Phenotypic and genotypic variation in Giardia lamblia isolates during chronic infection.

Two Giardia isolates were axenised in vitro after recovery by duodenal aspiration from a man with hypo-gamma globulinaemia and chronic giardiasis, before and after three unsuccessful courses of metronidazole. In vitro drug sensitivity assays showed that the pretreatment isolate was sensitive to metronidazole with minimum inhibitory concentration (MIC) and dose that inhibited growth by 50% (ED50) values of 0.1 and 0.03 mumol/l, respectively. The post-treatment isolate was 20-fold more resistant (MIC and ED50 4.3 and 0.58 mumol/l, respectively). Differences between these isolates were also found in the surface protein profiles after radioiodination, metabolic labelling patterns with 35S-methionine, malic enzyme isoenzyme patterns, and by DNA fingerprinting with a M-13 bacteriophage probe. The phenotypic and genotypic differences between the pretreatment and post-treatment isolates suggest that we have isolated two different strains from the same patient and that treatment with metronidazole resulted in selection of the more resistant strain.     

蓝氏贾第鞭毛虫感染的免疫学诊断方法

蓝氏贾第鞭毛虫感染可引起人及其他哺乳动物腹泻.近年来,贾第虫病的严重性和危害性日益受到重视.本文对蓝氏贾第鞭毛虫感染的免疫学诊断方法研究进行了综述,比较了各种方法的优缺点,简要介绍了一些商品化试剂盒的使用情况.贾第虫病免疫学诊断方法的应用,对贾第虫病的临床诊断、治疗、预后将带来极大的方便.     

Giardia lamblia infection of suckling mice

Axenically cultured Giardia lamblia trophozoites (2 x 10(5)) were inoculated by gavage into suckling mice. All mice three, seven, and 14 days old became infected, with the peak trophozoite count in the small bowel of 5.3 +/- 1.1 x 10(6) occurring seven days after inoculation of three-day-old mice. In addition to infecting each of 65 challenged mice, G. lamblia was able to complete its life cycle by encysting and, as cysts, to infect previously unchallenged animals. Control mice given culture medium alone, mice challenged with trophozoites when older than 14 days of age, and mothers of infected mice did not become infected. There was no difference in body weight between infected mice and control mice, nor were histopathologic changes in the small bowel noted at the time of peak infection. Infection was cleared in all mice by 17-21 days. Thus, axenically cultured G. lamblia trophozoites are capable of infecting and completing their life cycle in suckling mice. The susceptibility of mice to infection is remarkably age specific, and the infection is apparently without adverse effects on the murine host.     

Prevalence of Giardia lamblia infection in household dogs

A total of 1035 household dogs were examined for the presence of Giardia lamblia (G. lamblia) in their feces. Fecal samples from 151 (14.6%) of the dogs were positive for Giardia. The protozoan was more often detected in soft feces (26.4%) than in normal (10.0%) or diarrheic feces (13.7%) (p < 0.001 and p < 0.01, respectively). The forms of the organisms obtained from the 151 dogs were cysts (77.5%), trophozoites (9.9%), or both cysts and trophozoites (12.6%). Dogs kept indoors had a higher prevalence (18.5%) of Giardia than dogs kept outdoors (4.8%) (p < 0.001). Giardia infection was also more prevalent in 1-6 months old puppies (21.7%) compared to other groups (2.4%-7.5%) (p < 0.001). The prevalence of Giardia in dogs originally purchased from pet shops or breeding kennels was extremely high (21.5%) compared to that of dogs from individual households (4.3%) (p < 0.001). With regard to human public health, the high infection rate of Giardia in puppies and dogs kept indoors is a serious problem because G. lamblia in infected dogs may have zoonotic potential. No reports of human giardiasis transmitted from dogs have been made. However, the results of this study suggest that the risk of Giardia transmission from household dogs to humans is not negligible. Pet owners should be taught appropriate hygiene measures to prevent Giardia transmission from dogs to humans.     

