Aminoglycoside Resistance in Clinical Klebsiella pneumoniae Isolates

To analyze the Klebsiella pneumoniae (K. pneumoniae) susceptibility to aminoglycosides antibiotics in clinical isolates in Guangzhou, and to characterize the molecular resistance mechanisms of K. pneumoniae against aminoglycosides (AGs) agents. We examined 1495 strains clinical isolates of Klebsiella pneumoniae from Microbiology Laboratory of the Guangdong Provincial Traditional Chinese Medicine in China between 2008 and 2012 by MicroScan Wa1kAway-96. And detected Minimal inhibitory concentrations (MICs) of amikacin, gentamicin and tobramycin to K. pneumoniae by agar dilution methods. Isolates were analyzed by polymerase chain reaction (PCR) amplification techniques to determine whether six aminoglycoside modifying enzymes (AMEs) genes ( aac(3')-a', aac(6')-Ib, ant(3")-I, ant(2")-I, aac(3)-I, aac(6')-a')and six 16S rRNA mehtylases genes (armA, rmtA, rmtB, rmtC, rmtD, npmA) were present. Additionally, 16S rRNA methylase gene positive isolates were chosen for a plasmid transfer test to explore whether the resistance marker was located on the transfer plasmid. Pulsed-field gel electrophoresis was used for genotyping 16S rRNA methylase gene positive isolates. A total of 265 isolates was identified as resistant to one or more aminoglycosides, with resistance rates to amikacin, tobramycin and gentamicin of 4.15%(62/1495), 9.50%(142/1495), and 16.05%(240/1495), respectively. Among the 265 resistant aminoglycoside isolates, 84.5% carried resistance genes (180 isolates carried AMEs and 44 isolates carried both AMEs and methylase genes). Aminoglycoside resistance in Guangzhou clinical isolates of K. pneumoniae is still low, and kept stable over the last 5 years; frequency of AMEs and 16S rRNA methylase in K. pneumoniae was low.