High-level carbapenem tolerance requires antibiotic-induced outer membrane modifications

Area of Science:

• Microbiology
• Molecular Biology
• Drug Discovery

Background:

• Antibiotic tolerance contributes to treatment failure and multidrug resistance.
• Mechanisms of bacterial tolerance, especially to beta-lactams, are poorly understood.
• Cell wall-deficient spheroplasts maintain integrity via the outer membrane (OM) and lipopolysaccharide (LPS).

Purpose of the Study:

• Investigate the role of the PhoPQ two-component system in beta-lactam antibiotic tolerance.
• Elucidate the molecular mechanisms underlying meropenem tolerance in Enterobacterales.
• Identify potential therapeutic targets to overcome antibiotic tolerance.

Main Methods:

• Induction of PhoPQ by meropenem treatment.
• Analysis of 4-amino-4-deoxy-L-aminoarabinose (L-Ara4N) modification of LPS lipid A.
• Assessment of tolerance in wild-type and mutant strains (e.g., mgrB mutants).
• Screening of histidine kinase inhibitors for their effect on PhoPQ and meropenem.

Main Results:

• PhoPQ is induced by meropenem and increases L-Ara4N modification of LPS.
• L-Ara4N modifications enhance OM stability and meropenem tolerance in Enterobacterales.
• Inactivation of mgrB leads to PhoPQ overactivation and increased meropenem tolerance.
• Histidine kinase inhibitors potentiate meropenem by inhibiting PhoPQ-dependent LPS modifications.

Conclusions:

• PhoPQ-mediated LPS modifications are crucial for OM stabilization and bacterial survival during cell wall stress.
• Antimicrobial peptides like colistin can indirectly select for meropenem tolerance by activating PhoPQ.
• Targeting PhoPQ-dependent pathways offers a promising strategy to enhance meropenem efficacy against tolerant bacteria.