PubMed Health⌕ Search

Biomedical subjects

Govinda S Visvesvara

Publications and source records attributed to Govinda S Visvesvara.

At least 19 recordsLinked to original sources
PubMed2006

Multifocal Balamuthia mandrillaris infection in a dog in Australia.

A 6-year-old male golden retriever, with an 8-month history of seizures and a clinical diagnosis of lymphoma in the central nervous system, was (at the owner's request) euthanized after signs of respiratory distress and shock developed. Upon postmortem examination, the diagnoses of meningoencephalitis and pneumonia were made. A histological examination of selected tissues from both the lung and central nervous system revealed a severe, acute, multifocal, amoebic, embolic pneumonia and a severe, chronic, multifocal, nonsuppurative, amoebic meningoencephalitis. Indirect immunofluorescence analysis confirmed the presence of trophozoite and cyst stages of Balamuthia mandrillaris. This is the first report of B. mandrillaris (which is a free-living amoeba) causing fatal, multifocal granulomatous amoebiasis in a dog in Australia.

Amebiasis↗
PubMed2006

Fatal granulomatous Acanthamoeba encephalitis mimicking a stroke, diagnosed by correlation of results of sequential magnetic resonance imaging, biopsy, in vitro culture, immunofluorescence analysis, and molecular analysis.

Amebic infections involving the central nervous system are rare and difficult to diagnose. Magnetic resonance imaging (MRI) at timed intervals may be helpful, where scans reveal enhancing lesions and increased signal. We report a unique case of granulomatous amebic encephalitis that was proven pathologically with progressive radiological findings on MRI.

Acanthamoeba↗
PubMed2006

In vitro culture, serologic and molecular analysis of Acanthamoeba isolated from the liver of a keel-billed toucan (Ramphastos sulfuratus).

Members of the genus Acanthamoeba are usually free-living amebae and are found in a variety of ecological niches including soil, fresh and brackish water, dust in air, filters of heating, ventilating, and air conditioning units, swimming pools and hot tubs, etc. Occasionally, they are also known to cause central nervous system infections in humans and other animals. We isolated into culture an amoeba from the liver tissue of a keel-billed toucan and identified it as Acanthamoeba sp. based on culture characteristics and immunofluorescent analysis. Further, we characterized the cultured amoeba and also the amoeba in the liver tissue as Acanthamoeba, genotype T4, by sequencing a diagnostic region of the nuclear small subunit ribosomal RNA gene.

Acanthamoeba↗
PubMed2006

Detection of antibodies against free-living amoebae Balamuthia mandrillaris and Acanthamoeba species in a population of patients with encephalitis.

BACKGROUND: Balamuthia mandrillaris and Acanthamoeba species are 2 free-living amoebae responsible for granulomatous amoebic encephalitis in humans and animals. We have screened serum samples from hospitalized patients with encephalitis for antibodies against these 2 amoebae as a means of detecting a disease with few defining symptoms and a poor prognosis. METHODS: Indirect immunofluorescence antibody (IFA) staining of serum samples from patients with encephalitis was conducted over a period of 6 years to detect amoeba antibodies. More than 250 serum samples from patients hospitalized with encephalitis were screened. Most of the samples were from patients in California and were screened as part of the California Encephalitis Project, with a small number of specimens from other states. RESULTS: During the course of the study, 7 cases of Balamuthia encephalitis were detected; all cases were detected in Hispanic individuals, and all cases were fatal. Examination of hematoxylin-eosin-stained and immunostained sections of brain tissue obtained at biopsy or autopsy for amoebae confirmed balamuthiasis in all serum samples with positive IFA results. One case of Acanthamoeba encephalitis was detected in an immunocompromised individual with a normal antibody titer by identification of amoebae in immunostained brain tissue obtained at autopsy. CONCLUSIONS: IFA can be successfully used in screening for balamuthiasis and acanthamoebiasis in patients whose clinical presentation, laboratory results, and neuroimaging findings are suggestive of amoebic encephalitis. Ideally, this can lead to an earlier definitive diagnosis and earlier start of antimicrobial therapy. Without IFA staining, the balamuthiasis cases in our study would have been diagnosed as neurocysticercosis, tumor, tuberculosis, or viral encephalitis or would have been undiagnosed.

