Antisense Oligomer Targeting the Antibiotic Resistance Gene ermC Augments Erythromycin, Azithromycin, and...

Area of Science:

• Microbiology
• Molecular Biology
• Antimicrobial Resistance Research

Background:

• Antimicrobial resistance (AMR) poses a significant global health threat, rendering existing antibiotics ineffective.
• Macrolide, lincosamide, streptogramin B (MLS_B) antibiotics are losing efficacy due to resistance mechanisms, particularly in *Staphylococcus aureus*.
• The *ermC* gene is a key mediator of MLS_B resistance in bacteria.

Purpose of the Study:

• To develop and evaluate antisense oligomers (ASOs) capable of resensitizing *Staphylococcus aureus* to MLS_B antibiotics.
• To specifically target and inhibit the expression of the *ermC* gene responsible for MLS_B resistance.
• To assess the specificity and efficacy of ASOs in restoring antibiotic susceptibility.

Main Methods:

• Design and screening of antisense oligomers (ASOs) targeting the *ermC* mRNA.
• Utilizing a peptide nucleic acid (PNA) conjugated to a TAT cell-penetrating peptide for enhanced cellular delivery and target binding.
• In vitro binding assays, translation inhibition assays, and methylation activity assays to confirm ASO mechanism of action.
• Testing antibiotic susceptibility of *S. aureus* before and after ASO treatment.

Main Results:

• A specific TAT-conjugated PNA-ASO demonstrated high efficiency in targeting *ermC* mRNA within *S. aureus* cells.
• The ASO successfully reduced the translation of the *ermC* gene, leading to decreased ErmC protein methylation activity.
• Resensitization of *S. aureus* to specific MLS_B antibiotics was observed without impacting susceptibility to other antibiotic classes, confirming target specificity.
• Sequence analysis identified conserved *ermC* genes and target sites in other bacterial species, suggesting broader applicability.

Conclusions:

• Antisense oligomers, particularly TAT-conjugated PNA-ASOs, are effective tools for combating antimicrobial resistance by specifically targeting resistance genes like *ermC*.
• This approach offers a promising strategy to restore the efficacy of existing antibiotics against resistant bacterial strains.
• The conserved nature of the *ermC* gene and its mRNA target site suggests potential for developing similar ASO-based therapies against other bacterial pathogens.