[Emerging and comparative genomic analysis of a novel plasmid carrying blaKPC-2 in Citrobacter freundii]

Objective: To explore the drug resistance mechanism and gene structure characteristics of a carbapenemase-producing novel incompatibility group plasmid pNY2385-KPC from Citrobacter freundii. Methods: A multi-drug resistant strain was obtained from urine samples of patients with fever in the emergency ward of Li Huili Hospital, Ningbo Medical Center. Bacterial species was preliminary identified and finally confirmed by 16S rRNA gene amplification and the average nucleotide identity alignment, respectively. The minimum inhibitory concentrations of the antimicrobial agents were determined by VITEK 2 Compact System. The complete genome sequence was obtained by "third-generation" sequencing methods, and then detailed annotation of gene function and comparative genomic analysis of plasmid structure were carried out by BLASTP/BLASTN, RefSeq, ConservedDomains, ResFinder, Isfinder, etc. Results: The pNY2385-KPC carried by citrobacter freundii NY2385 belonged a novel incompatibility group, and contained blaKPC-2 and conjugative transfer (type Ⅳ secretory system, T4SS) genes, which could induce conjugative transfer. A total of 15 plasmids of the same type as pNY2385-KPC were retrieved by NCBI, which were from Citrobacter freundii, and the rest were from Serratia marcescens, Escherichia coli, Enterobacter cloacae, Klebsiella pneumoniae, Raoultella planticola and other bacteria, and were broad-host-range plasmids. The sequence comparative analysis of all 6 of the novel plasmid from Citrobacter freundii showed that the structure of the novel plasmid had certain conserved property, with Tn6296 variant structure carrying blaKPC-2, and plasmid pCF1807-3 had both repApNY2385-KPC and repAIncX8. Conclusion: The pNY2385-KPC type plasmids in Citrobacter freundii carried blaKPC-2 resistance gene, which were divided into two subtypes: repApNY2385-KPC single replicator and repApNY2385-KPC/repAIncX8 complex replicator, belonging to broad-host-range plasmids. And as a mobile genetic element, the plasmids promote the spread of blaKPC-2.

[Risk factors of carbapenem resistant Acinetobacter baumannii infection in intensive care unit]

Objective: This study will analyze the clinical characteristics and risk factors that may be related to the 30-day mortality of patients infected with CRAB in intensive care unit (ICU), and explore the resistance of CRAB and its influence on mortality. Methods: From December 2012 to February 2021, 173 ICU patients with CRAB infection in the Fifth Medical Center of PLA General Hospital were selected as the research objects, and the relevant data were collected for retrospective analysis. There were 119 cases (68.8%) in survival group and 54 cases (31.2%) in the non-survival group. Patients with CRAB infection were (52.9±13.5) years old, including 140 males (80.9%) and 33 females (19.1%).The first detected CRAB was collected, and antibiotic sensitivity test was conducted after the strain was resuscitated to analyze the antibiotic resistance. Univariate and multivariate Cox models were used to analyze independent risk factors associated with 30-day mortality in patients with CRAB infection. Results: Univariate and multivariate Cox analysis showed that acute physiology and chronic health evaluation scoring system Ⅱ(APACHE Ⅱ)(HR=1.058, 95%CI:1.012-1.106, P=0.013) and septic shock (HR=6.240, 95%CI:2.227-17.483, P<0.001) were independent risk factors related to 30-day mortality in ICU patients with CRAB. Treatment with β-lactamase inhibitor (HR=0.496, 95%CI: 0.275-0.893, P<0.019) can reduce the 30-day mortality of patients with CRAB infection in ICU. The resistance rate of CRAB to cephalosporins, carbapenems, aminoglycosides and quinolones were more than 80%. The survival rate of patients infected by aminoglycoside resistant CRAB is low(χ²=4.012,P<0.05). Conclusion: The APACHE Ⅱ score, septic shock and use of β-lactamase inhibitors were independent factors associated with the 30-day mortality in ICU patients with CRAB infection.