Adolescent↗
PubMed2006

Diagnosis of first case of Balamuthia amoebic encephalitis in Portugal by immunofluorescence and PCR.

We report here the first Portuguese case of acute fatal granulomatous encephalitis attributed to Balamuthia mandrillaris, initially thought to be a brain tumor, which had a progressive and fatal outcome. Balamuthia mandrillaris is a free-living amoeba recognized as an uncommon agent of granulomatous encephalitis. Infections have been identified in immunocompromised hosts and in immunocompetent pediatric patients. Balamuthia infections are very rare, with only two reported cases in Europe. The case presented here occurred in a previously healthy boy who died 5 weeks after the onset of the symptoms. No evidence of immunological deficiency was noted, and testing for human immunodeficiency virus antibodies was negative. The symptoms were initially thought to be the result of a tumor, but histopathologic examination showed evidence of amoebic infection. Immunofluorescence staining of brain tissue identified B. mandrillaris as the infectious agent. The diagnosis was confirmed with PCR by detecting Balamuthia DNA in formalin-fixed brain tissue sections. Despite initiation of empirical antimicrobial therapy for balamuthiasis, the patient died 3 weeks after being admitted to the hospital. No source of infection was readily apparent.

Amebiasis↗
PubMed2006

Multiplex real-time PCR assay for simultaneous detection of Acanthamoeba spp., Balamuthia mandrillaris, and Naegleria fowleri.

Infections caused by Naegleria fowleri, Acanthamoeba spp., and Balamuthia mandrillaris occur throughout the world and pose many diagnostic challenges. To date, at least 440 cases of severe central nervous system infections caused by these amebas have been documented worldwide. Rapid and specific identification of these free-living amebas in clinical samples is of crucial importance for efficient case management. We have developed a triplex real-time TaqMan PCR assay that can simultaneously identify Acanthamoeba spp., B. mandrillaris, and N. fowleri in the same PCR vessel. The assay was validated with 22 well-characterized amebic strains harvested from cultures and nine clinical specimens that were previously characterized by in vitro culture and/or immunofluorescence assay. The triplex assay demonstrated high specificity and a rapid test completion time of less than 5 h from the reception of the specimen in the laboratory. This assay was able to detect one single ameba per sample analyzed, as determined with cerebrospinal fluid spiked with diluted cultured amebas. This assay could become useful for fast laboratory diagnostic assessment of amebic infections (caused by free-living amebas) in laboratories with adequate infrastructure to perform real-time PCR testing.

Acanthamoeba↗
PubMed2006

Acanthamoeba encephalitis in patient with systemic lupus, India.

We report a fatal case of encephalitis caused by Acanthamoeba in a 24-year-old woman from India with systemic lupus erythematosus. Diagnosis was made by identification of amebas in brain sections by immunofluorescence analysis and confirmed by demonstrating Acanthamoeba mitochondrial 16S rRNA gene DNA in brain tissue sections.

Acanthamoeba↗
PubMed2005

Comparison of real-time PCR protocols for differential laboratory diagnosis of amebiasis.

Specific identification of Entamoeba spp. in clinical specimens is an important confirmatory diagnostic step in the management of patients who may be infected with Entamoeba histolytica, the species that causes clinical amebiasis. Distinct real-time PCR protocols have recently been published for identification of E. histolytica and differentiation from the morphologically identical nonpathogenic Entamoeba dispar. In this study, we compared three E. histolytica real-time PCR techniques published by December 2004. The limits of detection and efficiency of each real-time PCR assay were determined using DNA extracted from stool samples spiked with serially diluted cultured E. histolytica trophozoites. The ability of each assay to correctly distinguish E. histolytica from E. dispar was evaluated with DNA extracted from patients' stools and liver aspirates submitted for confirmatory diagnosis. Real-time PCR allowed quantitative analysis of the spiked stool samples, but major differences in detection limits and assay performance were observed among the evaluated tests. These results illustrate the usefulness of comparative evaluations of diagnostic assays.

