PubMed Health⌕ Search

Biomedical subjects

G S Visvesvara

Publications and source records attributed to G S Visvesvara.

At least 19 recordsLinked to original sources
PubMed1992

Amebic meningoencephalitis in a sheep.

A 1.5-year-old Suffolk ewe with acute onset of incoordination and blindness unresponsive to antibiotic treatment was examined at necropsy. The meninges were congested, opaque, and thick. Microscopically, focal areas of hypercellularity in the left cortical gray matter and the meninges were observed. The inflammatory response consisted of gliosis and perivascular cuffing (lymphocytes, plasma cells, and variable numbers of eosinophils). An amebic organism in 2 life stages was found in the cerebral parenchyma. Numerous large (15 to 35 microns in diameter) organisms, interpreted as trophozoites, were characterized by vacuolated cytoplasm and small nuclei with a prominent eosinophilic nucleolus (karyosome). The smaller (10 to 17 microns in diameter) encysted stage was surrounded by a capsule-like membrane, and contained a large central body sometimes surrounded by a clear halo. Immunofluorescence studies for amebic antigens were strongly positive for an ameba recently isolated in human beings and baboons (Leptomyxid sp).

Amebiasis↗
PubMed1992

Improved light-microscopical detection of microsporidia spores in stool and duodenal aspirates. The Enteric Opportunistic Infections Working Group.

BACKGROUND: The diagnosis of infection with Enterocytozoon bieneusi, a microsporidian organism that causes chronic diarrhea in patients infected with the human immunodeficiency virus (HIV), has depended on invasive procedures. We have developed a new method to detect microsporidia spores in feces and duodenal aspirates. METHODS: Stool was obtained from four HIV-infected patients with biopsy-confirmed intestinal microsporidiosis. Slides prepared from unconcentrated, formalin-fixed stool specimens were stained with a new chromotrope-based technique and examined by light microscopy. Methods of stool concentration were also compared. The technique was then evaluated by examining 215 specimens from 134 HIV-infected persons with or without diarrhea. In addition, duodenal aspirates from 10 patients with unexplained chronic diarrhea were examined by light microscopy after staining according to the new and the traditional techniques. RESULTS: E. bieneusi spores were found in all unconcentrated stool specimens from the four patients with microsporidiosis. The use of various methods of stool concentration did not improve the detection of microsporidia spores. In the prospective study, microsporidiosis was detected in samples from 6 of 27 patients with chronic diarrhea, but in none of those from 42 patients with acute diarrhea or 65 patients without diarrhea. The presence of microsporidia spores in stool specimens and duodenal aspirates allowed the successful prediction of the presence of microsporidia in small-bowel biopsy specimens from all four patients who subsequently underwent endoscopy. CONCLUSIONS: E. bieneusi is an important cause of chronic diarrhea in HIV-infected persons. This new diagnostic technique serves as a practical, noninvasive means to detect microsporidia spores in stool specimens and is also applicable to the examination of duodenal aspirates.

Animals↗
PubMed1992

Culture isolation of Acanthamoeba species and leptomyxid amebas from patients with amebic meningoencephalitis, including two patients with AIDS.

Acanthamoeba species and leptomyxid organisms are free-living amebas that cause meningoencephalitis, primarily in immunocompromised patients. We report the isolation and culture of Acanthamoeba species and leptomyxid amebas from four patients with fatal amebic meningoencephalitis. Acanthamoeba species were cultured from brain abscess specimens from three immunocompromised patients (including two patients with AIDS). In the case of the fourth patient, who had no identifiable immunodeficiency, leptomyxid amebas were cultured from a specimen from a subcutaneous nodule and were identified in amebic granulomas in brain tissue by the indirect immunofluorescence test. Persons with advanced infection due to the human immunodeficiency virus may be at increased risk for amebic meningoencephalitis, but the diagnosis should be considered in the differential diagnosis of any immunocompromised patient with cerebral abscesses.

AIDS-Related Opportunistic Infections↗
PubMed1992

Isolation of two Giardia lamblia (WB strain) clones with distinct surface protein and antigenic profiles and differing infectivity and virulence.