Saccharomyces boulardii and infection due to Giardia lamblia

Therapy with metronidazole is the recommended option in giardiasis. However, some clinical trial reports suggest the appearance of drug resistance to explain therapeutic failure. Several investigations have been carried out on the effect of probiotic microorganisms for preventing or treating gastrointestinal diseases, but little is known about their efficacy against protozoal infections. The principal objective of our study was to evaluate the efficacy of Saccharomyces boulardii against Giardia lamblia infections. A double-blind, placebo-controlled study was carried out on adult patients with giardiasis. Group 1 (30 patients) included metronidazole 750 mg 3 times daily along with S. boulardii capsules (250 mg b.i.d. orally) for 10 d while group 2 (35 patients) was treated with metronidazole 750 mg 3 times daily and with empty capsules as placebo for 10 d. Patients were re-examined at 2 and 4 weeks after treatment, and stool examinations were performed. At week 2, G. lamblia cysts were detected in 6 cases (17.1%) of group 2 and none in group 1. At the end of the fourth week, presence of the cysts continued in the same 6 cases in group 2 (control group). These findings indicated that S. boulardii may be effective in treating giardiasis when combined with metronidazole therapy.     

四川省华蓥市蓝氏贾第鞭毛虫感染情况的调查

目的调查华蓥市贾第虫感染情况 ,为临床诊治提供依据。方法取受检者粪便标本 ,用醛醚浓集法和碘液涂片法检查。结果共检查 16 32人 ,阳性率 6 .2 5 % (10 2 / 16 32 )。幼儿、小学生、中学生、大学生、成人阳性率分别为 8.77% (32 / 36 5 )、7.4 6 % (2 5 / 335 )、5 .5 9% (18/ 32 2 )、5 .16 % (16 / 310 )、3.6 7% (11/ 30 0 )。幼儿、小学生与成人相比 ,存在不同程度差异 (P <0 .0 1和P <0 .0 5 )。城乡人群阳性率分别为 4 .10 % (32 / 780 )、8.2 2 % (70 /85 2 ) ,差异有显著性 (P <0 .0 1)。 10 2例阳性者中 ,腹泻患者占 5 4 .90 % (5 6 / 10 2 )。结论本地人群感染贾第虫者颇多 ,且以幼儿和小学生为主。患者常表现为腹泻 ,建议临床诊治腹泻病人予以病原学检查 ,以免误诊     

Intestinal infection with Giardia spp. reduces epithelial barrier function in a myosin light chain kinase-dependent fashion

BACKGROUND & AIMS: Giardiasis causes malabsorptive diarrhea, and symptoms can be present in the absence of any significant morphologic injury to the intestinal mucosa. The effects of giardiasis on epithelial permeability in vivo remain unknown, and the role of T cells and myosin light chain kinase (MLCK) in altered intestinal barrier function is unclear. This study was conducted to determine whether Giardia spp. alters intestinal permeability in vivo, to assess whether these abnormalities are dependent on T cells, and to assess the role of MLCK in altered epithelial barrier function. METHODS: Immunocompetent and isogenic athymic mice were inoculated with axenic Giardia muris trophozoites or sterile vehicle (control), then assessed for trophozoite colonization and gastrointestinal permeability. Mechanistic studies using nontransformed human duodenal epithelial monolayers (SCBN) determined the effects of Giardia on myosin light chain (MLC) phosphorylation, transepithelial fluorescein isothiocyanate-dextran fluxes, cytoskeletal F-actin, tight junctional zonula occludens-1 (ZO-1), and MLCK. RESULTS: Giardia infection caused a significant increase in small intestinal, but not gastric or colonic, permeability that correlated with trophozoite colonization in both immunocompetent and athymic mice. In vitro, Giardia increased permeability and phosphorylation of MLC and reorganized F-actin and ZO-1. These alterations were abolished with an MLCK inhibitor. CONCLUSIONS: Disruption of small intestinal barrier function is T cell independent, disappears on parasite clearance, and correlates with reorganization of cytoskeletal F-actin and tight junctional ZO-1 in an MLCK-dependent fashion.     

