Sensitive PCR-restriction fragment length polymorphism assay for detection and genotyping of Giardia duodenalis in human feces

An assay that uses heminested PCR-restriction fragment length polymorphism analysis for the detection and genotyping of Giardia duodenalis on the basis of polymorphism in the triose phosphate isomerase (tpi) gene was developed. This assay was evaluated with DNA extracted from purified parasite material, bacterial cultures, whole human feces containing G. duodenalis and other parasites, and their corresponding immunofluorescence-stained fecal smears on glass microscope slides. The assay was specific and discriminated between G. duodenalis assemblages A and B. RFLP analysis further distinguished two groups (designated groups I and II) within assemblage A. Among 35 DNA samples extracted from whole feces from patients with confirmed sporadic giardiasis, the tpi gene was amplified from 33 (94%). Of these, nine (27%) samples contained assemblage A group II, 21 (64%) contained assemblage B, and 3 (9%) contained a mixture of assemblage A group II and assemblage B. The tpi gene of G. duodenalis assemblage B was amplified from 21 of 24 (88%) DNA samples extracted from whole feces from patients with confirmed cases of infection in a nursery outbreak. No amplification was detected from the remaining three DNA samples. Overall, analysis of DNA extracted from material recovered from stained microscope slides identified identical G. duodenalis genotypes in 35 (65%) of the 54 samples for which a genotype was established with DNA from whole feces. The heminested PCR method developed is sensitive, simple, and rapid to perform and is applicable for the analysis of other intestinal pathogens.     

Prevalence of enteroparasites and genotyping of Giardia lamblia in Peruvian children

Enteroparasites in children from three marginal urban districts of Trujillo (Peru) were studied to treat these children and to design a prevention and control programme. A total of 845 children were examined. The general prevalence of enteroparasites was of 66.3%, and 45.6% were multiparasitized. The pathogenic enteroparasite prevalence were 23.8% (Giardia lamblia), 4.6% (Iodamoeba buschlii), 2.6% (Cyclospora cayetanensis), 2.2% (Hymenolepis nana), and 2% (Cryptosporidium spp.). G. lamblia was the most frequent parasite both in diarrheic children (28.1%) as well as in nondiarrheic ones (19.5%). The G. lamblia genotypes were molecularly characterized by sequence analysis of the glutamate dehydrogenase (gdh) gene using PCR and RFLP. Sequence analysis revealed both Assemblage A (AI and AII) and Assemblage B (BIV), with the predominance of Assemblage AI. All the samples with Assemblage A were diarrheic but not those with Assemblage B. This is the first study of molecular characterization of G. lamblia in Peruvian children and confirms the importance of asymptomatic patients in the transmission of the giardiosis, especially in places with poor hygiene and sanitation.     

Application of HRM assays with EvaGreen dye for genotyping Giardia duodenalis zoonotic assemblages

A high-resolution melting (HRM) assay was applied to distinguish between Giardia duodenalis assemblages A and B from human and dog feces based on the triosephosphate isomerase gene (tpi). The genomic DNAs were selected from assemblages A (WB) and B (GS) as reference and plasmids were constructed. The reference plasmids and genomic DNAs from 15 Giardia-positive samples were analyzed by HRM assay. This was followed by separate real-time PCR assays specific for assemblages A and B using EvaGreen (EG) to identify PCR products by melting-point analysis. Our results indicate that PCR with HRM in a one-step closed-tube method is a reliable diagnostic method for G. duodenalis zoonotic assemblage identification and more rapid than restriction length polymorphism analysis and direct sequence analysis, HRM is specific, sensitive, reproducible, and rapid. This study is the first use of EG dye for Giardia genotyping. This assay is a promising approach to determine the presence and genotype of Giardia based on a highly variable gene.     

