Metagenomic next-generation sequencing for diagnosis of fatal Balamuthia amoebic encephalitis

INTRODUCTION

Balamuthia amoebic encephalitis (BAE), caused by Balamuthia mandrillaris, is a rare and life-threatening infectious disease with no specific and effective treatments available. The diagnosis of BAE at an early stage is difficult because of the non-specific clinical manifestations and neuroimaging.

CASE DESCRIPTION

A 52-year-old male patient, who had no previous history of skin lesions, presented to the emergency department with an acute headache, walking difficulties, and disturbance of consciousness. The patient underwent a series of examinations, including regular cerebrospinal fluid (CSF) studies and magnetic resonance imaging, and tuberculous meningoencephalitis was suspected. Despite being treated with anti-TB drugs, no clinical improvement was observed in the patient. Following corticosteroid therapy, the patient developed a rapid deterioration in consciousness with dilated pupils. Metagenomic next-generation sequencing (mNGS) revealed an unexpected central nervous system (CNS) amoebic infection, and the patient died soon after the confirmed diagnosis.

CONCLUSION

This study highlights the application of mNGS for the diagnosis of patients with suspected encephalitis or meningitis, especially those caused by rare opportunistic infections.

Unexpected trends of amoebic encephalitis in Pakistan

Annual reported cases of Naegleria fowleri (NF), popularly known as brain eating amoeba, are becoming a huge challenge for Pakistani health authorities. Karachi has seen cases regularly up till the present but Lahore has not. The spread of this amoeba in non-chlorinated water is a major concern for the authorities. NF is an amoeba commonly found in warm freshwater environments such as lakes, hot springs and poorly chlorinated swimming pools. It poses a significant risk during hot weather when water-related recreational activities are popular. Where there is a non-chlorinated water supply, its spread is aggravated.

Usefulness of a new immunochromatographic assay using fluorescent silica nanoparticles for serodiagnosis of Thai patients with amebiasis

A fluorescence immunochromatography (FIC) kit was developed recently using fluorescent silica nanoparticles coated with a recombinant C-terminal fragment of the surface lectin intermediate subunit (C-Igl) of Entamoeba histolytica to establish rapid serodiagnosis of amebiasis. We further evaluated the system using serum samples from 52 Thai patients with amebiasis. Of the patients, 50 (96%) tested positive using FIC. The samples were also tested using enzyme-linked immunosorbent assay (ELISA) with C-Igl as the antigen. Two samples were negative on ELISA but positive on FIC. The correlation coefficient between the fluorescence intensity using FIC and the optical density value using ELISA was 0.5390, indicating a moderate correlation between the two tests. Serum samples from 20 patients with malaria and 22 patients with Clostridioides difficile infection were also tested using FIC. The false-positive rates were 4/20 (20%) and 1/22 (4%) in patients with malaria and C. difficile infection, respectively. Combining the data from the present study with our previous study, the sensitivity and specificity of FIC were determined to be 98.5% and 95.2%, respectively. The results of the 50 samples were studied using a fluorescence scope and a fluorescence intensity reader, and the findings were compared. Disagreements were found in only two samples showing near-borderline fluorescence intensity, indicating that the use of scope was adequate for judging the results. These results demonstrate that FIC is a simple and rapid test for the serodiagnosis of amebiasis.

Amoebic colitis and liver abscess: A rare case of autochthonous invasive infection due to Entamoeba histolytica

We report an unusual and confirmed case of invasive amebiasis in a non-endemic area where the source of infection remains unknown. During her admission, the patient developed amebic colitis and extraintestinal liver abscess with a favorable outcome following the antiparasitic therapy.

