TY - JOUR

T1 - The Novel Membrane-Associated Auxiliary Factors AuxA and AuxB Modulate β-lactam Resistance in MRSA by stabilizing Lipoteichoic Acids

AU - Mikkelsen, Kasper

AU - Sirisarn, Wanchat

AU - Alharbi, Ohood

AU - Alharbi, Mohanned

AU - Liu, Huayong

AU - Nøhr-Meldgaard, Katrine

AU - Mayer, Katharina

AU - Vestergaard, Martin

AU - Gallagher, Laura A.

AU - Derrick, Jeremy P.

AU - McBain, Andrew J.

AU - Biboy, Jacob

AU - Vollmer, Waldemar

AU - O'Gara, James P.

AU - Grunert, Tom

AU - Ingmer, Hanne

AU - Xia, Guoqing

PY - 2021

Y1 - 2021

N2 - A 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.

AB - A 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.

KW - antibiotic resistance

KW - auxA

KW - auxB

KW - auxiliary factor

KW - lipoteichoic acid

KW - methicillin-resistant Staphylococcus aureus

KW - β-lactam resistance

U2 - 10.1016/j.ijantimicag.2021.106283

DO - 10.1016/j.ijantimicag.2021.106283

M3 - Journal article

C2 - 33503451

AN - SCOPUS:85101022574

VL - 57

JO - International Journal of Antimicrobial Agents

JF - International Journal of Antimicrobial Agents

SN - 0924-8579

IS - 3

M1 - 106283

ER -