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Prevalence and characterization of resistance to gentamicin in gram-negative bacteria
Abstract:
A survey of the occurrence of resistance to gentamicin in clinical isolates of Gram-negative bacteria revealed a 3-fold increase in the percentage of resistant strains between 1974 (4%), and 1976 (12%). Gentamicin resistance was mainly found in isolates from hospitalized patients. Serratia (35--78%), Proteus inconstans (53--62%), Klebsiella (6--21%), Acinetobacter (9--17%) and Pseudomonas (9--14%) exhibited the highest percentage of resistance to this drug. Gentamicin inactivating enzymes were detected in 16 selected resistant isolates. Of these, ten strains (Klebsiella, Serratia, Pseudomonas, E. coli) produced the aminoglycoside 2''-adenylyltransferase, five (Proteus, indole-positive) the aminoglycoside 2'-N-acetyltransferase and one isolate (Proteus mirabilis) the aminoglycoside 3-N-acetyltransferase. Eight of the 16 strains were able to transfer gentamicin resistance and certain other resistance markers to appropriate receptor strains during mixed cultivation, indicating the presence of transferable plasmid-mediated resistance.
Insights
Gentamicin resistance in Gram-negative bacteria increased threefold between 1974 and 1976, primarily in hospitalized patients. This resistance is often linked to specific enzymes and transferable plasmids.
Area of Science:
- Microbiology
- Bacterial genetics
- Antimicrobial resistance
Background:
- Gentamicin is a crucial antibiotic for treating Gram-negative bacterial infections.
- Monitoring antibiotic resistance patterns is essential for effective clinical practice.
Purpose of the Study:
- To investigate the prevalence of gentamicin resistance in clinical Gram-negative bacterial isolates.
- To identify the mechanisms and genetic basis of gentamicin resistance.
Main Methods:
- Survey of clinical isolates from 1974 and 1976.
- Detection of gentamicin-inactivating enzymes.
- Plasmid-mediated resistance transfer experiments.
Main Results:
- A 3-fold increase in gentamicin resistance observed from 4% (1974) to 12% (1976).
- Highest resistance rates in Serratia, Proteus inconstans, Klebsiella, Acinetobacter, and Pseudomonas.
- Identified aminoglycoside 2''-adenylyltransferase, aminoglycoside 2'-N-acetyltransferase, and aminoglycoside 3-N-acetyltransferase in resistant strains.
- Transferable plasmid-mediated resistance was confirmed in 8 of 16 resistant isolates.
Conclusions:
- Significant rise in gentamicin resistance in Gram-negative bacteria, particularly in hospital settings.
- Enzymatic inactivation and plasmid-mediated transfer are key mechanisms of gentamicin resistance.
- Findings highlight the need for continued surveillance of antibiotic resistance.