肠道细菌性疫苗研究进展

人肠道致病菌具有高度传染性，可引起多种疾病。目前已有多种肠道细菌灭活疫苗和减毒活疫苗通过安全性评价上市；重组蛋白疫苗、结合疫苗和亚单位疫苗等新型疫苗的研究已获得较好的结果。此文对人肠道致病菌及其相关新疫苗的研究进展做一综述。     

AcrAB-TolC外排泵在多重耐药肠杆菌中的作用研究进展

耐多药肠杆菌的出现严重威胁着人类健康。AcrAB-TolC外排泵的过量表达是引起肠杆菌多重耐药的主要机制之一,其主要由周质融合蛋白AcrA、外膜通道蛋白TolC和药物质子转运子AcrB构成,受整体调控因子、局部调控因子以及环境中的化学物质等调节。对AcrAB-TolC外排泵的研究,不仅有助于阐明相关耐药本质,还有助于研制有临床意义的外排泵抑制剂(EPIs),为解决肠杆菌多重耐药问题提供新思路。本文对AcrAB-TolC外排泵的结构、调控等方面的研究进展作一综述。     

Characteristics of KPC-2–producing Klebsiella pneumoniae (ST258) clinical isolates from outbreaks in 2 Mexican medical centers

The KPC-producing Klebsiella pneumoniae sequence type 258 (ST258) is an important pathogen widely spread in nosocomial infections. In this study, we identified the KPC-2–producing K. pneumoniae clinical isolates of 2 unrelated outbreaks that corresponded to pandemic strain ST258. The isolates showed high resistance to cephalosporins, carbapenems, quinolones, and colistin. The KPC-2–producing K. pneumoniae isolates were compared to the previously studied KPC-3–producing K. pneumoniae isolates from an outbreak in Mexico; they showed an unrelated pulsed-field gel electrophoresis fingerprinting pattern and a different plasmid profile. The KPC-2 carbapenemase gene was identified in two 230- and 270-kb non-conjugative plasmids; however, 1 isolate transferred the KPC-2 gene onto an 80-kb plasmid. These findings endorse the need of carrying out a continuous molecular epidemiological surveillance of carbapenem-resistant isolates in hospitals in Mexico.     

Isolation and characterization of a novel indigenous intestinal N4-related coliphage vB_EcoP_G7C

Lytic coliphage vB_EcoP_G7C and several other highly related isolates were obtained repeatedly from the samples of horse feces held in the same stable thus representing a component of the normal indigenous intestinal communities in this population of animals. The genome of G7C consists of 71,759 bp with terminal repeats of about 1160 bp, yielding approximately 73 kbp packed DNA size. Seventy-eight potential open reading frames, most of them unique to N4-like viruses, were identified and annotated. The overall layout of functional gene groups was close to that of the original N4 phage, with some important changes in late gene area including new tail fiber proteins containing hydrolytic domains. Structural proteome analysis confirmed all the predicted subunits of the viral particle. Unlike N4 itself, phage G7C did not exhibit a lysis-inhibited phenotype.     

Resistance to Apramycin in Two Enterobacterial Clinical Isolates: Detection of a 3-N-Acetyltransferase IV

Summary

Considering the possible role of farm animals in the contamination of human consumers by plasmid-mediated apramycin-resistant enterobacteria strains, this type of resistance should be tested more systematically in human isolates. Very recently we isolated in Zaragoza one apramycin-resistant Escheria coli strain obtained from the blood of a hospitalized patient; this clinical isolate produced a plasmid-mediated 3-N-aminoglycoside acetyltransferase IV. We describe also the isolation in Madrid of one multiresistant Klebsiella pneumoniae clinical strain. This isolate harbored a single plasmid and carried determinants for apramycin, gentamicin, tobramycin, hygromycin B, streptomycin, and ampicillin, which could be transferred en bloc to E. coli K-12 J62. Extracts from donor and transconjugant strains carrying pUZ6776 plasmid produce acetyltransferase activity AAC(3)-IV and double phosphotransferase activity (HPH and APH(3“)).     

