耐甲氧西林金黄色葡萄球菌的基因分型研究

目的明确本地区耐甲氧西林金黄色葡萄球菌(MRSA)的基因型别及其分布规律,探讨MR-SA菌株进化及遗传特性。方法收集2009年1月—2012年1月鄂尔多斯中心医院门诊及住院患者非痰标本分离的MRSA菌株61株,应用SCCmec基因分型和葡萄球菌A蛋白基因多态性分析(spa)方法进行基因分型。结果应用SCCmec的方法分离的MRSA以SCCmecⅡ、Ⅲ型为主,分别占50.8%和44.3%;应用spa的方法分离的MRSA以t030和t002为主,分别占39.3%和34.4%。结论本地区分离MRSA以SCCmecⅢ-t030和SCCmecⅡ-t002为主。     

鄂尔多斯地区耐甲氧西林金黄色葡萄球菌基因分型的研究

目的:了解本地区MRSA菌株的分子流行病学特点,明确本地区MRSA的基因型别及其分布规律.方法:收集2009年1月～2011年8月间鄂尔多斯地区门诊及住院患者非痰标本分离的MRSA菌株54株,应用SCCmec方法和spa方法进行基因分型.结果:应用SCCmec基因分型分离的MRSA以SCCmecⅡ、Ⅲ型为主,分别占本次分离的50％和46.4％;应用spa基因分型分离的MRSA以t030和t002为主,占该院分离率的41％和35.1％.结论:本地区分离MRSA以SCCmecⅢ- t030和SCCmecⅡ- t002为主.     

三株社区获得性耐甲氧西林金黄色葡萄球菌的基因分型研究

目的 了解西南地区社区获得性耐甲氧西林金黄色葡萄球菌(CA-MRSA)流行株的基因特征.方法 用葡萄球菌盒式染色体(SCCmec)多重PCR分型技术、葡萄球菌A蛋白基因(spa)分型技术和多位点测序分型(MLST)技术对3株分离自临床的CA-MRSA(s35301、s29635、s19165)进行基因分型,并检测其杀白细胞毒素(PVL)基因.结果 3株MRSA的mecA基因(147 bp)全部为阳性扩增,还同时扩增出750 bp左右的片段,该产物经测序后证实为SCCmecⅣa型.spa分型:s35301、s29635为t437,s19165为t008.MIJST分型:s35301、s29635为ST59型,s19165为ST8型.s19165、s35301 PVL基因扩增阳性,s29635 PVL基因扩增阴性.结论 西南地区分离到CA-MRSA ST8-t008克隆株及ST59-t437克隆株.应注意控制CA-MRSA感染及传播.     

耐甲氧西林金黄色葡萄球菌同源性分析及耐药性研究

目的对临床分离的耐甲氧西林金黄色葡萄球菌(MRSA)进行耐药情况和分子流行病学监测,探讨院内MRSA的流行趋势。方法收集我院2009年1月~2011年6月临床标本分离的MRSA菌株60株;采用Microscan WalkAway 40进行菌株鉴定,同时对所有金黄色葡萄球菌进行药物敏感性分析;采用脉冲场凝胶电泳技术对耐甲氧西林金黄色葡萄球菌进行分子分型。结果共收集60株MRSA菌株,其中17株被认为是可疑社区获得(CAMRSA),43株被认为是医院获得(HA-MRSA)。所有菌株均对万古霉素、替考拉宁、利奈唑胺、呋喃妥因和奎奴普丁/达福普汀敏感,未出现耐药菌株。CA-MRSA与HA-MRSA对左旋氧氟沙星和利福平的敏感性有明显差异。临床分离的MRSA菌株PFGE分型较为分散,共分为13种型别,每种型别的菌株数分别为2~6株不等,未出现大范围的院内流行克隆。结论本院收集的临床分离的MRSA菌株多重耐药性严重,其中CA-MRSA相对HAMRSA敏感性稍高。所有金黄色葡萄球菌未出现糖肽类抗菌药物耐药。MRSA菌株未出现大范围的院内流行株,但仍应加强院内感染流行控制。     

