The Epidemiology and Clinical Features of Balamuthia mandrillaris Disease in the United States, 1974-2016.

BACKGROUND: Balamuthia mandrillaris is a free-living ameba that causes rare, nearly always fatal disease in humans and animals worldwide. B. mandrillaris has been isolated from soil, dust, and water. Initial entry of Balamuthia into the body is likely via the skin or lungs. To date, only individual case reports and small case series have been published. METHODS: The Centers for Disease Control and Prevention (CDC) maintains a free-living ameba (FLA) registry and laboratory. To be entered into the registry, a Balamuthia case must be laboratory-confirmed. Several sources were used to complete entries in the registry, including case report forms, CDC laboratory results, published case reports, and media information. SAS© version 9.3 software was used to calculate descriptive statistics and frequencies. RESULTS: We identified 109 case reports of Balamuthia disease between 1974 and 2016. Most (99%) had encephalitis. The median age was 36 years (range 4 months to 91 years). Males accounted for 68% of the case patients. California had the highest number of case reports, followed by Texas and Arizona. Hispanics constituted 55% for those with documented ethnicity. Exposure to soil was commonly reported. Among those with a known outcome, 90% of patients died. CONCLUSIONS: Balamuthia disease in the United States is characterized by a highly fatal encephalitis that affects patients of all ages. Hispanics were disproportionately affected. The southwest region of the United States reported the most cases. Clinician awareness of Balamuthia as a cause of encephalitis might lead to earlier diagnosis and initiation of treatment, resulting in better outcomes.

Crosstalk between Entamoeba histolytica and the human intestinal tract during amoebiasis.

The protozoan parasite Entamoeba histolytica is the microbial agent of amoebiasis - an infection that is endemic worldwide and is associated with high morbidity and mortality rates. As the disease develops, virulent E. histolytica deplete the mucus layer, interact with the intestinal epithelium, and then degrade the colonic mucosa and disrupt the extracellular matrix (ECM). Our research demonstrated that virulent parasites with an invasive phenotype display rapid, highly specific changes in their transcriptome (notably for essential factors involved in carbohydrate metabolism and the processing of glycosylated residues). Moreover, combined activation of parasite and host lytic enzymes leads to the destruction of the intestinal parenchyma. Together, these enzymes degrade the mucus layer and the ECM, and trigger the inflammatory response essential to the development of amoebiasis.

Development of a high- versus low-pathogenicity model of the free-living amoeba Naegleria fowleri.

Species in the genus Naegleria are free-living amoebae of the soil and warm fresh water. Although around 30 species have been recognized, Naegleria fowleri is the only one that causes primary amoebic meningoencephalitis (PAM) in humans. PAM is an acute and fast progressing disease affecting the central nervous system. Most of the patients die within 1-2 weeks of exposure to the infectious water source. The fact that N. fowleri causes such fast progressing and highly lethal infections has opened many questions regarding the relevant pathogenicity factors of the amoeba. In order to investigate the pathogenesis of N. fowleri under defined experimental conditions, we developed a novel high- versus low-pathogenicity model for this pathogen. We showed that the composition of the axenic growth media influenced growth behaviour and morphology, as well as in vitro cytotoxicity and in vivo pathogenicity of N. fowleri. Trophozoites maintained in Nelson's medium were highly pathogenic for mice, demonstrated rapid in vitro proliferation, characteristic expression of surface membrane vesicles and a small cell diameter, and killed target mouse fibroblasts by both contact-dependent and -independent destruction. In contrast, N. fowleri cultured in PYNFH medium exhibited a low pathogenicity, slower growth, increased cell size and contact-dependent target cell destruction. However, cultivation of the amoeba in PYNFH medium supplemented with liver hydrolysate (LH) resulted in trophozoites that were highly pathogenic in mice, and demonstrated an intermediate proliferation rate in vitro, diminished cell diameter and contact-dependent target cell destruction. Thus, in this model, the presence of LH resulted in increased proliferation of trophozoites in vitro and enhanced pathogenicity of N. fowleri in mice. However, neither in vitro cytotoxicity mechanisms nor the presence of membrane vesicles on the surface correlated with the pathologic potential of the amoeba. This indicated that the pathogenicity of N. fowleri remains a complex interaction between as-yet-unidentified cellular mechanisms.