Development of diagnostic prediction tools for bacteraemia caused by third-generation cephalosporin-resistant enterobacteria in suspected bacterial infections: a nested case–control study

ObjectivesCurrent guidelines for the empirical antibiotic treatment predict the presence of third-generation cephalosporin-resistant enterobacterial bacteraemia (3GCR-E-Bac) in case of infection only poorly, thereby increasing unnecessary carbapenem use. We aimed to develop diagnostic scoring systems which can better predict the presence of 3GCR-E-Bac.MethodsA retrospective nested case–control study was performed that included patients ≥18 years of age from eight Dutch hospitals in whom blood cultures were obtained and intravenous antibiotics were initiated. Each patient with 3GCR-E-Bac was matched to four control infection episodes within the same hospital, based on blood-culture date and onset location (community or hospital). Starting from 32 commonly described clinical risk factors at infection onset, selection strategies were used to derive scoring systems for the probability of community- and hospital-onset 3GCR-E-Bac.Results3GCR-E-Bac occurred in 90 of 22 506 (0.4%) community-onset infections and in 82 of 8110 (1.0%) hospital-onset infections, and these cases were matched to 360 community-onset and 328 hospital-onset control episodes. The derived community-onset and hospital-onset scoring systems consisted of six and nine predictors, respectively. With selected score cut-offs, the models identified 3GCR-E-Bac with sensitivity equal to existing guidelines (community-onset: 54.3%; hospital-onset: 81.5%). However, they reduced the proportion of patients classified as at risk for 3GCR-E-Bac (i.e. eligible for empirical carbapenem therapy) with 40% (95%CI 21–56%) and 49% (95%CI 39–58%) in, respectively, community-onset and hospital-onset infections.ConclusionsThese prediction scores for 3GCR-E-Bac, specifically geared towards the initiation of empirical antibiotic treatment, may improve the balance between inappropriate antibiotics and carbapenem overuse.     

成都双流国际机场蝇类携带致病肠杆菌分离及耐药性检测

目的了解成都双流国际机场口岸蝇类携带致病肠杆菌耐药性及耐药基因携带情况。方法通过布放蝇笼捕捉蝇类,使用添加有头孢菌素(20μg/ml)的麦康凯平板从捕获的蝇类中分离其携带的致病肠杆菌,对分离株进行耐药性实验、超广谱β内酰胺酶(ESBL)测试及耐药基因型测定。结果从2011年4月至2011年9月捕获的蝇类中分离到致病肠杆菌48株,其中大肠杆菌37株,肺炎克雷伯菌6株,铜绿假单胞菌3株,嗜水气单胞菌2株。对分离到的48株肠杆菌进行抗生素耐药性实验,对阿莫西林、替卡西林、头孢噻吩和头孢呋辛耐药,对美罗培南和亚胺培南不耐药。所有菌株均对8种或8种以上的常见抗生素耐药。分离的大肠杆菌(n=37)和肺炎克雷伯菌(n=6)均产ESBL,对头孢噻肟的耐药率98.1%,对头孢他啶耐药率11.5%。对产ESBL菌株进行耐药基因测试,TEM型为常见型(67.4%),SHV型(16.3%)多见于肺炎克雷伯菌,未发现同时产生ESBL和AmpC的-超广谱层内酰胺酶(SSBLs)菌株。结论从双流国际机场口岸环境内蝇类分离到致病肠杆菌多重耐药,且携带有产ESBL的耐药基因。     

温和灸腹部募穴对实验性大鼠肠道菌群失调的影响

目的通过温和灸关元、天枢两个腹部募穴,观察其对肠道菌群失调的影响。方法清洁级Wistar大鼠50只,雌雄各半,体重（200±20）g,采用随机对照方法分为正常组（A）、模型组（B）、药物组（C）、关元组（D）、天枢组（E）,每组10只。用大量盐酸林可霉素灌胃造模,造模成功后,分别进行药物治疗和温和灸法治疗。1个疗程后,各组大鼠均被迫采取新鲜粪便0.1 g,应用双歧杆菌（BS）、乳酸杆菌（LBS）、肠杆菌（EMB）、肠球菌（EC）选择性培养基进行细菌培养,生化鉴定管和比浊法检测不同菌落生长情况和各组菌落数量。结果温和灸关元穴使BS、LBS数量有所增加,温和灸天枢穴使EMB、EC数量有所增加。结论温和灸不同部位的募穴可以选择性调整肠道优势益生菌群,从而治疗肠道菌群失调症。