广州市96株血流感染金黄色葡萄球菌的基因分型及耐药性分析

目的 分析血流感染中分离金黄色葡萄球菌的分子分型特征和药物敏感试验结果,为耐药性金黄色葡萄球菌防治提供基础依据。方法 对中山大学附属第一医院2013—2017年血流感染分离的96株金黄色葡萄球菌应用MLST和spa技术进行分子分型,同时进行药物敏感试验分析血流感染中金黄色葡萄球菌对万古霉素、奎奴普丁/达福普汀、利奈唑胺等14种抗生素的药敏特征。结果 96株金黄色葡萄球菌中40株为甲氧西林耐药金黄色葡萄球菌（Methicillin resistant Staphylococcus aureus, MRSA）,其主要型别为ST59-t437型7株（占17.5%）,ST1-t114型4株（占10.0%）,ST239-t030型3株（占7.5%）,ST239-t037、ST45-t116、ST5-t2595和ST7-t091型均为2株（均占5.0%）;56株甲氧西林敏感金黄色葡萄球菌（Methicillin susceptible Staphylococcus aureus, MSSA）,其主要型别为ST188-t189型14株（占25.0%）,ST7-t803型3株（占5.4%）,ST188-t2883、ST6-t701、ST30-t338和ST59-t437型均2株（均占3.6%）。spa分型中发现4个新型,分别为t17040、t17041、t17044、t17046。40株MRSA菌株对红霉素和克林霉素耐药率分别为82.9%和51.2%,对万古霉素、利奈唑胺、奎奴普丁/达福普汀耐药率均为0;56株MSSA对所试验抗生素敏感率均较高,对奎奴普丁/达福普汀、万古霉素、利奈唑胺、呋喃妥因、替加环素的敏感率为100.0%,复方新诺明的敏感率为94.5%,对庆大霉素和利福平的敏感率均为96.4%。结论 血流感染中金黄色葡萄球菌分子分型型别较多,应重视金黄色葡萄球菌的感染控制。     

DNA fingerprinting of methicillin-resistant Staphylococcus aureus (MRSA) by pulsed-field gel electrophoresis (PFGE) in a teaching hospital in Malaysia

Methicillin-resistant Staphylococcus aureus (MRSA) has been prevalent in our hospital over the last three years. Differentiation among MRSA strains by DNA typing in addition to antibiotic resistance pattern surveillance is crucial in order to implement infection control measures. The aim of this study was to characterize MRSA isolates from patients admitted to Hospital Universiti Kebangsaan Malaysia (HUKM) by phenotypic (analyses of antibiotic susceptibility pattern) and genotypic (PFGE) techniques to determine the genetic relatedness of the MRSA involved and to identify endemic clonal profiles of MRSA circulating in HUKM. Seventy one MRSA strains collected between January to March 2000 from patients from various wards in HUKM were tested for antimicrobial resistance and typed by pulsed-field gel electrophoresis (PFGE). Four major types of PFGE patterns were identified (A, B, C and D) among MRSA strains. Two predominant PFGE types were recognised, Type A (59.2%) and Type B (33.8%). Most of these strains were isolated from ICU, Surgical wards and Medical wards. MRSA strains with different PFGE patterns appeared to be widespread among wards. Strains with the same antibiotype could be of different PFGE types. Most of isolates were resistant to ciprofloxacin, erythromycin, gentamicin and penicillin. One isolate with a unique PFGE pattern Type D and susceptible to gentamicin was identified as a different clone. Some isolates obtained from the same patient showed different PFGE subtypes suggesting that these patients were infected/colonized with multiple MRSA strains. PFGE analysis suggests that MRSA strains with different PFGE types was propagated within our hospital. The relationship between antibiotic susceptibility and PFGE patterns was independent. The ability of PFGE technique in differentiating our MRSA strains make it a method of choice for investigating the source, transmission and spread of nosocomial MRSA infection, and thus an appropriate control programme can be implemented to prevent the spread of MRSA infection.     

Antimicrobial resistance and molecular epidemiological characteristics of clinical isolates of Staphylococcus aureus in Changsha area

Background  Increasing prevalence of Staphylococcus aureus (S. aureus), particularly methicillin-resistant S. aureus (MRSA) has been reported in China. In this study, we investigated the drug resistance characteristic, genetic background, and molecular epidemiological characteristic of S. aureus in Changsha.

