Abstract:

Objective: To study the carbapenem resistance genes of clinically isolated carbapenem-resistant Escherichia coli strains. Methods: Non-repetitive carbapenem-resistant Escherichia coli strains isolated from clinical specimens of inpatients in our hospital from March 2009 to October 2017 were collected. The strains were firstly confirmed by Microflex^TM MALDI-TOF MS, then drug sensitivity of isolates was tested by K-B method combined with Vitek-2 Compact Automatic Microbiological Analyzer. Rapid screening of carbapenemase-producing Escherichia coli was performed using the modified carbapenem inactivation method (mCIM). Commonly seen carbapenemase was detected by regular PCR and DNA sequencing. The clinical data of patients were analyzed. Result: From March 2009 to December 2017, a total of 84 non-repetitive carbapenem-resistant Escherichia coli strains were isolated. Drug resistance test showed that carbapenem-resistant Escherichia coli had a very high resistance rate (up to 80%-100%) for most of the commonly used drugs except amikacin, whose drug resistance rate was less than 50%. A total of 71 carbapenemase-producing strains were identified by mCIM. The PCR and DNA sequencing results for drug resistance genes showed that there were 65 strains carrying bla_NDM, with bla_NDM-5 (64.6%, 42/65) and bla_NDM-1(24.6%, 16/65) as the main types, and of them 2 strains carried both bla_NDM-1 and bla_MCR-1; 6s trains carriedblakpc-2; while no bla_GES, bla_IMP, bla_VIM, bla_OXA were detected. Altogether 17 types of clinical specimens and 23 departments were concerned, urine samples accounted for 30.95% (26/84) and sputum samples accounted for 21.43% (18/84). Carbapenemase-producing strains were mainly isolated from pediatric patients (66.7%, 56/84). Most of the strains isolated from children and infants were enzyme-producing (96.4%, 54/56), of which bla_NDM-5 accounted for 63.0%(34/54). Most of the strains isolated from elderly patients were non-enzyme-producing (62.5%, 10/16). Besides, 54% (45/84) of these patients underwent surgery, while 33% (28/84) of them were treated with indwelling deep vein catheter and invasive medical procedures. Conclusions: The carbapenem-resistant Escherichia coli strains isolated from patients in our hospital mostly are multi-drug resistant. NDM and KPC are the main carbapenemase, and NDM-5 is the major type with a detection rate as high as 50%(42/84). The isolated rate of carbapenem-resistant Escherichia coli in pediatric wards is high, especially in critical care wards.

Key words: Escherichia coli, Carbapenem, Resistance genes