Animals↗
PubMed2005

Identification and distribution of Acanthamoeba species genotypes associated with nonkeratitis infections.

Acanthamoeba is a free-living protozoan genus found in a wide variety of natural habitats, including water, soil, and air. Pathogenic isolates of Acanthamoeba are medically relevant as the causative agent of sight- threatening Acanthamoeba keratitis (AK), serious infections of other organs, and fatal granulomatous amebic encephalitis. Previous work employing DNA sequences of nuclear and mitochondrial small-subunit rRNA genes (SSU rRNA genes) determined the genotypic diversity of Acanthamoeba and found that many named species of Acanthamoeba are associated with particular genotypes. These studies also concluded that nearly all AK infections result from a single molecular genotype: T4. Here, we asked whether Acanthamoeba clinical isolates from non-AK infections are also associated with particular genotypes. DNA sequence determination of nuclear SSU rRNA genes was employed for genotypic identification of 29 isolates of Acanthamoeba from non-AK infections. Sequence analysis demonstrates that T4 is the predominant genotype in non-AK infections, including those in brain, cerebrospinal fluid, nasal passages, skin, and lung. Rare genotypes (T1, T10, and T12) have been isolated from brain infections. We conclude that genotype T4 is the primary genotype in non-AK Acanthamoeba infections, as was the case in AK infections. However, the genotypes that were isolated from brains have not been observed in environmental isolates of Acanthamoeba, and their natural ecological niche is unknown.

Acanthamoeba↗
PubMed2005

Detection of Balamuthia mitochondrial 16S rRNA gene DNA in clinical specimens by PCR.

Balamuthia mandrillaris is a free-living ameba that causes granulomatous amebic encephalitis in both immunocompromised and immunocompetent individuals. Because of a lack of pathognomonic symptoms and the difficulty in recognizing amebas in biopsied tissues, most cases are not diagnosed or effectively treated, leading to a >95% mortality. We report here on five cases of balamuthiasis that were diagnosed by indirect immunofluorescence (IIF) staining of serum for anti-Balamuthia antibodies (titer > or = 1:128) and confirmed by IIF of unstained brain tissue sections and/or detection of amebas in hematoxylin-eosin-stained slides. Additionally, we have used the PCR for the detection of mitochondrial 16S rRNA gene DNA from the ameba in clinical specimens such as brain tissue and cerebrospinal fluid (CSF) from individuals with Balamuthia encephalitis. Balamuthia DNA was successfully detected by the PCR in clinical samples from all five individuals. It was detected in brain tissue from three cases, in CSF from three cases, and in one of two samples of lung tissue from two individuals, but not in two samples of kidney tissue tested. One sample of unfixed brain tissue was culture positive for Balamuthia. In order to test the sensitivity of the PCR for detection of Balamuthia DNA, CSF specimens from two individuals negative for amebic infection were spiked with Balamuthia amebas. We found that it was possible to detect Balamuthia DNA in the PCR mixtures containing mitochondrial DNA from 1 to as little as 0.2 ameba per reaction mixture. A single Balamuthia ameba contains multiple mitochondrial targets; thus, 0.2 ameba represents multiple targets for amplification and is not equivalent to 0.2 of an ameba as a target.

Amebiasis↗
PubMed2005

Isolation and molecular typing of Naegleria fowleri from the brain of a cow that died of primary amebic meningoencephalitis.

Naegleria fowleri causes an acute and rapidly fatal central nervous system infection called primary amebic meningoencephalitis (PAM) in healthy children and young adults. We describe here the identification of N. fowleri isolated from the brain of one of several cows that died of PAM based on sequencing of the internal transcribed spacers, including the 5.8S rRNA genes.

Amebiasis↗
PubMed2005

Seasonal meningoencephalitis in Holstein cattle caused by Naegleria fowleri.