Methods  Between January 2006 and December 2008, 293 clinical isolates of S. aureus were collected from 11 hospitals in Changsha and identified by the Vitek-2 system. All the isolates were verified as MRSA by PCR amplification of both femA and mecA genes. K-B disk method was used to test drug sensitivity of S. aureus to antibiotics. Pulsed-field gel electrophoresis (PFGE) was performed for genotypic and homologous analysis of 115 isolates randomly selected from the original 293 clinical S. aureus isolates.

Results  S. aureus was highly resistant to penicillin, ampicillin, erythromycin, and clindamycin with resistant rates of 96.6%, 96.6%, 77.1%, and 67.2% respectively. All the isolates were susceptible to tecoplanin, vancomycin, and linezolid. MRSA accounted for 64.8% (190/293) of all the S. aureus strains. The 115 S. aureus isolates were clustered into 39 PFGE types by PFGE typing, with 13 predominant patterns (designated types A to M) accounting for 89 isolates. The most prevalent PFGE type was type A (n=56, 48.7%) and 100.0% of type A strains were MRSA. PFGE type A included 13 subtypes, and the most prevalent subtype was subtype A1 (46.4%, 26/56). Strains with PFGE type A were isolated from eight hospitals (8/11), and both subtypes A1 and A4 strains were isolated in a university hospital.

Conclusions  Clinical isolates of S. aureus in Changsha were resistant to multiple traditional antibiotics. There was an outbreak of PFGE type A MRSA in this area and the A1 subtype was the predominant epidemic clone. Dissemination of the same clone was an important reason for the wide spread of MRSA.     

北京地区宋内志贺菌分子流行病学特征分析

目的 了解北京地区宋内志贺菌毒力基因分布及分子流行病学特征. 方法 采用实时荧光PCR方法检测毒力基因、脉冲场凝胶电泳(PFGE)分型,多位点序列分型(MLST)及多位点可变数目串联重复序列分析(MLVA)等方法对北京地区2001～2009年50株志贺菌菌株进行分子流行病学特征分析. 结果 50株菌中,ipaH、set1、sen三种毒力基因的携带率分别为98％,18％和78％.选取19株流行病学和遗传背景无关的菌株,进行MLST、MLVA与PFGE分型方法的比较,MLST为1个序列型ST152 complex:adk(11)、fumC (63)、gyrB(7)、icd(1)、mdh(14)、purA (7)、recA(7); MLVA被分成15个型别,D值为0.9708;PFGE分成12个型别,D值为0.9532.MLVA初筛得到的8个可变数目串联重复(VNTR)位点用于扩大菌株分析,发现50株志贺菌被分为21个MLVA的型别,TS002和TS001为主要型别. 结论 北京地区近年来流行的宋内志贺菌存在毒力基因的丢失,MLVA分子型别复杂,存在多克隆来源,提示需要进行连续系统的分子流行病学监测.     

Molecular Typing of Leptospira interrogans Strains Isolated from Rattus tanezumi in Guizhou Province, Southwest of China

ObjectiveTo identify and type three leptospires isolated from Rattus tanezumi in Guizhou Province by using three molecular techniques (PFGE, MLVA, and MLST), reveal the molecular characteristic of causative agents of local leptospirosis and evaluate these three molecular methods based on their detection resolution and efficiency.MethodsThree Leptospira strains were isolated from the kidney of Rattus tanezumi and cultured with EMJH medium. PFGE, MLVA, and MLST assays were applied to type the three strains isolated from Rattus tanezumi in Guizhou Province.ResultsPFGE, MLVA, and MLST typing showed that the three leptospiral isolates matched with leptospiral serogroup Icterohaemorrhagiae serovar Lai. The findings of the genotyping methods were consistent. MLVA and MLST defined genotypes, whereas PFGE allowed the recognition of additional subgroups within the genotypes, and the findings of molecular typing were also consistent with those of traditional techniques.ConclusionThree leptospiral isolates from Guizhou Province matched with leptospiral serogroup Icterohaemorrhagiae serovar Lai, and PFGE, MLVA, and MLST, as reliable molecular techniques for identifying and typing of Leptospira interrogans, would contribute to the active surveillance, outbreak investigation and source tracking for leptospirosis in Guizhou Province.     

