Efficacy of Antimicrobial Peptide DP7, Designed by Machine-Learning Method, Against Methicillin-Resistant Staphylococcus aureus.

Rui Zhang,Li Yang,Bailing Zhou,Xingjun Cheng,Mao Lian,Qi Yin,Yaomei Tian,Xueyan Zhang,Zhenling Wang

doi:10.3389/fmicb.2019.01175

Abstract

Antimicrobial peptides (AMPs) provide a promising strategy against infections involving multidrug-resistant pathogens. In previous studies, we designed a short 12 amino acid AMP DP7, using a machine-learning method based on an amino acid activity contribution matrix. DP7 shows broad-spectrum antimicrobial activities both in vitro and in vivo. Here, we aim to investigate the efficacy of DP7 against multidrug resistant Staphylococcus aureus (S. aureus) and reveal the potential mechanisms. First, by measuring the killing kinetics of DP7 against S. aureus and comparing these results with antibiotics with different antimicrobial mechanisms, we hypothesize that DP7, in addition to its known ability to induce cell wall cation damage, can also exert a full killing effect. With FITC-conjugated or biotin-labeled DP7, we tracked DP7’s attachment, membrane permeation and subsequent intracellular distribution in S. aureus. These results indicated that the possible targets of DP7 were within the bacterial cells. Transcriptome sequencing of S. aureus exposed to DP7 identified 333 differentially expressed genes (DEGs) influenced by DP7, involving nucleic acid metabolism, amino acid biosynthesis, cell wall destruction and pathogenesis, respectively, indicating the comprehensive killing efficacy of DP7. In addition, the genome sequencing results of the induced DP7 resistant strain S. aureus DP7-R revealed two-point mutations in the mprF and guaA gene. Moreover, in a murine model for MRSA blood stream infection, intravenously treating mice with DP7 showed a good protective effect on mice. In conclusion, DP7 is an effective bactericide for S. aureus, which deserves further study for clinical application and drug development.

Highlights

The increasing frequency of multidrug-resistant bacterial infections is a rising threat to public health
Three S. aureus strains, the methicillin-sensitive strain ATCC 25923 (MSSA), the methicillin-resistant strain ATCC 33591 (MRSA), the sigma factor B (sigB)-defective strain RN4220 and Escherichia coli (ATCC 25922), as well as the Pseudomonas aeruginosa (PAO1) strain were all obtained from the American Type Culture
Exposing bacteria to DP7 decreased the CFU/ml (DP7 treatment at 2× and 4× minimum inhibitory concentrations (MIC)), and the number of living cells decreased 3 logs within 24 h; the number of bacteria did not increase over 2 h, indicating that DP7 was a bactericide

Summary

Introduction

The increasing frequency of multidrug-resistant bacterial infections is a rising threat to public health. There is an urgent need to develop novel antimicrobial agents against infections induced by multidrug-resistant bacteria. Owing to the broad spectrum of antibacterial activity properties, multiple targets and hardly leading to induce bacterial resistance, AMPs are currently. Efficacy of AMP DP7 Against MRSA under evaluation as a potential defense against multidrugresistant (MDR) pathogens (Fjell et al, 2012; Deslouches et al, 2013). AMPs have been successfully deployed against bacterial infections in clinical and agricultural settings. AMPs could be effective antibacterial agents against MDR bacteria without inducing further spread of antimicrobial resistance, which is a common outcome of the use of traditional antibiotics

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Conclusion