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Aminoglycoside-modifying enzyme content of a multiply resistant strain of Streptococcus faecalis
Abstract:
Streptococcus faecalis strain BM6217 was resistant to high levels of all the clinically useful aminoglycoside antibiotics. This broad aminoglycoside resistance was mediated by constitutively synthesized phosphotransferase, acetyltransferase, and adenylyltransferase activities. It was inferred that phosphorylation occurred at the 3', 5", and 2"-hydroxyl groups, acetylation at the 6'-amino group, and adenylylation, probably, at the 6-hydroxyl group of the aminoglycosides. Strain BM6217 remained susceptible to the aminocyclitol spectinomycin but the combination of penicillin G with that antibiotic appeared antagonistic to this strain.
Insights
This study found that Streptococcus faecalis strain BM6217 possesses broad aminoglycoside resistance due to specific enzyme activities. The strain remains susceptible to spectinomycin, though its combination with penicillin G shows antagonism.
Area of Science:
- Microbiology
- Molecular Biology
- Antimicrobial Resistance
Background:
- Streptococcus faecalis is a significant human pathogen.
- Aminoglycoside antibiotics are crucial for treating bacterial infections.
- Emergence of antibiotic resistance in bacteria poses a global health threat.
Purpose of the Study:
- To investigate the mechanism of high-level aminoglycoside resistance in Streptococcus faecalis strain BM6217.
- To characterize the enzymatic activities responsible for this resistance.
- To assess the susceptibility of the strain to other antibiotics.
Main Methods:
- Phenotypic characterization of antibiotic resistance.
- Enzyme assays to detect phosphotransferase, acetyltransferase, and adenylyltransferase activities.
- Determination of susceptibility to spectinomycin and combinations with penicillin G.
Main Results:
- Strain BM6217 exhibited resistance to all clinically relevant aminoglycosides.
- Constitutive expression of phosphotransferase, acetyltransferase, and adenylyltransferase activities was identified.
- Specific hydroxyl and amino groups on aminoglycosides were inferred as modification sites.
- The strain was susceptible to spectinomycin, but penicillin G showed antagonism.
Conclusions:
- Broad aminoglycoside resistance in strain BM6217 is mediated by specific enzymatic modification of antibiotics.
- Understanding these resistance mechanisms is vital for developing effective treatment strategies.
- The strain's susceptibility profile highlights potential alternative therapeutic options.