Community-acquired methicillin-resistant Staphylococcus aureus in a rural American Indian community

CONTEXT: Until recently, methicillin-resistant Staphylococcus aureus (MRSA) infections have been acquired primarily in nosocomial settings. Four recent deaths due to MRSA infection in previously healthy children in the Midwest suggest that serious MRSA infections can be acquired in the community in rural as well as urban locations. OBJECTIVES: To document the occurrence of community-acquired MRSA infections and evaluate risk factors for community-acquired MRSA infection compared with methicillin-susceptible S aureus (MSSA) infection. DESIGN: Retrospective cohort study with medical record review. SETTING: Indian Health Service facility in a rural midwestern American Indian community. PATIENTS: Patients whose medical records indicated laboratory-confirmed S aureus infection diagnosed during 1997. MAIN OUTCOME MEASURES: Proportion of MRSA infections classified as community acquired based on standardized criteria; risk factors for community-acquired MRSA infection compared with those for community-acquired MSSA infection; and relatedness of MRSA strains, determined by pulsed-field gel electrophoresis (PFGE). RESULTS: Of 112 S aureus isolates, 62 (55%) were MRSA and 50 (45%) were MSSA. Forty-six (74%) of the 62 MRSA infections were classified as community acquired. Risk factors for community-acquired MRSA infections were not significantly different from those for community-acquired MSSA. Pulsed-field gel electrophoresis subtyping indicated that 34 (89%) of 38 community-acquired MRSA isolates were clonally related and distinct from nosocomial MRSA isolates found in the region. CONCLUSIONS: Community-acquired MRSA may have replaced community-acquired MSSA as the dominant strain in this community. Antimicrobial susceptibility patterns and PFGE subtyping support the finding that MRSA is circulating beyond nosocomial settings in this and possibly other rural US communities.     

医院获得性感染中出现携带SCCmecⅣ/Ⅴ的耐甲氧西林金黄色葡萄球菌

目的 研究某院临床分离的医院获得性耐甲氧西林金黄色葡萄球菌(HA-MRSA)的葡萄球菌染色体mec盒(SCCmec)分型及分子流行病学特征.方法 收集中南大学湘雅医院2012年1月~2012年12月临床分离的71株HA-MRSA,采用多重PCR进行SCCmec分型,PCR检测PVL毒素基因,并用脉冲场凝胶电泳(PFGE)分析菌株间的同源性.结果 71株HA-MRSA以SCCmecⅢ型为主,占69.0%(49/71),其次为SCCmecⅣ型、SCCmecⅤ型和SCCmecⅡ型,分别占14.1%(10/71)、4.2%(3/71)和4.2%(3/71),另有6株(8.5%)菌株未能分型.HA-SCCmecⅣ/ⅤMRSA感染者年龄显著低于HA-SCCmecⅠ/Ⅱ/ⅢMRSA感染者,携带PVL基因阳性率显著高于HA-SCCmecⅠ/Ⅱ/ⅢMRSA感染者,而两者入院至检出菌株的时间及住院天数均未见明显差异.HA-SCCmecⅣ/ⅤMRSA对左旋氧氟沙星、环丙沙星、利福平、庆大霉素、四环素等的耐药率均显著低于HA-SCCmecⅠ/Ⅱ/ⅢMRSA(P<0.05).13株HA-SCCmecⅣ/ⅤMRSA菌株在55%的相似度水平形成一个大的组群.按照≥85%的相似度,这些菌株共形成3个PFGE簇以及4个单一菌株的PFGE型.结论 在国内首次发现携带SCCmecⅤ型的HA-MRSA菌株,HA-SCCmecⅣ/ⅤMRSA已有在医疗机构传播的趋势,并成为医院内感染的重要来源.     

耐甲氧西林金黄色葡萄球菌基因分型研究

目的 了解本地区耐甲氧西林金黄色葡萄球菌(MRSA)流行株的来源和遗传背景.方法 回顾分析华西医院127例MRSA感染者的病例资料,用SCCmec多重PCR技术、葡萄球菌A蛋白(spa)分型技术和多位点测序分型技术对其中10株MRSA临床分离株进行基因分型,并检测其杀白细胞毒素基因.结果 病例资料显示127株MRSA中3株为社区获得性MRSA(CA-MRSA),其余均为医院获得性MRSA(HA-MRSA).进行分型研究的10株MRSA中,7株HA-MRsA为SCCmecⅢ-ST239-PVL(一),呈现高度的克隆一致性,spa分型进一步显示4株为t030,另外3株为t037;CA-MRSA s19165分型为ST8-t008,与USA300属同一克隆,并且携带SCCmecⅣa和PVL基因,符合USA300一般基因特征.另外2株CA-MRSAs5301、s29635均为SCCmecⅣa-ST59-t437,与我国其他地区的报道不同.结论 该院分离的MRSA仍以医院获得性为主(124/127),HA-MRSA呈现高度的克隆一致性,并与我国的主要流行株为同一克隆;分离到与美国主要CA-MRSA流行株USA300相同克隆的菌株,另外分离到的CA-MRSA ST59-t437克隆株在我国其他地区未有报道.MLST和spa分型技术是金黄色葡萄球菌分子流行病学研究的更为简便快速的方法.     

