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NDM-1 and rmtC-Producing Klebsiella pneumoniae Isolates in Turkey
Tulin Guven Gokmen1, Togrul Nagiyev2, Melda Meral2
1Department of Microbiology, Ceyhan Veterinary Faculty, Cukurova University, Adana, Turkey.
Background:
The resistance of aminoglycosides in strains that produce beta-lactamase can be developed through the multidrug resistant encoding genes carried by common plasmids. Recently, the association between 16S rRNA methyltransferase resistance and beta-lactamase enzymes carried by the same plasmids has drawn increased attention from researchers, particularly the association in aminoglycoside-resistant strains with a minimum inhibitory concentration (MIC) of ≥ 256 µg/mL.
Objectives:
We aimed to investigate the co-existence of 16S rRNA methyltransferase and beta-lactamase genes in multidrug resistant (MDR) Klebsiella pneumoniae strains isolated from clinical samples.
Methods:
We determined the molecular mechanisms of aminoglycoside resistance and its relationship with resistance to carbapenem and beta-lactam group antibiotics in 40 extended-spectrum beta-lactamase (ESBL)-positive carbapenem- and aminoglycoside-resistant K. pneumoniae strains. Multidrug resistant K. pneumoniae was isolated from various clinical samples in the faculty of medicine of Cukurova University, Turkey. First, the resistance of aminoglycoside and beta-lactam antibiotics was phenotypically investigated using the Kirby-Bauer disk diffusion test, double disk synergy test, and modified Hodge test. The MIC values of aminoglycoside were determined using the agar dilution method. Polymerase chain reaction was performed to detect the carbapenemases, ESBL, and 16S rRNA methyltransferase genes. The results were confirmed by a sequence analysis.
Results:
Twenty K. pneumoniae strains showed resistance to amikacin, and 40 were resistant to gentamicin. The MIC value was found to be > 512 µg/mL in five amikacin-resistant strains and > 128 µg/mL in 10 gentamicin-resistant isolates. The rmtC gene, a type of 16S rRNA methyltransferase, was amplified in four isolates (MIC amikacin: > 512 µg/mL, gentamicin: > 128 µg/mL). Of these four isolates, three had the blaNDM-1 gene and all contained at least one ESBL gene.
Conclusions:
This study demonstrated the co-existence of rmtC and blaNDM-1 genes for the first time in Turkey. The spread of this resistant type should be monitored and limited through molecular surveillance.
Insights
Multidrug-resistant Klebsiella pneumoniae strains in Turkey were found to carry both 16S rRNA methyltransferase (rmtC) and beta-lactamase (blaNDM-1) genes. This co-existence of resistance genes highlights the need for molecular surveillance to control their spread.
Area of Science:
- Medical Microbiology
- Molecular Biology
- Genetics
Background:
- Aminoglycoside resistance in beta-lactamase-producing strains is often plasmid-mediated.
- Co-existence of 16S rRNA methyltransferase and beta-lactamase genes on plasmids is an emerging concern in aminoglycoside-resistant strains.
Purpose of the Study:
- To investigate the co-occurrence of 16S rRNA methyltransferase and beta-lactamase genes in multidrug-resistant Klebsiella pneumoniae clinical isolates.
- To determine the molecular mechanisms of aminoglycoside resistance and its association with carbapenem and beta-lactam antibiotic resistance.
Main Methods:
- Phenotypic antibiotic resistance testing (disk diffusion, double disk synergy, modified Hodge test) and MIC determination.
- Polymerase chain reaction (PCR) to detect carbapenemase, ESBL, and 16S rRNA methyltransferase genes.
- Sequence analysis for confirmation of genetic findings.
Main Results:
- Four Klebsiella pneumoniae isolates harbored the rmtC gene, conferring high-level aminoglycoside resistance (Amikacin MIC > 512 µg/mL, Gentamicin MIC > 128 µg/mL).
- Three of these four isolates also carried the blaNDM-1 gene, and all contained at least one extended-spectrum beta-lactamase (ESBL) gene.
Conclusions:
- This study reports the first documented co-existence of rmtC and blaNDM-1 genes in Klebsiella pneumoniae in Turkey.
- Molecular surveillance is crucial to monitor and limit the dissemination of this multidrug-resistant phenotype.
