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Query: UMLS:C0017536 (giardiasis)
 1,714 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

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.
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PMID:Classification of subgroups of Giardia lamblia based upon ribosomal RNA gene sequence using the polymerase chain reaction. 151 34

The patterns of transmission of Giardia lamblia and the potential contribution of strain differences to pathogenicity of infection is poorly understood. We used pulsed field gradient gel electrophoresis (PFGE) to separate chromosome-sized DNA molecules of 22 stocks of G. lamblia isolated from 13 individuals (6 symptomatic, 7 asymptomatic) living in Jerusalem. PGFE gels run under a variety of conditions revealed up to nine ethidium bromide-stained bands per isolate ranging in size from 0.7 to greater than 3 megabasepairs. Relative staining intensities indicated that some bands contained multiple chromosomes. Major differences in the number, size, and intensity of bands allowed a clear differentiation of the karyotypes of isolates from each of the different individuals. This is in contrast to previous studies where the karyotype of different isolates have been strikingly homogeneous. Hybridization of Southern blots with surface antigen, beta-tubulin, and ribosomal RNA genes revealed that these gene families were distributed to different sized chromosomes amongst the different isolates. PFGE thus revealed major differences in the karyotypes of different G. lamblia isolates that were obtained over a short period of time from a relatively confined geographic area. In contrast, karyotypes of isolates established either by direct cultivation of duodenal trophozoites or by excystation of stool cysts from the same individuals were almost identical. Also, isolates from the same individuals obtained over a prolonged period of time revealed only minor differences in their karyotype, suggesting that recurrent infection can be caused by genetically similar organisms. We conclude that chronic giardiasis can result from recurrence of occult infection or reinfection from a common source.
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PMID:Investigation of human giardiasis by karyotype analysis. 160 83

1,5-Di(4-amidinophenoxy)pentane (pentamidine) and 38 analogs of pentamidine were screened for in vitro activity against the enteric protozoan Giardia lamblia WB (ATCC 30957). All compounds were active against G. lamblia as measured by a [methyl-3H]thymidine incorporation assay. Antigiardial activity varied widely, with 50% inhibitory concentrations (IC50s) ranging from 0.51 +/- 0.13 microM (mean +/- standard deviation) for the most active compound to over 100.0 microM for the least active compounds. The IC50 of the most potent antigiardial agent, 1,3-di(4-amidino-2-methoxyphenoxy)propane compared favorably with the IC50s of the compounds currently used to treat giardiasis, i.e., furazolidone (1.0 +/- 0.03 microM), metronidazole (2.1 +/- 0.80 microM), quinacrine HCl (0.03 +/- 0.02 microM), and tinidazole (0.78 +/- 0.48 microM). A mode of antigiardial activity for these compounds was suggested by the correlation observed between antigiardial activity and the binding of the compounds to calf thymus DNA and poly(dA).poly(dT).
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PMID:Structure-activity relationships of pentamidine analogs against Giardia lamblia and correlation of antigiardial activity with DNA-binding affinity. 192 49

Since the first description of Giardia by Antony van Leeuwenhoek in 1681, this parasite has proved to be enigmatic with a much more complicated epidemiology than originally envisaged. Even the nomenclature of this organism is confused. Despite numerous community prevalence studies, it was not until 1970 that the first proven report of waterborne transmission occurred. In 1981 the first common source outbreak due to contaminated food was recorded. It is also now recognized that venereal transmission occurs, especially among homosexual males. The faecal-oral route still remains the most important mode of infection despite the elucidation of these other methods of transmission. Recent developments in molecular biology especially DNA 'fingerprinting' and karyotyping which allow individual strain identification are being used to answer key epidemiological questions; for example are there truly pathogenic strains of Giardia, does drug resistance develop in vivo and is giardiasis a zoonotic disease? These and other molecular biological approaches will form the basis of research into the epidemiology of giardiasis and other intestinal protozoal infections until the end of the century and are certain to hold many surprises.
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PMID:Changing approaches to the study of Giardia epidemiology: 1681-2000. 221 Sep 41

