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Dissemination of an antibiotic resistance plasmid in hospital patient flora
Abstract:
The 2'' aminoglycoside nucleotidyltransferase, AAD (2''), which adenylates gentamicin, tobramycin, and kanamycin, became prevalent over several months in multiple strains and species of Enterobacteriaceae isolated at one hospital. Eight plasmids with the gene for this enzyme purified from different strains and species isolated at different times had similar EcoRI digestion fragments, indicating that the gene had disseminated on one plasmid without transposition. This 56.5-megadalton plasmid of incompatibility group M, which also carried three other resistance genes, spread, at first, largely in one strain of Klebsiella pneumoniae, which later disappeared. It transferred to some strains which tended not to colonize other patients and later circulated predominantly in Serratia marcescens. Computer surveillance of routine hospital laboratory results was able to detect and trace the gene and the plasmid and measure their effect on resistance prevalence.
Insights
A novel aminoglycoside nucleotidyltransferase (AAD(2
Area of Science:
- Molecular Biology
- Microbiology
- Genetics
Background:
- The emergence and spread of antibiotic resistance genes are critical challenges in healthcare settings.
- Aminoglycoside nucleotidyltransferase (AAD(2'')) confers resistance to important antibiotics like gentamicin, tobramycin, and kanamycin.
- Understanding the dissemination mechanisms of resistance genes is crucial for infection control.
Purpose of the Study:
- To investigate the prevalence and dissemination of the AAD(2'') gene in Enterobacteriaceae within a hospital environment.
- To identify the genetic elements, specifically plasmids, responsible for the spread of this resistance gene.
- To evaluate the utility of computer surveillance in tracking antimicrobial resistance trends.
Main Methods:
- Isolation and characterization of Enterobacteriaceae strains exhibiting AAD(2'') activity.
- Plasmid DNA purification and analysis using EcoRI digestion to assess genetic similarity.
- Plasmid incompatibility grouping and characterization of carried resistance genes.
- Utilizing computer surveillance of hospital laboratory data to monitor gene and plasmid prevalence.
Main Results:
- The AAD(2'') gene rapidly became prevalent across multiple Enterobacteriaceae strains and species within months.
- Eight distinct plasmids carrying the AAD(2'') gene shared similar EcoRI digestion patterns, suggesting dissemination via a single plasmid.
- This 56.5-megadalton plasmid, belonging to incompatibility group M and carrying additional resistance genes, initially spread in Klebsiella pneumoniae before predominantly circulating in Serratia marcescens.
- Computer surveillance effectively detected and traced the gene and plasmid, quantifying their impact on resistance prevalence.
Conclusions:
- A single, highly transmissible plasmid carrying the AAD(2'') gene was responsible for its rapid dissemination in a hospital.
- The study highlights the dynamic nature of antimicrobial resistance spread within clinical settings.
- Computerized surveillance systems are valuable tools for monitoring and managing antibiotic resistance.