Primary amoebic meningoencephalitis is a fulminant infection of the human central nervous system caused by Naegleria fowleri, a free-living amoeba that thrives in artificially or naturally heated water. The infection usually is acquired while bathing or swimming in such waters. The portal of entry is the olfactory neuroepithelium. This report describes fatal meningoencephalitis caused by N. fowleri in Holstein cattle that consumed untreated surface water in an area of California where summer temperatures at times exceed 42 degrees C. In the summers of 1998 and 1999, severe multifocal necrosuppurative hemorrhagic meningoencephalitis was observed in brain samples from nine 10-20-month-old heifers with clinical histories of acute central nervous system disease. Olfactory lobes and cerebella were most severely affected. Lesions were also evident in periventricular and submeningeal neuropil as well as olfactory nerves. Naegleria fowleri was demonstrated by immunohistochemistry in brain and olfactory nerve lesions and was isolated from one brain. Even though cultures of drinking water did not yield N. fowleri, drinking water was the likely source of the amoeba. The disease in cattle closely resembles primary amoebic meningoencephalitis in humans. Naegleria meningoencephalitis should be included among differential diagnoses of central nervous system disease in cattle during the summer season in areas with high ambient temperatures.

Amebiasis↗
PubMed2005

Public health importance of Brachiola algerae (Microsporidia)--an emerging pathogen of humans.

Brachiola algerae, a parasite of Anopheles mosquitoes, has also been isolated from a human cornea, a cutaneous nodule and deep muscle tissue. All three human isolates of B. algerae are morphologically, serologically, and genetically similar to the mosquito-derived isolates including the original isolate of Vavra and Undeen. All of these isolates grew well in mammalian cell cultures at 37 degrees C and produced spores. Transmission electron microscopy revealed that all developmental stages including meronts, sporoblasts and spores were diplokaryotic and developed in direct contact with the host cell cytoplasm, a feature characteristic of the genus Brachiola. Spores of all isolates reacted well, in the immunofluorescence assay, with the rabbit anti-B. algerae serum. In the immunoblot assay, although the overall banding patterns of the human and mosquito isolates were similar, minor differences could be discerned. Sequencing of the PCR products of the amplified SSU rRNA gene revealed the existence of two distinct genotypes; the original mosquito (Undeen) isolate belonged to genotype 1 and the isolate from cornea and that from the deep muscle biopsy to genotype 2, whereas the isolates from a mosquito and one of the other two human isolates (one from skin abscess) had both genotypes, 1 and 2. It is known that spores of mosquito-derived B. algerae can not only proliferate in mammalian cell cultures at 37 degrees C but also can infect mice when injected into footpads or deposited on the corneal surface. These observations indicate that the spores have potential to be a risk factor for humans, especially those with immunodeficiency.

Animals↗
PubMed2005

Multinucleate host cells induced by Vittaforma corneae (Microsporidia).

The microsporidium Vittaforma corneae develops within the target cell cytoplasm. In the present study, green monkey kidney (E6) cells infected at 30 degrees C, 35 degrees C or 37 degrees C with V. corneae developed enlarged multinucleate structures of up to 200 microm in any horizontal dimension made up either of a single cell or of multiple fused cells. A number of epithelial cell types (SW-480, HT-29, Caco-2 and HCT-8) were infected with V. corneae but did not induce the same highly organized structures, suggesting that for the structure to develop, the host cell must be capable of continued mitosis, and not be differentiated or be detaching from the surface matrix. Live cell imaging of infected E6 cells revealed large, multinucleate infected cells characterized by a central focus from which radiated parasite stages and host cell mitochondria. Immunocytochemistry identifying gamma and alpha tubulin suggested that a single centrally-located microtubule organizing centre governed the distribution of parasite stages and host cell organelles, with mitochondria and parasites being eventually transported towards the periphery of the structure. Whole cell patch clamp analysis of infected cells indicated an average five-fold increase in total membrane capacitance, consistent with an enlarged single cell. Scanning electron microscopy revealed cell-like protrusions around the periphery of the structure with the intervening space being made up of parasites and cell debris. Clearly in the case of V. corneae-infected E6 cells the parasite-host cell relationship involves subverting the host cell cytoskeleton and cell volume control, providing the parasite with the same protected niche as does a xenoma.

