Related Experiment Video
Updated: Aug 12, 2025
Preparation of Agar Bead Embedded Mycobacterium abscessus to Inoculate Immunocompetent Mice Intratracheally
Published on: April 25, 2025
C25-modified rifamycin derivatives with improved activity against Mycobacterium abscessus
Laura Paulowski1, Katherine S H Beckham2, Matt D Johansen3
1National and WHO Supranational Reference Center for Mycobacteria, Research Center Borstel, Leibniz Lung Center, 23845 Borstel, Germany.
Abstract:
Infections caused by Mycobacterium abscessus are difficult to treat due to its intrinsic resistance to most antibiotics. Formation of biofilms and the capacity of M. abscessus to survive inside host phagocytes further complicate eradication. Herein, we explored whether addition of a carbamate-linked group at the C25 position of rifamycin SV blocks enzymatic inactivation by ArrMab, an ADP-ribosyltransferase conferring resistance to rifampicin (RMP). Unlike RMP, 5j, a benzyl piperidine rifamycin derivative with a morpholino substituted C3 position and a naphthoquinone core, is not modified by purified ArrMab. Additionally, we show that the ArrMab D82 residue is essential for catalytic activity. Thermal profiling of ArrMab in the presence of 5j, RMP, or rifabutin shows that 5j does not bind to ArrMab. We found that the activity of 5j is comparable to amikacin against M. abscessus planktonic cultures and pellicles. Critically, 5j also exerts potent antimicrobial activity against M. abscessus in human macrophages and shows synergistic activity with amikacin and azithromycin.
Insights
A novel rifamycin derivative, 5j, effectively treats Mycobacterium abscessus infections by evading enzymatic inactivation. This compound shows potent activity in macrophages and synergistic effects with other antibiotics.
Area of Science:
- Microbiology
- Drug Discovery
- Antimicrobial Resistance
Background:
- Mycobacterium abscessus infections are challenging due to antibiotic resistance.
- Biofilm formation and intracellular survival complicate treatment.
- Enzymatic inactivation by ArrMab is a key resistance mechanism.
Purpose of the Study:
- To investigate if a carbamate modification at the C25 position of rifamycin SV can prevent inactivation by ArrMab.
- To evaluate the antimicrobial activity of the novel rifamycin derivative 5j against M. abscessus.
Main Methods:
- Synthesis and characterization of rifamycin derivative 5j.
- Enzymatic assays using purified ArrMab and various rifamycin compounds.
- Antimicrobial activity testing against M. abscessus planktonic cultures, pellicles, and within human macrophages.
- Thermal shift assays to assess compound binding to ArrMab.
Main Results:
- Rifamycin derivative 5j is not inactivated by ArrMab, unlike rifampicin.
- The D82 residue of ArrMab is crucial for its catalytic activity.
- 5j demonstrates comparable activity to amikacin against M. abscessus cultures and pellicles.
- 5j exhibits potent activity within human macrophages and synergistic effects with amikacin and azithromycin.
Conclusions:
- The carbamate modification in 5j confers resistance to ArrMab-mediated inactivation.
- 5j represents a promising therapeutic candidate for treating difficult-to-treat Mycobacterium abscessus infections.
- Combination therapy with 5j may enhance treatment efficacy.
