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At least 19 recordsLinked to original sources
PubMed1979

Ultrastructural observations on giardiasis in a mouse model. II. Endosymbiosis and organelle distribution in Giardia muris and Giardia lamblia.

Ultrastructural observations of Giardia muris in a mouse model revealed endosymbiotic microbes not previously reported in Giardia. Endosymbionts 240--360 nm wide, 600--1,400 nm long, and with an internal structure similar to that of bacilli were not seen entering Giardia but were found and appeared to divide within Giardia. No evidence was found of digestion of the endosymbionts by the giardia host in either the trophozoite or the cyst form. Endosymbionts were concentrated centrally around the nuclear area and were uncommon in peripheral feeding regions. The same cellular organelles seen in G. muris were found in Giardia lamblia from human jejunal biopsy material, but no endosymbionts were identified in G. lamblia trophozoites from the seven patients examined. Endosymbionts within Giardia may be found to alter trophozoite pathogenicity, metabolism, range of infectivity, antigenic surface characteristics, and host specificity, as they do in other protozoa.

Animals↗
PubMed1992

Protection against infection with Giardia lamblia by breast-feeding in a cohort of Mexican infants.

To determine whether breast-feeding protects infants against symptomatic and asymptomatic infection by Giardia lamblia, we followed 197 infants in a poor area of Mexico City from birth to 18 months of age; symptoms and feeding status were recorded weekly. Stool specimens were collected every 1 to 2 weeks and tested for Giardia by enzyme-linked immunosorbent assay. A mean of 1.0 Giardia infection per child-year was detected; 94 infants had a total of 139 infections; 17% of infections were symptomatic. Ninety-one percent of infants were breast fed from birth and 38% were breast fed at 1 year of age. Lack of breast-feeding was a significant risk factor for first Giardia infection at all ages. The adjusted incidence rate ratio for first Giardia infection for none versus complete breast-feeding was 5.0 (confidence interval (CI) 1.5 to 16.9; p = 0.009), and for none versus any breast-feeding, 1.8 (CI 1.1 to 2.8; p = 0.013). Symptomatic Giardia infection was also associated with lack of breast-feeding (none vs any: incidence rate ratio = 2.5; CI 0.9 to 6.8; p = 0.077), but breast-feeding did not protect against chronic carriage of Giardia. Other significant risk factors for Giardia infection were presence of animals in the household (p = 0.005) and the use of water or nonmilk liquid for infant feedings (p = 0.035). We conclude that breast-feeding protects infants against Giardia by mechanisms that include preventing the establishment of infection.

Animals↗
PubMed1992

Detection of specific anti-Giardia antibodies in the serodiagnosis of symptomatic giardiasis.

The roles of circulating anti-Giardia IgM and IgG antibodies were assayed by the Enzyme linked immunosorbent assay (ELISA) using axenic Giardia lamblia whole trophozoites as antigen for routine serodiagnosis of Giardia infection. Detection of anti-Giardia IgM antibody was found to be useful in the early detection of symptomatic giardiasis, whereas IgG detection was not, since the latter could not discriminate between present infection and previous exposure. A mean optical density (OD) +/- 2 standard deviation (SD) value of 0.088 at 1:100 serum dilution was found optimal for the detection of anti-Giardia IgM antibodies as it completely separated out the acute Giardia cases from the Giardia-free controls. The same sera did not reveal any marked differences when tested for anti-Giardia IgG antibodies. Detection of IgM antibodies correlated with high sensitivity and specificity (96%) in an evaluation of a large number of sera collected from Giardia cases and controls.

Animals↗
PubMed1992

Guanine nucleotide-binding proteins in the intestinal parasite Giardia lamblia. Isolation of a gene encoding an approximately 20-kDa ADP-ribosylation factor.