Primary amebic meningoencephalitis: a case report and literature review.

Primary amebic meningoencephalitis (PAM) is a rare but nearly always fatal disease caused by infection with Naegleria fowleri, a thermophilic, free-living ameba found in freshwater environments. Cases of N. fowleri infection have been reported from many of the southern-tier states in the United States, with Florida and Texas disproportionately represented among them. Primary amebic meningoencephalitis presents clinically in a fashion that may be indistinguishable from bacterial and viral meningitis. Unfortunately, because the disease is so rare, PAM is often excluded from the differential diagnosis of children with meningitis resulting in delayed diagnostic and therapeutic efforts.Pediatric acute care practitioners in emergency departments, general pediatric wards, and critical care units, especially those practicing in the southern United States, should be familiar with the risk factors for acquisition of PAM, its clinical presentation, and the fact that common empiric treatment of bacterial meningitis will not treat N. fowleri. Herein, we present the case of an adolescent who died of PAM and review the (a) epidemiology, (b) pathophysiology, (c) available diagnostic modalities, (d) treatment options, and (e) outcomes of patients treated for N. fowleri infection of the central nervous system.

Primary amebic meningoencephalitis caused by Naegleria fowleri, Karachi, Pakistan.

We report 13 cases of Naegleria fowleri primary amebic meningoencephalitis in persons in Karachi, Pakistan, who had no history of aquatic activities. Infection likely occurred through ablution with tap water. An increase in primary amebic meningoencephalitis cases may be attributed to rising temperatures, reduced levels of chlorine in potable water, or deteriorating water distribution systems.

Isolation and Identification of Pathogenic Acanthamoeba Species from Air Conditioning Systems, Egypt.

Acanthamoeba are free-living amoebae that cause granulomatous amoebic encephalitis and keratitis. In this study, we aimed to isolate and identify Acanthamoeba from air conditioning systems using in vitro cell culture and polymerase chain reaction assays. We also estimated the pathogenicity of the isolates by measuring their thermotolerance and studying mice models inoculated with these isolates. Of the 80 dust samples acquired, 41 (51.25%) were found to be positive for Acanthamoeba spp. using in vitro cell culture and the results were validated using PCR. Out of these 41 samples, 27 (65.9%) were thermotolerant and 16 (39%) samples could infect mice and cause histopathological effects. Highly pathogenic Acanthamoeba isolates were characterized by their thermotolerance and the ability to disseminate in all organs after infection, causing early death of infected animals. Our study thus validated the presence of pathogenic isolates of Acanthamoeba in air conditioners that may be potentially infectious to humans.

[Blastocystis hominis and nonpathogenic enteric protozoa in patients with pulmonary tuberculosis and those with HIV infection].

Blastocystis hominis and nonpathogenic enteric protozoa were diagnosed in 300 patients with pulmonary tuberculosis mainly of its infiltrative form and 500 with Stages II and III HIV infection; the patients received antituberculosis therapy (ATT) and antiretroviral therapy (ART), respectively. Control groups included 200 Tashkent dwellers and 350 patients with various noninfectious diseases of the gastrointestinal tract. Triple coproscopy was made. B. hominis was significantly more frequently detected in patients with pulmonary tuberculosis and those with HIV infection than in healthy individuals: in 53.6 +/- 2.9, 42.2 +/- 2.2, and 18.0 +/- 2.5, respectively (P < 0.01). Only did the tuberculosis or HIV-infected patients show a high intensity of B. hominis infection, which was accompanied by recurring diarrhea and nausea. The high activity of alanine aminotransferase and aspartate aminotransferase was observed in 20% of the patients with tuberculosis + blastocytosis; that of alkaline phosphatase was seen in 25%. The tuberculosis or HIV-infected patients were more frequently found to have Chylomastix mesnili, Jodamoeba butschlii, and Endolimax nana. The specific features of intestinal colonization seem to reflect changes in local immunity; the drugs included into ATT and ART have no substantial effects on the viability of protozoa.

Cecal amebiasis mimicking inflammatory bowel disease.