北京地区实验动物绿脓杆菌分离株MLVA分型

目的 通过多位点可变数目串联重复序列分析(multiple-locus variable-number tandem-repeat analysis,MLVA)分型方法,研究北京地区实验动物绿脓杆菌分离株基因型和分布情况.方法 选择13个可变数目重复序列(variable-number tandem-repeat,VNTR)位点,对实验动物及设施中检测出的141株绿脓杆菌的基因组DNA进行重复序列扩增,所得指纹图谱使用BioNumerics软件进行聚类分析,绘制系统发育树和最小生成树(minimum spanning tree,MST).结果 所采用的13个VNTR位点能够对全部分离株进行有效分型.141株绿脓杆菌主要被分为了3个基因群,56个基因型.各群所占比例分别为A群82.3％,B群占12.8％,C群占5.0％,辛普森多样性指数为0.763.同一区域内相邻实验动物单位的绿脓杆菌分离株同源关系较远.结论 MLVA方法对绿脓杆菌具有很好的分型能力,能够有效的追踪绿脓杆菌的来源.北京地区实验动物中绿脓杆菌分离株基因型多态性丰富,但无地域性同源关系.     

耐碳青霉烯类鲍曼不动杆菌同源性研究

目的探讨我院2001年8月至2002年3月显著增多的耐碳青霉烯类鲍曼不动杆菌之间的同源性.方法用脉冲场凝胶电泳对7株耐碳青霉烯类鲍曼不动杆菌进行分型,明确其是否为同一菌株的克隆.结果7株不动杆菌分为:A型2株,A1型2株,A2型1株.A1型与A2型之间的相似系数达94.6%,它们与A型的相似系数达84.9%,其余两株各有独特的PFGE分型.结论其中5株耐碳青霉烯类鲍曼不动杆菌有高度同源性,第5号株极可能是此次院内感染的源头.     

Detection and molecular typing of methicillin-resistant Staphylococcus aureus from northeastern part of India

BackgroundIn Staphylococcus aureus, methicillin resistance is exhibited by modifications in penicillin-binding protein that minimises the binding affinity to beta-lactam antibiotics. The present study investigated the occurrence of methicillin-resistant S. aureus (MRSA) in community-acquired infections, that is, community-acquired MRSA (CA-MRSA) and in-hospital–acquired infections, that is, hospital-acquired MRSA (HA-MRSA) from Northeast India.MethodsA total of 197 consecutive non-duplicate isolates were collected from Silchar Medical College and Hospital and other private diagnostic laboratories. The isolates were confirmed to be S. aureus at our centre. All isolates were subjected to antibiotic susceptibility testing and were screened for methicillin resistance using cefoxitin disc test. All MRSA were subjected to Polymerase Chain Reaction (PCR) assay for detection of mecA and mecC genes. DNA fingerprinting was performed for determining clonal diversity.ResultsSeventy-one isolates of 127 confirmed S. aureus were found to be methicillin resistant by screening test. mecA gene was detected in 43 isolates, and none of the isolates were positive for mecC gene. Linezolid and teicoplanin showed better activity with susceptibility pattern being 83.6% and 72.44%, respectively, whereas 66.14% were sensitive to vancomycin. Other antibiotic showed low level of activity. Pulsed Field Gel Electrophoresis (PFGE) showed 14 different banding patterns that suggest isolates were of different clonal types.ConclusionmecA was responsible for methicillin resistance in majority of strains. Polyclonal spread of MRSA infection in the study area indicates its diverse origin and possible lateral transfer. Thus, this study is of clinical interest in terms of selection of proper antimicrobial chemotherapy and infection control management.     