Giardia lamblia is a protozoan intestinal parasite that has characteristics of both eukaryotes and prokaryotes. To determine whether genes for guanine nucleotide-binding proteins are present in Giardia, genomic DNA and cDNA libraries were screened by polymerase chain reaction and by hybridization with mixed oligonucleotide probes complementary to sequences encoding conserved GTP-binding domains. A gene with a high degree of sequence identity with mammalian ADP-ribosylation factors (ARFs), believed to be important in vesicular transport, was identified. The Giardia ARF gene had a 573-base open reading frame encoding 191 amino acids which are 63-70% identical with known mammalian and yeast ARFs. Sequence conservation among ARFs was greatest in putative GTP-binding domains. A single ARF mRNA species of approximately 750 bases was found in two different Giardia isolates. Primer extension and RNA sequencing of the Giardia ARF transcript revealed a short (6-base) 5'-untranslated region similar in size to those found in other Giardia transcripts. Giardia extracts contained ARF activity, as shown by stimulation of cholera toxin-catalyzed ADP-ribosylation and a Giardia ARF expressed in Escherichia coli as a fusion protein likewise exhibited biochemical activity. Its presence in Giardia is consistent with the view that ARF emerged before the divergence of this protozoan from other eukaryotes (approximately 1.5 billion years ago), and that an ARF-like protein may have been the ancestor of several other classes of signal-transducing guanine nucleotide-binding proteins, including the alpha subunits of the heterotrimeric G proteins.

ADP-Ribosylation Factors↗
PubMed1992

Evaluation of a new monoclonal antibody combination reagent for direct fluorescence detection of Giardia cysts and Cryptosporidium oocysts in human fecal specimens.

Giardia lamblia and Cryptosporidium parvum can cause severe symptoms in humans, particularly in the immunologically compromised. Monoclonal antibody reagents offer increased sensitivity and an excellent alternative to conventional staining methods. These reagents are helpful when screening large numbers of patients or those with minimal symptoms. Problems of false-positive and false-negative results with routine staining methods for stool parasites can be eliminated with monoclonal antibody reagents. Known positive formalinized specimens [Giardia sp. (n = 60), Cryptosporidium sp. (n = 55), and mixed Giardia-Cryptosporidium spp. (n = 10)] and negative formalinized specimens (n = 105), of which 46 contained other yeast or human cells or protozoa), were tested by the MERIFLUOR Cryptosporidium-Giardia direct immunofluorescence detection procedure. The MERIFLUOR reagent exhibited +/- to 4+ (majority, 2+ to 3+) on all Giardia cysts and 2+ to 4+ (majority, 3+ to 4+) on all Cryptosporidium oocysts. The cysts were generally oval (11 to 15 microns), while the oocysts were round (4 to 6 microns); both showed apple-green fluorescence against a background free of nonspecific fluorescence. All specimens positive for Giardia sp. and/or Cryptosporidium sp. showed fluorescence, and all specimens negative for the two organisms showed no fluorescence. There were eight specimens previously negative by the ova and parasite examination which were positive by the direct fluorescence method; four contained Giardia sp., and four contained Cryptosporidium sp. These positive results were confirmed after the examination of additional trichrome and modified acid-fast smears. The MERIFLUOR reagent was very easy to use, and even with a lower fluorescence intensity for Giardia sp. cysts, no false-negative or false-positive results among the specimens tested for either organism were found.

Animals↗
PubMed1992

Isolation and characterization of a NADP-dependent glutamate dehydrogenase gene from the primitive eucaryote Giardia lamblia.

