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Diagnostic microbiology laboratory susceptibility test results discriminate distinctive antibiotic resistance
Abstract:
The sizes of the zones of inhibition around routinely tested antibiotic disks classified gentamicin-resistant isolates of Klebsiella pneumoniae from one hospital into four major antibiotype classes. From each isolate of the prevalent class (A1), two plasmids could be transferred conjugally. One carried genes for resistance to tetracycline, sulfonamides, and chloramphenicol, and for the SHV beta lactamase. The other carried genes for two aminoglycoside-inactivating enzymes, APH (3')-I and AAC (3)-III, for the TEM 1 beta lactamase, and for resistance to sulfonamides. Transconjugants of either plasmid from any A1 isolate yielded the same DNA fragments after restriction endonuclease digestion, but the two plasmids had no fragments in common. Fragments or genes from either plasmid were variously combined or lacking in plasmids from variant isolates (A2, A3, and A4). Plasmids transferable from isolates of classes B and C shared no common DNA restriction fragments with each other or with either plasmid from Class A. Fragments and genes of the plasmids from C isolates, however, were identical with those of a plasmid endemic in a nearby hospital. Routine monitoring by diagnostic microbiology laboratories of distinctive antibiotypes and of the plasmids that produce them would aid infection control and antibiotic usage policy.
Insights
This study identified distinct plasmid types in gentamicin-resistant Klebsiella pneumoniae, revealing specific resistance genes and beta-lactamases. Monitoring these antibiotypes and plasmids can improve infection control and antibiotic stewardship.
Area of Science:
- Medical Microbiology
- Molecular Biology
- Infectious Diseases
Background:
- Gentamicin-resistant Klebsiella pneumoniae poses a significant public health threat.
- Understanding the genetic basis of antibiotic resistance in Klebsiella pneumoniae is crucial for effective treatment and control.
Purpose of the Study:
- To classify gentamicin-resistant Klebsiella pneumoniae isolates based on antibiotype.
- To characterize the plasmids responsible for antibiotic resistance in these isolates.
- To assess the potential for plasmid monitoring in infection control.
Main Methods:
- Antibiotic disk diffusion assays to determine antibiotype classes.
- Conjugal transfer experiments to isolate and analyze plasmids.
- Restriction endonuclease digestion to compare plasmid DNA fragments.
- Analysis of resistance genes and beta-lactamase types carried by plasmids.
Main Results:
- Four major antibiotype classes of gentamicin-resistant Klebsiella pneumoniae were identified.
- Two distinct plasmids were characterized in the prevalent class (A1), carrying various resistance genes (tetracycline, sulfonamides, chloramphenicol) and beta-lactamases (SHV, TEM 1).
- Plasmid profiles varied among different antibiotype classes, with some showing similarities to plasmids found in a nearby hospital.
Conclusions:
- Distinct plasmid types are associated with specific antibiotypes of Klebsiella pneumoniae.
- Routine monitoring of antibiotypes and their associated plasmids can enhance infection control strategies.
- This approach can inform antibiotic usage policies to combat the spread of resistant bacteria.