Project description:Multi-drug resistant Gram-negative bacteria (GNB) are major contributors to the anti-microbial resistance (AMR) burden in humans and animals. AMR mechanisms are primarily mediated by proteoforms and, therefore, proteomic analyses of GNB offers a significant advantage in understanding the mechanisms of AMR. A large portion of these mechanisms are mediated by membrane proteins, however, they are often difficult to extract due to their hydrophobic nature and complex interactions with other components of the cell membrane. To extract the greatest number of proteoforms, an efficient ho-mogenisation protocol is required to effectively disrupt the rigid cell wall and membrane. Using Escherichia coli, Klebsiella pneumoniae, Acinetobacter baumannii and Pseudomonas aeruginosa we systematically compared the extraction efficiency of bead-beating with flash frozen and lyophilized cell pellets. We demonstrate that lyophilization prior to ho-mogenisation by bead-beating increases the detection of hydrophobic, membrane pro-teins. We detected numerous unique membrane proteins in each bacterial isolate, in-cluding ABC transporters and proteins involved in lipopolysaccharide synthesis, when lyophilizing prior to bead-beating compared to only flash freezing prior. As membrane proteins play a central role in AMR resistance mechanisms, this improvement in their isolation and identification will aid in understanding the resistance and molecular mechanisms associated with multi-drug resistant GNB.
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: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:<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>