Research ArticleInfectious Disease

TarO-specific inhibitors of wall teichoic acid biosynthesis restore β-lactam efficacy against methicillin-resistant staphylococci

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Science Translational Medicine  09 Mar 2016:
Vol. 8, Issue 329, pp. 329ra32
DOI: 10.1126/scitranslmed.aad7364

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Addressing antibiotic resistance with nonantibiotic adjuvants

Coupled with the crisis in antibiotic drug resistance is a dearth of mechanistically new classes of antibacterial agents. One possible solution to this problem is to improve the efficacy of existing antibiotics against otherwise resistant bacteria using a combination agent approach. Lee et al. now describe just such a combination agent strategy to resuscitate the efficacy of β-lactam antibiotics. They identify nonantibiotic adjuvants termed tarocins that restore the killing activity of β-lactams against methicillin-resistant staphylococci, thereby enabling the application of β-lactams to treat Gram-positive bacterial infections.


The widespread emergence of methicillin-resistant Staphylococcus aureus (MRSA) has dramatically eroded the efficacy of current β-lactam antibiotics and created an urgent need for new treatment options. We report an S. aureus phenotypic screening strategy involving chemical suppression of the growth inhibitory consequences of depleting late-stage wall teichoic acid biosynthesis. This enabled us to identify early-stage pathway-specific inhibitors of wall teichoic acid biosynthesis predicted to be chemically synergistic with β-lactams. We demonstrated by genetic and biochemical means that each of the new chemical series discovered, herein named tarocin A and tarocin B, inhibited the first step in wall teichoic acid biosynthesis (TarO). Tarocins do not have intrinsic bioactivity but rather demonstrated potent bactericidal synergy in combination with broad-spectrum β-lactam antibiotics against diverse clinical isolates of methicillin-resistant staphylococci as well as robust efficacy in a murine infection model of MRSA. Tarocins and other inhibitors of wall teichoic acid biosynthesis may provide a rational strategy to develop Gram-positive bactericidal β-lactam combination agents active against methicillin-resistant staphylococci.

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