Carriage of methicillin-resistant Staphylococcus aureus in a Queensland Indigenous community

OBJECTIVE: To determine the prevalence of community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) carriage and infection among children living in an Indigenous community in Queensland. DESIGN, SETTING AND PARTICIPANTS: Swabs for culture of S. aureus were collected from the nose, throat and skin wounds of primary school children. MAIN OUTCOME MEASURES: MRSA carriage, antibiotic sensitivity, genotype, and presence of the virulence factor Panton-Valentine leukocidin (PVL); and epidemiological risk factors for MRSA carriage. RESULTS: 92 (59%) of 157 eligible children were included in the study. Twenty-seven (29%) carried S. aureus; 14 of these (15% of total) carried MRSA. MRSA was isolated from 29% of wound swabs, 8% of nose swabs, and 1% of throat swabs. Fourteen of 15 MRSA isolates were sensitive to all non-beta-lactam antibiotics tested. Eight children (9%) carried CA-MRSA clonal types: six carried the Queensland clone (ST93), and two carried the South West Pacific clone (ST30). All these isolates carried the virulence factor PVL. The remaining six children carried a hospital-associated MRSA strain (ST5), negative for PVL. CONCLUSIONS: We have identified a high prevalence of CA-MRSA carriage in school children from a Queensland Indigenous community. In this setting, antibiotics with activity against CA-MRSA should be considered for empiric therapy of suspected staphylococcal infection. Larger community-based studies are needed to improve our understanding of the epidemiology of CA-MRSA, and to assist in the development of therapeutic guidelines for this important infection.     

多重耐药大肠埃希菌质粒介导耐药性的研究

目的：了解临床收集的多重耐药大肠埃希菌克隆播散状况及质粒介导耐药性的特性。方法通过K- B纸片法明确细菌耐药谱,脉冲场凝胶电泳（PFGE）进行耐药菌株的克隆分型,了解其克隆播散情况,通过质粒接合实验获得耐药性质粒的接合菌,用PCR方法筛选接合菌株的常见耐药基因,并利用S1酶切质粒再进行PFGE的方法判读分析质粒的分子大小,分析菌株间的质粒水平迁移状况。结果临床分离95株大肠埃希菌均为多重耐药菌,对青霉素类、头孢菌素类、喹诺酮类、四环素类等药物显示出广泛耐药性,PFGE分型显示克隆传播趋势不明显。耐药菌株常携带可接合性耐药质粒,质粒分子量大小分布在40-330kb,编码多种对青霉素类、头孢菌素类等药物耐药的耐药基因,包括CTX- M型、TEM型β-内酰胺酶基因,以及质粒介导喹诺酮耐药基因qnr等等。结论临床大肠埃希菌多重耐药性严重,耐药性的快速传播已非同源克隆细菌的简单播散,可接合质粒造成的耐药基因水平转移可能起到了相当重要的作用。     

Molecular epidemiology of serotype 19A Streptococcus pneumoniae isolated from children in Beijing, 1997–2006

Background  Despite the prevalence of Streptococcus pneumoniae serotype 19A, the molecular characteristics of this serotype are yet to be fully elucidated. The aim of this study was therefore to determine the homology of the serotype 19A in China.

Methods  Pulsed-field gel electrophoresis and multilocus sequence typing were done to these forty-nine serotype 19A isolates to investigate the relationship between the strains prevalent in Beijing and other regions.

Results  From 1997 to 2006, the percentage of serotype 19A isolates increased. The susceptibility rate to penicillin and amoxicillin decreased and the resistance rate to cefuroxime increased. ST320 was the most prevalent ST, followed by ST3546. There were six new STs identified in our study. The serotype 19A strains were classified into six different pulsed-field gel electrophoresis (PFGE) patterns. ST320, which was associated with two different PFGE patterns (A and D), accounted for 32 isolates, and ST3546, which was associated with two PFGE patterns (B and E), accounted for eight isolates.

Conclusions  From 2003 onwards, ST320 was the most common ST and the rate of resistance to cefuroxime increased significantly. Further long-term surveys of Streptococcus pneumoniae serotype 19A are required to monitor ST prevalence and antimicrobial resistance in this important human pathogen.

