Burkholderia pseudomallei, the causative agent of
melioidosis, is among a growing number of bacterial pathogens that are increasingly
antibiotic resistant.
Antimicrobial peptides (AMPs) have been investigated as an alternative approach to treat microbial
infections, as generally, there is a lower likelihood that a pathogen will develop resistance to AMPs. In this study, 36 candidate Caenorhabditis elegans genes that encode secreted
peptides of <150
amino acids and previously shown to be overexpressed during
infection by B. pseudomallei were identified from the expression profile of infected nematodes. RNA interference (RNAi)-based knockdown of 12/34
peptide-encoding genes resulted in enhanced nematode susceptibility to B. pseudomallei without affecting worm fitness. A microdilution test demonstrated that two
peptides, NLP-31 and Y43C5A.3, exhibited anti-B. pseudomallei activity in a dose dependent manner on different pathogens. Time kill analysis proposed that these
peptides were bacteriostatic against B. pseudomallei at concentrations up to 8× MIC90. The
SYTOX green assay demonstrated that NLP-31 and Y43C5A.3 did not disrupt the B. pseudomallei membrane. Instead, gel retardation assays revealed that both
peptides were able to bind to
DNA and interfere with bacterial viability. In parallel, microscopic examination showed induction of cellular filamentation, a hallmark of
DNA synthesis inhibition, of NLP-31 and Y43C5A.3 treated cells. In addition, the
peptides also regulated the expression of inflammatory
cytokines in B. pseudomallei infected macrophage cells. Collectively, these findings demonstrate the potential of NLP-31 and Y43C5A.3 as anti-B. pseudomallei
peptides based on their function as immune modulators.