Mechanism of aminoglycoside resistance and molecular epidemiology of amikacin-resistant Klebsiella pneumoniae in hospital

Abstract

Objective To study the genetics relationship among clinical isolates of Klebsiella pneumoniae and the prevalence and sources of aminoglycoside resistant genes, as to provide evidence for clinical infection control. Methods Walkaway 96 plus automatic bacterial identification and drug sensitivity analyzer were used. Twenty-seven strains of amikacin-resistant Klebsiella pneumonia isolated from June 2013 to November 2014 were identified and tested. The susceptibility of some antimicrobial agents was detected by disk diffusion and E-test, and aminoglycoside resistance genes were detected by polymerase chain reaction (PCR). Some positive genes were sequenced. Multilocus sequence typing (MLST) was used to identify the genetic relationship among the strains. Results Among the 27 strains, 88.9% (24/27) isolates harbored the 16S rRNA methylase gene rmtB. The positive rates of the aminoglycoside modifying enzyme gene aac(3)-II, aac(6′)-I and ant(3″)-I were 51.9% (14/27), 40.7% (11/27), and 40.7% (11/27), respectively. MLST analysis revealed nine sequence types (STs), which were ST37 (40.7%), ST11 (40.7%), ST1 (11.1%), ST789 (11.1%), ST15 (7.4%), ST147 (7.4%), ST76 (3.7%), ST722 (3.7%) and ST290 (3.7%). 29.6%(8/27) specimens were found in ICU, and 18.5%(5/27) were from neurology ward. The bacterial strains were mainly isolated from sputum and urine, accounting for 51.9% (14/27) and 37.04% (10/27), respectively. Conclusions The amikacin-resistant Klebsiella pneumonia strains belonging to ST11 spread in hospital; and these isolates harbored the rmtB gene. The drug-resistance of Klebsiella pneumoniae to amikacin is closely associated with rmtB and aac(6′)-I. Key words: Amikacin-resistant; Klebsiella pneumoniae; Aminoglycosides resistance gene; Multilocus sequence typing