To determine the relationship between antigenic profiles and pathogenicity among Giardia lamblia clones (WB strain), trophozoites were cloned by the technique of limiting dilution. The phenotype of each clone was determined by an indirect immunofluorescence test using a polyclonal rabbit anti-G. lamblia trophozoite serum made against the parent strain. Two clones were chosen for further studies: a highly fluorescent clone, F+, in which more than 95% of the trophozoites fluoresced, and a low-fluorescence clone, F-, in which fewer than 5% fluoresced. Sodium dodecyl sulfate-polyacrylamide gradient gel electrophoresis and enzyme-linked immunotransfer blot studies of the membrane fractions of the two clones and parent strain revealed differences in both the total protein and antigenic profiles. A serum cytotoxicity test with the polyclonal serum showed that the F+ clones were more susceptible to immobilization and killing, while the majority of cells of the F- clones were resistant to such killing. Assessment of the infectivity of the two clones in the Mongolian gerbil animal model indicated that the F- clone more readily initiated infections, produced more cysts, had a higher intestinal trophozoite load, and produced a more severe clinical syndrome, while the F+ clone was less phenotypically stable in vivo and in some cases took longer to be cleared from the intestine.

Animals↗
PubMed1992

Acanthamoeba meningoencephalitis in a patient with acquired immunodeficiency syndrome.

Several cases of Acanthamoeba encephalitis (ie, granulomatous amebic encephalitis) have been reported in patients with acquired immunodeficiency syndrome from the United States. To our knowledge, none so far has been reported from Europe, and this is the first case of amebic meningoencephalitis due to Acanthamoeba in a patient with acquired immunodeficiency syndrome from Italy. The patient was a 24-year-old, human immunodeficiency virus-positive heterosexual man with a 6-year history of intravenous drug use. He was admitted to the hospital because of severe headache, confusion, nuchal rigidity, jaundice, and ascites. He died 5 days later. At autopsy, the brain showed extensive hemorrhagic necrosis with numerous trophic and cyst forms of Acanthamoeba. The amebas were identified as Acanthamoeba divionensis by the indirect immunofluorescence test.

AIDS-Related Opportunistic Infections↗
PubMed1992

Disseminated microsporidiosis (Encephalitozoon hellem) and acquired immunodeficiency syndrome. Autopsy evidence for respiratory acquisition.

Microsporidia are obligate intracellular protozoal parasites that infect a variety of cell types in a broad range of invertebrates and vertebrates. They have recently come to medical attention due to the increased frequency with which members of two microsporidian genera, Enterocytozoon and Encephalitozoon, are being diagnosed in patients with the acquired immunodeficiency syndrome (AIDS). The majority of published reports of human microsporidiosis describe Enterocytozoon infection of small intestinal enterocytes. In addition, a growing number of AIDS patients have been identified with infection due to the two species of Encephalitozoon-Encephalitozoon cuniculi and Encephalitozoon hellem, observed in conjunctival, corneal, and, recently, sinonasal tissues. However, there are scant data regarding the systemic pathology and epidemiology of these infections. This article describes a patient with AIDS who died with systemic Encephalitozoon infection. The etiologic microsporidian was found to be E hellem by using antemortem biochemical and antigenic analyses. A complete autopsy, the first to be reported in a patient with this infection, revealed organisms in the eyes, urinary tract, and respiratory tract. A surprising observation was the occurrence of numerous organisms within the lining epithelium of almost the entire length of the tracheobronchial tree, suggestive of respiratory acquisition. Detailed light and electron microscopic findings and the biological and diagnostic features of microsporidiosis are discussed.

Acquired Immunodeficiency Syndrome↗
PubMed1991

Purification and characterization of Giardia lamblia antigens in the feces of Mongolian gerbils.

