Newly Detected Transmission of bla_(KPC-2) by Outer Membrane Vesicles in Klebsiella Pneumoniae

Objective The prevalence of carbapenem-resistant Klebsiella pneumoniae(CR-KP)is a global public health problem.It is mainly caused by the plasmid-carried carbapenemase gene.Outer membrane vesicles(OMVs)contain toxins and other factors involved in various biological processes,includingβ-lactamase and antibiotic-resistance genes.This study aimed to reveal the transmission mechanism of OMV-mediated drug resistance of Klebsiella(K.)pneumoniae.Methods We selected CR-KP producing K.pneumoniae carbapenemase-2(KPC-2)to study whether they can transfer resistance genes through OMVs.The OMVs of CR-KP were obtained by ultracentrifugation,and incubated with carbapenem-sensitive K.pneumoniae for 4 h.Finally,the carbapenem-sensitive K.pneumoniae was tested for the presence of bla_(KPC-2)resistance gene and its sensitivity to carbapenem antibiotics.Results The existence of OMVs was observed by the electron microscopy.The extracted OMVs had bla_(KPC-2)resistance gene.After incubation with OMVs,bla_(KPC-2)resistance gene was detected in sensitive K.pneumoniae,and it became resistant to imipenem and meropenem.Conclusion This study demonstrated that OMVs isolated from KPC-2-producing CR-KP could deliver bla_(KPC-2)to sensitive K.pneumoniae,allowing the bacteria to produce carbapenemase,which may provide a novel target for innovative therapies in combination with conventional antibiotics for treating carbapenem-resistant Enterobacteriaceae.

Protein Phosphatase 2A as a Drug Target in the Treatment of Cancer and Alzheimer's Disease

Protein phosphatase 2A(PP2A)is a major serine/threonine phosphatase which participates in the regulation of multiple cellular processes.As a confirmed tumor suppressor,PP2A activity is downregulated in tumors and its re-activation can induce apoptosis of cancer cells.In the brains of Alzheimer's disease(AD)patients,decreased PP2A activity also plays a key role in promoting tau hyperphosphorylation and A0 generation.In this review,we discussed compounds aiming at modulating PP2A activity in the treatment of cancer or AD.The upstream factors that inactivate PP2A in diseases have not been fully elucidated and further studies are needed.It will help for the refinement and development of novel and clinically tractable PP2A-targeted compounds or therapies for the treatment of tumor and AD.

Erratum to: Protein Phosphatase 2A as a Drug Target in the Treatment of Cancer and A zheimer's Disease

The article“Protein Phosphatase 2A as a Drug Target in the Treatment of Cancer and Alzheimer's Disease”,written by Hui WEI,Hui-liang ZHANG,Jia-zhao XIE,Dong-li MENG,Xiao-chuan WANG,Dan KE,Ji ZENG,Rong LIU,was originally published electronically on the publisher's internet portal on 13 March 2020 without open access.With the author(s)'decision to opt for Open Choice the copyright of the article changed to O The Author(s)2020 and the article is forthwith distributed under a Creative Commons Attribution 4.0 International License(https://creativecommons.org/licenses/by/4.0/),which permits use,sharing,adaptation,distribution and reproduction in any medium or format,as long as you give appropriate credit to the original author(s)and the source,provide a link to the Creative Commons license,and indicate if changes were made.

Fight or flee,a vital choice for Clostridioides difficile

Clostridioides difficile is a leading cause of healthcare-associated infections,causing billions of economic losses every year.Its symptoms range from mild diarrhea to life-threatening damage to the colon.Transmission and recurrence of c.difficile infection(CDl)are mediated by the metabolically dormant spores,while the virulence of C.difficile is mainly due to the two large clostridial toxins,TcdA and TcdB.Producing toxins or forming spores are two different strategies for C.difficile to cope with harsh environmental conditions.It is of great significance to understand the molecular mechanisms for C.difficile to skew to either of the cellular processes.Here,we summarize the current understanding of the regulation and connections between toxin production and sporulation in C.difficile and further discuss the potential solutions for yet-to-be-answered questions.

