Project description:Acinetobacter baumannii is an ESKAPE pathogen that rapidly develops resistance to antibiotics and persists for extended periods in the host or on abiotic surfaces. Survival in environmental stress such as phosphate scarcity, represents a clinically significant challenge for nosocomial pathogens. In the face of phosphate starvation, certain bacteria encode adaptive strategies, including the substitution of glycerophospholipids with phosphorus-free lipids. In bacteria, phosphatidylethanolamine, phosphatidylglycerol, and cardiolipin are conserved glycerophospholipids that can form lipid bilayers, particularly in the presence of other lipids. Here, we demonstrate that in response to phosphate limitation, conserved regulatory mechanisms induce alternative lipid production in A. baumannii. Specifically, phosphate limitation induces formation of three lipids, including amine-containing ornithine and lysine aminolipids. Mutations that inactivate aminolipid biosynthesis exhibit fitness defects relative to wild type in colistin growth and killing assays. Furthermore, we show that other Gram-negative ESKAPE pathogens accumulate aminolipids under phosphate limiting growth conditions, suggesting aminolipid biosynthesis may represent a broad strategy to overcome cationic antimicrobial peptide-mediated killing.
Project description:Traditional vaccines are difficult to deploy against the diverse antibiotic-resistant, nosocomial pathogens that cause Hospital Acquired Infections (HAIs). We developed a unique, protein-free vaccine to present antibiotic-resistant HAIs. This vaccine protected mice from invasive infections caused by methicillin-resistant Staphylococcus aureus, vancomycin-resistant Enterococcus faecalis, multidrug resistant Acinetobacter baumannii, Klebsiella pneumoniae, Pseudomonas aeruginosa, Rhizopus delemar, and Candida albicans. Protection persisted even in neutropenic mice infected with A. baumannii or R. delemar. Protection was already apparent after 24 hours and lasted for up to 21 days after a single dose, with a second dose restoring efficacy. Protection persisted without lymphocytes but was abrogated with macrophages depletion. This vaccine induced trained immunity by altering the macrophage epigenetic landscape and the inflammatory response to infection.
Project description:<p>We report identification of 3,6-dihydroxy-1,2-benzisoxazole (DHB) in a screen of Photorhabdus and Xenorhabdus, whose symbiotic relationship with eukaryotic nematodes favors secondary metabolites that meet several requirements matching those for clinically useful antibiotics. DHB is produced by Photorhabdus laumondii and is selective against Gram-negative species Escherichia coli, Enterobacter cloacae, Serratia marcescens, Klebsiella pneumoniae, Proteus mirabilis and Acinetobacter baumannii. It is inactive against anaerobic gut bacteria and nontoxic to human cells. Mutants resistant to DHB map to the ubiquinone biosynthesis pathway. DHB binds to 4-hydroxybenzoate octaprenyltransferase (UbiA) and prevents the formation of 4-hydroxy-3-octaprenylbenzoate. Remarkably, DHB itself is prenylated, forming an unusable chimeric product that likely contributes to the toxic effect of this antimicrobial. DHB appears to be both a competitive enzyme inhibitor and a prodrug; this dual mode of action is unusual for an antimicrobial compound.</p>
Project description:Objectives: This study aimed to investigate the microbiological characteristics of outer membrane vesicles (OMVs) derived from Pseudomonas aeruginosa (P. aeruginosa) to understand their mechanisms of inhibition of Acinetobacter baumannii (A. baumannii) in vitro. Methods: We assessed the inhibitory effects of P. aeruginosa on A. baumannii using a modified cross-streak assay. Subsequently, OMVs were extracted from P. aeruginosa strains using high-speed centrifugation, tangential flow filtration, ultrafiltration, and ultracentrifugation. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), transmission electron microscopy (TEM), and nanoparticle tracking assays (NTAs) were performed to confirm the presence of the extracted OMVs. P. aeruginosa-derived OMVs’ inhibitory activity against A. baumannii was tested using a modified time-kill assay. The proteomic analysis of OMVs revealed potential antibacterial protein clusters with diverse functions. Results: P. aeruginosa 022 (PA022) demonstrated inhibition of A. baumannii in the cross-streak assay. The protein levels of OMVs for PA022 and P. aeruginosa ATCC 27853 (PA ATCC 27853) were 1665 and 428.6 μg/mL, respectively. Additionally, PA 022 and PA ATCC 27853 exhibited variable patterns and sizes in the SDS-PAGE, TEM, and NTA. Furthermore, the growth inhibitory effect of PA022 OMVs on A. baumannii was evaluated using a modified time-kill assay. The proteomic analysis of OMVs revealed potential antibacterial protein clusters in PA 022 associated with virulence, motility, and post-translational modifications. Conclusion: Our study contributes to the understanding of P. aeruginosa OMVs characteristics and their inhibitory effect against A. baumannii, providing insights into the development of alternative therapeutic approaches against multi-drug resistance.