     

Epidemiologic Study of Pseudomonas aeruginosa in critical patients and reservoirs

BACKGROUND: Pseudomonas aeruginosa is a common cause of nosocomial infections, particularly in intensive care units (ICUs). The aim of this study was to characterize P. aeruginosa clinical isolates by comparing antimicrobial susceptibility patterns with the presence of plasmids and to establish the clonal relatedness by pulsed-field gel electrophoresis (PFGE) typing. METHODS: The patients included those with isolation of P. aeruginosa hospitalized for more than 48 h in the ICU from April to May 1998. Environmental and staff cultures were obtained simultaneously. Minimal inhibitory concentrations, plasmid DNA profiles, and PFGE genomic patterns of enzyme restriction chromosomal DNA were compared. RESULTS: Sixty P. aeruginosa isolates were obtained from 197 clinical specimens, 178 environmental samples, and 47 hand cultures of personnel. Antimicrobial resistance was as follows: tobramycin 100%; ticarcillin, cefotaxime, ceftriaxone, ceftazidime, and gentamicin 80%; cefepime 60%; amikacin, ticarcillin/clavulanate, imipenem, and meropenem 40%; piperacillin and norfloxacin 20%; carbenicillin 12%, and ciprofloxacin 0%. Plasmids were detected in 11 isolates (18%). PFGE typing showed that 23 isolates belonged to a common clone (pattern A), identified from five patients, two nurses, and 10 environmental samples. Ten isolates were grouped in four clusters and 27 isolates had unrelated genomic patterns. There was no relationship among DNA genomic patterns, plasmid profiles, and susceptibility patterns. CONCLUSIONS: PFGE demonstrated the existence of a common clone in a critical care area. Reinforcement of infection control measures is needed to avoid horizontal transmission and severe infections.     

Investigation of the prevalence of patients co-colonized or infected with methicillin-resistant Staphylococcus aureus and vancomycin- resistant enterococci in China: a hospital-based study

Background Nosocomial infection caused by methicillin-resistant Staphylococcus aureus （MRSA） and vancomycin-resistant enterococci （VRE） could lead to increased morbidity and mortality. In 2006, VRE nosocomial spread became a reality in our hospital since the first VRE nosocomial infection in 2003. Little is known about the prevalence of coexistence with VRE and MRSA in the patients. The primary objective of the study was to identify the molecular characteristics of epidemic MRSA clones in our hospital and the prevalence of the coexistence with MRSA and VRE in same patients during the 2-year period, 2006-2007. Methods The clinical features, laboratory test results, and therapeutic outcomes of 129 cases who isolated MRSA collected from January 2006 to December 2007 were retrospectively analyzed. Polymerase chain reaction （PCR） was used to determine mecA-femB type and staphylococcal cassette chromosome mec （SCCmec） type. All the participants were screened for clinical and microbiological data to identify the coexistence of VRE strains with MRSA. Results One hundred and twenty-nine MRSA isolates were included in the study： 71 （55%） from the intensive care unit, 35 （27.2%） from the surgical wards and 23 （17.8%） from the medical wards. The most frequent source of isolation of MRSA was sputum （76.7%）. From seven patients we isolated MRSA and VRE （E. faecium） simultaneously during their inpatient stay. One hundred and twenty-seven （127/129, 98.4%） MRSA isolates harboured SCCmec type Ⅲ, only 2 MRSA strains contained SCCmec type Ⅱ. All of the 129 MRSA isolates remained sensitive to vancomycin, teicoplanin and linezolid. Higher sensitivity rates were noted for chloramphenicol 99.2% （128/129）. Only 20.2% （26/129） of the MRSA isolates were sensitive to rifampin. All isolates presented resistance to multiple antimicrobial agents with high minimum inhibitory concentrations （MICs）, including： β-Iactams （penicillin, oxacillin, cefoxitin, and cefazolin）, tetracycline, erythromycin, gentamicin, and quinolones （ciprofloxacin, levofloxacin, and moxifloxacin）. Conclusions The predominant MRSA clone at Beijing Chaoyang Hospital from 2006 to 2007 had the type Ⅲ SCCmec element. All of the MRSA isolates were multiresistant to antimicrobial agents. Emergence of coexistence of MRSA and VRE in the same patient was not rare. Physicians should pay more attention to infections resulting from MRSA and VRE. Aggressive infection control measures should be taken to prevent the transmission of the multidrug resistance organism.