Multiplex real-time PCR assay using Scorpion probes and DNA capture for genotype-specific detection of Giardia lamblia on fecal samples

Two major genotypic assemblages of Giardia lamblia infect humans; the epidemiologic significance of this phenomenon is poorly understood. We developed a single-vessel multiplex real-time PCR (qPCR) assay that genotypes Giardia infections into assemblages A and/or B directly from fecal samples. The assay utilized Scorpion probes that combined genotype-specific primers and probes for the 18S rRNA gene into the same molecule. The protocol was capable of detecting as few as 20 trophozoites per PCR on fecal DNA isolated using a commercial method or 1.25 trophozoites per PCR on fecal DNA isolated using a G. lamblia-specific oligonucleotide capture technique. The assay was specific for fecal specimens, with no amplification of the discordant genotype with the opposite Scorpion probe. When 97 clinical specimens from Bangladesh were used, the multiplex PCR assay detected 95% (21 of 22) of Giardia microscopy-positive specimens and 18% (13 of 74) of microscopy-negative specimens. Microscopy-negative and qPCR-positive specimens had higher average cycle threshold values than microscopy-positive and qPCR-positive specimens, suggesting that they represented true low-burden infections. Most (32 of 35) infections were assemblage B infections. This single-reaction multiplex qPCR assay distinguishes assemblage A Giardia infections from assemblage B infections directly on fecal samples and may aid epidemiologic investigation.     

Fish as a possible reservoir for zoonotic Giardia duodenalis assemblages

Giardiasis is a re-emerging infectious disease of worldwide significance caused by Giardia duodenalis. This study investigated the occurrence of zoonotic G. duodenalis assemblages in fish to explore the possible role of fish in the epidemiology of human giardiasis. For this purpose, 92 fish (Tilapia nilotica and Mugil cephalus) collected from (fish farms and Nile River) at different governorates in Egypt were examined for the presence of G. duodenalis in their feces by using enzyme linked immunosorbent assay, then positive fecal samples were tested by duplex PCR for identification of triose phosphate isomerase (tpi) gene specific for zoonotic assemblages A and B. The overall prevalence of G. duodenalis in the examined fish was 3.3%, while the detection rates among the examined fish species were 2.9% and 4.2% for T. nilotica and M. cephalus, respectively. G. duodenalis was detected in the feces of both farmed and wild fish whereas all isolates were genotyped as assemblage A. In conclusion, the occurrence of zoonotic G. duodenalis assemblage A in the examined fish species at two different aquatic environments underlines the possibility of fish to be an additional reservoir for zoonotic G. duodenalis assemblages that contributes in the contamination of water with this pathogen and thus the role of fish in the epidemiology of human giardiasis cannot be ruled out.     

用PCR扩增tim基因检测蓝氏贾第鞭毛虫

采用聚合酶链反应 (PCR)对蓝氏贾第鞭毛虫 (Giardialamblia)的磷酸丙糖异构酶 (triosephosphateisomerase ,缩写为tim)基因进行特异性扩增 ,结果扩增出 1条 6 83bp的DNA片段。此方法的特异性可高达10 0 % ,而其它DNA样本 ,如日本血吸虫 (Schistosomajaponicum)、刚地弓形虫 (Toxoplasmagondii)、微小隐孢子虫 (Cryptosporidiumparvum)、溶组织内阿米巴 (Entamoebahistolytica)、旋毛虫 (Trichinellaspiralis)和阴道毛滴虫 (Trichomonasvaginalis) ,以及人体血细胞等均未出现扩增反应。本法的敏感性也很高 ,可检测到0 4pg贾第虫包囊的DNA。 13株来自不同地理位置和 或宿主的贾第虫DNA样本在PCR中均各产生 1条长为 6 83bp的目的片段。上述结果表明本实验建立的检测贾第虫的PCR方法有效     

Classification of subgroups of Giardia lamblia based upon ribosomal RNA gene sequence using the polymerase chain reaction.