Evidence for drug resistance in giardiasis is reviewed and biochemical studies undertaken to determine the basis for this resistance are discussed. Metronidazole and furazolidone, which produce toxic radicals within the cell, have different biochemical mechanisms of action. Resistance to metronidazole is negatively correlated with the intracellular concentration of pyruvateferredoxin oxidoreductase leading to a concomitant decrease in the uptake of free metronidazole into the cell, while resistance to furazolidone appears to be due to an increase in thiol cycling enzymes. At the molecular level resistance to metronidazole is associated with DNA changes. DNA probes which hybridize with specific chromosomes and repetitive sequences indicate that rearrangements both at the chromosome and repetitive DNA level occurred concurrently with the development of metronidazole resistance. The problems of cross-resistance and treatment failures that occur in the absence of resistance are additional difficulties which have important implications for the management of individual patients. New drugs such as azithromycin, while showing great variation in activity against different stocks may be useful in treating some refractory cases of giardiasis. In the community, it is important to recognize the occurrence and spread of drug resistant Giardia, and markers, such as DNA probes, provide methods to monitor potential epidemics and the spread of drug resistant Giardia.
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PMID:Drug resistance in Giardia intestinalis. 221 Sep 42

Several studies suggested that some water-borne epidemics of giardiasis in the U.S.A. were of zoonotic origin. Also, cats and dogs were suspected of being sources of giardiasis for man. These observations have been partly supported by experimental cross-transmissions. However, there are also some indications that zoonotic giardiasis may not be common. The host-specificity of Giardia spp. is still controversial. To date, morphological characteristics can only differentiate three very basic types of Giardia: G. intestinalis, G. muris and G. agilis. Host-specific and morphometric criteria resulted in the description of more than 40 species of Giardia; many of them probably invalid. Only a few subtle antigenic differences among G. intestinalis (lamblia) strains have been observed. The comparison of isoenzymes and DNA banding patterns revealed 3 basic groups, not necessarily related to host origin. Further biochemical, immunological, genetic and cross-transmission studies in host and parasite populations are needed to better understand host-specificity of various Giardia isolates. At the present time one may only conclude that although mammals and man do not seem to possess their own unique species of Giardia, in reality the major methods of transmission of giardiasis probably remain basically host-specific.
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PMID:Zoonotic aspects of giardiasis: a review. 267 45

Forty-seven isolates, identified morphologically as Giardia duodenalis, were compared by restriction endonuclease analysis of DNA with hybridization to a non-radiolabeled probe. Seven schizodemes were distinguished, compared to 15 zymodemes identified by isoenzyme electrophoresis. Despite the greater sensitivity of isoenzyme electrophoresis, DNA analysis did detect previously unsuspected variations between isolates in 1 zymodeme. Eighteen different genetic groups were detected among the 49 isolates by isoenzyme and DNA analyses. Genetic differences between groups, calculated from DNA restriction fragment variation, were significantly correlated with differences calculated from allozyme variation. This correlation between the 2 techniques suggests that G. duodenalis consists of a complex of genetically diverse clones. Such a genetic structure has important implications for the taxonomy of Giardia and the epidemiology of giardiasis.
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PMID:Characterization of Giardia isolates using a non-radiolabeled DNA probe, and correlation with the results of isoenzyme analysis. 274 39

