Persistence of Legionella pneumophila in a hospital's water system: a 13-year survey.

OBJECTIVE: To describe the molecular epidemiology of Legionella pneumophila infections in the University of Iowa Hospitals and Clinics (UIHC). DESIGN: Molecular epidemiological study using pulsed-field gel electrophoresis (PFGE). SETTING: A large university teaching hospital. ISOLATES: All surviving isolates obtained from culture-proven nosocomial L. pneumophila infections and all surviving isolates obtained from the University of Iowa Hospital and Clinics' water supply between 1981 and 1993. RESULTS: Thirty-three isolates from culture-proven nosocomial cases of L. pneumophila pneumonia were available for typing. PFGE of genomic DNA from the clinical isolates identified six different strains. However, only strain C (16 cases) and strain D (13 cases) caused more than 1 case. Strain C caused clusters of nosocomial infection in 1981, 1986, and 1993 and also caused 4 sporadic cases. Strain D caused a cluster in 1987 and 1988 plus 4 sporadic cases. Of the six strains causing clinical infections, only strains C and D were identified in water samples. PFGE identified three strains in the water supply, of which strains C and D caused clinical disease and also persisted in the water supply during most of the study period. CONCLUSION: Specific strains of L. pneumophila can colonize hospital water supplies and cause nosocomial infections over long periods of time.     

Molecular typing of clinical isolates of Stenotrophomonas maltophilia by pulsed-field gel electrophoresis and random primer PCR fingerprinting

During a 1-year study period, 96 strains of Stenotrophomonas maltophilia were isolated from different specimens of 59 patients admitted to a 1500 bed tertiary care university hospital. The strains were identified by commercially available API system and genotyped by pulsed-field gel electrophoresis (PFGE) and random primer PCR fingerprinting. The wide variation of the molecular profiles of the investigated S. maltophilia isolates shown by PFGE as well as PCR typing suggests that there was no outbreak situation with a particular S. maltophilia strain.     

Aeromonas isolates from human diarrheic stool and groundwater compared by pulsed-field gel electrophoresis

Gastrointestinal infections of Aeromonas species are generally considered waterborne; for this reason, Aeromonas hydrophila has been placed on the United States Environmental Protection Agency Contaminant Candidate List of emerging pathogens in drinking water. In this study, we compared pulsed-field gel electrophoresis patterns of Aeromonas isolates from stool specimens of patients with diarrhea with Aeromonas isolates from patients' drinking water. Among 2,565 diarrheic stool specimens submitted to a Wisconsin clinical reference laboratory, 17 (0.66%) tested positive for Aeromonas. Groundwater isolates of Aeromonas were obtained from private wells throughout Wisconsin and the drinking water of Aeromonas-positive patients. The analysis showed that the stool and drinking water isolates were genetically unrelated, suggesting that in this population Aeromonas gastrointestinal infections were not linked with groundwater exposures.     

Epidemiology of Aeromonas species in a hospital

The occurrence of Aeromonas spp. in a hospital water supply, in patients and in the local community was investigated. In healthy persons outside the hospital the isolation rate was 3.6% and among hospital patients it was 6%. Seven per cent of water samples yielded Aeromonas strains. Isolates were typed by sodium dodecyl sulphate polyacrylamide gel electrophoresis of sulphur-35 methionine labelled proteins of Aeromonas isolates. No relationship between water and human isolates could be established, even when a strain of A. hydrophila producing Vero cell cytotoxin contaminated enteral feeds given to patients in the intensive care unit.     

深圳市1993-2002年霍乱弧菌的脉冲场凝胶电泳分析

目的 分析深圳市1993—2002年霍乱弧菌菌株的相关性。方法 60株霍乱弧菌基因组DNA经Not Ⅰ酶切，通过脉冲场凝胶电泳获得电泳图谱，利用BioNumerics软件对图谱进行聚类分析。结果 60株霍乱弧菌被分为39种脉冲场凝胶电泳图谱，聚类分析将大部分菌株分为A、B两群。结论 深圳地区霍乱弧菌存在紧密相关的流行克隆群。霍乱弧菌的脉冲场凝胶电泳分析，有助于霍乱的主动监测和传染来源追踪。     

Molecular characterization of Streptococcus pyogenes isolates to investigate an outbreak of puerperal sepsis.