Giardia lamblia is believed to be the earliest branching derivative from the eucaryotic lineage. Genomic and cDNA clones encoding the giardia NADP-dependent glutamate dehydrogenase have been isolated and characterized. Southern hydridization using genomic DNA indicates that the gene encoding this activity is unique and single copy. Primer extension, S1 nuclease protection, and genomic and cDNA sequence analysis demonstrate that gene transcripts are initiated within a conserved AT-rich sequence element immediately preceding the ATG translation initiation codon and the short 5' untranslated region is not extended by transsplicing. The open reading frame is 1350 nucleotides in length and encodes a protein of 449 amino acids. The reading frame is not interrupted by introns and the primary transcript is probably not subjected to RNA editing. In the strictly anaerobic metabolism of giardia, NADP-dependent glutamate dehydrogenase activity participates along with alanine aminotransferase, in the cyclic dissipation of reducing equivalents (NADPH) through the conversion of pyruvate to alanine. The deduced amino acid sequence of the giardia protein exhibits substantial homology to numerous fungal and eubacterial NADP-dependent glutamate dehydrogenases. Comparisons of alignment gap positions and amino acid identities indicate that the giardia sequence is at least as similar or more similar to the eubacterial sequence than it is to the fungal sequence. This supports the hypothesis that giardia diverged very early from the eucaryotic lineage.

Amino Acid Sequence↗
PubMed1992

[Studies on the giardiasis as the zoonosis. III. Prevalence of Giardia among the dogs and the owners in Japan].

To obtain the basic data on the route of Giardia infection as zoonosis, of many regions in Japan, the feces from 2218 dogs were examined for detection of Giardia cysts. Giardia cysts were detected in 239 of the 2218 dogs (10.9%), which was the same as previous reports from America. None were found from the owners of 51 dogs in which Giardia cysts were detected. The detection rates of each facilities were, 68 of 366 (18.6%) from the breeder's kennels, 169 of 1811 (9.3%) in individual houses, 2 of 42 (4.9%) from research institutes. The detection rate of the breeder's kennels was higher than the other two facilities (p less than 0.05, p less than 0.001). The detection rates of Kanagawa and Shizuoka prefectures among 17 regions in Japan were higher than the others (p less than 0.001, p less than 0.05). Especially in Shizuoka, the rate of the individual houses was higher than from breeder's kennels. In kanagawa the rates of the individual houses and the breeders kennels were higher than the mean in Japan (p less than 0.001). Therefore one must instruct the breeders when teaching health education to included zoonosis, and that the detection rate of the age groups of less than 3 years old was high-221 of 1276 (17.3%). Since the detection rates of Giardia cysts in the dogs were low, the possibility that human infection acquired from dogs was low. However, some of patients with giardiasis we encountered had never been abroad, and it is not yet clear whether Giardia is strictly host specific or not, so attention should be paid to the possibility of cross-infection between man and animals.

Animals↗
PubMedDate not supplied

Suppression of resistance to Giardia muris and cytokine production in a murine model of acquired immune deficiency syndrome.

Peyer's patch (PP) T cells through the production of appropriate cytokines foster the development of immunity to the intestinal protozoan parasites such as Giardia. T cell destruction by the human immunodeficiency virus precedes the development of acquired immune deficiency syndrome. Thus, HIV may increase susceptibility to intestinal parasite infections. Therefore, we measured the resistance and T cell cytokine responses to Giardia in C57B1/6 mice infected with the retrovirus LP-BM5 which produces a murine AIDS (MAIDS). Mice with MAIDS and controls were intragastrically challenged with 1 x 10(5) G. muris cysts. Fecal counts were measured weekly following challenge. Also, PP T cell production of interleukin (IL)2, IL3, IL4, and Interferon-gamma in response to G. muris trophozoite antigens displayed on antigen presenting cells were measured at these times. Prior to day 14 of the infection, the number of Giardia cysts in the retrovirus group paralleled that in controls. However, by day 21 after Giardia infection, mice with MAIDS failed to clear the Giardia cysts from the intestine while the control mice were completely free of cysts. IL2 and IL4 production in response to Giardia trophozoites by unfractionated PP lymphocytes were severely depressed in the retrovirus infected group, while IFN-gamma production was increased. Depressed cytokine production was most likely due to depressed PP T cell numbers. When fractionated enriched T cells were adjusted to a uniform concentration in in vitro immunization cultures, the production of IL2 and IL4/IL5 were similar between retrovirus infected compared with control mice. Recoverable PP T cells were lower in mice with MAIDS.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1979

Ultrastructural observations on giardiasis in a murine model. I. Intestinal distribution, attachment, and relationship to the immune system of Giardia muris.

