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The Novel Membrane-Associated Auxiliary Factors AuxA and AuxB Modulate β-lactam Resistance in MRSA by stabilizing Lipoteichoic Acids

Lookup NU author(s): Dr Jacob BiboyORCiD, Professor Waldemar Vollmer



This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License (CC BY-NC-ND).


© 2021 The AuthorsA major determinant of β-lactam resistance in methicillin-resistant Staphylococcus aureus (MRSA) is the drug insensitive transpeptidase, PBP2a, encoded by mecA. Full expression of the resistance phenotype requires auxiliary factors. Two such factors, auxiliary factor A (auxA, SAUSA300_0980) and B (auxB, SAUSA300_1003), were identified in a screen against mutants with increased susceptibility to β-lactams in the MRSA strain, JE2. auxA and auxB encode transmembrane proteins, with AuxA predicted to be a transporter. Inactivation of auxA or auxB enhanced β-lactam susceptibility in community-, hospital- and livestock-associated MRSA strains without affecting PBP2a expression, peptidoglycan cross-linking or wall teichoic acid synthesis. Both mutants displayed increased susceptibility to inhibitors of lipoteichoic acid (LTA) synthesis and alanylation pathways and released LTA even in the absence of β-lactams. The β-lactam susceptibility of the aux mutants was suppressed by mutations inactivating gdpP, which was previously found to allow growth of mutants lacking the lipoteichoic synthase enzyme, LtaS. Using the Galleria mellonella infection model, enhanced survival of larvae inoculated with either auxA or auxB mutants was observed compared with the wild-type strain following treatment with amoxicillin. These results indicate that AuxA and AuxB are central for LTA stability and potential inhibitors can be tools to re-sensitize MRSA strains to β-lactams and combat MRSA infections.

Publication metadata

Author(s): Mikkelsen K, Sirisarn W, Alharbi O, Alharbi M, Liu H, Nohr-Meldgaard K, Mayer K, Vestergaard M, Gallagher LA, Derrick JP, McBain AJ, Biboy J, Vollmer W, O'Gara JP, Grunert T, Ingmer H, Xia G

Publication type: Article

Publication status: Published

Journal: International Journal of Antimicrobial Agents

Year: 2021

Volume: 57

Issue: 3

Print publication date: 01/03/2021

Online publication date: 24/01/2021

Acceptance date: 19/12/2020

Date deposited: 08/04/2021

ISSN (print): 0924-8579

ISSN (electronic): 1872-7913

Publisher: Elsevier B.V.


DOI: 10.1016/j.ijantimicag.2021.106283

PubMed id: 33503451


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Funder referenceFunder name
UKRI Strategic Priorities Fund (grant no. EP/T002778/1) to WV