A sensitive and specific polymerase chain reaction-based assay has been developed to detect and analyze polymorphism in the Giardia lamblia 18S ribosomal RNA gene. Efficient amplification required the inclusion of cosolvents (glycerol and dimethyl sulfoxide) in the reaction. Following the optimization of conditions for amplification and subsequent hybridization of amplified product with radiolabeled oligonucleotide probe, a detection limit of less than one organism's worth of DNA was achieved. Thirty-five different G. lamblia strains obtained from various human and animal host types and geographic locations were analyzed by this method. The strains could be divided into 3 groups on the basis of defined nucleotide substitutions within the 183-bp amplified DNA fragment of the 18S ribosomal RNA gene. The groupings based upon the 18S ribosomal RNA gene sequence correlated with groupings previously assigned based upon patterns of surface antigens and restriction enzyme analysis. Analysis of the G. lamblia 18S ribosomal RNA gene sequences present in fecal specimens obtained from giardiasis patients revealed the presence of the different sequence types in these specimens. Some specimens contained more than one sequence type. The identification of subgroups of G. lamblia may facilitate studies of virulence, infectivity, and the epidemiology of giardia infection.     

人源性蓝氏贾第鞭毛虫Elp3基因的克隆及序列分析

目的克隆蓝氏贾第鞭毛虫Elp3基因,并应用生物信息学方法进行分析。方法根据蓝氏贾第鞭毛虫Elp3已知基因序列的特点设计引物,利用PCR技术扩增获得Elp3的核苷酸序列,连接到pET28a载体并测定序列。应用生物信息学方法分析Elp3基因的序列同源性与结构特征。结果扩增片段长度为1767bp,测序结果与蓝氏贾第鞭毛虫WB株（GL50830）同源性100%。可构建生物进化树,进行同源结构建模发现,71-362aa具有一个保守的S-腺甙基蛋氨酸区域,458-584aa具有组蛋白乙酰基转移酶区域。结论成功克隆了蓝氏贾第鞭毛虫Elp3基因,生物信息学分析发现,其在进化上与其它物种不属同一起源,具有SAM和HAT的结构和功能,这些发现为进一步研究其生物学功能提供了依据和线索。     

Clinical significance of a set of single nucleotide polymorphisms of hepatitis B virus core gene in Chinese Han patients with chronic hepatitis B

To evaluate clinical significance of a set of SNPs of HBV core gene, a modified PCR-RFLP assay developed by Hannoun was adapted to determine HBV SNPs in 312 Chinese Han patients with chronic hepatitis B. Five typical RFLP patterns were found and named RFLP patterns C, D, E, G, and C/G mixture. The distribution of RFLP patterns was as follows: C, 61.5%; D, 2.6%; E, 9.6%; G, 16.7%; C/G mixture, 9.6%. The PCR amplicons of core gene were cloned into pGM-T, then colony PCR combined with RFLP and sequencing were used to confirm the presence of cleavage sites of Tsp509I and SNPs. 5 SNPs, A261T, A336C, A336T T337C and T385C, were found to be associated with RFLP patterns change and only SNP A336C or A336T caused the substitution of Glu-83 with Asp in HBcAg. The serum HBV DNA level in RFLP pattern C was higher than that in RFLP pattern G and C/G mixture, respectively, most possibly which associating with aminoacid change, Glu83Asp. The rate of elevated serum ALT levels in RFLP pattern C/G mixture was significantly lower than that in RFLP patterns C and G, respectively. The PCR amplicons of HBV S gene were sequenced and genotyped with HBV genotyping tools. It was found that RFLP patterns E and G were categorized into genotype B, RFLP pattern C showed two genotypes (B, C), and RFLP pattern D coincided with HBV genotype D, therefore, the modified PCR-RFLP can be adapted to determine HBV SNPs, not genotypes in Chinese Han patients with chronic hepatitis B.     

Predominance of two Bartonella henselae variants among cat-scratch disease patients in the Netherlands.

