NDM-1 and rmtC-Producing Klebsiella pneumoniae Isolates in Turkey

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. We aimed to investigate the co-existence of 16S rRNA methyltransferase and beta-lactamase genes in multidrug resistant (MDR) strains isolated from clinical samples. 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 strains. Multidrug resistant 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. Twenty 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 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. This study demonstrated the co-existence of and genes for the first time in Turkey. The spread of this resistant type should be monitored and limited through molecular surveillance.