Infected immunocompetent mice were studied prospectively in a well-described murine model system with the use of ultrastructural techniques to establish normal distribution of Giardia muris trophozoites, their relationships to intestinal mucosa, particularly Peyer's patches, and structural indications of the normal reaction of intestine and intestinal immune organs. Trophozoites colonized the proximal 25% of the intestine, adhered to microvilli of columnar cells near the bases of villi, wedged into furrows in the epithelial surface, or lodged in mucus within the unstirred layer. Density of trophozoite colonization of the jejunal epithelium correlated with stool cyst excretion. Over Peyer's patches, Giardia adhered to columnar cells and not to M-cells, which transport soluble antigens and particulate material from the lumen into the lymphoid system. Giardia entered intestinal lymphoid structures by incursions through defects in the lymphoid follicle epithelial barrier. During clearance of parasites, lymphocytes crossed the epithelium and attached to Giardia in the lumen. Giardia produced no apparent ultrastructural damage in normal mice but elicited a previously undescribed intraluminal cellular immune response during clearance by the host.

Animals↗
PubMed1992

The nucleotide sequence of the entire ribosomal DNA operon and the structure of the large subunit rRNA of Giardia muris.

The total nucleotide sequence of the rDNA of Giardia muris, an intestinal protozoan parasite of rodents, has been determined. The repeat unit is 7668 basepairs (bp) in size and consists of a spacer of 3314 bp, a small-subunit rRNA (SSU-rRNA) gene of 1429, and a large-subunit rRNA (LSU-rRNA) gene of 2698 bp. The spacer contains long direct repeats and is heterogeneous in size. The LSU-rRNA of G. muris was compared to that of the human intestinal parasite Giardia duodenalis, to the bird parasite Giardia ardeae, and to that of Escherichia coli. The LSU-rRNA has a size comparable to the 23S rRNA of E. coli but shows structural features typical for eukaryotes. Some variable regions are typically small and account for the overall smaller size of this rRNA. The structure of the G. muris LSU-rRNA is similar to that of the other Giardia rRNA, but each rRNA has characteristic features residing in a number of variable regions.

Animals↗
PubMed1992

A gene associated with cell division and drug resistance in Giardia duodenalis.

A 3000 bp cDNA insert (G6/1) from Giardia duodenalis, cloned into Escherichia coli is located on chromosome 3 of Giardia stocks which have 3 chromosomes detectable by field-inversion gel electrophoresis in the range 650-800 kb and on chromosome 3 and/or 4 of stocks with 4 chromosomes in this size range. The loss of this sequence from chromosome 4 but not chromosome 3 was associated with the induction of drug resistance in a previously sensitive laboratory stock. G6/1 appears to represent a single copy gene in Giardia as determined by hybridization of the probe to cleaved genomic DNA. Furthermore, the sequences flanking at least 12 kb of G6/1 are the same when G6/1 appears on both chromosomes 3 and 4. The cDNA encodes a protein associated with the nuclei of trophozoites during some stages of growth of the parasite. In a non-dividing culture, the antigen is associated with the nuclei of about 30% of trophozoites and fewer in a dividing culture. Three Giardia stocks with obvious chromosome rearrangements, which grow poorly and fail to divide normally, apparently lack the DNA sequence G6/1.

Animals↗
PubMed1992

Giardia antigen detection in patients with chronic gastrointestinal disturbances.