Restriction endonuclease analysis of the PCR-amplified 16S-23S rRNA gene spacer region was used to investigate the prevalence of Bartonella henselae variants in samples from cat-scratch disease (CSD) patients. Analysis of spacer PCR fragments from 27 Bartonella DNA-positive samples from Dutch patients with CSD with AluI revealed two restriction fragment length polymorphism (RFLP) patterns, patterns A and B. Twenty samples yielded B. henselae pattern A, and 7 samples yielded B. henselae pattern B. Three samples from North American patients with CSD were shown to contain B. henselae with RFLP pattern B. To be able to detect and differentiate Bartonella DNA in clinical material more sensitively and faster, two B. henselae PCRs which amplify part of the 16S rRNA gene and which can discriminate between two B. henselae variants were developed. Thirty-two of 41 Bartonella DNA-positive samples from Dutch patients with CSD contained type I B. henselae, 7 samples contained type II B. henselae, and two samples were negative in both type-specific PCRs. Two samples from North American patients with CSD both contained type II B. henselae. A 100% correlation was found between the AluI spacer RFLP pattern and the 16S rRNA PCR type. We have shown that Dutch patients with CSD contain a limited number of B. henselae variants, suggesting that, in contrast to systemic bartonellosis, CSD in immunocompetent patients is caused by a limited number of B. henselae variants.     

Antigenic variation of Giardia lamblia in the feces of Mongolian gerbils.

Enzyme-linked immunoelectrotransfer blot was used to study variations in Giardia lamblia antigens in extracts of feces from infected Mongolian gerbils. A 65-kilodalton antigen was found in feces that contained strain WB (ATCC 30957) cysts and in axenic culture of strains WB and CDC:0284:1 that contained trophozoites. The 65-kilodalton antigen from trophozoites of both strains was membrane associated. A 70-kilodalton antigen was found in feces that contained strain CDC:0284:1 cysts. It was persistent in 16 fecal collections and may be strain specific. Similar variations in antigens may occur in human feces. Coproimmunodiagnostic assays that use monoclonal antibodies will have to include all varieties of G. lamblia antigens present in the feces of giardiasis patients.     

Rapid detection and characterization from field cases of infectious laryngotracheitis virus by real-time polymerase chain reaction and restriction fragment length polymorphism.

A real-time polymerase chain reaction (PCR) assay was developed to specifically amplify infectious laryngotracheitis virus (ILTV) DNA from field samples. The 222-base-pair PCR fragment was amplified using primers located in a conserved region of the infected cell protein 4 gene that was demonstrated in this work to encompass a single nucleotide polymorphism. Subsequent restriction fragment length polymorphism (RFLP) analysis of real-time PCR amplified fragments from a range of ILTV isolates using the restriction endonuclease MspI enabled differentiation between older ILTV isolates that were prevalent in the 1960s prior to the availability of vaccine strains and more recent isolates that predominantly are identical to vaccine strains. The assay, using real-time PCR, RFLP and sequence analysis, was used to characterize two recent field cases of infectious laryngotracheitis from Northern Ireland. One of the field cases was demonstrated to be similar to older "wild-type" isolates, while the other field case was identified to have a concurrent ILTV infection of both "wild-type" and vaccinal type origin. The assay described here using real-time PCR and RFLP provides a rapid, specific method that enables detection and characterization of ILTV directly from field cases.     

Differentiation of Burkholderia Species by PCR-Restriction Fragment Length Polymorphism Analysis of the 16S rRNA Gene and Application to Cystic Fibrosis Isolates

Burkholderia cepacia, which is an important pathogen in cystic fibrosis (CF) owing to the potential severity of the infections and the high transmissibility of some clones, has been recently shown to be a complex of five genomic groups, i.e., genomovars I, II (B. multivorans), III, and IV and B. vietnamiensis. B. gladioli is also involved, though rarely, in CF. Since standard laboratory procedures fail to provide an accurate identification of these organisms, we assessed the ability of restriction fragment length polymorphism (RFLP) analysis of amplified 16S ribosomal DNA (rDNA), with the combination of the patterns obtained with six endonucleases, to differentiate Burkholderia species. This method was applied to 16 type and reference strains of the genus Burkholderia and to 51 presumed B. cepacia clinical isolates, each representative of one clone previously determined by PCR ribotyping. The 12 Burkholderia type strains tested were differentiated, including B. cepacia, B. multivorans, B. vietnamiensis, and B. gladioli, but neither the genomovar I and III reference strains nor the genomovar IV reference strain and B. pyrrociniaT were distinguishable. CF clinical isolates were mainly distributed in RFLP group 2 (which includes B. multivoransT) and RFLP group 1 (which includes B. cepacia genomovar I and III reference strains, as well as nosocomial clinical isolates). Two of the five highly transmissible clones in French CF centers belonged to RFLP group 2, and three belonged to RFLP group 1. The remaining isolates either clustered with other Burkholderia species (B. cepacia genomovar IV or B. pyrrocinia, B. vietnamiensis, and B. gladioli) or harbored unique combinations of patterns. Thus, if further validated by hybridization studies, PCR-RFLP of 16S rDNA could be an interesting identification tool and contribute to a better evaluation of the respective clinical risks associated with each Burkholderia species or genomovar in patients with CF.     

