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PubMed1983

Mode of action of metronidazole on anaerobic bacteria and protozoa.

Metronidazole and related 5-nitroimidazoles are relatively nontoxic. Reduction of their nitro group, however, leads to the production of short-lived cytotoxic intermediates, which finally decompose into nontoxic end products. The toxicity of the intermediates is due to their interaction with deoxyribonucleic acid and possibly with other macromolecules. Metabolic pathways of low redox potential that are linked to ferredoxin or flavodoxin-like electron transport components reduce nitroimidazoles with great efficacy. Such pathways are characteristic of susceptible anaerobic protozoa and bacteria and are absent in nonsusceptible aerobic cells of the host.

Animals↗
PubMed1981

[Contribution to the knowledge of intestinal protozoa infestation in the hospital population of Barcelona (author's transl)].

This report concerns the analysis of 650 fecal samples submitted for parasitic investigation to the Microbiology Service of the Hospital de la Santa Creu i Sant Pau of Barcelona. The samples were analyzed by the technique of fixation and direct observation of Sapero and Lawless (MIFD), and with the biphasic concentration method of Blagg et al (MIFC). Intestinal protozoa were detected in 183 samples (28.2%), with a total of 232 protozoosis uncovered. The specific analysis gave the following results: Giardia lamblia, 10.9%; Dientamoeba fragilis, 7.8%; Entamoeba coli, 4.6%; Endolimax nana, 4.5%; Entamoeba hartmanni, 4.0%; Iodamoeba buetschlii, 2.9%; Entamoeba histolytica, 0.7%; Chilomastix mesnili, 0.2%; Trichomonas hominis, 0.2%. The results obtained by the two methods have been compared, observing the highest number of positive results with MIFD technique. Especial mention is made of the higher incidence of Dientamoeba fragilis in samples positive for Oxyuris further studies being needed to establish the basis for the relationship between both species of parasites.

Animals↗
PubMed1981

Inhibition of in vitro macrophage digestion capacity by infection with Leishmania donovani (Protozoa: Kinetoplastida).

Promastigotes of Leishmania donovani transformed into amastigotes and survived in cultured macrophages. Promastigotes of Leptomonas costoris, a kinetoplastid parasite of water striders, transformed into amastigotes but did not survive in cultured macrophages. A significant difference in size between the two species of parasitic protozoa allowed development of a bioassay in which the in vitro digestion rate of L. costoris was taken as a measure of macrophage digestive capacity following preinfection with L. donovani. In a 12- to 24-hr period, macrophage cultures infected with the 2S strain of L. donovani retained 50% more L. costoris than did control macrophages infected with L. costoris alone. The 2S strain has been in culture since 1967 and has retained its infectivity for hamsters, although its virulence is attenuated. In similar experiments with promastigotes of the Khartoum strain of L. donovani, a strain but evidently has lots its infectivity for hamsters, no such suppression of macrophage ability to digest L. costoris was observed. The results suggests that infective strains of Leishmania donovani suppress macrophage function beyond the time at which initial lysosomal fusion with the parasitophorous vacoule occurs.

Animals↗
PubMed1995

How many stool examinations are necessary to detect pathogenic intestinal protozoa?

Recent reports have suggested that examination of one stool specimen is sufficient to detect protozoa in symptomatic patients. To verify this hypothesis, we examined specimens submitted to the regional laboratory of a large, prepaid health plan that provides primary care to a membership representative of the general population in northern California. We examined the number and results of stool specimen examinations in the two-month period before detection of Entamoeba histolytica in 125 infected persons, of Giardia lamblia in 154 infected persons, and of Dientamoeba fragilis in 60 persons infected with this parasite. About 13% of the entire group had a single stool specimen examined, 19% had two examined, 65% had three examined, and 6% had more than three examined. Most infections were detected in the first specimen or specimens submitted, but many were not detected until later examination. Thirteen patients with E. histolytica (10.4%) required 4-9 examinations. The sensitivity of one examination was compared with that of three examinations; with the additional examinations, the yield increased 22.7% (95% confidence interval [CI] = 11.8-33.5%) for E. histolytica, 11.3% (95% CI = 6.9-81.8%) for G. lamblia, and 31.1% (95% CI = 17.7-54.4%) for D. fragilis. Our results suggest that a single stool specimen examination will miss many pathogenic protozoan infections in symptomatic persons.

