Drug-resistant genes and virulence factors of carbepenem-resistant Klebsiella peumoniae

Abstract

Objective To investigate the resistance mechanism and virulence genes of clinical strains of carbapenem-resistant Klebsiella pneumonia (CRKP). Methods Twenty clinical CRKP strains were collected from Tianjin Medical University General Hospital during May 2014 and May 2015. Vitek-2 Compact system was used for identification of the strains and antibiotic susceptibility test. Modified Hodge Test and EDTA double disk phenotypic test were performed for screening of drug-resistant phenotypes. Drug-resistant genes, capsular serotypes and associated virulence genes were amplified by PCR, and positive products were sequenced and analyzed by DNA sequencing. Results Resistance to beta-lactam antibiotics including cephalosporins and carbapenems was observed in 80.0% and above strains, but more than 70.0% strains were sensitive to tigecycline, amikacin and levofloxacin. KPC gene and NDM gene were found in 7 strains (35.0%) and 8 strains (40.0%), respectively. SHV, the most common extended-spectrum β-lactamases (ESBLs) gene, was found in 16 strains (80.0%). DHA plasmid-mediated AmpC β-lactamase was found in 2 strains (10.0%). Deletions of porin-coding genes OmpK35 and OmpK36 were found in 8 stains (40.0%) and 13 strains (65.0%), respectively. Carbapenem-resistant genes in combination with ESBLs genes and/or variation of porin was found in 14 strains (70.0%), and ESBLs genes in combination with variation of porin was found in 4 strains (30.0%). Three strains were of capsular serotype K1 and 1 was of K57, and all of them carried KPC genes. Virulence gene rmpA was found in 8 strains and all carried carbapenemases, among which 5 strains with KPC, 2 strains with NDM, 1 strain with both KPC and NDM. Six strains were aerobactin gene positive, among which 4 strains carried KPC genes. FimH-1 was positive in all strains. Conclusions KPC and NDM genes mainly account for resistance in CPKP, and ESBLs with OmpK gene deletion may also be an important cause. Strains with capsular serotypes K1 and K57 carrying KPC genes are common. Key words: Klebsiella pneumonia; Drug resistance, multiple; Bacterial capsules; Virulence factors