慢性乙肝患者HBV核心基因一组单核苷酸多态性与血清HBV DNA水平的相关性研究

目的 研究慢性乙肝患者HBV核心基因的单核苷酸多态性(SNP)与血清HBV DNA水平的相关关系.方法 采用PCR-RFLP和限制性内切酶Tsp509I榆测HBV核心基因的SNP,采用双脱氧终止法对核心基因进行序列测定,实时荧光PCR技术用于HBVDNA水平的定量检测.结果 慢性乙肝人群中发现5种典型的PCR-RFLP图谱,分别是RFLP-C、RFLP-D、RFLP-E、RFLP-G和RFLP-C/G,各种RFLP图谱的分布频率依次为61.5%、2.6%、9.6%、16.7%和9.6%.A165T、A336C、A336T、T337C和T385C等5种SNP与RFLP图谱的变化有关,但是只有SNP A336C和A336T会导致HBcAg第83位的Glu被Asp所替代.RFLP-C组患者的血清HBV DNA水平显著高于RFLP-G组(P=0.02)和RFLP-C/G组(P=0 006),而且RFLP-C/G组患者血清ALT的阳性率显著低于RFLP-C、RFLP-E和RFLP-G组;当HBeAg阳性时,RFLP-C组患者的血清HBV DNA水平显著高于RFLP-G组(P=0.015)和RFLP-C/G组(P=0.008).结论 本研究中使用的PCR-RFLP能够用于检测核心基因的SNP,RFLP-C组患者的血清HBV DNA水平显著高于RFLP-G组和RFLP-C/G组,可能与Glu83 Asp突变有关.

Abstract：

Objective To investigate the relation between a set of single nucleotide polymorphisms (SNP) in core gene of HBV in chronic hepatitis B patients and HBV DNA levels. Methods PCR restriction fragment length polymorphism(PCR-RFLP) assay and restriction enzyme Tsp509I were adopted to determine HBV SNP in HBV core gene. Nucleotide sequences of core gene were determined using the dideoxy chain termination method. HBV DNA levels were quantitated with real-time PCR. Results Five typical RFLP patterns, RFLP-C, RFLP-D, RFLP-E, RFLP-G and RFLP-C/G mixture were found and the distribution of HBV RFLP patterns was as follows: C, 61. 5% ; D, 2. 6% ; E, 9.6%; G, 16.7%; C/G mixture, 9.6%. Five SNPs, A165T, A336C, A336T, T337C and T385C, were found to be associated with RFLP patterns change and only SNP A336C or A336T caused the substitution of Glu-83 with Asp in HBcAg. The serum HBV DNA levels in RFLP-C group were higher than that in RFLP-G (P =0. 02) and RFLP-C/G group(P = 0. 006) , respectively, furthermore, the positive rate of serum ALT in RFLP-C/G group was lower than that in RFLP-C, RFLP-E and RFLP-G group, respectively. Under the condition of HBeAg-positive, the serum HBV DNA levels in RFLP-C group were higher than that in RFLP-G (P = 0. 015) and RFLP-C/G group(P =0.008) , respectively. Conclusion PCR-RFLP used in this study can be adopted to determine HBV SNPs, not genotypes in Chinese patients with chronic hepatitis B. The serum HBV DNA level in RFLP-C group higher than that in RFLP-G or RFLP-C/G group maybe associated with amino acid mutation, Glu83 Asp.     