Case Report: A Series of Three Meningoencephalitis Cases Caused by Acanthamoeba spp. from Eastern India

Acanthamoeba spp. are rare etiological agents of meningoencephalitis with high mortality. We present three cases of Acanthamoeba meningoencephalitis in immunocompetent individuals from Eastern India. The first patient presented with fever and headache; the second with headache, visual disturbance, and squint; and the third presented in a drowsy state. The cases presented on March 3, 18, and 21, 2023 respectively. The first two patients had concomitant tubercular meningitis for which they received antitubercular therapy and steroid. Their cerebrospinal fluid showed slight lymphocytic pleocytosis and increased protein. The diagnosis was done by microscopy, culture, and polymerase chain reaction. They received a combination therapy comprising rifampicin, fluconazole, and trimethoprim-sulfamethoxazole. The first patient additionally received miltefosine. She responded well to therapy and survived, but the other two patients died despite intensive care. Detection of three cases within a period of 1 month from Eastern India is unusual. It is imperative to sensitize healthcare providers about Acanthamoeba meningoencephalitis to facilitate timely diagnosis and treatment of the disease.

Balamuthia mandrillaris amoebic encephalitis mimicking tuberculous meningitis

A 76-year-old female with no apparent immunosuppressive conditions and no history of exposure to freshwater and international travel presented with headache and nausea 3 weeks before the presentation. On admission, her consciousness was E4V4V6. Cerebrospinal fluid analysis showed pleocytosis with mononuclear cell predominance, elevated protein, and decreased glucose. Despite antibiotic and antiviral therapy, her consciousness and neck stiffness gradually worsened, right eye-movement restriction appeared, and the right direct light reflex became absent. Brain magnetic resonance imaging revealed hydrocephalus in the inferior horn of the left lateral ventricle and meningeal enhancement around the brainstem and cerebellum. Tuberculous meningitis was suspected, and pyrazinamide, ethambutol, rifampicin, isoniazid, and dexamethasone were started. In addition, endoscopic biopsy was performed from the white matter around the inferior horn of the left lateral ventricle to exclude brain tumor. A brain biopsy specimen revealed eosinophilic round cytoplasm with vacuoles around blood vessels, and we diagnosed with amoebic encephalitis. We started azithromycin, flucytosine, rifampicin, and fluconazole, but her symptoms did not improve. She died 42 days after admission. In autopsy, the brain had not retained its structure due to autolysis. Hematoxylin and eosin staining of her brain biopsy specimen showed numerous amoebic cysts in the perivascular brain tissue. Analysis of the 16S ribosomal RNA region of amoebas from brain biopsy and autopsy specimens revealed a sequence consistent with Balamuthia mandrillaris. Amoebic meningoencephalitis can present with features characteristic of tuberculous meningitis, such as cranial nerve palsies, hydrocephalus, and basal meningeal enhancement. Difficulties in diagnosing amoebic meningoencephalitis are attributed to the following factors: (1) excluding tuberculous meningitis by microbial testing is difficult, (2) amoebic meningoencephalitis has low incidence and can occur without obvious exposure history, (3) invasive brain biopsy is essential in diagnosing amoebic meningoencephalitis. We should recognize the possibility of amoebic meningoencephalitis when evidence of tuberculosis meningitis cannot be demonstrated.

Peristomal cutaneous amebiasis causing rapidly progressive necrotic wound of a left lower quadrant end colostomy

Cutaneous amebiasis is a rare clinical entity caused by the invasive protozoan parasite Entamoeba histolytica that can be readily diagnosed with skin biopsy if suspected. It presents as a rapidly progressive and destructive ulceration with necrosis. A man in his 40s with metastatic rectal cancer who underwent palliative abdominal perineal resection with end colostomy in his left lower quadrant and on systemic chemotherapy developed progressive breakdown of his peristomal skin unresponsive to antibiotics that was then diagnosed to be cutaneous amebiasis. It is important to be aware of cutaneous amebiasis and include it in the differential diagnosis when peristomal wounds do not respond to treatment.

