Antimicrobial Action of the Cyclic Peptide Bactenecin on Burkholderia pseudomallei Correlates with Efficient Membrane Permeabilization

Abstract

Burkholderia pseudomallei is a category B agent that causes Melioidosis, an acute and chronic disease with septicemia. The current treatment regimen is a heavy dose of antibiotics such as ceftazidime (CAZ); however, the risk of a relapse is possible. Peptide antibiotics are an alternative to classical antibiotics as they exhibit rapid action and are less likely to result in the development of resistance. The aim of this study was to determine the bactericidal activity against B. pseudomallei and examine the membrane disrupting abilities of the potent antimicrobial peptides: bactenecin, RTA3, BMAP-18 and CA-MA. All peptides exhibited >97% bactericidal activity at 20 µM, with bactenecin having slightly higher activity. Long term time-kill assays revealed a complete inhibition of cell growth at 50 µM bactenecin and CA-MA. All peptides inhibited biofilm formation comparable to CAZ, but exhibited faster kinetics (within 1 h). Bactenecin exhibited stronger binding to LPS and induced perturbation of the inner membrane of live cells. Interaction of bactenecin with model membranes resulted in changes in membrane fluidity and permeability, leading to leakage of dye across the membrane at levels two-fold greater than that of other peptides. Modeling of peptide binding on the membrane showed stable and deep insertion of bactenecin into the membrane (up to 9 Å). We propose that bactenecin is able to form dimers or large β-sheet structures in a concentration dependent manner and subsequently rapidly permeabilize the membrane, leading to cytosolic leakage and cell death in a shorter period of time compared to CAZ. Bactenecin might be considered as a potent antimicrobial agent for use against B. pseudomallei.

Two-Phase Bactericidal Mechanism of Silver Nanoparticles against Burkholderia pseudomallei

“…The bacteria were streaked on nutrient agar (NA) and then cultured at 37°C overnight. Colonies were selected and inoculated in 5 mL of Luria-Bertani (LB) broth (no salt) at 37°C in an incubator overnight and then subcultured in 50 mL of the same medium at 37°C in a 190 rpm shaker-incubator for 2–3 h to yield a mid-logarithmic growth phase culture, which were used to investigate the antibacterial activity and mechanism of action [26]. …”

Treatment and prophylaxis of melioidosis

“…The monosulfactam BAL30072 is some 2 log more active than ceftazidime and carbapenems against B. pseudomallei [83] . Various other classes of compounds, such as novel quinolones like sitafloxacin [84] , COX-2 inhibitors [85] , antimicrobial peptides [86–90] , farnesol [91] , CpG oligodeoxynucleotides [92,93] , glycogen synthase kinase inhibitors [94] , sulfonylureas [95] , cethromycin [96] , plant extracts [97–99] , snake venoms [100] , methionine aminopeptidase inhibitors [101] and monoclonal antibody-based approaches [102] , are under investigation for their in vitro activity against B. pseudomallei and therapeutic efficacy in animal models, but these are a long way from being used in human infections. These and other potential novel therapeutic approaches for melioidosis and glanders have recently been comprehensively reviewed [103–105] .…”

Rapid Antimicrobial Susceptibility Testing of Bacillus anthracis, Yersinia pestis, and Burkholderia pseudomallei by Use of Laser Light Scattering Technology

“…4). These observations were likely due to the slow kinetics of bactericidal activity by CAZ on B. pseudomallei (20) due to this drug's mechanism of action. The target of CAZ is penicillin-binding protein 3 (PBP3).…”