Giardia lamblia, a flagellated parasitic protozoan and the causative agent of giardiasis, lacks de novo purine biosynthesis and exists on salvage of adenine and guanine by adenine phosphoribosyltransferase and guanine phosphoribosyltransferase. Guanine phosphoribosyltransferase from G. lamblia crude extracts has been purified to apparent homogeneity by Sephacryl S-200 gel filtration followed by C-8-GMP-agarose and 2',3'-GMP-agarose affinity chromatography, resulting in an overall recovery of 77% and a purification of 83,000-fold. The molecular weight of the native enzyme as estimated by gel filtration and isokinetic sucrose gradients was found to be 58,000-63,000, with a subunit molecular weight of approximately 29,000, as shown by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Mono P chromatofocusing chromatography gives rise to a major activity peak eluting from the column at a pH of 6.75 and two minor activity peaks at pH of 5.3 and 5.2. Hypoxanthine and xanthine can be recognized by the enzyme as substrates but at Km values 20 times higher than that observed with guanine. G. lamblia guanine phosphoribosyltransferase is immunologically distinct from human hypoxanthine-guanine phosphoribosyltransferase and Escherichia coli xanthine-guanine phosphoribosyltransferase, and G. lamblia DNA fragments are incapable of hybridizing with mouse neuroblastoma hypoxanthine-guanine phosphoribosyltransferase DNA or E. coli xanthine phosphoribosyltransferase DNA under relatively relaxed conditions. All evidence presented suggests that G. lamblia guanine phosphoribosyltransferase may be qualified as a potential target for antigiardiasis chemotherapy.
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PMID:Purification and characterization of guanine phosphoribosyltransferase from Giardia lamblia. 308 75

The article comprises a critical review on practical applications of molecular technology in parasitological diagnostics in a broad sense, also as a diagnosis of species and a method of epidemiological analysis. Techniques of genome analysis at different levels, as specific nucleic acid probes, DNA restriction profiles (RFLP), hybridization techniques, pulse-field gel electrophoresis, in vitro nucleic acid amplification, and DNA fingerprint technique used in studies on Giardia and Cryptosporidium were discussed. The essential reservation as far as this technology is concerned refers to its usefulness in parasitological diagnostics; there is no sense in working out methods for recognizing parasites which could otherwise be identified by well trained parasitologists and simple microscopic methods. The improved diagnosis of parasites resulting from the application of molecular technology significantly contributed to the armarium of parasitologists. Application of recent molecular technology in diagnosis of giardiasis and cryptosporidiosis may basically support clinical diagnosis which provides possibilities of early and selective treatment and makes possible epidemiological studies. These assays will permit not only a rapid diagnosis and exact differentiation but will also enable a better recognition of Giardia and Cryptosporidium genome organization. However, in spite of the wide availability of this new techniques they have not been fully applied--as yet--in diagnosis and in epidemiological studies on these parasites. The authors share the opinion of Busch (1991) on the need of proper recognition of high-quality and rigorous work in employing new molecular assays, because their wide availability and high sensitivity could cause "false-positive" results by contamination with amplified DNA sequences.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:[Usefulness of genome analysis methods for diagnosis of giardiasis and cryptosporidiosis]. 763 61

A 36-year-old man, with a history of recurrent respiratory infection, dermatomycosis, arthralgia and abnormal stools for 12 years, developed a febrile illness (up to 40 degrees C). A Serratia marcescens septicaemia responded to antibiotics. Four months later cervical and abdominal lymph-adenopathies were noticed. Cervical lymph node biopsy revealed lymphadenitis with epithelioid cell nests. Duodenoscopy with biopsy demonstrated Whipple's disease associated with lambliasis. Electron-microscopy showed rod-shaped bacteria typical of Whipple's disease, and Giardia lamblia. Using the polymerase chain reaction, Whipple-specific DNA fragments of 284 base pairs from the genome of the Whipple bacterium (Tropheryma whippelii) were demonstrated. Antibiotic treatment with Ampicillin (2 g three times daily) and ceftriaxone (2 g once daily) i.v. for 21 days, followed by oral ofloxacin (200 mg daily) and co-trimoxazole (three times daily 800 mg sulfamethoxazole and 160 mg trimethoprim), brought about remission of Whipple's disease. Long-term antibiotic treatment was continued with co-trimoxazole. Lambliasis recurred after 3 and 5 months, despite treatment with metronidazole, 250 mg three times daily for 7 days.
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PMID:[Whipple's disease associated with opportunistic infections]. 768 63


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