Study on the resistance genes of carbapenem-resistant Enterobacteriaceae collected from 5 hospitals in Northeast China

Abstract

Objective To investigate the antibiotic resistance and resistance genes of carbapenem-resistant Enterobacteriaceaes (CRE) isolated from 5 hospitals in Northeast China. Methods This study collected 85 CRE isolates during January 2013 to June 2015 from five hospitals in Northeast China. Drug sensitivities of 14 antimicrobial agents were determined by the broth microdilution method. The phenotypes of carbapenemases were screened by modified Hodge test and EDTA test respectively. The genotypes of carbapenemases and other extended spectrum β-lactamases (ESBL) were detected by PCR gene amplification and DNA sequencing method. Using the PCR result as gold standard, the performances of other two carbapenemase detection methods were evaluated. Results Among the 85 CRE strains collected in this study, Klebsiella pneumoniae was the most frequently isolated species (61/85, 71.8%). The results of antimicrobial agent sensitivity showed that the 85 CRE strains had resistance rate of cephalosporin and β-lactams/enzyme inhibitor (piperacillin-tazobactam) over 80.0%. The resistance rate of carbapenem was high, with ertapenem 100.0% (85/85), meropenem 65.9% (56/85), imipenem 71.8% (61/85). There were 36 isolates resistant to both meropenem and imipenem. For fluoroquinolones, the resistance rates of levofloxacin and ciprofloxacin were 72.9% (62/85) and 65.9% (56/85), respectively. The resistance rate to fosfomycin and amikacin were 65.0% (55/85) and 54.1% (46/85), respectively. The resistance rate of colistin (21.2%, 18/85) and tigecycline (20.5%, 17/85) were low. Forty-nine strains were modified Hodge test positive and 12 strains were EDTA test positive. By PCR gene amplification and DNA sequencing method, 64 strains carried carbapenemase-encoding genes, of which KPC-2 was the main type (53/85, 62.4%), followed by IMP-4 (10/85, 11.8%), NDM-5 (7/85, 8.2%) and NDM-6 (1/85, 1.2%). At the same time, 85 CRE isolates had the ESBL gene detection and 47 isolates were CTX-M type ESBLs (47/85, 55.3%), with no TEM or SHV type. Conclusions Klebsiella pneumoniae is the majority of CRE strains from 5 large hospitals in Northeastern China. The CRE strains are resistant to most of antimicrobials. Most carbapenemases-producing isolates have the KPC-2 type. Nearly half of the carbapenemase-producing strains also carry ESBL genes, which makes the resistance mechanisms more complicated. Key words: Enterobacteriaceae; Carbapenemase; Extended-spectrum β-lactamases