The Synergistic Effect of Mud Crab Antimicrobial Peptides Sphistin and Sph12-38 With Antibiotics Azithromycin and Rifampicin Enhances Bactericidal Activity Against Pseudomonas Aeruginosa.

Jie Liu,Xiaofei Wang,Ke-Jian Wang,Hui Peng,Hua Zhang,Fangyi Chen

doi:10.3389/fcimb.2020.572849

Jie Liu, Xiaofei Wang + Show 4 more

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https://doi.org/10.3389/fcimb.2020.572849

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Abstract

Overuse or abuse of antibiotics has undoubtedly accelerated the increasing prevalence of global antibiotic resistance crisis, and thus, people have been trying to explore approaches to decrease dosage of antibiotics or find new antibacterial agents for many years. Antimicrobial peptides (AMPs) are the ideal candidates that could kill pathogens and multidrug-resistant bacteria either alone or in combination with conventional antibiotics. In the study, the antimicrobial efficacy of mud crab Scylla paramamosain AMPs Sphistin and Sph12−38 in combination with eight selected antibiotics was evaluated using a clinical pathogen, Pseudomonas aeruginosa. It was interesting to note that the in vitro combination of rifampicin and azithromycin with Sphistin and Sph12−38 showed significant synergistic activity against P. aeruginosa. Moreover, an in vivo study was carried out using a mouse model challenged with P. aeruginosa, and the result showed that the combination of Sph12−38 with either rifampicin or azithromycin could significantly promote the healing of wounds and had the healing time shortened to 4–5 days compared with 7–8 days in control. The underlying mechanism might be due to the binding of Sphistin and Sph12−38 with P. aeruginosa lipopolysaccharides (LPS) and subsequent promotion of the intracellular uptake of rifampicin and azithromycin. Taken together, the significant synergistic antibacterial effect on P. aeruginosa in vitro and in vivo conferred by the combination of low dose of Sphistin and Sph12−38 with low dose of rifampicin and azithromycin would be beneficial for the control of antibiotic resistance and effective treatment of P. aeruginosa-infected diseases in the future.

Highlights

Pseudomonas aeruginosa is an opportunistic Gram-negative bacterial pathogen and can cause infections and mass mortality in patients that have cystic fibrosis, AIDS, severe burns, organ transplants, and cancer (Lyczak et al, 2000; Blonder et al, 2004)
As for Sphistin and/or rifampicin treatment, only ∼7.73% and ∼20.06% of the bacterial cells were completely killed by Sphistin and rifampicin, respectively (Figures 1D,E), while when Sphistin is in combination with rifampicin, ∼35.19% of the bacterial cells were completely killed (Figure 1F). These findings indicated that exposure to both Sphistin in combination with azithromycin or rifampicin resulted in the uptake of propidium iodide (PI) by more bacterial cells than Sphistin and these two antibiotics alone, suggesting a significant increase in cell permeability and the synergistic activity of Sphistin in combination with these two antibiotics, especially with the azithromycin
The abuse of antibiotic inevitably leads to the rapid emergence of drug-resistant bacteria including multidrug resistant (MDR) bacteria, and even the extremely drug-resistant (XDR) or totally drug-resistant (TDR) phenotypes worldwide, which have seriously endangered the efficacy of antibiotics and have become a serious threat to human health

Summary

Introduction

Pseudomonas aeruginosa is an opportunistic Gram-negative bacterial pathogen and can cause infections and mass mortality in patients that have cystic fibrosis, AIDS, severe burns, organ transplants, and cancer (Lyczak et al, 2000; Blonder et al, 2004). From 2003 to 2011, the rates of carbapenemresistant P. aeruginosa (CRPA) isolated from patients with hospital-acquired infections in a tertiary care hospital in northeast China were 14.3, 17.1, 21.1, 24.6, 37.0, 48.8, 56.4, 51.2, and 54.1% over time (Xu et al, 2013). In another hospital, First Affiliated Hospital of Nanjing Medical University, in 2008, the resistant rates of P. aeruginosa to cephalosporins (Ceftazidime, Cefotaxime, and Cefepime) were 5.9, 82.4, and 17.6%, respectively, while by the end of 2011, only 4 years passed, those numbers increased to 37.8, 85.7, and 27.8%, respectively (Zhang et al, 2015). Exploration of new antipseudomonal agents is desperately needed to take control of the ubiquitous and acute drug resistance of P. aeruginosa

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