Amebiasis is a frequently occurring parasitic infection in South East Asia. We present a case of a 54-year-old man with right lower quadrant abdominal pain that persisted for longer than 1 year. He had been diagnosed with inflammatory bowel disease in Indonesia. His abdominal pain persisted, despite therapy, and he visited Malaysia for transnational medical advice. Abdominal ultrasound showed fatty liver, gallbladder polyps, and a small left renal stone. Colonoscopy showed multiple ulcers in the cecum and a histopathological examination confirmed amebic infection of the cecum. The colonic ulcers subsided after anti-amebic treatment. This case highlights the need to consider the differential diagnosis of amebic colitis in patients presenting with manifestations of inflammatory bowel disease, especially in patients who live in or have traveled to endemic areas.

Under the radar: balamuthia amebic encephalitis.

BACKGROUND: We present data from 9 years (1999-2008) of tests for Balamuthia mandrillaris, an agent of amebic encephalitis that were conducted as part of the California Encephalitis Project. METHODS: Specimens obtained from patients with encephalitis were sent to the California Encephalitis Project for diagnostic testing; a subset of these specimens were tested for Balamuthia species. Tests included indirect immunofluorescent staining of sections for amebae, fluorescent antibody staining and enzyme-linked immunosorbent assay for serum titers, and polymerase chain reaction for Balamuthia 16S mitochondrial DNA. Cerebrospinal fluid (CSF) samples obtained from patients with diverse types of encephalitis were also tested for a broad range of cytokines. RESULTS: Of >3500 cases referred to the California Encephalitis Project, 10 were found to be amebic encephalitis on the basis of serologic and CSF tests and examination of stained tissue sections. Most of these cases would have been described as "encephalitis of unknown origin" if it were not for the California Encephalitis Project. Nine of the 10 patients were male; ages ranged from 1.5 to 72 years. All patients had abnormal neuroimaging findings and abnormal CSF composition. The more common symptoms at presentation included headache, seizures, cranial nerve palsies, and lethargy. CSF specimens from patients with Balamuthia infection had significant elevations in the levels of cytokines IL-6 and IL-8, compared with specimens obtained from persons with viral or noninfectious encephalitides. CONCLUSIONS: Balamuthiasis is difficult to diagnose, and it is likely that cases go unrecognized because clinicians and laboratorians are unfamiliar with the disease. Alerting the medical community to this disease may lead to earlier diagnosis and improve the chances of survival.

Entamoeba histolytica causes intestinal secretion: role of serotonin.

Lysates of the protozoan parasite Entamoeba histolytica altered active electrolyte transport when present on the serosal surface of rabbit ileum and rat colon. The lysate-induced effects on electrolyte transport were similar to those caused by serotonin, and were blocked by bufotenine, an analog known to inhibit the action of serotonin. The transport effects were partially inhibited by antibody to serotonin. The amebic lysates were shown to contain serotonin by radioimmunoassay, high-performance liquid chromatography, and thin-layer chromatography. These results suggest that the serotonin present in Entamoeba histolytica may be important in the diarrhea seen in amebiasis.

Characterization of brain inflammation during primary amoebic meningoencephalitis.

Naegleria fowleri is a free-living amoeba and the etiologic agent of primary amoebic meningoencephalitis (PAM). Trophozoites reach the brain by penetrating the olfactory epithelium, and invasion of the olfactory bulbs results in an intense inflammatory reaction. The contribution of the inflammatory response to brain damage in experimental PAM has not been delineated. Using both optical and electron microscopy, we analyzed the morphologic changes in the brain parenchyma due to inflammation during experimental PAM. Several N. fowleri trophozoites were observed in the olfactory bulbs 72 h post-inoculation, and the number of amoebae increased rapidly over the next 24 h. Eosinophils and neutrophils surrounding the amoebae were then noted at later times during infection. Electron microscopic examination of the increased numbers of neutrophils and the interactions with trophozoites indicated an active attempt to eliminate the amoebae. The extent of inflammation increased over time, with a predominant neutrophil response indicating important signs of damage and necrosis of the parenchyma. These data suggest a probable role of inflammation in tissue damage. To test the former hypothesis, we used CD38-/- knockout mice with deficiencies in chemotaxis to compare the rate of mortality with the parental strain, C57BL/6J. The results showed that inflammation and mortality were delayed in the knockout mice. Based on these results, we suggest that the host inflammatory response and polymorphonuclear cell lysis contribute to a great extent to the central nervous system tissue damage.