In a recent study, we identified Giardia lamblia 65- and 70-kDa antigens in the feces of infected Mongolian gerbils. The 65-kDa antigen was from a strain isolated from a human with symptoms of giardiasis, and the 70-kDa antigen was from a strain isolated from a human with no symptoms of giardiasis. In this study, we used preparative electrophoresis and electroelution techniques to purify these antigens to a degree which showed a single discrete protein band on silver-stained polyacrylamide gels. By enzyme-linked immunoelectrotransfer blot, common epitopes on the 65- and 70-kDa antigens were indicated by their cross-reactivity with rabbit anti-65-kDa and anti-70-kDa sera. By indirect immunofluorescence assay, the cysts and trophozoites of the two strains cross-reacted with these sera. Of seven lectins tested, only concanavalin A bound to the 70-kDa antigen, suggesting a glycoprotein, and it possessed a low isoelectric point as assessed by preparative isoelectric focusing. Molecular mass estimations of these antigens by sodium dodecyl sulfate-polyacrylamide gradient gel electrophoresis were similar to the 65- and 70-kDa estimations obtained by native polyacrylamide gradient gel electrophoresis. Although the 65- and 70-kDa antigens proved to be resistant to 100 degrees C heat and stable in storage for up to 25 months at -20 degrees C, neither appeared to be the same as a fecal G. lamblia antigen with similar molecular mass found by other investigators. This suggests that variable G. lamblia antigens may be found in the feces of infected humans.

Animals↗
PubMed1991

Granulomatous amebic encephalitis in an AIDS patient.

A 39-year-old man with AIDS died after developing a variety of neurologic symptoms and signs. CT showed multiple enhancing lesions in the cerebral hemispheres and cerebellum. Postmortem examination revealed parenchymal hemorrhagic and necrotizing lesions with a thrombo-occlusive vasculitis due to Acanthamoeba, which was typed as Acanthamoeba group 2, probably A rhysodes, by immunofluorescence.

Acanthamoeba↗
PubMed1991

Isoenzyme profiles of four strains of Giardia lamblia and their infectivity to jirds.

The infectivity to jirds (Meriones unguiculatus) and the cyst excretion pattern of a recently isolated strain of Giardia lamblia from Egypt, Strain CDC:1088:1 (EGY), were compared to those of three well-established strains. All five jirds inoculated orally with strain UNO:0487:1 (UNO) became infected and began excreting cysts 3-6 days post-infection (dpi); no cysts were detected between 8-12 dpi after which time cysts were produced through day 19. Four of the five jirds infected with Strain ATCC:30957 (WB) and three of the five jirds infected with strain CDC:0284:1 (VA) excreted cysts from 6-20 dpi and 6-22 dpi, respectively. One of five jirds inoculated with EGY excreted cysts on 8 dpi only. At necropsy, trophozoites were recovered from only three UNO-infected jirds but from all WB- and VA-infected jirds that excreted cysts. The one jird which excreted cysts of EGY was negative at necropsy, but EGY trophozoites were found in one non-patient jird. Isoelectric focusing indicated that these four strains of G. lamblia represented three zymodemes. WB and VA were assigned to one zymodeme, EGY to a second, and UNO, which shared common bands with both other zymodemes, to the third. Although the similarities and differences in infectivity and cyst excretion patterns appear to coincide with the zymodemes to which the strains can be assigned, further study is needed to examine the parasitologic behavior of these strains in relation to isoenzyme patterns.

Animals↗
PubMed1991

Laboratory diagnosis of pathogenic free-living amoebas: Naegleria, Acanthamoeba, and Leptomyxid.

Pathogenic free-living amebae of the genera Naegleria, Acanthamoeba, and Leptomyxid are still unfamiliar to pathologists, clinicians, and public health workers. These amebae are distributed worldwide in fresh water, dust, soil, sewage, and air conditioning units. The diagnosis, identification, and culture of the amebae, and risk factors, clinical manifestations, and histopathologic features of the diseases produced by these amebae are reviewed in this article.

Acanthamoeba↗
PubMed1991

Infectivity of cryopreserved Giardia cysts for Mongolian gerbils (Meriones unguiculatus).

Although Giardia species trophozoites have been cryopreserved successfully, no report on the successful cryopreservation of cysts could be found. Using infectivity to Mongolian gerbils (Meriones unguiculatus) as a measure of cyst viability, we tested the viability of 4 strains of Giardia cysts that had been cryopreserved for 1-67 wk. Cysts were frozen in either Keister's medium or physiological saline, both containing 5% or 7.5% dimethylsulfoxide as the cryoprotectant. Viability of cryopreserved cysts was dependent upon the number of cysts inoculated, the length of time cysts were held at 4 C before cryopreservation, and the cryopreserving medium. Infection was established in gerbils by inoculating them with cysts that had been cryopreserved for up to 67 wk, cysts that had been held for less than 30 days before cryopreservation, and cysts frozen in Keister's medium. Saline appears to be unsuitable as a freezing medium for the cryopreservation of Giardia cysts.

