Investigation of Plasmid-mediated High-level Aminoglycoside Resistance in Carbapenem-resistant Klebsiella pneumoniae Isolates

Abstract

Introduction: Carbapenemase-producing Klebsiella pneumoniae has become a leading cause of nosocomial infections in recent years, and aminoglycoside antibiotics have gained importance in the treatment of these infections due to their broad antimicrobial spectra, rapid bactericidal effects, and synergistic interactions with other antimicrobials. However, the excessive use of aminoglycosides has led to resistance. The aim of this study was to investigate plasmid-mediated, high-level resistance to aminoglycosides associated with 16S ribosomal RNA methyltransferases (16S-RMTase) in carbapenem-resistant K. pneumoniae isolates. Materials and Methods: The study included 67 consecutively isolated carbapenem-resistant K. pneumoniae isolates obtained in 2014 (n= 32) and 2015 (n= 35). Identification and antimicrobial susceptibility testing were performed using a BD Phoenix automated system. Aminoglycoside (amikacin and gentamicin) susceptibility tests were also repeated by disk diffusion method. In-house polymerase chain reaction (PCR) was performed to detect genes for carbapenemase resistance and 16S-RMTase in the isolates. Results: The blaOXA-48 gene was detected in all 32 isolates obtained in 2014. Of the isolates from 2015, 10 were positive for blaOXA-48 and 6 were positive for blaNDM. Positivity for both blaOXA-48 and blaNDM was observed in 19 isolates. All of the isolates from 2014 were negative for armA while 28 of the isolates from 2015 were positive for armA. Positivity for armA was observed in all isolates that carried the blaNDM gene alone versus 5 of the isolates that carried blaOXA-48 alone. Seventeen of the armA-positive isolates carried both blaOXA-48 and blaNDM. Four of the armA-positive isolates were sensitive to amikacin in the automated analyzer, but were found to be amikacin-resistant in disk diffusion test. Conclusion: Although 16S-RMTase genes were not detected in any of the carbapenem-resistant K. pneumoniae isolates obtained from inpatients in our hospital in 2014, armA positivity emerged the following year. The coincident appearance of armA and blaNDM-positive isolates indicates a positive correlation. Our findings are significant since armA-type 16S-RMTase gene positivity, detected in 28 isolates in this study, has not been reported previously in Turkey.

Keywords

• 16s ribosomal rna methyltransferases
• high-level aminoglycoside resistance
• klebsiella pneumoniae
• arma