Fatal subacute necrotising brainstem encephalitis in a young man due to a rare parasitic (Balamuthia) infection.

We describe a case of brainstem inflammation in a young man which at first defied diagnosis. However, after his death, and notwithstanding our inability to find a cause at autopsy, we did not give up. After sending paraffin blocks to the Centers for Disease Control in Atlanta, Georgia, USA, they suggested the diagnosis of Balamuthia (amoebic) infection.

Pathogenic and opportunistic free-living amoebae: Acanthamoeba spp., Balamuthia mandrillaris, Naegleria fowleri, and Sappinia diploidea.

Among the many genera of free-living amoebae that exist in nature, members of only four genera have an association with human disease: Acanthamoeba spp., Balamuthia mandrillaris, Naegleria fowleri and Sappinia diploidea. Acanthamoeba spp. and B. mandrillaris are opportunistic pathogens causing infections of the central nervous system, lungs, sinuses and skin, mostly in immunocompromised humans. Balamuthia is also associated with disease in immunocompetent children, and Acanthamoeba spp. cause a sight-threatening infection, Acanthamoeba keratitis, mostly in contact-lens wearers. Of more than 30 species of Naegleria, only one species, N. fowleri, causes an acute and fulminating meningoencephalitis in immunocompetent children and young adults. In addition to human infections, Acanthamoeba, Balamuthia and Naegleria can cause central nervous system infections in animals. Because only one human case of encephalitis caused by Sappinia diploidea is known, generalizations about the organism as an agent of disease are premature. In this review we summarize what is known of these free-living amoebae, focusing on their biology, ecology, types of disease and diagnostic methods. We also discuss the clinical profiles, mechanisms of pathogenesis, pathophysiology, immunology, antimicrobial sensitivity and molecular characteristics of these amoebae.

Identification and properties of proteases from an Acanthamoeba isolate capable of producing granulomatous encephalitis.

BACKGROUND: Granulomatous amoebic encephalitis due to Acanthamoeba is often a fatal human disease. However, the pathogenesis and pathophysiology of Acanthamoeba encephalitis remain unclear. In this study, the role of extracellular Acanthamoeba proteases in central nervous system pathogenesis and pathophysiology was examined. RESULTS: Using an encephalitis isolate belonging to T1 genotype, we observed two major proteases with approximate molecular weights of 150 KD and 130 KD on SDS-PAGE gels using gelatin as substrate. The 130 KD protease was inhibited with phenylmethylsulfonyl fluoride (PMSF) suggesting that it is a serine protease, while the 150 KD protease was inhibited with 1, 10-phenanthroline suggesting that it is a metalloprotease. Both proteases exhibited maximal activity at neutral pH and over a range of temperatures, indicating their physiological relevance. These proteases degrade extracellular matrix (ECM), which provide structural and functional support to the brain tissue, as shown by the degradation of collagen I and III (major components of collagenous ECM), elastin (elastic fibrils of ECM), plasminogen (involved in proteolytic degradation of ECM), as well as casein and haemoglobin. The proteases were purified partially using ion-exchange chromatography and their effects were tested in an in vitro model of the blood-brain barrier using human brain microvascular endothelial cells (HBMEC). Neither the serine nor the metalloprotease exhibited HBMEC cytotoxicity. However, the serine protease exhibited HBMEC monolayer disruptions (trypsin-like) suggesting a role in blood-brain barrier perturbations. CONCLUSION: Overall, these data suggest that Acanthamoeba proteases digest ECM, which may play crucial role(s) in invasion of the brain tissue by amoebae.

Experimental amebiasis: a selected review of some in vivo models.