Effects of Serum Antibody Test Reagent Discontinuation on Diagnosis of Amebiasis in Japan: Interrupted Time-Series Analysis

Amebiasis is a notifiable infectious disease in Japan, and the number of reported cases had been on the rise, but since the discontinuation of insurance-covered serum antibody testing reagent in 2017, concerns have arisen regarding the decrease in reported cases. This study aimed to investigate changes occurring after discontinuation of the serum antibody test reagent production. We retrospectively analyzed amebiasis cases from January 2014 to December 2019 using the National Center for Epidemiology of Infectious Diseases system. Interrupted time-series regression analysis was used to evaluate trends in weekly amebiasis cases before and after the discontinuation period. The study period was divided into prediscontinuation (2014-2017) and discontinuation (2018-2019) periods. A total of 6,179 amebiasis cases were reported. The average numbers of weekly cases were 21.5 during 2014-2017 and 16.3 during 2018-2019. The frequency of diagnoses decreased in the discontinuation period (prevalence rate ratio = 0.78; 95% CI, 0.67-0.89; P < 0.01). Subgroup analysis showed lower diagnostic rates, particularly for extraintestinal amebiasis (prevalence rate ratio = 0.37; 95% CI, 0.22-0.55; P < 0.01). We observed a significant decrease in the number of reported amebiasis cases per week after discontinuation of the serum antibody test reagent in Japan. Our findings hold significance for both public health policy and practice in Japan, underscoring the requirement for enhanced amebiasis diagnostic tools and strategies. To ensure accurate diagnosis, availability of antibody reagents for serum testing, covered by insurance, should be encouraged.

Clinical manifestations and outcome of patients with primary amoebic meningoencephalitis in Pakistan. A single-center experience

Primary amoebic meningoencephalitis (PAM) is a rapidly progressing central nervous system (CNS) infection caused by Naegleria fowleri, a free-living amoeba found in warm freshwater. The disease progression is very rapid, and the outcome is nearly always fatal. We aim to describe the disease course in patients admitted with PAM in a tertiary care center in Karachi, Pakistan between the periods of 2010 to 2021. A total of 39 patients were included in the study, 33 males (84.6%). The median age of the patients was 34 years. The most frequent presenting complaint was fever, which was found in 37 patients (94.9%) followed by headache in 28 patients (71.8%), nausea and vomiting in 27 patients (69.2%), and seizures in 10 patients (25.6%). Overall, 39 patients underwent lumbar puncture, 27 patients (69.2%) had a positive motile trophozoites on CSF wet preparation microscopy, 18 patients (46.2%) had a positive culture, and 10 patients had a positive PCR. CSF analysis resembled bacterial meningitis with elevated white blood cell counts with predominantly neutrophils (median, 3000 [range, 1350-7500] cells/μL), low glucose levels median, 14 [range, 1-92] mg/dL), and elevated protein levels (median, 344 [range, 289-405] mg/dL). Imaging results were abnormal in approximately three-fourths of the patients which included cerebral edema (66.7%), hydrocephalus (25.6%), and cerebral infarctions (12.8%). Only one patient survived. PAM is a fatal illness with limited treatment success. Early diagnosis and prompt initiation of treatment can improve the survival of the patients and reduce mortality.

A primary amoebic meningoencephalitis case associated with swimming in seawater

This case report describes a 62-year-old male fisherman who presented with persistent vomiting, headache, and behavior changes. Despite initial antibiotic and corticosteroid treatment, his condition worsened, leading to coma and subsequent death. Macro-genome sequencing of cerebrospinal fluid (CSF) revealed the presence of Naegleria fowleri infection, which had been missed during initial laboratory tests. The patient's exposure history included sea-swimming near Zhoushan Island.