Giardia lamblia infection in a patient with myotonic dystrophy

Myotonic dystrophy is an autosomal dominant muscle disorder characterized by muscle wasting and weakness and a number of other systemic abnormalities. Some patients have hypo-IgG that is asymptomatic in most of them. We report the case of a 42-year-old woman with myotonic dystrophy and hypo-IgG who experienced asthenia and weight loss secondary to Giardia lamblia bowel infection.     

Association between Whipple's disease and Giardia lamblia infection.

Whipple' disease is mainly characterized by affecting the digestive system, although it can be a multisystemic process with different clinical symptoms. The bacillus causing the disease has been isolated and cultivated in 2000 and the genome sequence has been recently analyzed in 2003, which means new perspectives for its diagnosis and treatment. Giardiasis is an infestation caused by a protozoo and may cause a malabsorption syndrome or run in a subclinic way. The case of a middle-aged male is described, who after a three-year period of migratory arthralgias, showed weight loss, diarrheas and abdominal pain, being diagnosed of Giardiasis, and after the persistent symptoms and a number of studies, was diagnosed with Whipple disease. Nineteen cases of Giardia-Whipple coinfection have been described in the literature, but the reason of this association has not been found yet. The discussion on whether there is an alteration in the immunitary system which facilitates infections or, the development of an infection lead to the other one, goes on.     

Attachment of Giardia lamblia to rat intestinal epithelial cells.

The human enteric protozoan, Giardia lamblia, has surface membrane lectin activity which mediates parasite adherence to erythrocytes. To determine whether an intestinal binding site exists for this lectin we have studied the interaction in vitro between axenically cultured Giardia trophozoites and isolated rat intestinal epithelial cells. Scanning electron microscopy showed that Giardia attached to the apical microvillus membrane and basolateral membrane of rat enterocytes. Any location on the parasite surface could mediate attachment without predeliction for the ventral disc. Trophozoites attached more avidly to jejunal compared with colonic epithelial cells. Attachment was inhibited at 4 degrees C, by sugars and glycoproteins containing D-mannosyl residues and by subagglutinating concentrations of anti-Giardia rabbit serum and two monoclonal antibodies, all with reactivity to parasite surface membrane determinants. Trypsinisation of trophozoites also reduced attachment but the ability to attach was rapidly restored after returning trophozoites to TYI-S culture medium for 4 h at 37 degrees C. Attachment was unaltered by the presence of the microfilament inhibitor cytochalasin B and in the absence of Ca++ and Mg++ ions. These findings support previous work that Giardia possesses a surface membrane mannose binding lectin and indicate that appropriate binding sites are present on rat intestinal epithelial cells. This lectin may play a part in mediating adherence of Giardia to mammalian intestine and could be a target for host immune defence.     

Modulation of human enteric epithelial barrier and ion transport function by Peyer＇s patch lymphocytes

AIM: To investigate the role of Peyer‘s patch lymphocytes in the regulation of enteric epithelial barrier and ion transport function in homeostasis and host defense. METHODS: Mouse Peyer‘s patch lymphocytes were co-cultured with human intestinal epithelial cell line Caco-2 either in the mixed or separated (isolated but permeable compartments) culture configuration. Barrier and transport functions of the Caco-2 epithelial monolayers were measured with short-circuit current (Isc) technique. Release of cytokines was measured by enzyme-linked immunosorbent assay (ELISA) and cytokine mRNA expression was analyzed by semi-quantitative RT-PCR. Barrier and iontransport functions of both culture conditions following exposure to Shigella lipopolysaccharide (LPS) were also examined. RESULTS: The transepithelial resistance (TER) of the epithelial monolayers co-cultured with Peyer‘s patch lymphocytes was maintained whereas that of the Caco-2 monolayers alone significantly decreased after eight days in culture. The forskolin-induced anion secretion, in either absence or presence of LPS, was significantly suppressed in the both co-cultures as compared with the Caco-2 cells alone. Furthermore, only the mixed co-culture condition induced the expression and release of mIL-6 from Peyer‘s patch lymphocytes, which could be further enhanced by LPS. However, both co-culture conditions suppressed expression and release of epithelial hIL-8 under the unstimulated conditions, while the treatment with LPS stimulated their hIL-8 expression and release. CONCLUSION: Peyer‘s patch lymphocytes may modulate intestinal epithelial barrier and ion transport function in homeostasis and host defense via cell-cell contact and cytokine signaling.     