PCR-Based Detection and Identification of Burkholderia cepacia Complex Pathogens in Sputum from Cystic Fibrosis Patients

PCR amplification of the recA gene followed by restriction fragment length polymorphism (RFLP) analysis was investigated for the rapid detection and identification of Burkholderia cepacia complex genomovars directly from sputum. Successful amplification of the B. cepacia complex recA gene from cystic fibrosis (CF) patient sputum samples containing B. cepacia genomovar I, Burkholderia multivorans, B. cepacia genomovar III, Burkholderia stabilis, and Burkholderia vietnamiensis was demonstrated. In addition, the genomovar identifications determined directly from sputum were the same as those obtained after selective culturing. Sensitivity experiments revealed that recA-based PCR could reliably detect B. cepacia complex organisms to concentrations of 10(6) CFU g of sputum(-1). To fully assess the diagnostic value of the method, sputum samples from 100 CF patients were screened for B. cepacia complex infection by selective culturing and recA-based PCR. Selective culturing identified 19 samples with presumptive B. cepacia complex infection, which was corroborated by phenotypic analyses. Of the culture-positive sputum samples, 17 were also detected directly by recA-based PCR, while 2 samples were negative. The isolates cultured from both recA-negative sputum samples were subsequently identified as Burkholderia gladioli. RFLP analysis of the recA amplicons revealed 2 patients (12%) infected with B. multivorans, 11 patients (65%) infected with B. cepacia genomovar III-A, and 4 patients (23%) infected with B. cepacia genomovar III-B. These results demonstrate the potential of recA-based PCR-RFLP analysis for the rapid detection and identification of B. cepacia complex genomovars directly from sputum. Where the sensitivity of the assay proves a limitation, sputum samples can be analyzed by selective culturing followed by recA-based analysis of the isolate.     

Distribution of Porphyromonas gingivalis strains with fimA genotypes in periodontitis patients

Fimbriae (FimA) of Porphyromonas gingivalis are filamentous components on the cell surface and are thought to play an important role in the colonization and invasion of periodontal tissues. We previously demonstrated that fimA can be classified into four variants (types I to IV) on the basis of the nucleotide sequences of the fimA gene. In the present study, we attempted to detect the four different fimA genes in saliva and plaque samples isolated from patients with periodontitis using the PCR method. Four sets of fimA type-specific primers were designed for the PCR assay. These primers selectively amplified 392-bp (type I), 257-bp (type II), 247-bp (type III), and 251-bp (type IV) DNA fragments of the fimA gene. Positive PCR results were observed with reference strains of P. gingivalis in a type-specific manner. All other laboratory strains of oral and nonoral bacteria gave negative results. The sensitivity of the PCR assay for fimA type-specific detection was between 5 and 50 cells of P. gingivalis. Clinical samples were obtained from saliva and subgingival plaque from deep pockets (>/=4 mm) of 93 patients with periodontitis. Bacterial genomic DNA was isolated from the samples, and the targeted fragments were amplified by PCR. The presence of P. gingivalis was demonstrated in 73 patients (78.5%), and a single fimA gene was detected in most patients. The distribution of the four fimA types among the P. gingivalis-positive patients was as follows: type I, 5.4%; type II, 58.9%; type III, 6. 8%; type IV, 12.3%; types I and II, 6.8%; types II and IV, 2.7%; and untypeable, 6.8%. P. gingivalis with type II fimA was detected more frequently in the deeper pockets, and a significant difference of the occurrence was observed between shallow (4 mm) and deep (>/=8 mm) pockets. These results suggest that P. gingivalis strains that possess type II fimA are significantly more predominant in periodontitis patients, and we speculate that these organisms are involved in the destructive progression of periodontal diseases.     

Detection and differentiation of old world orthopoxviruses: restriction fragment length polymorphism of the crmB gene region

A restriction fragment length polymorphism (RFLP) assay was developed to identify and differentiate Old World, African-Eurasian orthopoxviruses (OPV): variola, vaccinia, cowpox, monkeypox, camelpox, ectromelia, and taterapox viruses. The test uses amplicons produced from virus genome DNA by PCR with a consensus primer pair designed from sequences determined for the cytokine response modifier B (crmB) gene of 43 different OPV strains of known taxonomic origin. The primer pair amplified a single specific product from each of the 115 OPV samples tested. Size-specific amplicons identified and differentiated ectromelia and vaccinia virus strains, which contain a truncated crmB gene, and enabled their differentiation from other OPV species. Restriction digests of amplified products allowed the identification and differentiation of variola, monkeypox, camelpox, vaccinia, and cowpox virus species and strains.     

