Co-infections of two carbapenemase-producing Enterobacter hormaechei clinical strains isolated from the same diabetes individual in China

Introduction. Since mcr-1 was first reported in China, there have been ten variants of MCR appearing nationwide so far. Multidrug-resistant Enterobacteriaceae bacteria carrying both NDM and MCR have become a serious threat to global public health. Hypothesis/Gap Statement. The genetic structure of mcr-9 needs to be better understood in order to better prevent and control the transmission of drug-resistant genes. Aims. The aim of this study was to characterize the presence of two Enterobacter hormaechei isolates, which carries bla(NDM-5) CME2 and the coexistence of mcr-9 and bla(NDM-1) strain CMD2, which were isolated from a patient with diabetes in Sichuan, China. Methodology. The microbroth dilution method was used for antibiotic susceptibility. Conjugation experiment was used to investigate the transferability of bla(NDM-1), bla(NDM-5) and mcr-9. Whole-genome sequencing was performed on Illumina HiSeq platform. The ability of biofilm formation was detected by crystal-violet staining, the virulence of the bacteria was measured by Galleria mellonella killing assay. Results. bla(NDM-5) carrier CME2 and CMD2 with bla(NDM-1) and mcr-9 were resistant to carbapenems, beta-lactam, aminoglycoside, quinolone and tetracycline, while CMD2 was also resistant to colistin. Conjugation assay and plasmid replicon typing further demonstrated that both bla(NDM-1) and bla(NDM-5) were respectively present on the self-transferrable IncX3 plasmid, mcr-9 was located on the self-transferrable IncHI2 plasmid. Through the analysis of mcr-9 gene context, the structure was DUF4942-rcnR-rcnA-copS-IS903-mcr-9-wbuC-qseC-qseB-IS1R-Delta silR-IS903, bla(NDM-1) context was IS3000-Delta ISAba125-IS5-bla(NDM-1)-ble-trpF-groS-groL-insE-Delta IS26 structure, bla(NDM-5) structure was IS3000-bla(NDM-5)-ble-trpF-dsbC-Delta IS26-umuD-ISKox3-tnpR-parA. Biofilm formation of CME2 was stronger than CMD2. There was no significant difference in virulence between the two strains. Conclusion. This study reveals two multiple drug-resistant E. hormaechei isolates from diabetes patient samples. E. hormaechei carrying two NDM-resistant genes is already a serious threat, where MCR is an important cause of treatment failure in bacterial infections. This study is a reminder not only to prevent infection in patients with diabetes, but also to constantly monitor the epidemic and spread of the drug-resistant gene.

Automated summary

This study characterized two multi-drug resistant E. hormaechei isolates from a diabetes patient in Sichuan, China, revealing their resistance to various antibiotics, biofilm formation ability, and virulence. The presence of resistant genes in these strains poses a serious threat to global public health and highlights the importance of constant monitoring and prevention strategies.