The use of in vivo animal models in amebiasis has contributed significantly to the knowledge of this common human parasitic disease. Although there is no animal model that mimics the whole cycle of the human disease, the use of different susceptible and resistant laboratory animals and the availability for many years of techniques for the axenic culture of trophozoites of Entamoeba histolytica have allowed a better understanding of the parasite and the host-parasite relationship. The recent introduction of frontier methodologies in biology has increased our comprehension of this parasite. New information on the cellular and molecular biology and genetics of this organism has been extensively reported, and much of this has clearly required the more frequent use of animal models to verify specific facts. Based on experimental animals characterized previously, the introduction of new animal models with genetic or surgical modifications, especially in mice, has allowed a more adequate analysis of the mechanisms of pathogenesis. Multiple factors have been considered in the promotion of the invasiveness and virulence of E. histolytica. Additionally, the immunological and physiological responses of the host, depending on the environmental conditions, lead to the establishment or the rejection of the parasite. The role of inflammatory reaction to amebic infection constitutes one of the controversies that has been studied by several authors. In susceptible animals (hamsters and gerbils), inflammatory cell damage seems to be related to target cell lysis, while in resistant animals (mice), inflammatory cells appear to protect the host by lysing the parasite. Presently, the involvement of various substances in the development of lesions including lectins, proteases, amebapores, promoters of apoptosis, cytokines, nitric oxide, etc., is being examined using different in vivo models.

Primary amebic meningoencephalitis.

This case is reported with the intention of highlighting the presentation of primary amebic meningoencephalitis as acute meningitis, a rare differential diagnosis with presence of free living amoebas in the CSF.

September 2004: a 6-year-old girl with headache and stiff neck.

Free-living amebas in the genera Naegleria, Acanthamoeba and Balamuthia are known to cause CNS infections. Here we report a case of fatal granulomatous amebic meningoencephalitis (GAE) caused by Balamuthia mandrillaris in a 6-year-old previously healthy girl who presented with headache and stiff neck. She was treated medically for brain abscess after a CT scan identified a ring-enhancing lesion in the right temporo-parietal area. A brain biopsy showed necrosis and granulomatous inflammation. Subsequently, multiple new lesions appeared in the brain bilaterally. A second brain biopsy revealed viable amebic trophozoites that were most abundant in perivascular spaces, accompanied by neutrophils, macrophages and eosinophils. Immunofluorescence study confirmed the amoeba as Balamuthia mandrillaris. This case demonstrates that making diagnosis of GAE pre-mortem requires a high index of suspicion. Amebic infection should be included in the differential diagnosis of any granulomatous lesion in CNS; and careful search for amebic parasites should be carried out especially when necrosis predominates in the pathological material.

Effects of gill abrasion and experimental infection with Tenacibaculum maritimum on the respiratory physiology of Atlantic salmon Salmo salar affected by amoebic gill disease.

The effects of gill abrasion and experimental infection with Tenacibaculum maritimum were assessed in Atlantic salmon Salmo salar with underlying amoebic gill disease. The respiratory and acid-base parameters arterial oxygen tension (P(a)O2), arterial whole blood oxygen content (C(a)O2), arterial pH (pHa), haematocrit and haemoglobin concentrations were measured at intervals over a 48 h recovery period following surgical cannulation of the dorsal aorta. Mortality rates over the recovery period were variable, with gill abrasion and inoculation with T. maritimum causing the highest initial mortality rate and unabraded, uninoculated controls showing the lowest overall mortality rate. Fish with abraded gills tended to show reduced P(a)O2 and lower C(a)O2 compared with unabraded fish. Infection with T. maritimum had no effect on P(a)O2 or C(a)O2. All fish showed an initial alkalosis at 24 h post-surgery/inoculation which was more pronounced in fish inoculated with T. maritimum. There were no significant effects of gill abrasion or infection upon the ratio of oxygen specifically bound to haemoglobin or mean cellular haemoglobin concentration. Histologically, 48 h following surgery, abraded gills showed multifocal hyperplastic lesions with pronounced branchial congestion and telangiectasis, and those inoculated with T. maritimum exhibited focal areas of branchial necrosis and erosion associated with filamentous bacterial mats. All fish examined showed signs of amoebic gill disease with multifocal hyperplastic and spongious lesions with parasome-containing amoeba associated with the gill epithelium. The results suggest that respiratory compromise occurred as a consequence of gill abrasion rather than infection with T. maritimum.