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The β-lactam-resistance modifier (–)-epicatechin gallate alters the architecture of the cell wall of Staphylococcus aureus

¹ Microbiology Group, School of Pharmacy, 29–39 Brunswick Square, London WC1N 1AX, UK
² Bayer Healthcare AG, Pharma Research Center, D-42096 Wuppertal, Germany
³ Mitsui Norin Co. Ltd, 1-2-9 Nishi-Shinbashi, Minato-Ku, Tokyo 105-8427, Japan

Correspondence
Peter W. Taylor
peter.taylor{at}pharmacy.ac.uk

(–)-Epicatechin gallate (ECg), a component of green tea, sensitizes meticillin-resistant Staphylococcus aureus (MRSA) to β-lactam antibiotics, promotes staphylococcal cell aggregation and increases cell-wall thickness. The potentiation of β-lactam activity against MRSA by ECg was not due to decreased bacterial penicillin-binding protein (PBP) 2a expression or ECg binding to peptidoglycan. A 5–10 % reduction in peptidoglycan cross-linking was observed. Reduced cross-linking was insufficient to compromise the integrity of the cell wall and no evidence of PBP2a activity was detected in the muropeptide composition of ECg-grown cells. ECg increased the quantity of autolysins associated with the cell wall, even though the cells were less susceptible to Triton X-100-induced autolysis than cells grown in the absence of ECg. ECg promoted increased lysostaphin resistance that was not due to alteration of the pentaglycine cross-bridge configuration or inhibition of lysostaphin activity. Rather, decreased lysostaphin susceptibility was associated with structural changes to wall teichoic acid (WTA), an acid-labile component of peptidoglycan. ECg also promoted lipoteichoic acid (LTA) release from the cytoplasmic membrane. It is proposed that ECg reduces β-lactam resistance in MRSA either by binding to PBPs at sites distinct from the penicillin-binding site or by intercalation into the cytoplasmic membrane, displacing LTA from the phospholipid palisade. Thus, ECg-mediated alterations to the physical nature of the bilayer will elicit structural changes to WTA that result in modulation of the cell-surface properties necessary to maintain the β-lactam-resistant phenotype.