OBJECTIVE: To describe microbiological characteristics and epidemiologic features of an outbreak of postpartum endometritis. METHODS: Various markers were investigated in five patients and three throat carriage isolates of Streptococcus pyogenes obtained during an outbreak of endometritis occurring in a 13-week period. Molecular characterization included biotyping, T-serotyping, emm gene sequence and restriction, pulsed-field gel electrophoresis (PFGE), and random amplified polymorphic DNA (RAPD) analysis. RESULTS: Biotype, T-serotype, and genotypic data (emm analysis, PFGE, and RAPD analysis) revealed a close relationship among the isolates from three patients, suggesting that cross-contamination had occurred. These isolates were biotype 1, T type 28, and emm type 28. The isolates from one patient and one carrier differed from those of the index patient by minor variations of the emm amplicon restriction pattern, PFGE pattern, or RAPD pattern. The remaining isolates were phenotypically and genetically different. CONCLUSION: Identification of different isolates demonstrated that different strains may circulate simultaneously during a true outbreak and that the predominant strain might persist for several months.     

Genetic typing of human and food isolates of Listeria monocytogenes from episodes of listeriosis

Ten clinical and food Listeria monocytogenes strains isolated during the epidemiological investigations of episodes of listeriosis (one outbreak and two sporadic cases) that occurred in northern Italy during 1993–1995 have been examined by DNA macrorestriction pattern analysis obtained by PFGE and RAPD typing, in order to confirm the food vehicle of infections. The same DNA profiles within the isolates from the three episodes were obtained by both techniques. The ApaI and SmaI PFGE profiles and RAPD patterns with primer OPM-01 confirmed the close relationship between strains from two distinct episodes. However, RAPD analysis with primer UBC-127 distinguished between these L. monocytogenes isolates.     

副溶血弧菌脉冲场凝胶电泳技术分子分型分析

目的分析副溶血弧菌菌株之间的相关性,建立深圳市副溶血弧菌的DNA指纹图谱数据库。方法56株副溶血弧菌基因组DNA经NotI酶切,通过脉冲场凝胶电泳获得电泳图谱,利用BioNumerics软件对图谱进行聚类分析。结果56株副溶血弧菌被分为34种脉冲场凝胶电泳技术（PFGE）图谱,聚类分析显示,在90%的相似性水平上,28株细菌谱型属于同一个群,其中27株均为食物中毒患者分离株,并各年度均有分离。结论深圳地区存在遗传谱系紧密相关的副溶血弧菌流行克隆。建立DNA指纹图谱数据库为建立分子分型监测网络打下了良好的基础,有助于副溶血弧菌所致食源性疾病的及时主动监测和传染来源追踪。     

嗜麦芽寡养单胞菌分子流行病学的研究

目的探讨嗜麦芽寡养单胞菌分子流行病学特点,为预防与控制医院感染提供理论依据。方法对92株嗜麦芽寡养单胞菌进行脉冲场凝胶电泳(PFGE)同源性分析,细菌包埋在低熔点琼脂糖中,经染色体DNA的原位纯化后,用低频限制性内切酶XbaⅠ进行染色体DNA的原位消化;使用PFGE对限制性酶切片段进行分离,通过对染色体DNA限制性内切酶谱比较,确定菌株亲缘关系。结果嗜麦芽寡养单胞菌为多克隆构成模式,92株菌共有63个克隆;有10个克隆出现了克隆传播,涉及39株菌;克隆A涉及10个菌株,分离间期最长达24个月,克隆A中来自同一医院的9株菌中有5株来自外科ICU,3株来自呼吸病房;克隆E有7个菌株,经过4次传播后,环丙沙星的MIC值由1 mg/L升高至8 mg/L。结论同一医疗单元环境的污染是克隆传播的主要原因;不同医疗单元医源性传播是克隆传播的主要途径;克隆传播是细菌产生耐药的原因之一。     

