Molecular mechanism and clinical characteristics of colistin resistance gene mcr-1 in Carbapenem-resistant Enterobacteriaceae from Liaocheng area,Shandong Province
Molecular mechanism and clinical characteristics of colistin resistance gene mcr-1 in Carbapenem-resistant Enterobacteriaceae from Liaocheng area,Shandong Province
Objective To explore the molecular mechanism and clinical characteristics of Carbapenem-resistant Enterobacteriaceae(CRE)-related infections carrying colistin-resistance gene mcr-1,and to provide a reference basis for the clinical diagnosis and treatment of infections with such strains as well as for the prevention of spread of outbreaks and epidemics in the region.Methods Non-repetitive CRE were collected from clinical isolates in the Second People's Hospital of Liaocheng from January 2016 to December 2022,and the carbapenemase phenotype was detected using modified carbapenemase inactivation test(mCIM)combined with ethylenediamine tetra-acetic acid carbapenemase inactivation test(eCIM).The microbroth dilution method or agar dilution method were used for in vitro drug susceptibility test,polymerase chain reaction(PCR)was used to detect mcr-1 gene associated with colistin resistance and Carbapenem resistance genes.The multilocus sequence typing(MLST)technique was used to determine the sequence typing(ST)of strains.Case data of patients infected with mcr-1-positive strains were collected,and the relevant information was statistically analyzed.Results A total of 127 CRE strains were isolated,including 65 strains of Escherichia coli,52 strains of Klebsiella pneumoniae,3 strains of Enterobacter cloacae,3 strains of Klebsiella acidogenes,2 strains of Proteus mirabilis,1 strain of Citrobacter freundii and 1 strain of Enterobacter aerogenes;among which 6 strains carried the colistin-resistant gene mcr-1 and were also blaNDM-5 gene positive.The 6 strains of CRE carrying mcr-1 were only highly susceptible to Tigecycline,which demonstrated a low level of resistance.The results of MLST typing showed that there were four different ST phenotypes,2 strains of which were ST167,2 strains were ST410,and the remaining two strains were ST48 and ST361,respectively.The 6 patients were with different genders,ages,underlying diseases,antibiotic history and severity of illness,with different degrees of elevation of various infection indexes,and they were all finally cured and discharged from the hospital.Conclusions The detectable rate of colistin resistance gene mcr-1 was low in the clinical isolates of CRE in Liaocheng area,and the drug resistance was low,but the coexistence of mcr-1 and carbapenemase resistance genes was found,suggesting that clinical attention should be paid and its monitoring should be strengthened.
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