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Updated: May 9, 2026
Antibiotic Dereplication Using the Antibiotic Resistance Platform
Published on: October 17, 2019
Ipso-hydroxylation and subsequent fragmentation: a novel microbial strategy to eliminate sulfonamide antibiotics
Benjamin Ricken1, Philippe F X Corvini, Danuta Cichocka
1Institute for Ecopreneurship, School of Life Sciences, University of Applied Sciences and Arts Northwestern Switzerland, Muttenz, Switzerland.
Abstract:
Sulfonamide antibiotics have a wide application range in human and veterinary medicine. Because they tend to persist in the environment, they pose potential problems with regard to the propagation of antibiotic resistance. Here, we identified metabolites formed during the degradation of sulfamethoxazole and other sulfonamides in Microbacterium sp. strain BR1. Our experiments showed that the degradation proceeded along an unusual pathway initiated by ipso-hydroxylation with subsequent fragmentation of the parent compound. The NADH-dependent hydroxylation of the carbon atom attached to the sulfonyl group resulted in the release of sulfite, 3-amino-5-methylisoxazole, and benzoquinone-imine. The latter was concomitantly transformed to 4-aminophenol. Sulfadiazine, sulfamethizole, sulfamethazine, sulfadimethoxine, 4-amino-N-phenylbenzenesulfonamide, and N-(4-aminophenyl)sulfonylcarbamic acid methyl ester (asulam) were transformed accordingly. Therefore, ipso-hydroxylation with subsequent fragmentation must be considered the underlying mechanism; this could also occur in the same or in a similar way in other studies, where biotransformation of sulfonamides bearing an amino group in the para-position to the sulfonyl substituent was observed to yield products corresponding to the stable metabolites observed by us.
Insights
Sulfonamide antibiotics degrade via a novel ipso-hydroxylation pathway in Microbacterium sp. strain BR1, releasing sulfite and other compounds. This mechanism is crucial for understanding antibiotic resistance and environmental persistence.
Area of Science:
- Environmental microbiology
- Biochemistry
- Antimicrobial resistance
Background:
- Sulfonamide antibiotics are widely used but persist in the environment.
- Persistence contributes to the propagation of antibiotic resistance.
- Understanding sulfonamide degradation is vital for environmental and health safety.
Purpose of the Study:
- To identify metabolites of sulfamethoxazole and related sulfonamides during degradation by Microbacterium sp. strain BR1.
- To elucidate the degradation pathway of sulfonamides.
- To investigate the mechanism of sulfonamide biotransformation.
Main Methods:
- Microbial degradation experiments using Microbacterium sp. strain BR1.
- Identification of degradation metabolites using analytical techniques.
- Analysis of the chemical transformations of various sulfonamides.
Main Results:
- Degradation proceeds via an unusual ipso-hydroxylation pathway.
- NADH-dependent hydroxylation releases sulfite, 3-amino-5-methylisoxazole, and benzoquinone-imine.
- Benzoquinone-imine is further transformed into 4-aminophenol.
- Multiple sulfonamides, including sulfadiazine and asulam, undergo similar transformations.
Conclusions:
- Ipso-hydroxylation followed by fragmentation is the primary mechanism for sulfonamide degradation in this bacterium.
- This pathway explains the observed stable metabolites in other studies of sulfonamide biotransformation.
- The findings are critical for assessing the environmental fate and impact of sulfonamide antibiotics.
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