Poster Presentation HUPO 2019 - 18th Human Proteome Organization World Congress

Deciphering host-pathogen-drug interactions: optimisation of antibiotic therapy (#614)

Zhi Ying Kho 1 , Meiling Han 1 , Yan Zhu 1 , Cheng Huang 2 , Ralf Schittenhelm 2 , Joel Selkrig 3 , Mohammad Azad 1 , Jian Li 1
  1. Biomedicine Discovery Institute, Infection and Immunity Program, Department of Microbiology, Monash University, Clayton, Victoria, Australia
  2. Monash Proteomics & Metabolomics Facility and Monash Biomedicine Discovery Institute, Monash University, Clayton, Victoria, Australia
  3. European Molecular Biology Laboratory, Genome Biology Unit, Heidelberg, Baden-Württemberg, Germany

Background: Opportunistic pathogen Acinetobacter baumannii is a leading cause of nosocomial infections worldwide. Polymyxins are the last-resort antibiotics to treat multidrug resistant (MDR) A. baumannii infections. However, the elusive complex interplay among human innate immunity, A. baumannii and polymyxins has limited the optimisation of current antibiotic therapy.

Aim: This study aimed to elucidate this tripartite crosstalk using a label-free liquid chromatography-mass spectrometry-based proteomics approach.

Methods: THP-1 human macrophages were infected by a highly virulent MDR A. baumannii isolate AB5075 at multiplicity of infection (MOI) 1000 for 3 h, followed by another 1 h polymyxin B (30 mg/L) treatment. Protein expression profiling of both macrophages and interacting bacteria were conducted.

Results: Our results identified 202, 549 and 607 differentially expressed bacterial proteins post macrophage monotherapy, polymyxin monotherapy, and macrophage-polymyxin combination treatment, respectively. Notably, macrophage-polymyxin combination augmented the number of down-regulated bacterial proteins involved in the following fitness-related pathways compared to each individual treatment: (i) cell wall/membrane/envelope biogenesis (KdsD, KdsB biosynthetic enzymes of lipopolysaccharide); (ii) translation, ribosomal structure and biogenesis (aminoacyl-tRNA synthetases); (iii) central metabolism (transport and metabolism of amino acids, lipids, carbohydrates, nucleotides); and (iv) energy production (NuoA, PPA, CyoB enzymes in oxidative phosphorylation). Besides, macrophage-polymyxin combination enhanced down-regulation of regulatory and transport proteins in bacterial two-component systems (BaeR, PstS), and siderophore biosynthetic enzymes (EntABCE) associated with iron uptake. Our results indicate reduced bacterial adaptive capability particularly in macrophage-polymyxin combination, and dysregulated iron homeostasis necessary for bacterial survival and virulence. The ongoing macrophage proteomics analysis will facilitate identification of key candidate host factors and provide a better picture in depicting such tripartite crosstalk. 

Conclusion: This is the first proteomics study revealing the adaptive response of A. baumannii in macrophage and/or polymyxin treatment. Our mechanistic findings will contribute to optimising polymyxin therapy in patients.