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Metabolic Profiling Reveals the Importance of Arginine Metabolism via the Arginine Deiminase Pathway in Vancomycin-intermediate S. aureus

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Abstrak

Mutasi gen dalam VraSR dan GraSR, dua sistem pengawalseliaan dua komponen telah dilaporkan menyebabkan rintangan vankomisin dalam Staphylococcus aureus berkerintangan perantaraan vankomisin (VISA). Pemprofilan proteomik perbandingan antara S. aureus rentan vankomisin (VSSA) dan Staphylococcus aureus rintang vankomisin (VISA) daripada keturunan genetik Mu50 mendedahkan pengekspresan yang meningkat untuk protein katabolik ornithine carbamoyltransferase (ArcB); ini mencadangkan peranan katabolisme arginin dalam pembentukan VISA. Kajian ini bertujuan untuk menyiasat dengan lebih lanjut tapak laluan metabolik yang berkaitan dengan pembentukan VISA menggunakan pemprofilan metabolomik tidak bersasar berasaskan "liquid chromatography mass spectrometry" (LCMS). Profil metabolit antara 3 strain isogenik keturunan Mu50 iaitu Mu50Ω (VSSA), Mu50Ω-vraSm (VISA) dan Mu50Ω-vraSm-graRm (VISA) telah dibanding. Paras intrasel bagi asid α-hidroksiglutarik, kolin, lisin, asid malik, N-asetilornithine, nikotinamida dan cystathionine didapati berbeza dengan ketara antara VISA berbanding VSSA. Sel VISA didapati mempunyai tahap citrulline intraselular dan arginin ekstraselular yang lebih rendah, dengan tahap ornithine ekstraselular yang lebih tinggi berbanding VSSA. Perbezaan tahap metabolit antara VISA dan VSSA ini mencadangkan kepentingan metabolisme arginine dalam kerintangan perantaraan kepada vankomisin. Pengaktifan tapak laluan arginine deiminase (ADI) dalam VISA dari keturunan Mu50 boleh diterokai lebih lanjut sebagai sasaran untuk pembangunan antibiotik.

Abstract

Gene mutations located in VraSR and GraSR, two-component regulatory systems have been reported to cause vancomycin resistance in vancomycin-intermediate Staphylococcus aureus (VISA). Subsequent comparative proteomic profiling between vancomycin-susceptible S. aureus (VSSA) and VISAs of the Mu50 genetic lineage revealed up-regulated level of catabolic ornithine carbamoyltransferase (ArcB) in the latter, suggesting a role of arginine catabolism in VISA development. This study aimed to further investigate metabolic pathways associated with VISA development using liquid chromatography mass spectrometry (LCMS)-based untargeted metabolomic profiling. Metabolite profiles were compared among 3 isogenic strains of the Mu50 lineage: Mu50Ω (VSSA), Mu50Ω-vraSm (VISA) and Mu50Ω-vraSm-graRm (VISA). Intracellular levels of α-hydroxyglutaric acid, choline, lysine, malic acid, N-acetylornithine, nicotinamide, and cystathionine were found to be significantly different between VISAs compared to VSSA. VISA cells were found to have lower levels of intracellular citrulline and extracellular arginine, with higher extracellular level of ornithine compared to VSSA. These differences in metabolite levels between VISA and VSSA suggested the importance of arginine metabolism. Activation of the arginine deiminase pathway (ADI) in VISAs of the Mu50 lineage could be further explored as a target for antibiotic development.