脉冲场凝胶电泳技术在铜绿假单胞菌现场调查中的应用研究

目的建立铜绿假单胞菌脉冲场凝胶电泳分子分型方法,对某医院患者送检标本及桶装矿泉水中分离到的铜绿假单胞菌进行分子分型,开展分子流行病学分析。方法将铜绿假单胞菌标准株和分离株进行复苏生化鉴定,用SpeI内切酶对试验株菌悬液凝胶块原位消化酶切后进行脉冲场凝胶电泳,比较获得的分子分型指纹图谱,运用Bionumerics5．1聚类分析。结果6株试验菌株中,有3株分离自患者,3株分离自桶装矿泉水,以及1株标准菌种,均获得清晰指纹图谱,条带数在20至25个之间,可分为A、B、C、D、E、F共6个基因型,相似度在70．6％～100．0％之间,其中两株患者来源的菌株相似度为100．O％。结论铜绿假单胞菌基因组经SpeI内切酶酶切后可获得理想的条带数便于分型。患者标本和饮用桶装矿泉水分离株没有直接相关性,但提醒仍需加强桶装矿泉水污染铜绿假单胞菌的管理;脉冲场凝胶电泳技术可有效应用于铜绿假单胞菌遗传学特征、传播途径及分布规律的分子流行病学研究。     

Molecular typing of Mannheimia (Pasteurella) haemolytica serotype A1 isolates from cattle in Japan

Pulsed field gel electrophoresis (PFGE) and random amplified polymorphic DNA (RAPD) methods were applied for molecular typing of 130 Mannheimia (Pasteurella) haemolytica serotype A1 isolates obtained from 13 prefectures in Japan. These isolates were divided into 15 ApaI PFGE profiles that formed six distinct clusters (clusters A-F). Fifty-three (40.7%) isolates were classified in cluster B, and 20.0, 13.8, 12.3, 6.9 and 6.1% of isolates were in clusters E, A, F, D and C, respectively. The isolates of cluster B were differentiated into seven subtypes (B1-B7) and subtype B5 contained 63% (34/53) of isolates. RAPD revealed four banding patterns (types I-IV), and among 130 isolates 60.7% (79/130) of isolates were RAPD type I. All of the RAPD type I isolates were grouped into clusters A-C by PFGE. There was no relationship between molecular typing and geographic origin of these isolates. These results indicate that isolates of M. haemolytica A1 strain with various molecular profiles have already spread in Japan and may have caused sporadic infections.     

Genotypic analysis of Staphylococcus aureus from milk of dairy cows with mastitis in Argentina

Staphylococcus aureus is the most prevalent pathogen causing mastitis of dairy ruminants. This study was developed to ascertain the genotypes and genealogical relationship among strains isolated from milk of bovines with mastitis in Argentina. Molecular epidemiological analysis of S. aureus was performed on 112 isolates from 21 districts. Clonality was assessed by SmaI pulsed-field gel electrophoresis (PFGE) typing, automated EcoRI ribotyping and restriction enzyme analysis of plasmid (REAP) DNA profiles. A total of 22 band patterns distributed in four clusters were found by SmaI PFGE analysis. The similarity of clusters 2, 3 and 4 with cluster 1 was 0.73, 0.69 and 0.33, respectively, and 101 of 112 isolates belonged in cluster 1. PFGE band patterns from 42 isolates within cluster I were indistinguishable from each other (type A). The second largest group of isolates with indistinguishable PFGE band patterns was subtype A11, which was composed of 19 isolates. Automated ribotyping assigned the 112 isolates into 13 ribotypes. Among these, the most prevalent ribotypes I and VI were composed of 49 and 35 isolates respectively. Although there was certain correspondence between PFGE genotypes and ribotypes, further discrimination was achieved by combining both methods. REAP DNA profile analysis was useful to provide even further discrimination between isolates with identical PFGE genotype and ribotype. The most prevalent S. aureus strains A/I and A11/VI were widely distributed in the country and were not restricted to individual nearby locations. Prevalence of these two strains varied consecutively within a period of 8 years. Whether the shift in type prevalence was due to selection of a phenotypic trait remains undisclosed.     