Animals↗
PubMed1991

Amebic meningoencephalitis in a patient with AIDS caused by a newly recognized opportunistic pathogen. Leptomyxid ameba.

A fatal case of meningoencephalitis due to a leptomyxid ameba in a patient with the acquired immunodeficiency syndrome is presented. This opportunistic organism has not been previously recognized as a human pathogen. A 36-year-old male intravenous drug abuser died after an 18-day hospital course heralded by fever and headache and followed by nuchal rigidity and hemiparesis. Computed tomography of the head showed multiple hypodense lesions. Neuropathologic examination showed that in addition to human immunodeficiency virus encephalomyelitis, there was multifocal meningoencephalitis with trophozoites and cysts morphologically indistinguishable from those of Acanthamoeba. These organisms were also found in the kidneys and adrenal glands. By immunofluorescence, the parasites showed antigenic identity with a free-living leptomyxid ameba and failed to react with any of a spectrum of antiacanthamoeba antisera. This emphasizes the importance of immunofluorescence identification of morphologically indistinguishable ameba species.

Acquired Immunodeficiency Syndrome↗
PubMed1990

Leptomyxid ameba, a new agent of amebic meningoencephalitis in humans and animals.

Amebae belonging to the order Leptomyxida are regarded as innocuous soil organisms incapable of infecting mammals. We report here the isolation of a leptomyxid ameba from the brain of a pregnant baboon (Papio sphinx) that died of meningoencephalitis at the San Diego Zoo Wild Animal Park. By using rabbit anti-leptomyxid serum in the immunofluorescence assay, we have identified the leptomyxid ameba in the brain sections of a number of human encephalitic cases from around the world as well as a few cases of meningoencephalitis in animals in the United States, which suggests that the leptomyxid amebae are potential etiologic agents of fatal meningoencephalitis in humans and animals.

Amebiasis↗
PubMed1990

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.

Animals↗
PubMed1989

The epidemiology of Acanthamoeba keratitis in the United States.

We surveyed members of the Ocular Microbiology and Immunology Group and reviewed laboratory requests at the Centers for Disease Control to determine better the epidemiology of Acanthamoeba keratitis in the United States. A total of 208 cases of Acanthamoeba keratitis were identified. The number of cases increased gradually between 1981 and 1984, with a dramatic increase beginning in 1985. Males and females were equally affected. Of the 208 patients, 85 (41%) resided in California, Texas, Florida, or Pennsylvania. Of 189 patients, 160 (85%) wore contact lenses, predominantly daily-wear or extended-wear soft lenses. Of the 138 patients who wore contact lenses and for whom information was available, 88 (64%) used saline prepared by dissolving salt tablets in distilled water. Patients aged 50 years and older were more likely to have had a history of trauma than younger patients, and males were more likely to have a history of trauma than females.

Acanthamoeba↗
PubMed1989

Viability of Acanthamoeba cysts in ophthalmic solutions.

Acanthamoeba keratitis is a chronic infection of the human cornea. Many people who have this infection wear soft contact lenses. Usually lens wearers clean and maintain their lenses with various ophthalmic solutions including homemade saline. Recently it has been shown that homemade saline solutions play a role in lens contamination and thus in Acanthamoeba keratitis. We therefore evaluated the viability of cysts of three species of Acanthamoeba by exposing them for various time periods to saline, cleaning, and disinfectant solutions generally used to care for these lenses. We found that the viability of the cysts in saline solutions ranged from a minimum of 14 days to 90 days of exposure. In cleaning solutions, the survival times ranged from a minimum of 1 day to 90 days of exposure. Disinfectants, as expected, were the most effective of all tested solutions in killing Acanthamoeba cysts. The survival times ranged from 6 h to 14 days. None of these products were effective in destroying Acanthamoeba cysts in less than 6 h of exposure, which exceeds the suggested time that any given solution should be used for lens care.

Acanthamoeba↗