Animals↗
PubMed1994

Trypanosomatid protozoa provide paradigms of eukaryotic biology.

Over the last 10 years, trypanosomatid protozoa have been the subject of intense investigation particularly focusing on their parasitic lifestyle and their intriguing and novel cell properties. These studies have furthered our understanding of the physiology and functioning of these cells and have identified a large number of biochemical and metabolic peculiarities, including mitochondrial function, enzymatic compartmentalization, and gene expression. This review focuses on the mode of gene expression and highlights areas of trypanosome research that have provided paradigms of eukaryotic biology.

Animals↗
PubMed1994

The requirements for GPI-attachment are similar but not identical in mammalian cells and parasitic protozoa.

To test whether the requirements for GPI-attachment are the same in mammalian cells and parasitic protozoa, we expressed the GPI-linked variant surface glycoprotein (VSG) of Trypanosoma brucei (T. brucei) in COS cells. Although large amounts of VSG were produced, only a small fraction became GPI-linked. This impaired processing is not due to the VSG ectodomain since replacement of the VSG GPI-signal with that of decay accelerating factor (DAF) produced GPI-linked VSG. Further, whereas fusion of the DAF GPI-signal to the COOH-terminus of human growth hormone (hGH) produces GPI-linked hGH, an analogous fusion using the VSG GPI-signal does not, indicating that the VSG GPI-signal functions poorly in mammalian cells. By constructing chimeric VSG-DAF GPI-signals and fusing them to the COOH-terminus of hGH, we show that of the two critical elements that comprise the GPI-signal--the cleavage/attachment site and the hydrophobic domain--the former is responsible for the impaired activity of the VSG GPI-signal in COS cells. To confirm this, we show that the VSG GPI-signal can be converted to a viable signal for mammalian cells by altering the amino acid configuration at the cleavage/attachment site. We also show that when fused to hGH, the putative GPI-signal from the malaria circumsporozoite (CS) protein produces low levels of GPI-anchored hGH, suggesting that the CS protein is indeed GPI-linked, but that the CS protein GPI-signal, like the VSG-signal, functions poorly in COS cells.

Amino Acid Sequence↗
PubMed1993

[Carriers and excretors of protozoa].

Causative agents of intestinal infections in humans are about 10 pathogenic or facultative pathogenic species of protozoa of which Giardia lamblia, Entamoeba histolytica, Cryptosporidium parvum and Enterozytozoon bieneusi are discussed. G. lamblia from humans is morphologically indistinguishable from Giardia isolates originating from several species of domestic and wild mammals. Swiss Giardia isolates of human, sheep, cattle and dog origin could be transmitted to Giardia-free rodents and were rather homogenous in biochemical parameters. These data support the hypothesis that zoonotic transmission of Giardia may occur. Routine faecal examinations in Zürich in 1991 revealed 3.61% of Giardia excretors among 5017 examined patients. Of the same group of persons 3.95% excreted E. histolytica. At present it is anticipated that the species E. histolytica consists of invasive and non-invasive strains which can be differentiated by isoenzyme electrophoresis. The confirmation of this assumption could deeply influence the opinion about medical and epidemiological significance of Entamoeba infections. Cryptosporidium parvum is an important cause of diarrhea in HIV-infected patients. Person-to-person, zonnotic and waterborne transmission may play a role. A short review of new data on Enterozytozoon bieneusi and other microsporidia is presented. E. bieneusi appears to be an important causative agent of diarrhea in HIV-infected persons.

Animals↗
PubMed1996

[Protozoa as reservoirs for human bacterial pathogens].