Animals↗
PubMed2004

Amebae and ciliated protozoa as causal agents of waterborne zoonotic disease.

The roles free-living amebae and the parasitic protozoa Entamoeba histolytica and Balantidium coli play as agents of waterborne zoonotic diseases are examined. The free-living soil and water amebae Naegleria fowleri, Acanthamoeba spp., and Balamuthia mandrillaris are recognized etiologic agents of mostly fatal amebic encephalitides in humans and other animals, with immunocompromised and immunocompetent hosts among the victims. Acanthamoeba spp. are also agents of amebic keratitis. Infection is through the respiratory tract, breaks in the skin, or by uptake of water into the nostrils, with spread to the central nervous system. E. histolytica and B. coli are parasitic protozoa that cause amebic dysentery and balantidiasis, respectively. Both intestinal infections are spread via a fecal-oral route, with cysts as the infective stage. Although the amebic encephalitides can be acquired by contact with water, they are not, strictly speaking, waterborne diseases and are not transmitted to humans from animals. Non-human primates and swine are reservoirs for E. histolytica and B. coli, and the diseases they cause are acquired from cysts, usually in sewage-contaminated water. Amebic dysentery and balantidiasis are examples of zoonotic waterborne infections, though human-to-human transmission can occur. The epidemiology of the diseases is examined, as are diagnostic procedures, anti-microbial interventions, and the influence of globalization, climate change, and technological advances on their spread.

Acanthamoeba↗
PubMed2004

Opportunistic amoebae: challenges in prophylaxis and treatment.

This review focuses on free-living amoebae, widely distributed in soil and water, causing opportunistic and non-opportunistic infections in humans: Acanthamoeba spp., Balamuthia mandrillaris, Naegleria fowleri, and Sappinia diploidea. Diseases include primary amoebic meningoencephalitis (N. fowleri), granulomatous amoebic encephalitis, cutaneous and nasopharyngeal infections (Acanthamoeba spp., Balamuthia mandrillaris, S. diploidea), and amoebic keratitis (Acanthamoeba spp). Acanthamoeba, Balamuthia, and Naegleria have been repeatedly isolated; S. diploidea has been reported only once, from a brain infection. Antimicrobial therapy for these infections is generally empirical and patient recovery often problematic. N. fowleri is highly sensitive to the antifungal agent amphotericin B, but delay in diagnosis and the fulminant nature of the disease result in few survivors. Encephalitis and other infections caused by Acanthamoeba and Balamuthia have been treated, more or less successfully, with antimicrobial combinations including sterol-targeting azoles (clotrimazole, miconazole, ketoconazole, fluconazole, itraconazole), pentamidine isethionate, 5-fluorocytosine, and sulfadiazine. The use of drug combinations addresses resistance patterns that may exist or develop during treatment, ensuring that at least one of the drugs may be effective against the amoebae. Favorable drug interactions (additive or synergistic) are another potential benefit. In vitro drug testing of clinical isolates points up strain and species differences in sensitivity, so that no single drug can be assumed effective against all amoebae. Another complication is risk of activation of dormant cysts that form in situ in Acanthamoeba and Balamuthia infections, and which can lead to patient relapse following apparently effective treatment. This is particularly true in Acanthamoeba keratitis, a non-opportunistic infection of the cornea, which responds well to treatment with chlorhexidine gluconate and polyhexamethylene biguanide, in combination with propamidine isothionate (Brolene), hexamidine (Désomodine), or neomycin. Acanthamoeba spp. may also be carriers of endosymbiotic bacteria (Legionella and Legionella-like pathogens) and have been implicated in outbreaks of pneumonias in debilitated hosts. As with other infectious diseases, recovery is dependent not only on antimicrobial therapy, but also on patient's immune status, infective dose and virulence of the ameba strain, and on how early the disease is diagnosed and drug therapy initiated.

Acanthamoeba↗