Molecular epidemic mechanisms of ESBLS-producing strains in bloodstream infections caused by Escherichia coli
Objective To investigate and analyze the molecular epidemic mechanisms of Esche-richia coli bloodstream infection producing super-broad spectrum β-lactamase(ESBLs)strains and elucidate the drug resistance mediated by different drug resistance genes. Methods Fifty ESBLS-positive Escherichia coli strains were isolated from hospitalized patients with bloodstream infection from January 2019 to December 2022 at Huizhou Third People's Hospital. The expression of drug resistance genes in these strains was detected through polymerase chain reaction(PCR)amplification,and some of the positively amplified products were sent for sequencing to determine gene subtypes and corresponding drug resistance patterns. Results 45 out of the 50 Escherichia coli strains tested positive for ESBLs,carrying the blaCTX-M gene,which accounted for 90.00％(45/50),while 30 strains carried the blaTEM gene,accounting for 60.00％(30/50). Within the CTX-M genes,16 strains belonged to the CTX-M-1 subgroup,making up 35.56％(16/45),and 29 strains belonged to the CTX-M-9 subgroup,accounting for 64.4％(29/45). No blaSHV gene was found. Upon sequencing,it was revealed that the CTX-M-1 subgroup was primarily composed of the CTX-M-15 subtype,while the CTX-M-9 subgroup was dominated by CTX-M-14 subtype. The resistance rates of ceftazidime and cefepime in the CTX-M-9 group were lower compared to those in the CTX-M-1 group,with statistically significant differences (P<0.05). Conclusion In Huizhou,ESBLSS-positive Escherichia coli strains,the dominant drug resistance gene,is CTX-M type,with the CTX-M-9 subgroup being the main type. Within the CTX-M-9 subgroup,the dominant subtype is CTX-M-14. The resistance rate of the CTX-M-14 subtype to ceftazidime and cefepime was lower than that of the CTX-M-1 subgroup and CTX-M-15 subtype.
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