Laboratory Diagnosis of Primary Amoebic Meningoencephalitis

Primary amebic meningoencephalitis (PAM) is a fulminant fatal human disease caused by the free-living amoeba Naegleria fowleri. Infection occurs after inhalation of water containing the amoeba, typically after swimming in bodies of warm freshwater. N. fowleri migrates to the brain where it incites meningoencephalitis and cerebral edema leading to death of the patient 7 to 10 days postinfection. Although the disease is rare, it is almost always fatal and believed to be underreported. The incidence of PAM in countries other than the United States is unclear and possibly on track to being an emerging disease. Poor prognosis is caused by rapid progression, suboptimal treatment, and underdiagnosis. As diagnosis is often performed postmortem and testing is only performed by a few laboratories, more accessible testing is necessary. This article reviews the current methods used in the screening and confirmation of PAM and makes recommendations for improved diagnostic practices and awareness.

Fatal Primary Amebic Meningoencephalitis in Nebraska: Case Report and Environmental Investigation, August 2022

Primary amebic meningoencephalitis (PAM) is a rare and lethal infection caused by Naegleria fowleri. We report an epidemiological and environmental investigation relating to a case of PAM in a previously healthy boy age 8 years. An interview of the patient's family was conducted to determine the likely exposure site and to assess risk factors. Data from the United States Geological Survey site at Waterloo, NE, on the Elkhorn River were used to estimate water temperature and streamflow at the time and site of exposure. Data from the National Weather Service were used to estimate precipitation and ambient air temperature at the time and site of exposure. Despite conventional treatment, the patient died 2 days after hospital admission. The patient participated in recreational water activities in the Elkhorn River in northeastern Nebraska 5 days before symptom onset. In the week before exposure, water and ambient air high temperatures reached annual highs, averaging 32.4°C and 35.8°C, respectively. The day before infection, 2.2 cm of precipitation was reported. Streamflow was low (407 ft3/s). Infections in several northern states, including Nebraska, suggest an expanding geographic range of N. fowleri transmission, which may lead to increased incidence of PAM in the United States. Similar environmental investigations at suspected exposure sites of future cases will allow data aggregation, enabling investigators to correlate environmental factors with infection risk accurately.

Fatal granulomatous amebic encephalitis initially presenting with a cutaneous lesion

We present a case of a 66-year-old man with a cutaneous Balamuthia mandrillaris lesion that progressed to fatal granulomatous amoebic encephalitis. We provide a summary of Australian cases and describe the clinical features and approach to diagnosing this rare but devastating condition, including the importance of PCR for diagnosis.

Amebic encephalitis and meningoencephalitis: an update on epidemiology, diagnostic methods, and treatment

PURPOSE OF REVIEW

Free-living amebae (FLA) including Naegleria fowleri , Balamuthia mandrillaris , and Acanthamoeba species can cause rare, yet severe infections that are nearly always fatal. This review describes recent developments in epidemiology, diagnosis, and treatment of amebic meningoencephalitis.

RECENT FINDINGS

Despite similarities among the three pathogenic FLA, there are notable variations in disease presentations, routes of transmission, populations at risk, and outcomes for each. Recently, molecular diagnostic tools have been used to diagnose a greater number of FLA infections. Treatment regimens for FLA have historically relied on survivor reports; more data is needed about novel treatments, including nitroxoline.

SUMMARY

Research to identify new drugs and guide treatment regimens for amebic meningoencephalitis is lacking. However, improved diagnostic capabilities may lead to earlier diagnoses, allowing earlier treatment initiation and improved outcomes. Public health practitioners should continue to prioritize increasing awareness and providing education to clinicians, laboratorians, and the public about amebic infections.

