Staphylococcal phenotypes induced by naturally occurring and synthetic membrane-interactive polyphenolic β-lactam resistance modifiers.
Galloyl catechins, in particular (-)-epicatechin gallate (ECg), have the capacity to abrogate β-lactam resistance in methicillin-resistant strains of Staphylococcus aureus (MRSA); they also prevent biofilm formation, reduce the secretion of a large proportion of the exoproteome and induce profound changes to cell morphology. Current evidence suggests that these reversible phenotypic traits result from their intercalation into the bacterial cytoplasmic membrane. We have endeavoured to potentiate the capacity of ECg to modify the MRSA phenotype by stepwise removal of hydroxyl groups from the B-ring pharmacophore and the A:C fused ring system of the naturally occurring molecule. ECg binds rapidly to the membrane, inducing up-regulation of genes responsible for protection against cell wall stress and maintenance of membrane integrity and function. Studies with artificial membranes modelled on the lipid composition of the staphylococcal bilayer indicated that ECg adopts a position deep within the lipid palisade, eliciting major alterations in the thermotropic behaviour of the bilayer. The non-galloylated homolog (-)-epicatechin enhanced ECg-mediated effects by facilitating entry of ECg molecules into the membrane. ECg analogs with unnatural B-ring hydroxylation patterns induced higher levels of gene expression and more profound changes to MRSA membrane fluidity than ECg but adopted a more superficial location within the bilayer. ECg possessed a high affinity for the positively charged staphylococcal membrane and induced changes to the biophysical properties of the bilayer that are likely to account for its capacity to disperse the cell wall biosynthetic machinery responsible for β-lactam resistance. The ability to enhance these properties by chemical modification of ECg raises the possibility that more potent analogs could be developed for clinical evaluation.
School of Pharmacy, University College London, London, United Kingdom.
Lucia
L
Palacios
School of Pharmacy, University College London, London, United Kingdom.
Helena
H
Rosado
Universidad Miguel Hernández, Elche, Alicante, Spain.
Vicente
V
Micol
The Methodist Hospital Research Institute, Houston, Texas, United States of America.
Adriana E
AE
Rosato
School of Pharmacy, University College London, London, United Kingdom.
Patricia
P
Bernal
School of Pharmacy, University College London, London, United Kingdom.
Raquel
R
Arroyo
Department of Chemistry, University College London, London, United Kingdom.
Helen
H
Grounds
Department of Chemistry, University College London, London, United Kingdom.
James C
JC
Anderson
London School of Hygiene and Tropical Medicine, London, United Kingdom.
Richard A
RA
Stabler
School of Pharmacy, University College London, London, United Kingdom.
Peter W
PW
Taylor
D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D002473:Cell Wall / Q000187:drug effects / Q000378:metabolism*; D024881:Drug Resistance, Bacterial / Q000235:genetics*; D015964:Gene Expression Regulation, Bacterial / Q000187:drug effects; D055624:Methicillin-Resistant Staphylococcus aureus / Q000235:genetics* / Q000378:metabolism; D008826:Microbial Sensitivity Tests; D010641:Phenotype
D000900:Anti-Bacterial Agents