PubMed Health⌕ Search

Biomedical subjects

Frederick L Schuster

Publications and source records attributed to Frederick L Schuster.

At least 19 recordsLinked to original sources
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

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

Inability to make a premortem diagnosis of Acanthamoeba species infection in a patient with fatal granulomatous amebic encephalitis.

Granulomatous amebic encephalitis (GAE), an infection of immunocompromised hosts, is almost uniformly fatal. A case of GAE in a patient who failed to mount a serologic response to Acanthamoeba polyphaga is presented. Although Acanthamoeba polyphaga that is sensitive to multiple antimicrobials grew from brain tissue, an inability to make a premortem diagnosis precluded therapy.

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↗
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↗
PubMed2004

Free-living amoebae as opportunistic and non-opportunistic pathogens of humans and animals.

Knowledge that free-living amoebae are capable of causing human disease dates back some 50 years, prior to which time they were regarded as harmless soil organisms or, at most, commensals of mammals. First Naegleria fowleri, then Acanthamoeba spp. and Balamuthia mandrillaris, and finally Sappinia diploidea have been recognised as etiologic agents of encephalitis; Acanthamoeba spp. are also responsible for amoebic keratitis. Some of the infections are opportunistic, occurring mainly in immunocompromised hosts (Acanthamoeba and Balamuthia encephalitides), while others are non-opportunistic (Acanthamoeba keratitis, Naegleria meningoencephalitis, and cases of Balamuthia encephalitis occurring in immunocompetent humans). The amoebae have a cosmopolitan distribution in soil and water, providing multiple opportunities for contacts with humans and animals, as evidenced by antibody titers in surveyed human populations. Although, the numbers of infections caused by these amoebae are low in comparison to other protozoal parasitoses (trypanosomiasis, toxoplasmosis, malaria, etc.), the difficulty in diagnosing them, the challenge of finding optimal antimicrobial treatments and the morbidity and relatively high mortality associated with, in particular, the encephalitides have been a cause for concern for clinical and laboratory personnel and parasitologists. This review presents information about the individual amoebae: their morphologies and life-cycles, laboratory cultivation, ecology, epidemiology, nature of the infections and appropriate antimicrobial therapies, the immune response, and molecular diagnostic procedures that have been developed for identification of the amoebae in the environment and in clinical specimens.

Amebiasis↗
PubMed2004

Balamuthia mandrillaris from soil samples.

Balamuthia mandrillaris amoebas are recognized as a causative agent of granulomatous amoebic encephalitis, a disease that is usually fatal. They were first recognized when isolated from the brain of a mandrill baboon that died in the San Diego Zoo Wild Life Animal Park. Subsequently, the amoebas have been found in a variety of animals, including humans (young and old, immunocompromised and immunocompetent persons), in countries around the world. Until recently, the amoebas had not been recovered from the environment and their free-living status was in question. The recovery of a Balamuthia amoeba from a soil sample taken from a plant at the home of a child from California, USA, who died of Balamuthia amoebic encephalitis, was reported previously. In a continued investigation, a second amoeba was isolated from soil that was obtained from an outdoor potted plant in a spatially unrelated location. A comparison of these two environmental amoebas that were isolated from different soils with the amoeba that was obtained from the child's clinical specimen is reported here. Included are the isolation procedure for the amoebas, their growth requirements, their immunological response to anti-Balamuthia serum, their sensitivity to a selection of antimicrobials and sequence analysis of their 16S rRNA gene. The evidence is consistent that the amoebas isolated from both soil samples and the clinical isolate obtained from the Californian child are B. mandrillaris.

Amphotericin B↗
PubMed2003

Successful treatment of Balamuthia amoebic encephalitis: presentation of 2 cases.

Case histories are presented of 2 individuals (a 5-year-old girl and 64-year-old man) who developed encephalitis caused by the free-living amoeba Balamuthia mandrillaris. Both individuals survived after diagnosis and initiation of effective antimicrobial therapy. Immunostaining for Balamuthia-specific antibody levels identified the causative agent of the infections. Antimicrobial therapy with flucytosine, pentamidine, fluconazole, sulfadiazine, and a macrolide antibiotic (azithromycin or clarithromycin) was initiated. Phenothiazines (thioridazine and trifluoperazine) were also used. Both patients recovered, and there was no evidence of recrudescence of the disease at 2 and 6 years after onset of symptoms. Awareness of Balamuthia as the causative agent of encephalitis and early initiation of antimicrobial therapy were critical to the recovery of both patients. Although optimal antimicrobial therapy for Balamuthia amoebic encephalitis has yet to be determined, the antimicrobials used in these 2 cases effectively controlled the disease. These 2 individuals are the only known survivors of this otherwise fatal type of amoebic encephalitis.

Amebiasis↗
PubMed2003

Amebic encephalitis caused by Balamuthia mandrillaris: report of four cases.

