Exposure of clinical MRSA heterogeneous strains to β-lactams redirects metabolism to optimize energy production through the TCA cycle.
Methicillin-resistant Staphylococcus aureus (MRSA) has emerged as one of the most important pathogens both in health care and community-onset infections. The prerequisite for methicillin resistance is mecA, which encodes a β-lactam-insensitive penicillin binding protein PBP2a. A characteristic of MRSA strains from hospital and community associated infections is their heterogeneous expression of resistance to β-lactam (HeR) in which only a small portion (≤ 0.1%) of the population expresses resistance to oxacillin (OXA) ≥ 10 µg/ml, while in other isolates, most of the population expresses resistance to a high level (homotypic resistance, HoR). The mechanism associated with heterogeneous expression requires both increase expression of mecA and a mutational event that involved the triggering of a β-lactam-mediated SOS response and related lexA and recA genes. In the present study we investigated the cellular physiology of HeR-MRSA strains during the process of β-lactam-mediated HeR/HoR selection at sub-inhibitory concentrations by using a combinatorial approach of microarray analyses and global biochemical profiling employing gas chromatography/mass spectrometry (GC/MS) and liquid chromatography/mass spectrometry (LC/MS) to investigate changes in metabolic pathways and the metabolome associated with β-lactam-mediated HeR/HoR selection in clinically relevant heterogeneous MRSA. We found unique features present in the oxacillin-selected SA13011-HoR derivative when compared to the corresponding SA13011-HeR parental strain that included significant increases in tricarboxyl citric acid (TCA) cycle intermediates and a concomitant decrease in fermentative pathways. Inactivation of the TCA cycle enzyme cis-aconitase gene in the SA13011-HeR strain abolished β-lactam-mediated HeR/HoR selection demonstrating the significance of altered TCA cycle activity during the HeR/HoR selection. These results provide evidence of both the metabolic cost and the adaptation that HeR-MRSA clinical strains undergo when exposed to β-lactam pressure, indicating that the energy production is redirected to supply the cell wall synthesis/metabolism, which in turn contributes to the survival response in the presence of β-lactam antibiotics.
Metabolon, Inc, Durham, North Carolina, United States of America.
Mignon A
MA
Keaton
Roberto R
RR
Rosato
Konrad B
KB
Plata
Christopher R
CR
Singh
Adriana E
AE
Rosato
D000154:Aconitate Hydratase / Q000235:genetics; D000596:Amino Acids / Q000378:metabolism; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D050260:Carbohydrate Metabolism; D002462:Cell Membrane / Q000378:metabolism; D002473:Cell Wall / Q000378:metabolism; D002952:Citric Acid Cycle; D004249:DNA Damage; D004269:DNA, Bacterial / Q000235:genetics; D004734:Energy Metabolism; D055624:Methicillin-Resistant Staphylococcus aureus / Q000187:drug effects / Q000378:metabolism*; D008826:Microbial Sensitivity Tests; D010068:Oxacillin / Q000494:pharmacology*; D012329:RNA, Bacterial / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D059467:Transcriptome; D018440:beta-Lactam Resistance
D000596:Amino Acids; D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D004269:DNA, Bacterial; D012329:RNA, Bacterial; D012333:RNA, Messenger; D000154:Aconitate Hydratase; D010068:Oxacillin