BACKGROUND: Giardia lamblia, a protozoan parasite, is transmitted by cysts in contaminated water or food or by person-to-person contact. The standard in diagnosis has been the microscopic demonstration of fecal cysts, which yields many false negatives due to high variability in cyst excretion. A new method that detects infection even when few parasites are present is now available. This immunodiagnostic test is rapid, sensitive, and specific, and typically requires only a single stool specimen. In this study patients with gastrointestinal (GI) complaints were screened for Giardia antigens, and the test results were compared to conventional microscopy. Costs incurred by patients with chronic GI problems were documented. METHODS: Twelve patients with GI complaints were tested for Giardia by microscopy and 13 patients by the immunodiagnostic test. Patient charts were evaluated for pertinent history and the diagnostic tests ordered before giardiasis was considered. RESULTS: For all patients, microscopy was uniformly negative, but 6 of 13 patients were antigen positive. Patients with chronic complaints, later found to test positive for Giardia, typically underwent five diagnostic tests at a cost of $338. CONCLUSIONS: Giardiasis, an increasing problem in family practice, should be considered early in patients with GI disturbances. New, sensitive immunodiagnostic tests that usually require a single specimen are more useful than microscopy. Prompt diagnosis of giardiasis not only relieves patients of unpleasant symptoms, but can avoid unnecessary and costly evaluations.

Adult↗
PubMed1992

Comparison of Giardia isolates from different laboratories by isoenzyme analysis and recombinant DNA probes.

A total of 13 new Giardia isolates were established in axenic culture. All of the new isolates were obtained by excystation of Giardia cysts from the feces of patients in Dutch hospitals. These isolates were subjected to isoenzyme and DNA analysis together with isolates from Poland, Belgium, and various other parts of the world. Isoenzyme analysis revealed that nearly all of the newly established isolates exhibited unique zymodemes. Isolates obtained from individuals from Belgium and Poland, on the other hand, displayed single zymodemes. Genomic DNA libraries were constructed from isolates belonging to the latter two zymodemes; specific and common recombinant DNA clones were selected from these libraries. Differential screening revealed that the two isolates had only 80% of the clones in common. Restriction-fragment-length polymorphism analysis using three different probes together with two synthetic probes that are complementary to Giardia structural protein genes led to the separation of all isolates into two major groups; within these groups, a further division could be made by application of other techniques or probes. The results of DNA analysis and zymodeme classification were in general agreement; in the present report they are compared with the data in the literature and discussed.

Animals↗
PubMed1992

The uptake and conversion of L-[U14C-] aspartate and L-[U14C-] alanine to 14CO2 by intact trophozoites of Giardia duodenalis.

1. Intact trophozoites of Giardia duodenalis (clone P1C10) took up and metabolised L-[U14C-] aspartate to 14CO2 at rates of 10.27 +/- 0.76 and 27.6 +/- 2.07 ng hr-1 10(-6) cells in a simple maintenance medium (MM) and in a complex bile supplemented (BIS-33) medium respectively. 2. Intact trophozoite of G. duodenalis (clone P1C10) also took up and metabolised L-[U14C-] alanine to 14CO2 at rates of 20.6 +/- 1.1 and 91.4 +/- 17.5 ng hr-1 10(-6) cells in the simple (MM) and complex (BIS-33) medium respectively. 3. trophozoite sonicates contained significant levels of aspartate-2-oxoglutarate transaminase (AST; EC 2.6.1.1) and alanine-2-oxoglutarate transaminase (ALT; EC 2.6.2.2.). Specific activities (at 23 degrees C) were 95.1 +/- 11.3 and 87.3 +/- 9.8 nmol (min)-1 (mg protein)-1 respectively. 4. These observations suggest that Giardia has the capacity to utilise aspartate and alanine and possibly other amino acids as alternative sources of energy. 5. The extrusion or uptake of alanine by Giardia trophozoites may be dictated by the intracellular redox-status of the protozoan parasite or components in the external mileu.

Alanine↗
PubMed1992

Distinct genetic groups of Giardia intestinalis distinguished by restriction fragment length polymorphisms.

