ABSTRACT
Objective:To investigate the bacterial composition and antimicrobial resistance profile of clinical isolates from bloodstream infections in China.Methods:The clinical bacterial strains isolated from blood culture were collected during January 2020 to December 2020 in member hospitals of Blood Bacterial Resistant Investigation Collaborative System (BRICS). Antibiotic susceptibility tests were conducted by agar dilution or broth dilution methods recommended by Clinical Laboratory Standards Institute(CLSI, USA). WHONET 5.6 was used to analyze data.Results:During the study period, 10 043 bacterial strains were collected from 54 hospitals, of which 2 664 (26.5%) were Gram-positive bacteria and 7 379 (73.5%) were Gram-negative bacteria. The top 10 bacterial species were Escherichia coli (38.6%), Klebsiella pneumoniae (18.4%), Staphylococcus aureus (9.9%), coagulase-negative Staphylococci (7.5%), Pseudomonas aeruginosa (3.9%), Enterococcus faecium (3.3%), Enterobacter cloacae (2.8%), Enterococcus faecalis (2.6%), Acinetobacter baumannii (2.4%) and Klebsiella spp (1.8%). The prevalence of methicillin-resistant Staphylococcus aureus (MRSA) and methicillin-resistant coagulase-negative Staphylococcus aureus were 27.6% and 74.4%, respectively. No glycopeptide- and daptomycin-resistant Staphylococci were detected. More than 95% of Staphylococcus aureus were sensitive to rifampicin and SMZco. No vancomycin-resistant Enterococci strains were detected. Extended spectrum β-lactamase (ESBL) producing Escherichia coli, Klebsiella pneumoniae and Proteus mirabilis were 48.4%, 23.6% and 36.1%, respectively. The prevalence rates of carbapenem-resistance in Escherichia coli and Klebsiella pneumoniae were 2.3% and 16.1%, respectively; 9.6% of carbapenem-resistant Klebsiella pneumoniae strains were resistant to ceftazidime/avibactam combination. The prevalence rate of carbapenem-resistance in Acinetobacter baumannii was 60.0%, while polymyxin and tigecycline showed good activity against Acinetobacter baumannii. The prevalence rate of carbapenem-resistance of Pseudomonas aeruginosa was 23.2%. Conclusions:The surveillance results in 2020 showed that the main pathogens of bloodstream infection in China were gram-negative bacteria, while Escherichia coli was the most common pathogen, and ESBL-producing strains declined while carbapenem-resistant Klebsiella pneumoniae kept on high level. The proportion and the prevalence of carbapenem-resistant Pseudomonas aeruginosa were on the rise slowly. On the other side, the MRSA incidence got lower in China, while the overall prevalence of vancomycin-resistant Enterococci was low.
ABSTRACT
Objective To investigate the effects of hypoxia-inducible factor-1α (HIF-1α)expression on pathogenesis of retinopathy of prematurity (ROP) and to find new target for gene therapy.Methods After liposome-mediated small interference RNA (siRNA) transfection into rat retinal endothelial cells,the cells were cultured in medium with CoCl2-induced hypoxic condition.Expression of HIF-1α mRNA was determined by fluorenscence quantitative reverse transcription-polymerase chain reaction(RT-PCR),HIF-1α protein expression was detected by Western Blot after cocultured for 8 hours.Cell proliferation was measured with 3-(4,5)-dimethylthiazol (-2-yl)-2,5-diphenyltetrazolium bromide(MTT) assay after cocultured for 24 hours.Difference between groups was compared with independent samples t test.Results Rat retinal vascular endothelial cells were successfully transfected with siRNA.Fluorescence quantitative RT-PCR results showed that at 48 hours of transfection,the expression of HIF-1α mRNA in the interference group of siRNA1,siRNA2 and siRNA4 were 0.1620 ± 0.0147,0.2034 ± 0.0251 and 0.3049 ± 0.0165,which were 16.20％,20.34 ％ and 30.49％ of blank control group (1.0000±0.0344),and were lower than that of negative control group (0.8334±0.0242) (t=16.786,8.953 and 4.087,P＜0.05 respectively).Western Blot results showed that HIF-1α protein expression was significantly inhibited by siRNA1(0.4956 ± 0.0421 ) and siRNA2 (0.6544 ± 1.0032) comparing with blank control group (3.5105 ±0.4084) and negative control group (3.4019 ± 1.0677) (t =6.861,2.893,4.567 and 5.072,P＜0.05 respectively).As for cellular proliferation activity,(49.5±2.9) ％ and (67.4±1.2) ％ of cells growth inhibition were observed after transfection with siRNA1 and siRNA2,which were higher than those of negative control group [(15.7±1.5) ％ ] (t=2.786 and 6.904,P＜0.05).Conclusions The synthetic HIF-1α siRNA could effectively inhibit the expression of HIF-1α gene and reduce cell proliferation in rat retinal endothelial cells under hypoxic condition.RNA interference technology targeting HIF-1α might become a new strategy for gene therapy of ROP.