The ability of bacterial pathogens to survive within the human host cells results from their evolutional adaptation of which the most important stage could be the development of parasitic relations between bacteria and free-living protozoa. This paper shows the bacterial species, pathogenic for man, surviving in protozoans cells.

Adaptation, Physiological↗
PubMedDate not supplied

[Scanning electron microscopy in studies of parasitic protozoa of fish].

It is expedient to use the scanning electron microscopy for studies of parasitic Protozoa of fishes. The structure of myxosporidians (Henneguya psorospermica, Myxidium rhodei, Chloromyxum truttae) and Chilodenella cyprini was analysed. Microphotos taken by "CWIKscan-100-4" are given. The technique of the preparation of the object for scanning microscopy with regard for its structure is discussed.

Animals↗
PubMedDate not supplied

[Infection by intestinal protozoa and helminths in schoolchildren from riverside sectors, with different fecal contamination levels, of Valdivia River, Chile].

During 1993, the prevalences of infection by intestinal protozoa and helminths (IPH) in the riverside schoolchildren population of two sectors of Valdivia river, with different levels of fecal contamination, were compared in relation to their contact with river water (swimming, bathing) and basic sanitation elements (BSE) of their houses: feces and garbage disposal, and water supply. Populations of children from sectors A (n = 418), with significatively greater (SG) total coliform most probable number (MPN), and sector B (n = 400), were examined. PAFS test was used for the stool examination of one sample, from each child. The global prevalence of infection by IPH was similar in A (74.8%) and B (72.5%) sectors. From 10 identified IPH, only Entamoeba histolytica and Hymenolepis nana showed prevalences of infection SG in sector A, than in sector B. The contact of the children with the water of the river showed association with SG prevalences for E. histolytica, Entamoeba coli and Endolimax nana in sector B and for E. histolytica in sector A. No sanitary condition for the different BSE contributed to SG prevalences for E. histolytica, Ascaris lumbricoides and Trichuris trichiura in both sectors, and for E. coli in sector B. The contact with the river water and the different BSE contributed to prevalences SG in 5 and 3 IPH in sectors B and A, respectively. The results suggest that a project in study for the development of a treatment plant of wastewater in sector A, could contribute to control infection by IPH. But, this measure must be associated with improvement of the BSE, health education, and application of chemotherapy measures for geohelminthosis in both sectors.

Adolescent↗
PubMedDate not supplied

[Human infection by intestinal protozoa and helminths in Calbuco County, X Region, Chile, 1997].

By the performance of parasitological examination of one fecal sample per individual, a total of 256 persons from a rural county in the X Region (41 degrees 50 minutes South lat., 73 degrees 05 minutes West long.) were studied. The general rates of infection by intestinal parasite and/or commensal protozoa and helminths found were: Giardia intestinalis 14.1%, Entamoeba histolytica 11.7%, Blastocystis hominis 36.0%, Entamoeba coli 9.8%, Endolimax nana 16.4%, Iodamoeba buetschlii 1.2%, Chilomastix mesnili 0.8%, Ascaris lumbricoides 13.7% and Trichuris trichiura 9.8%. The prevalence rates of intestinal infection led us to conclude that environmental conditions favorable for its transmission remain and show that intestinal parasitoses are still a public health problem in this region, affecting mostly children.

Adolescent↗
PubMed1976

Observations on the intestinal protozoa infecting man in Rhodesia.

Humans in Rhodesia harbour a wide range of intestinal protozoa. Of the species included, Entamoeba histolytica, Entamoeba coli and Giardia lamblia have previously been recorded. Other species which are either rarely reported or which have previously never been reported from this country, include Trichomonas hominis, Chilomastix mesnili, Enteromonas hominis, Retortamonas intestinalis, Balantidum coli,Entamoeba hartmanni,Entamoeba histolytica Laredo. Endolimax nana, Dientamoeba fragilis and Isospora belli. The importance in Rhodesia of these species, and especially of E. histolytica, is discussed.

Balantidiasis↗