Defining the roles of pyruvate oxidation, TCA cycle, and mannitol metabolism in methicillin resistance Staphylococcus aureus urinary tract infection

Methicillin resistant Staphylococcus aureus (MRSA) is an important cause of complicated urinary tract infection (UTI) associated with the use of indwelling urinary catheters. Previous reports have revealed host and pathogen effectors critical for MRSA uropathogenesis. Here, we sought to determine the significance of specific metabolic pathways during MRSA UTI. First, we identified 16 mutants from the Nebraska transposon mutant library in the MRSA JE2 background with significantly reduced growth in pooled human urine (HU). Among these, five genes targeted by transposon mutation also showed significant upregulation upon exposure to HU for 2 h. This prompted us to generate transposon insertion mutants in the uropathogenic MRSA 1369 strain that were defective in TCA cycle ({Delta}sucD, {Delta}fumC), mannitol metabolism ({Delta}mtlD), and pyruvate oxidation and branched chain fatty acid synthesis ({Delta}lpdA). Compared to the WT, the {Delta}lpdA mutant showed a significant defect growth in HU and colonization of the urinary tract and dissemination to spleen in the mouse model of catheter-associated UTI (CAUTI), which may be attributed to its increased membrane hydrophobicity and higher susceptibility to killing in blood. MRSA 1369 {Delta}sucD, {Delta}fumC, and {Delta}mtlD mutants were not defective for in vitro growth in HU but showed significant fitness defects in the CAUTI mouse model. Overall, identification of novel metabolic pathways important for the urinary fitness and survival of MRSA can be used for the development of novel therapeutics. ImportanceWhile Staphylococcus aureus has historically not been considered a uropathogen, S. aureus urinary tract infection (UTI) is clinically significant in certain patient populations, including those with chronic indwelling urinary catheters. Moreover, most S. aureus strains causing catheter-associated UTI (CAUTI) are methicillin-resistant S. aureus (MRSA), which is difficult to treat as it limits treatment options and has the potential to deteriorate into life-threatening bacteremia, urosepsis, and shock. In this study, we found that pathways involved in pyruvate oxidation, TCA cycle, and mannitol metabolism are important for MRSA fitness and survival in the urinary tract. Improved understanding of the metabolic needs of MRSA in the urinary tract may help us develop novel inhibitors of MRSA metabolism that can be used to treat MRSA-CAUTI more effectively.