2011年、2013年和2016年医院内获得性血流感染常见病原菌分布及其耐药性分析

动态监测2011年、2013年和2016年我国不同地区医院内获得性血流感染病原菌分布及耐药进展趋势。从全国10个城市回顾性收集血流感染病原菌非重复性株,采用琼脂稀释法或微量肉汤稀释法进行药物敏感性试验,采用Whonet 5.6软件对药敏试验结果进行分析。收集的2 248株血流感染病原菌中革兰阴性杆菌为1 657株(占73.7%),革兰阳性球菌为591株(占26.3%)。分离率排名前五的病原菌依次为大肠埃希菌(32.6%,733株/2 248株)、肺炎克雷伯菌(14.5%,327株/2 248株)、金黄色葡萄球菌(10.0%,225株/2 248株)、鲍曼不动杆菌(8.7%,196株/2 248株)和铜绿假单胞菌(6.2%,140株/2 248株)。血流感染分离的革兰阴性杆菌对抗菌药物体外敏感率较高的抗菌药物依次为粘菌素(96.5%,1 525株/1 581株,不包括天然耐药菌株)、替加环素(95.6%,1 375株/1 438株,不包括天然耐药菌株)、头孢他啶/克拉维酸(89.2%,1 112株/1 246株)、阿米卡星(86.4%,1 382株/1 599株)和美罗培南(85.7%,1 376株/1 605株);革兰阳性球菌对抗菌药物体外敏感率较高的抗菌药物依次为替加环素、替考拉宁和达托霉素(敏感率均为100.0%)、万古霉素和利奈唑胺(敏感率均为99.7%)。2011年、2013年和2016年产超广谱β-内酰胺酶肠杆菌科细菌分离率分别为50.6%(206株/407株)、49.8%(136株/273株)和38.9%(167株/429株);碳青霉烯不敏感肠杆菌科细菌分离率分别为2.2%(9株/408株)、4.0%(16株/402株)和3.9%(17株/439株);多重耐药鲍曼不动杆菌分离率分别为76.4%(55株/72株)、82.7%(43株/52株)和87.5%(63株/72株),多重耐药铜绿假单胞菌分离率分别为9.8%(5株/51株)、20.0%(7株/35株)和13.0%(7株/54株);甲氧西林耐药金黄色葡萄球菌的分离率分别为51.9%(41株/79株)、29.7%(19株/64株)和31.7%(26株/82株)。屎肠球菌和粪肠球菌中高水平庆大霉素耐药株分离率分别为43.2%(48株/111株)和40.9%(27株/66株)。碳青霉烯不敏感肠杆菌科细菌中肺炎克雷伯菌居首位,占57.1%(24株/42株)。肠杆菌科细菌中分离出30株替加环素不敏感株,其中肺炎克雷伯菌占76.7%(23株/30株);分离出粘菌素耐药肠杆菌科细菌39株,其中大肠埃希菌、阴沟肠杆菌和肺炎克雷伯菌分别占43.6%(17株/39株)、35.9%(14株/39株)和15.4%(6株/39株)。医院获得性血流感染病原菌主要为革兰阴性杆菌(以大肠埃希菌和肺炎克雷伯菌为主),其对替加环素、粘菌素和碳青霉烯类药物的敏感率较高;革兰阳性球菌中分离率最高的为金黄色葡萄球菌,其次为屎肠球菌,这两种细菌对替加环素、达托霉素、利奈唑胺、万古霉素和替考拉宁的敏感率较高。粘菌素耐药肠杆菌科细菌、替加环素不敏感肠杆菌科细菌、利奈唑胺或万古霉素不敏感革兰阳性球菌的分离,警示临床高度关注,仍需动态监测耐药进展趋势。

Effect of inhibiting tyrosine kinase Src expression on protein phosphatase 2A and tau phosphorylation

The aim of this study is to investigate the effect of tyrosine kinase Src on Tyrosine 307(Y307)phosphor-ylation,protein phosphatase 2A(PP2A)activity,and on tau phosphorylation.Specific Src siRNA was transfected into cultured mouse neuroblastoma N2a cells to inhibit the expression of Src protein,and the phosphorylation levels of PP2A Y307 and tau at different sites,as well as PP2A activity were detected at different time points after siRNA transfection.Twelve hours after siRNA transfec-tion,the protein level of Src was dramatically decreased,with decreased PP2A Y307 phosphorylation.However,the total PP2A protein level was also decreased,together with a decreased PP2A activity.Tau was hyperpho-sphorylated at the Ser198/199/202 sites.Multiple factors may be involved in the cellular regulation of PP2A activ-ity.Inhibiting Src expression could induce inactivation of PP2A and tau hyperphosphorylation.