The Killing Mechanism of Teixobactin against Methicillin-Resistant Staphylococcus aureus: an Untargeted Metabolomics Study

Antibiotics have served humankind through their use in modern medicine as effective treatments for otherwise fatal bacterial infections. Teixobactin is a first member of newly discovered natural antibiotics that was recently identified from a hitherto-unculturable soil bacterium, Eleftheria terrae, and recognized as a potent antibacterial agent against various Gram-positive bacteria, including methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant enterococci. The most distinctive characteristic of teixobactin as an effective antibiotic is that teixobactin resistance could not be evolved in a laboratory setting. It is purported that teixobactin’s “resistance-resistant” mechanism of action includes binding to the essential bacterial cell wall synthesis building blocks lipid II and lipid III. In the present study, metabolomics was used to investigate the potential metabolic pathways involved in the mechanisms of antibacterial activity of the synthetic teixobactin analogue Leu(10)-teixobactin against a MRSA strain, S. aureus ATCC 700699. The metabolomes of S. aureus ATCC 700699 cells 1, 3, and 6 h following treatment with Leu(10)-teixobactin (0.5 μg/ml, i.e., 0.5× MIC) were compared to those of the untreated controls. Leu(10)-teixobactin significantly perturbed bacterial membrane lipids (glycerophospholipids and fatty acids), peptidoglycan (lipid I and II) metabolism, and cell wall teichoic acid (lipid III) biosynthesis as early as after 1 h of treatment, reflecting an initial activity on the cell envelope. Concordant with its time-dependent antibacterial killing action, Leu(10)-teixobactin caused more perturbations in the levels of key intermediates in pathways of amino-sugar and nucleotide-sugar metabolism and their downstream peptidoglycan and teichoic acid biosynthesis at 3 and 6 h. Significant perturbations in arginine metabolism and the interrelated tricarboxylic acid cycle, histidine metabolism, pantothenate, and coenzyme A biosynthesis were also observed at 3 and 6 h. To conclude, this is the first study to provide novel metabolomics mechanistic information, which lends support to the development of teixobactin as an antibacterial drug for the treatment of multidrug-resistant Gram-positive infections. IMPORTANCE Antimicrobial resistance is one of the greatest threats to the global health system. It is imperative that new anti-infective therapeutics be developed against problematic “superbugs.” The cyclic depsipeptide teixobactin holds much promise as a new class of antibiotics for highly resistant Gram-positive pathogens (e.g., methicillin-resistant Staphylococcus aureus [MRSA]). Understanding its molecular mechanism(s) of action could lead to the design of new compounds with a broader activity spectrum. Here, we describe the first metabolomics study to investigate the killing mechanism(s) of teixobactin against MRSA. Our findings revealed that teixobactin significantly disorganized the bacterial cell envelope, as reflected by a profound perturbation in the bacterial membrane lipids and cell wall biosynthesis (peptidoglycan and teichoic acid). Importantly, teixobactin significantly suppressed the main intermediate d-alanyl-d-lactate involved in the mechanism of vancomycin resistance in S. aureus. These novel results help explain the unique mechanism of action of teixobactin and its lack of cross-resistance with vancomycin.