[Inactivation of aminoglycoside antibiotics by clinically isolated Pseudomonas aeruginosa]
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Abstract:
Minimal inhibitory concentrations (MIC) of micronomicin (MCR) and gentamicin (GM) against clinically isolated Pseudomonas aeruginosa F 4150 were 1.56 mcg/ml and 6.25 mcg/ml, respectively. Sisomicin, dibekacin, amikacin, netilmicin, tobramycin ribostamycin and kanamycin did not inhibit the strain at the concentrations less than 25 mcg/ml. Each aminoglycoside antibiotic was incubated in Tris-HCl buffer solutions (pH 7.8) containing cell free crude enzyme preparations obtained by sonic oscillation of intact cells of P. aeruginosa F 4150, coenzyme A and adenosine-5'-triphosphate. The residual activity at 3 hours of incubation at 37 degrees C was 88% for MCR and 33.6% for GM, while all of the other aminoglycoside antibiotics tested were completely inactivated under this condition.
Insights
Micronomicin (MCR) and gentamicin (GM) show varying efficacy against Pseudomonas aeruginosa F 4150. MCR demonstrated higher residual activity and lower MIC, suggesting greater stability and potential against this clinical isolate.
Area of Science:
- Microbiology
- Pharmacology
- Biochemistry
Background:
- Pseudomonas aeruginosa is a significant opportunistic pathogen.
- Aminoglycoside antibiotics are crucial for treating P. aeruginosa infections.
- Understanding antibiotic resistance mechanisms is vital for effective treatment.
Purpose of the Study:
- To determine the minimal inhibitory concentrations (MIC) of various aminoglycosides against a clinical isolate of Pseudomonas aeruginosa F 4150.
- To evaluate the in vitro stability and inactivation of these antibiotics by bacterial enzyme preparations.
Main Methods:
- MIC determination for micronomicin (MCR), gentamicin (GM), and other aminoglycosides against P. aeruginosa F 4150.
- Incubation of antibiotics with cell-free enzyme preparations from P. aeruginosa in Tris-HCl buffer.
- Assay of residual antibiotic activity after incubation.
Main Results:
- MIC values were 1.56 mcg/ml for MCR and 6.25 mcg/ml for GM. Other tested aminoglycosides showed no inhibition at < 25 mcg/ml.
- Residual activity after 3 hours was 88% for MCR and 33.6% for GM.
- All other tested aminoglycosides were completely inactivated by the enzyme preparations.
Conclusions:
- Micronomicin exhibits superior stability and lower MIC against this P. aeruginosa isolate compared to gentamicin.
- The bacterial enzyme preparation significantly inactivates most tested aminoglycosides, highlighting a potential resistance mechanism.