Impact of Helicobacter pylori and Giardia lamblia infections on chronic urticaria.

The etiology of chronic urticaria is largely unknown. The role of Helicobacter pylori infection, which is the most important cause of gastritis and peptic ulcer, is not clear in the pathophysiology of chronic urticaria. In this study, we aimed to define the impact of H. pylori on chronic urticaria. Thirty-eight patients who had chronic urticaria of unknown origin and dyspepsia were included in the study. In all patients, standard laboratory tests for detection of urticaria etiology were performed. Mean urticaria symptom scores of patients were carried out. All patients underwent upper gastrointestinal endoscopy. The presence of H. pylori was investigated using urease testing and histopathology. Duodenal fluid aspirated during upper endoscopy was examined for the presence of Giardia lamblia. H. pylori infection was detected in 29 patients. After successful eradication of H. pylori infection, the mean symptom score of patients did not change significantly (2.6 +/- 0.6 vs., 2.4 +/- 0.8). Only one patient had a total disappearance of urticaria symptoms. Out of 38 patients, only one had G. lamblia infection. The results of our study suggest that there is no association between H. pylori infection and chronic urticaria.     

Current infection rate of Giardia lamblia in two provinces of Thailand

The aim of this study was to survey for the current rate of Giardia lamblia infection in three different districts in two provinces of Thailand, Surin and Samut Sakhon, in March 2002, October 2003, and March 2004. Two districts are rural areas and another is sub-urban. Volunteers of any age from Surin Province and children aged between 5 to 7 years old from three secondary schools in Samut Sakhon were enrolled for the stool examination. The method used was stool examination by both simple smear and normal saline concentration technique on fresh collected feces. All samples were tested in duplicate. Out of 3,358 healthy individuals from rural Surin Province, 75 cases (2.2%) were found positive for G. lamblia, 30 of which were below 10 years of age. By comparison, 656 individuals from sub-urban Samut Sakhon Province volunteered and 43 (6.5%) were positive for G. lamblia. Other intestinal parasites, both helminth and protozoa, were also identified from these two groups: hookworm, Enterobius vermicularis, Strongyloides stercoralis, Trichuris trichiura, Taenia species, Entamoeba histolytica, Entamoeba coli, Endolimax nana, and Blastocystis hominis. From this study, the data showed that parasitic infection acquired via fecal-oral route is still a significant problem for these two provinces of Thailand.     

A longitudinal study of Giardia lamblia infection in north-east Brazilian children

OBJECTIVE: To evaluate the epidemiology of Giardia lamblia infection, investigate factors which might be associated with clinical manifestations and recurrence, and examine the role of copathogens in disease course. METHODS: Prospective 4-year cohort study of children born in an urban slum in north-eastern Brazil. RESULTS: Of 157 children followed for > or = 3 months, 43 (27.4%) were infected with Giardia. The organism was identified in 8.8% of all stool specimens, and although found with similar frequency in non-diarrhoeal (7.4%) and diarrhoeal stools (9.7%), was more common in children with persistent (20.6%) than acute diarrhoea (7.6%, P=0.002). Recurrent or relapsing infections were common (46%). Children with symptomatic infections had significantly lower weight-for-age and height-for-age than asymptomatic children. Copathogens were not associated with disease course. CONCLUSION With its protean clinical manifestations, Giardia may be associated with substantial morbidity amongst children in Brazil.     

Giardia lamblia: phospholipid analysis of human isolates.