Methicillin-resistant Staphylococcus aureus ST30-SCCmec IVc clone as the major cause of community-acquired invasive infections in Argentina

Community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) infections have become a major concern worldwide. We conducted a prospective multicenter study of invasive CA-MRSA to evaluate clinical features and genotype of strains causing invasive infections in Argentina. A total of 55 patients with invasive CA-MRSA infections were included. Most patients (60%) had bloodstream infections, 42% required admission to intensive care unit and 16% died. No CA-MRSA isolates were multiresistant (resistant ⩾3 classes of antibiotics). All isolates carried Panton-Valentine leukocidin (PVL) genes and staphylococcal cassette chromosome (SCCmec) type IV. The majority CA-MRSA strains belonged to ST30 and had identical pulsed-field gel electrophoresis (PFGE) patterns, qualifying as a clonal dissemination of a highly transmissible strain. The main clone recovered from patients with CA-MRSA invasive infections was genotyped as pulsed-field gel electrophoresis type C-ST30, SCCmec type IVc-spa type 019, PVL positive. It has become predominant and replaced the previously described CA-MRSA clone (PFGE type A, ST5, SCCmec type IV, spa type 311).     

扩增片段长度多态性分析用于霍乱弧菌分子分型的方法建立和应用评价

目的建立霍乱弧菌的基于红外荧光标记引物的扩增片段长度多态性(AFLP)分型方法,评价脉冲场凝胶电泳(PFGE)和AFLP对霍乱弧菌的分型能力。方法选择PFGE带型均不相同的47株霍乱弧菌作为评价菌株,建立AFLP对于霍乱弧菌的分型方法;确定操作程序后选择83株分离自1962-2005年11个省的霍乱弧菌,进行AFLP和PFGE对于霍乱弧菌分型能力的比较。AFLP分型方法采用了红外荧光标记PCR引物,利用LI-COR4300自动测序仪完成电泳、SagaMX软件对电泳图谱进行编辑。PFGE采用PulseNet提供的标准化程序。结果AFLP用于霍乱弧菌分型时选择性引物携带碱基数为1,最优引物组合为EcoRⅠ-G／MseⅠ-T,AFLP分型实验的重复性达到99．2％。AFLP将83株霍乱弧菌分为52个型别,D值为0．9545;PFGE将此83株菌分为44种带型,D值为0．9251。结论优化固定了AFLP对于霍乱弧菌的分型程序,重复性好;AFLP比PFGE具有更好的分型能力,能够用于分离菌株的分子分型。结合已成为实验室网络监测标准分析方法的PFGE,可对分离株做更细致的分型比较。     

单核细胞增生李斯特菌PFGE分型与血清学分型的联合分析

目的:采用国际标准化的脉冲场凝胶电泳(PFGE)分析方法对单核细胞增生李斯特菌(Lm)进行基因分型,同时进行血清学分型,比较分析两种分型方法的优劣和之间的关系。方法:按照标准化的Lm-PFGE方法对17株Lm进行PFGE分型,分别用限制性内切酶ApaI和AscI酶对菌株进行酶切,通过脉冲场凝胶电泳获得电泳图谱,利用B ioNum erics软件对图谱进行聚类分析。同时对上述菌株进行血清学分型。结果:17株Lm被内切酶ApaI分为13种带型,被内切酶AscI分为14种PFGE型。17株Lm分为5种血清型。结论:Lm-PFGE分型方法是一种高分辨力、稳定可靠的技术。PFGE的分辨力高于血清学分型,两种分型方法密切相关。聚类分析结果显示ApaI酶切分型与H抗原密切相关。     

Discriminating between strains of Escherichia coli using pulsed-field gel electrophoresis and BOX-PCR