Characterization of Giardia duodenalis by polymerase-chain-reaction fingerprinting

The development of a polymerase chain reaction (PCR) based fingerprinting method for the characterization of Giardia duodenalis isolates is described. The method uses three different PCRs; one is specific for the A (“Polish”) major group of G. duodenalis isolates, another is specific for the B (“Belgian”) group of isolates; and one amplifies a fragment of the glutamate dehydrogenase gene present in all G. duodenalis isolates. The PCRs perform highly sensitively on DNA from cultured trophozoites. Isolates were further characterized by restriction-fragment-length polymorphism (RFLP) analysis of the PCR products. In this way, representative isolates from the A and B groups could be grouped together into a number of subgroups. The stability of the genotypes with time and the reproducibility of the two methods were tested on cloned and subcloned lines from a number of isolates and proved to be highly satisfactory. The PCR/RFLP method was evaluated on cysts derived from a number of human patients. It is concluded that the PCR fingerprinting method described in this paper provides a reliable characterization method for Giardia isolates and has the potential to be used as a direct method of typing G. duodenalis cysts from feces. Received: 7 January 1998 / Accepted: 7 April 1998     

限制性片段长度多态性分析拉米夫定治疗引起乙型肝炎病毒耐药基因变异的研究

目的　应用聚合酶链反应限制性片段长度多态性分析方法 (PCRRFLP) ,研究拉米夫定治疗引起慢性乙型肝炎患者血清中乙型肝炎病毒耐药基因 (HBVDNA)变异。方法　收集 2 4 0例用拉米夫定治疗 5 2～ 78周慢性乙型肝炎患者的血清标本 ,应用PCRRFLP方法扩增HBV 5 5 2 ,5 2 8两个基因位点片段 ,用限制性内切酶NdeⅠ ,NlaⅢ酶切分析 ,同时测定HBVDNA含量 ,并用DNA序列分析测定 3例患者HBVDNAP区基因序列 (1例野毒株 ,1例M5 5 2V伴L5 2 8M变异 ,1例M5 5 2I变异 )。结果　 2 4 0例患者应用拉米夫定治疗 5 2～ 78周后 ,5 1例血清HBVDNA出现YMDD变异 ,其中M5 5 2V变异 38例 ,M5 5 2I变异 13例 ,L5 2 8M和M5 5 2V同时变异 2 6例 ,L5 2 8M和M5 5 2I同时变异 1例。与定量PCR比较 ,可以测定YMDD变异的最低含量为 1× 10 4 copies mlHBVDNA序列分析结果与RLFP测定一致。结论　PCRRLFP方法是一种快速、简便的检测HBVDNA聚合酶变异的方法 ,可以用来筛查大量的血清标本 ,适宜作为临床用来观察拉米夫定治疗慢性乙型肝炎患者检测HBV变异的方法     

Incidence and clinical features of Giardia lamblia

To determine the incidence and clinical features of Giardia lamblia infection, we studied 1790 patients at Kochi Medical School Hospital from April 1998 to July 2001. Fecal samples were examined microscopically by the direct smear method, direct immunofluorescent assay and by Kohn's one-step staining for G. lamblia cysts. Cysts of G. lamblia were found in 17 of 1,790(0.95%) stool samples, indicating that G. lamblia infection is not rare in Kochi. The most characteristic feature was that G. lamblia-positive cases were more frequent in the advanced age group(41-79 years old) and most of the subjects (except 2 cases) with G. lamblia had no history of traveling overseas. Four subjects had symptoms related to G. lamblia infection. Thus, more attention should be given to parasitic infections in laboratory stool examinations in order to detect cyst carriers as potential sources of infection.