Xiaochun Chen,1,* Benhong Zhang,2,* Jin He,3,* Xiaohong Rui,4 Tian He,4 Lizhu Zhang,5 Junfeng Bao,6 Yanfei Jing,7 Futao Cao8 

1Department of Laboratory Medicine, Taizhou Second People’s Hospital, Taizhou, People’s Republic of China; 2Department of Laboratory Medicine, Hangzhou Gongshu District Integrated Traditional Chinese and Western Medicine Hospital, Hangzhou, People’s Republic of China; 3Department of Laboratory Medicine, Hangzhou Yuhang Jiamu Nursing Home, Hangzhou, People’s Republic of China; 4Department of Laboratory Medicine, Affiliated Wuxi Fifth Hospital of Jiangnan University, Wuxi, People’s Republic of China; 5Department of Research, Nanxin Pharm, Nanjing, People’s Republic of China; 6Department of Laboratory Medicine, Wuxi Maternal and Child Health Care Hospital, Women’s Hospital of Jiangnan University, Wuxi, People’s Republic of China; 7Department of Function, Affiliated Wuxi Fifth Hospital of Jiangnan University, Wuxi, People’s Republic of China; 8Department of Emergency, Jiangnan University Medical Center, Wuxi, People’s Republic of China

*These authors contributed equally to this work

Correspondence: Yanfei Jing, Department of Function, Affiliated Wuxi Fifth Hospital of Jiangnan University, Wuxi, Jiangsu, 214005, People’s Republic of China, Email tengfeiba0002@163.com Futao Cao, Department of Emergency, Jiangnan University Medical Center, Wuxi, Jiangsu, 214000, People’s Republic of China, Email caofutao999@163.com

Introduction: The emergence of multidrug-resistant Klebsiella pneumoniae (K. pneumoniae) and the decline of effective antibiotics lead to the urgent need for new antibacterial agents. The aim of this study is to investigate the therapeutic effect of antimicrobial peptides against gentamicin-resistant (RT) K. pneumoniae and to screen effective antimicrobial peptides.
Methods: In this study, the RT strains were induced by gradient gentamicin, and the RT strains were selected by detecting the expression levels of efflux pump genes, porin genes, and biofilm formation genes of the strains combined with their effects on the cells. Then the effects of four antimicrobial peptides on the efflux pump activity, biofilm formation level and cell condition after infection were detected to explore the effects of antimicrobial peptides on RT strains. Finally, the RT strain was used to induce a mouse model of pneumonia, and the four antimicrobial peptides were used to treat pneumonia mice for in vivo experiments. The pathological changes in lung tissues in each group were detected to explore the antimicrobial peptide with the most significant effect on the RT strain in vivo.
Results: The results showed that the minimal inhibitory concentrations of the RT strains (strain C and strain I) were significantly higher than those of the wild-type strain, and the expression of efflux pump, porin and biofilm formation genes was significantly increased. The antimicrobial peptides could effectively inhibit the biofilm formation and efflux pump protein function of the RT strains. In addition, the antimicrobial peptides showed promising antibacterial effects both in vitro and in vivo.
Discussion: Our study provided a theoretical basis for the treatment of gentamicin resistant K. pneumoniae infection with antimicrobial peptides, and found that KLA was significantly superior to LL37, Magainin I, KLA and Dermaseptin (10 μg/mL in cells, 50 μg in mice).

Keywords: Klebsiella pneumoniae, K. pneumoniae, antibiotics, antimicrobial peptide, gentamicin-resistant, RT, microenvironment