux pump, decreased the levels of intracellular ATP and resulted in the accumulation of reactive oxygen species (ROS) (Figure 6)
Summary
Antimicrobial resistance has become one of the greatest global public health challenges. In 2019, Centers for Disease Control and Prevention (CDC) listed carbapenem-resistant Enterobacteriaceae as an urgent threat for the public (Centers for Disease Control and Prevention, 2019). Infections caused by carbapenem-resistant Klebsiella pneumoniae (CRKP) have been an urgent concern because it is associated with high mortality and morbidity (Jin et al, 2021). The resistance mechanism of tigecycline in K. pneumoniae is extensively related to the upregulated transcription of acrAB, oqxAB, and macAB efflux pumps, which results from mutations in transcriptional regulator ramR and acrR (Sheng et al, 2014; Zheng et al, 2018). Mutations in rpsJ, which encodes the ribosome S10 protective protein targeted by tetracyclines, are associated with tigecycline resistance (He et al, 2018). Mutations in tet (A), which was another tetracycline efflux pump gene, have been reported to cause resistance to tigecycline (Yao et al, 2018). There is an urgent need to explore alternative strategies against tigecycline-resistant pathogens
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
