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Transferable amikacin resistance in Acinetobacter spp. due to a new type of 3'-aminoglycoside phosphotransferase
T Lambert1, G Gerbaud, P Courvalin
1Hôpital Saint-Michel, Paris, France.
Abstract:
Acinetobacter baumannii BM2580 resistant to kanamycin and structurally related antibiotics, including amikacin, was isolated from a clinical specimen. A phosphocellulose paper-binding assay and DNA annealing studies indicated that resistance to aminoglycosides in BM2580 was due to synthesis of a new type of 3'-aminoglycoside phosphotransferase. The gene conferring resistance to kanamycin-amikacin in this strain was carried by a 63-kilobase plasmid, pIP1841, self-transferable to A. baumannii, A. haemolyticus, and A. lwoffii but not to Escherichia coli. The aminoglycoside resistance gene of pIP1841 was cloned in E. coli, where it was expressed.
Insights
Acinetobacter baumannii BM2580 exhibits resistance to kanamycin and amikacin due to a novel 3'-aminoglycoside phosphotransferase. This resistance is plasmid-mediated and transferable to related Acinetobacter species.
Area of Science:
- Microbiology
- Molecular Biology
- Antimicrobial Resistance
Background:
- Acinetobacter baumannii is an opportunistic pathogen known for its increasing resistance to antibiotics.
- Aminoglycosides are crucial antibiotics for treating serious bacterial infections.
- Emergence of aminoglycoside resistance in A. baumannii poses a significant public health threat.
Purpose of the Study:
- To characterize the mechanism of aminoglycoside resistance in a clinical isolate of Acinetobacter baumannii.
- To identify and analyze the genetic element responsible for conferring resistance.
- To investigate the transferability and expression of the resistance gene.
Main Methods:
- Isolation and characterization of antibiotic-resistant Acinetobacter baumannii BM2580.
- Biochemical assays (phosphocellulose paper-binding assay) to determine resistance mechanism.
- DNA annealing studies to analyze gene interactions.
- Plasmid analysis and conjugation experiments to assess transferability.
- Gene cloning and expression studies in Escherichia coli.
Main Results:
- A novel 3 -aminoglycoside phosphotransferase was identified as the cause of kanamycin and amikacin resistance in BM2580.
- The resistance gene was located on a self-transferable 63-kilobase plasmid, pIP1841.
- Plasmid pIP1841 successfully transferred to other Acinetobacter species (A. baumannii, A. haemolyticus, A. lwoffii) but not to Escherichia coli.
- The cloned aminoglycoside resistance gene was expressed in E. coli, confirming its functional activity.
Conclusions:
- Acinetobacter baumannii BM2580 possesses a new mechanism of aminoglycoside resistance mediated by a plasmid-borne phosphotransferase.
- The self-transferable plasmid pIP1841 facilitates the spread of aminoglycoside resistance among Acinetobacter species.
- This finding highlights the need for continued surveillance of antibiotic resistance mechanisms in clinical settings.