[Evaluation of the Methods Used for the Detection of Entamoeba histolytica in Stool Samples of Patients with Diarrhea]

Amoebic dysentery (amebiasis) is a parasitic infection caused by Entamoeba histolytica. The diagnosis of invasive amebiasis has traditionally been based on direct and stained microscopic examination of stool samples. Stool microscopy exhibits low sensitivity and it is difficult to distinguish E.histolytica cysts and trophozoites from cells such as leukocytes, macrophages and non-pathogenic Entamoeba species in the stool by microscopy. Therefore more sensitive and specific diagnostic methods such as enzyme linked immunosorbent assay (ELISA) tests which investigate the presence of E.histolytica-specific antigen in stool, and polymerase chain reaction (PCR) are being widely used. In this study it was aimed to study stool samples of the patients who applied with the clinical signs of amebiasis by using direct and permanent stained microscopy, E.histolytica adhesin antigen ELISA test and real-time PCR-based BD Max Enteric Parasite Panel (BD Max EPP) test and to evaluate the diagnostic values of these tests. A total of 546 faecal samples with blood and/or mucus were analyzed in the study. In these samples, the presence of E.histolytica was investigated by direct and permanent stained microscopy, E.histolytica adhesin antigen ELISA and BD Max EPP PCR. Of the samples 36.3% were suspected to contain E.histolytica/dispar/moshkovskii cyst and/or trophozoite by direct microscopic examination. Trichrome staining was performed on these samples and 49 samples were found suspicious for the presence of E.histolytica/dispar/moshkovskii cysts and/or trophozoites. The presence of E.histolytica and other Entamoeba species was not confirmed in 75.2% of the samples. BD Max EPP PCR and E.histolytica adhesin antigen ELISA tests were studied in 49 faecal samples that were suspected by trichrome staining. None of these samples were positive by ELISA. Forty-four samples were negative by PCR and invalid test results were obtained in five samples. In this study, E.histolytica was not detected in the patient population. The results of this study showed that microscopic examination alone is not sufficient for the detection of E.histolytica. It is concluded that it is necessary to use a more sensitive and specific also rapid diagnostic test such as E.histolytica-specific antigen detection test or PCR in the diagnosis of amebiasis to avoid misdiagnosis and unnecessary treatment of patients.

Facial Balamuthia mandrillaris infection with neurological involvement in an immunocompetent child

Cutaneous infection by Balamuthia mandrillaris is a rare condition that is sometimes complicated by life-threatening CNS involvement. It often evades timely diagnosis due to its rarity and non-specific clinical manifestations. Patients can be either immunocompetent or immunocompromised. It is probably transmitted via inhalation or inoculation through broken skin, and then spreads to the brain and other organs through haematogenous spread. It is important for clinicians to be aware of this disease because rapid diagnosis and subsequent therapy has, in some cases, been associated with survival. In this Grand Round, we report the case of a 7-year-old boy who presented with large, chronic plaques on his face. Several biopsies showed non-specific granulomatous inflammation. The patient deteriorated rapidly and died within 1 month of displaying abnormal symptoms in the CNS. Immunohistochemical staining of skin tissue identified B mandrillaris as the infectious agent. The diagnosis was confirmed with PCR, which detected B mandrillaris DNA in formalin-fixed skin tissue sections. B mandrillaris infection should be considered in the differential diagnosis of patients with chronic granulomatous lesions. We also reviewed the epidemiology, B mandrillaris in nature and in the laboratory, clinical manifestations, histopathology, diagnosis, and treatment of infection.

Acanthamoeba castellanii encephalitis in a patient with AIDS: a case report and literature review

Amoebic encephalitis is a rare cause of CNS infection for which mortality exceeds 90%. We present the case of a 27-year-old man with AIDS who presented to a hospital in Atlanta (Georgia, USA) with tonic-clonic seizures and headache. His clinical condition deteriorated over several days. Brain biopsy revealed lymphohistiocytic inflammation and necrosis with trophozoites and encysted forms of amoebae. Immunohistochemical and PCR testing confirmed Acanthamoeba castellanii encephalitis, typically described as granulomatous amoebic encephalitis (GAE). No proven therapy for GAE is available, although both surgical and multiagent antimicrobial treatment strategies are often used. Most recently, these include the antileishmanial agent miltefosine. Here we review all cases of GAE due to Acanthamoeba spp in people with HIV/AIDS identified in the literature and reported to the Centers for Disease Control and Prevention. We describe this case as a reminder to the clinician to consider protozoal infections, especially free-living amoeba, in the immunocompromised host with a CNS infection refractory to traditional antimicrobial therapy.