We report four fatal cases of amebic encephalitis in children caused by the free-living pathogenic ameba Balamuthia mandrillaris. The clinical course ranged from subacute to fulminant. Provisional diagnoses were made either shortly before death or postmortem by an indirect immunofluorescent antibody test. Although the four cases occurred in different geographic locations, their common features may have diagnostic value for recognizing future cases of amebic encephalitis. The cases occurred in children 2 to 7.5 years old who were ostensibly immunocompetent and of Hispanic ethnicity. Three of the four children developed hydrocephalus during their illness. Increased awareness and timely diagnosis of this disease entity might lead to earlier intervention with improved outcome.

Amebiasis↗
PubMed2003

Environmental isolation of Balamuthia mandrillaris associated with a case of amebic encephalitis.

This report describes the first isolation of the ameba Balamuthia mandrillaris from an environmental soil sample associated with a fatal case of amebic encephalitis in a northern California child. Isolation of the ameba into culture from autopsied brain tissue confirmed the presence of Balamuthia: In trying to locate a possible source of infection, soil and water samples from the child's home and play areas were examined for the presence of Balamuthia: The environmental samples (plated onto nonnutrient agar with Escherichia coli as a food source) contained, in addition to the ameba, a variety of soil organisms, including other amebas, ciliates, fungi, and nematodes, as contaminants. Presumptive Balamuthia amebas were recognized only after cultures had been kept for several weeks, after they had burrowed into the agar. These were transferred through a succession of nonnutrient agar plates to eliminate fungal and other contaminants. In subsequent transfers, axenic Naegleria amebas and, later, tissue cultures (monkey kidney cells) served as the food source. Finally, the amebas were transferred to cell-free axenic medium. In vitro, the Balamuthia isolate is a slow-growing organism with a generation time of approximately 30 h and produces populations of approximately 2 x 10(5) amebas per ml. It was confirmed as Balamuthia by indirect immunofluorescence staining with rabbit anti-Balamuthia serum and human anti-Balamuthia antibody-containing serum from the amebic encephalitis patient. The environmental isolate is similar in its antimicrobial sensitivities and identical in its 16S ribosomal DNA sequences to the Balamuthia isolate from the deceased patient.

Amebiasis↗
PubMed2002

Cultivation of pathogenic and opportunistic free-living amebas.

Free-living amebas are widely distributed in soil and water, particularly members of the genera Acanthamoeba and NAEGLERIA: Since the early 1960s, they have been recognized as opportunistic human pathogens, capable of causing infections of the central nervous system (CNS) in both immunocompetent and immunocompromised hosts. Naegleria is the causal agent of a fulminant CNS condition, primary amebic meningoencephalitis; Acanthamoeba is responsible for a more chronic and insidious infection of the CNS termed granulomatous amebic encephalitis, as well as amebic keratitis. Balamuthia sp. has been recognized in the past decade as another ameba implicated in CNS infections. Cultivation of these organisms in vitro provides the basis for a better understanding of the biology of these amebas, as well as an important means of isolating and identifying them from clinical samples. Naegleria and Acanthamoeba can be cultured axenically in cell-free media or on tissue culture cells as feeder layers and in cultures with bacteria as a food source. Balamuthia, which has yet to be isolated from the environment, will not grow on bacteria. Instead, it requires tissue culture cells as feeder layers or an enriched cell-free medium. The recent identification of another ameba, Sappinia diploidea, suggests that other free-living forms may also be involved as causal agents of human infections.

Acanthamoeba↗
PubMed2002

Cultivation of plasmodium spp.

Cultivation of both human and non-human species of Plasmodium spp., the causal agent of malaria, has been a major research success, leading to a greater understanding of the parasite. Efforts at cultivating the organisms in vitro are complicated by the parasites' alternating between a human host and an arthropod vector, each having its own set of physiological, metabolic, and nutritional parameters. Life cycle stages of the four species that infect humans have been established in vitro. Of these four, P. falciparum remains the only species for which all stages have been cultured in vitro; different degrees of success have been achieved with the other human Plasmodium spp. The life cycle includes the exoerythrocytic stage (within liver cells), the erythrocytic stage (within erythrocytes or precursor reticulocytes), and the sporogonic stage (within the vector). Culture media generally consist of a basic tissue culture medium (e.g., minimal essential medium or RPMI 1640) to which serum and erythrocytes are added. Most of the efforts have been directed toward the stage found in the erythrocyte. This stage has been cultivated in petri plates or other growth vessels in a candle jar to generate elevated CO(2) levels or in a more controlled CO(2) atmosphere. Later developments have employed continuous-flow systems to reduce the labor-intensive nature of medium changing. The exoerythrocytic and sporogonic life cycle stages have also been cultivated in vitro. A number of avian, rodent, and simian malarial parasites have also been established in vitro. Although cultivation is of great help in understanding the biology of Plasmodium, it does not lend itself to use for diagnostic purposes.

Animals↗