In this study, we evaluated two biomolecular techniques for discriminating between strains of Escherichia coli isolated form a variety of sources. The DNA of 211 strains of E. coli collected from dairy farms, calves, feces, pigs, primates, humans, and food products was analyzed by pulsed-field gel electrophoresis (PFGE) and repetitive-element polymerase chain reaction using the BOXA1 primer (BOX-PCR). Objectives of the present study were to compare PFGE and BOX-PCR for discriminating among strains of E. coli and investigate their capability in clustering E. coli strains according to the origin of bacterial isolation. Our results showed that PFGE and BOX-PCR were both able to distinguish closely related strains of E. coli; however, PFGE was able to discriminate between isolates indistinguishable by BOX-PCR and interpretation of PFGE data was easier. BOX-PCR proved to have good discrimination power, was less expensive, and could be performed in a PCR thermocycler. Neither of the methods used were effective in clustering E. coli strains according to the source of the organism.     

Genomic characterization of oxacillin-resistant Staphylococcus epidermidis and Staphylococcus haemolyticus isolated from Brazilian medical centres

Studies on the genetic diversity of oxacillin-resistant coagulase-negative staphylococcal (CNS) isolates are important for the control and prevention of infections. The present study evaluated the clonal diversity of oxacillin-resistant Staphylococcus epidermidis (ORSE) and Staphylococcus haemolyticus (ORSH) strains, isolated from patients in nine Brazilian medical centres by using pulsed-field gel electrophoresis (PFGE) after digestion of bacterial DNA using SmaI. PFGE analysis of ORSE (N=44) and ORSH (N=25) strains showed the presence of 29 restriction profiles clustered in 16 PFGE types, and 21 distinct profiles in 15 PFGE types, respectively, indicating a large genetic diversity among isolates of both of these species. Among the ORSE isolates, 23 (52%) strains belonged to two predominant PFGE types (named A and B), which were observed in most of the hospitals assessed, indicating the spread of these PFGE types in hospitals located in Rio de Janeiro. The spread of PFGE types of ORSH was also detected in some of the hospitals investigated. The results show that PFGE is a suitable tool for epidemiological studies of oxacillin-resistant CNS, and can be used as a basis for infection control procedures for these multiresistant organisms.     

A clone of coagulase-negative staphylococci among patients with post-cardiac surgery infections

Coagulase-negative staphylococci (CoNS) are important causes of hospital-acquired infections such as infections after cardiac surgery. Efforts to reduce these infections are hampered by the lack of knowledge concerning the epidemiology of CoNS in this setting. Forty strains of CoNS collected during the surgical revision of 27 patients operated on between 1997 and 2000 were analysed. Strains were also collected from the ambient air in the operating suite. Their pulsed-field gel electrophoresis (PFGE) characteristics and antibiotic resistance were analysed. Using PFGE 19 of 40 strains from 15 of 27 patients were shown to belong to one clone, and strains from this clone were also isolated from the ambient air. This clone had caused infections throughout the period. Antibiotic resistance did not correlate with PFGE patterns. Using PFGE one clone could be identified that caused 56% of the CoNS infections during this period. A strain from this clone was also found in the air of the operating suite suggesting the origin of the CoNS causing infections was the hospital environment.     

2007年上海市部分嗜肺军团菌血清1型菌株PFGE分型研究

[目的]研究2007年上海市公共场所部分空调冷却塔水中分离出来的嗜肺军团菌1型（L01）的基因特征。[方法]从空调冷却塔水中检测到26株Lp1嗜肺军团菌后,使用脉冲场凝胶电泳（pulsed－field gel electrophorefiifl,PFGE）技术对酶切后的L01军团菌全染色体DNA进行电泳获得指纹图谱,并用BioNumerics软件对其进行聚类分析。[结果]26株LO1军团菌可分为15个PFGE型。菌株间相似性系数在30．00％～100．00％之间不等,大部分菌株的PFGE型别差异明显,无优势型别。大部分PFGE型别的菌株来源场所单一;而大部分同一场所来源的军团菌菌株为相同的PFGE型。[结论]2007年上海市公共场所部分空调冷却塔水中分离出来的Lp1军团菌呈现基因多样性。