Pathogens and Disease, 77, 2019, ftz066 doi: 10.1093/femspd/ftz066 Advance Access Publication Date: 17 December 2019 Research Article RESEARCH ARTICLE Meso-tartrate inhibits intracellular replication of Coxiella burnetii, the causative agent of the zoonotic disease Q fever Mebratu A. Bitew 1 , Nadeeka K. Wawegama 1 , Hayley J. Newton 2 and Fiona M. Sansom 1, * 1 Asia-Pacifc Centre for Animal Health, Veterinary Preclinical Centre, Melbourne Veterinary School, The University of Melbourne, Parkville 3010, Victoria, Australia and 2 Department of Microbiology and Immunology at the Peter Doherty Institute for Infection and Immunity, The University of Melbourne, Melbourne 3000, Victoria, Australia ∗ Corresponding author: Veterinary Preclinical Centre, University of Melbourne, Parkville, VIC, Australia, 3010. Tel: +613 90353179; E-mail: fsansom@unimelb.edu.au One sentence summary: The growth of the disease-causing bacterium Coxiella burnetii inside human cells can be signifcantly decreased by using a compound non-toxic to human cells. Editor: Andrew Olive ABSTRACT The zoonotic disease Q fever caused by the intracellular bacterium Coxiella burnetii remains a global health threat due to its high infectivity, environmental stability, the debilitating nature and the long duration of treatment. Designing new and potent drugs that target previously unexplored pathways is essential to shorten treatment time and minimise antibiotic resistance. Nicotinamide adenine dinucleotide (NAD) is an essential and ubiquitous cofactor in all living organisms. NadB, an L-aspartate oxidase catalysing the frst step of the prokaryotic-specifc NAD de novo biosynthetic pathway, is required for C. burnetii growth and replication inside host cells. In this study, in vitro enzyme assays utilising recombinant glutathione S-transferase tagged NadB (GST-NadB) demonstrated inhibition of the L-aspartate oxidase activity of NadB by meso-tartrate. Furthermore, meso-tartrate inhibits intracellular growth and replication of C. burnetii inside host cells in a dose-dependent manner, and has no effect on the viability of mammalian cells. Unexpectedly, meso-tartrate also inhibited growth of C. burnetii in axenic medium, and further reduces replication of the nadB mutant inside host cells, suggesting it is acting more widely than simple inhibition of NadB. Overall, these results suggest that the antibacterial activity of meso-tartrate warrants further study, including investigation of its additional target(s). Keywords: Q fever; Coxiella burnetii; antimicrobial; meso-tartrate; NAD synthesis; enzyme inhibition INTRODUCTION Coxiella burnetii, an intracellular Gram-negative pathogenic bac- terium, is the causative agent of Q fever in humans, a disease that presents in both acute and chronic forms and which is transmitted primarily by inhalation of contaminated aerosols. Disease in humans is usually acquired from animals, with rumi- nant livestock a major reservoir (Moffatt, Newton and New- ton 2015). Coxiella burnetii is a pleomorphic organism with a bi- phasic life cycle comprised of the replicating large cell variant Received: 26 September 2019; Accepted: 16 December 2019 C  FEMS 2019. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com 1 Downloaded from https://academic.oup.com/femspd/article-abstract/77/8/ftz066/5679890 by guest on 23 July 2020