The taxonomic status of the parasitic protozoal species Giardia intestinalis depends on the morphological similarity of all Giardia isolated from humans and the presumption that Giardia are host-specific. On the basis of electrophoretic data derived from examination of 26 enzyme loci in Australian isolates, it has been proposed that G. intestinalis is a species complex comprising three or four genetically distinct (but morphologically cryptic) species. These received the tentative designations of genetic groups I-IV (R. H. Andrews, M. Adams, P. F. L. Boreham, G. Mayrhofer & B. P. Meloni. International Journal for Parasitology 19, 183-190, 1989). In the present study, two unrelated DNA probes (one specific for a gene encoding a trophozoite surface protein, the other detecting a non-coding repetitive sequence within the G. intestinalis genome) were used in Southern hybridization analyses to examine 10 axenic isolates of G. intestinalis, established from diverse geographical regions in Australia, together with the Portland-1 isolate from the USA. Both probes identified every isolate unambiguously as belonging to one or other of two genetic clusters. Electrophoretic analysis of the same samples indicated that these clusters correspond to the previously defined genetic groups I and II. No heterogeneity was apparent within the seven group I isolates using either probe. However, when probed with the repetitive sequence, the four isolates belonging to group II exhibited small differences in banding patterns, suggesting that this group may be less homogeneous than group I.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Immune response to Giardia lamblia in a water-borne outbreak of giardiasis in Sweden.

In one of the largest outbreaks of waterborne giardiasis reported from Europe, more than 3000 persons were exposed to contaminated water and over 1400 cases of giardiasis were diagnosed by microscopy. The outbreak resulted from an overflow of sewage water into the drinking water system of a Swedish ski resort. The period of contamination was about 1 week. Sweden is a non-endemic area for Giardia lamblia infection and, for most individuals affected, this was their first contact with the parasite. Few other enteropathogens were isolated from the patients involved. Therefore, an immune response to Giardia was unlikely to be biased by other concomitant infections. Serum samples from 352 exposed persons were collected and analysed for specific IgG and IgA antibodies to G. lamblia by indirect immunofluorescence and the results were related to the microscopic examination of faeces and the occurrence of diarrhoea. As controls, sera from 428 healthy persons were analysed at the same time by identical methods. IgG or IgA antibodies, or both, were found in 68% of patients whose diagnosis was made by microscopy, and in 22% of exposed by microscopically Giardia-negative persons, but in only 10% of healthy controls. The findings show that patients reported as negative for parasites might be infected. The time between infection and blood sampling influenced the result of the antibody test. The results suggest that stool examination should be the primary means of diagnosis of G. lamblia infection and that serological analysis performed at least 3 weeks after infection could contribute to diagnosis in a non-endemic region, when giardiasis is suspected but the parasite has not been detected.

Adolescent↗
PubMedDate not supplied

Serial subcultivation of Giardia lamblia in Keister's modified TYI-S-33 medium containing ultroser G.

The ability of Giardia strains of the duodenalis type to grow in Keister's modified TYI-S-33 medium varies with serum lot. Recently, strains of Giardia including MR4, WB, and Human-1-Portland, have been cultivated in Keister's modified TYI-S-33 medium containing the serum substitute Ultroser G and have been cultured serially as least 40 times. An optimal concentration of 8% Ultroser G promotes maximal growth in Keister's modified TYI-S-33 medium for all three strains. This concentration of Ultroser G will produce a two-log increase in the number of trophozoites in approximately three days post-inoculation. Generation times for the trophozoites ranging from 6 to 11 h have been achieved in Keister's modified TYI-S-33 containing 10% adult bovine serum and from 8 to 13 h in Keister's modified TYI-S-33 with 8% Ultroser G. Despite the excellent growth of Giardia strains in medium containing Ultroser G, the maximum trophozoite density is only about half of that achieved in Keister's modified TYI-S-33 medium supplemented with 10% adult bovine serum. Comparisons of trophozoites grown with serum or the serum substitute reveal no discernable differences in morphology and motility. Additionally, these strains have been successfully cryopreserved and revived in Keister's modified TYI-S-33 medium supplemented with Ultroser G. Because Ultroser G is a characterized mixture of six main groups of ingredients (growth factors, adhesion factors, mineral trace elements, hormones, binding proteins, and vitamins), the variability in cell proliferation that may occur when changing serum lots should be minimized when using this product.

Animals↗