Thin layer chromatograms for phospholipids obtained from 11 human Giardia lamblia isolates and their culture media have shown that phosphatidylcholine and sphingomyelin are the predominant phospholipid classes in all samples. A decrease in the relative percentage of the different classes, especially of phosphatidylcholine, was noticed in the medium after Giardia growth. Fatty acid analysis of the parasite phosphatidylcholine demonstrated that while oleate and palmitate were the major fatty acids in most isolates, arachidonate predominated in two of those studied. Some isolates contained small amounts of myristate, which was not present in the phosphatidylcholine of the culture medium. Moreover, stearate and linoleate predominated in phosphatidylcholine obtained from both media types. The saturated/unsaturated fatty acid ratio also varied for the different isolates. These results appear to suggest heterogeneity in the metabolic activity and utilization of lipid molecules between Giardia isolates.     

Giardia lamblia infection induces different secretory and systemic antibody responses in mice

The adult mouse model of Giardia lamblia infection serves as an excellent animal model to understand the immunological mechanisms involved in the control and clearance of Giardia infection. Little is known about the G. lamblia-specific antigens that stimulate the humoral immune response in this model of giardiasis. We analysed the secretory and systemic antibody responses to G. lamblia during primary and secondary infection in C3H/HeJ adult mice. Faecal IgA and Serum IgG anti-G. lamblia antibodies were observed at week 2 post-infection. Serum IgG responses remained constant over the next several weeks, whereas faecal IgA titres continued to rise from weeks 2-6 post-infection. Western blot analysis revealed that intestinal IgA and serum IgG antibody responses were directed toward several distinct proteins of G. lamblia. Certain proteins appeared to be recognized by both faecal IgA and serum IgG, whereas other antigens were specific for either the secretory or systemic antibody responses. G. lamblia primary and secondary infections were associated with differences in the antibody recognition pattern. The biochemical and immunological characterization of these antigens will help us to better understand the immunobiology of the G. lamblia-host interaction.     

双氢青蒿素对体外蓝氏贾第鞭毛虫滋养体细胞骨架的损伤作用

目的：观测双氢青蒿素(dihydroartemisinin,DHA)对体外培养的蓝氏贾第鞭毛虫滋养体细胞骨架的损伤作用.方法：将用含双氢青蒿素的改良TYI-S-33培养基培养后的蓝氏贾第鞭毛虫滋养体,用专一性结合f-肌动蛋白(f-actin)的荧光染料罗丹明-鬼笔环肽(rhodanmine phalloidin,RDP)标记微丝,结合微管的紫杉醇(Paclitaxel,Oregen Green 488,P22310)标记微管,用流式细胞术(flow cytometry,FCM)检测、分析,用激光共聚焦显微镜(confocal microscopy,CFM)观察滋养体微丝和微管的变化.结果：经双氢青蒿素0.002mg/L(LC_(50))作用12h,RDP标记后,流式细胞仪检测结果显示,滋养体的微丝结构有明显的损伤,其FCM激发光荧光强度值(16.18±11.02)明显低于对照组(81.7±6.43),二者有显著性差异(P＜0.01);激光共聚焦显微镜观察显示,虫体形态及轮廓不完整.经P22310标记后,共聚焦显微镜下显示.虫体的吸盘和鞭毛轮廓不清,荧光强度降低或消失,实验组吸盘面积的荧光强度值与对照组比较有显著性差异(χ~2=3.154,P<0.01).结论：双氢青蒿素对体外蓝氏贾第鞭毛虫滋养体的细胞骨架有明显的损伤作用.     

Single dose treatment with Tiberal of Giardia lamblia infection in children.

A new metronidazole derivative, Tiberal (Ro-07-0207, Roche Laboratories), was evaluated in 22 children with Giardia lamblia infection. Seven patients received an oral dose of 1 g twice daily for one day; the remaining 15 patients received a single dose of 50 mg/kg. Parasitological cure was noted in all 22 patients. Significant side effects were observed only in those children who received the drug at the higher dosage regime. The present study also confirms the findings of other authors that a mucosal imprint method is more reliable than examination of stools, duodenal juice or jejunal biopsy material for the detection of G. lamblia infection.