Systemic Responses of Multidrug-Resistant Pseudomonas aeruginosa and Acinetobacter baumannii Following Exposure to the Antimicrobial Peptide Cathelicidin-BF Imply Multiple Intracellular Targets

Abstract

Cathelicidin-BF, derived from the banded krait (Bungarus fasciatus), is a typically cationic, amphiphilic and α-helical antimicrobial peptide (AMP) with 30 amino acids that exerts powerful effects on multidrug-resistant (MDR) clinical isolates, including Pseudomonas aeruginosa, Acinetobacter baumannii, and Klebsiella pneumoniae, but whether it targets plasma membranes or intracellular targets to kill bacteria is still controversial. In the present study, we demonstrated that the disruption of bacterial membranes with high concentrations of cathelicidin-BF was the cause of bacterial death, as with conventional antibiotics at high concentrations. At lower concentrations, cathelicidin-BF did not cause bacterial plasma membrane disruption, but it was able to cross the membrane and aggregate at the nucleoid regions. Functional proteins of the transcription processes of P. aeruginosa and A. baumannii were affected by sublethal doses of cathelicidin-BF, as demonstrated by comparative proteomics using isobaric tags for relative and absolute quantification and subsequent gene ontology (GO) analysis. Analysis using the Kyoto Encyclopedia of Genes and Genomes showed that cathelicidin-BF mainly interferes with metabolic pathways related to amino acid synthesis, metabolism of cofactors and vitamins, metabolism of purine and energy supply, and other processes. Although specific targets of cathelicidin-BF must still be validated, our study offers strong evidence that cathelicidin-BF may act upon intracellular targets to kill superbugs, which may be helpful for further efforts to discover novel antibiotics to fight against them.

Tachyplesin Causes Membrane Instability That Kills Multidrug-Resistant Bacteria by Inhibiting the 3-Ketoacyl Carrier Protein Reductase FabG

“…These studies were carried out as we previously reported with slight modifications and briefly introduced as follows ( Liu et al, 2017 ). Serum stability was assessed with increases over the minimal inhibitory concentration (MIC) of tachyplesin III (KW C FRVCYRGICYRK C R; cysteines with the same type font formed on disulfide; purity ≥ 95%, synthesized by GL Biochem Co., Ltd, Shanghai, China) on Escherichia coli strain DH5α after incubation in serum.…”

Effects of C-terminal amidation and heptapeptide ring on the biological activities and advanced structure of amurin-9KY, a novel antimicrobial peptide identified from the brown frog, Rana kunyuensis

“…Previous studies have demonstrated that AMPs achieve antimicrobial activity by disrupting various key microorganism cell processes, with some AMPs possessing multiple mechanisms (Brogden, 2005; Nguyen et al, 2011). There are many specific targets in microbial cells for AMPs, including external proteins, outer surface lipids, outer membrane proteins (gram-negative bacteria), inner membrane, integral membrane proteins, nucleic acids and intracellular proteins (Liu et al, 2017, 2018; Nguyen et al, 2011). Among them, disrupting the integrity of the microbial inner membrane is the most common mode for AMPs (Liu et al, 2017, 2018; Nguyen et al, 2011), the disruption of which results in obvious morphological alteration.…”

“…There are many specific targets in microbial cells for AMPs, including external proteins, outer surface lipids, outer membrane proteins (gram-negative bacteria), inner membrane, integral membrane proteins, nucleic acids and intracellular proteins (Liu et al, 2017, 2018; Nguyen et al, 2011). Among them, disrupting the integrity of the microbial inner membrane is the most common mode for AMPs (Liu et al, 2017, 2018; Nguyen et al, 2011), the disruption of which results in obvious morphological alteration. Here, the antimicrobial results showed that S. aureus ATCC25923 was most sensitive to amurin-9KY, and therefore it was selected to examine the induced membrane morphological alterations by SEM.…”

Novel Alligator Cathelicidin As-CATH8 Demonstrates Anti-Infective Activity against Clinically Relevant and Crocodylian Bacterial Pathogens

“…Second, at concentrations near the MIC, As-CATH8 showed only modest effects on the membranes, while peptide internalization and intracellular signaling may still have occurred at these concentrations. Interaction with bacterial DNA has been shown to be important for the antimicrobial mechanism of several vertebrate cathelicidins, including LL-37 [ 46 , 47 , 48 ]. This interaction can potentially interfere with several bacterial processes, such as replication and transcription, and usually leads to bacterial death [ 47 , 49 ].…”