Potential Biomarkers in Diagnosis of Renal Acanthamoebiasis

Recent studies indicate that Acanthamoeba spp. may play a significant role in kidney dysfunction. The aim of the study was to examine the levels of kidney injury molecule 1 (KIM-1), neutrophil gelatinase-associated lipocalin (NGAL), and monocyte chemotactic protein 1 (MCP-1), as well as an activity of matrix metalloproteinases 2 and 9 (MMP-2 and MMP-9, respectively) in the kidneys of immunocompetent and immunosuppressed mice infected with Acanthamoeba spp. The levels of KIM-1, NGAL, and MCP-1 were analyzed by enzyme-linked immunosorbent assay (ELISA), and the activity of MMPs was determined by gelatin zymography. The elevated KIM-1 level was found in the kidneys of immunocompetent mice at the beginning of Acanthamoeba spp. infection. In the immunosuppressed mice, the KIM-1 level was statistically different. The statistically decreased NGAL level was found in the kidneys of immunocompetent mice compared to the uninfected mice. In the immunocompromised mice, we found statistically significant differences in MCP-1 levels between the uninfected and infected groups. There was an increase in the expression of both MMP-2 and MMP-9 in the kidneys of immunocompetent and immunosuppressed mice infected with Acanthamoeba spp. compared to the uninfected mice. The results indicate that KIM-1, NGAL, MCP-1, MMP-2, MMP-9, and MMP-9/NGAL might be promising biomarkers of renal acanthamoebiasis.

Method for cryopreservation of Paramoeba perurans

Paramoeba perurans causes amoebic gill disease (AGD), which is a major problem in aquaculture worldwide. The parasite can be cultured in vitro, but to this date, no method for long-term storage of the clones exists. In this study, we describe a method for cryopreservation of Paramoeba perurans. The method was successfully employed on four out the five clones we tested. The thawing success rate, that is the percentage of successfully thawed vials relative to the total number of vials that were thawed, differed for the clones and ranged from 25% to 100%. The age of the clones seemed to have a negative impact on the ability to survive cryopreservation.

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.

Cluster of Post-Operative Endophthalmitis Caused by Acanthamoeba T10 Genotype - A First Report

PURPOSE

To report a cluster of postoperative Acanthamoeba endophthalmitis after routine cataract surgeries.

METHODS

A brief summary of sentinel events leading to the referral of 4 patients of postoperative endophthalmitis to our hospital is followed by clinical descriptions and the various diagnostic approaches and interventions used. Genotyping and phylogenetic analysis are also discussed.

RESULTS

Four cases of postoperative cluster endophthalmitis, presumed to be bacterial and treated as such, were referred to our hospital. The presence of an atypical ring infiltrate in the first case facilitated the diagnosis of Acanthamoeba endophthalmitis. All patients had vitritis, corneal involvement, and scleral inflammation. Multiple diagnostic methods, such as corneal scrapings, confocal microscopy, aqueous and vitreous taps, scleral abscess drainage, histopathological studies, polymerase chain reaction, and genotyping and phylogenetic analyses of isolated Acanthamoeba, were used to confirm the diagnosis of endophthalmitis and to establish the extent of ocular involvement. Various medical and therapeutic interventions used to control the infections were also documented. The isolated Acanthamoeba were confirmed as belonging to the T10 genotype, an environmentally and clinically rare variety.

CONCLUSIONS

This is the first report of a cluster of postoperative T10 genotype Acanthamoeba endophthalmitis, occurring after routine cataract surgery in immunocompetent individuals. Contrary to current perceptions, a rapidly evolving infection can occur with Acanthamoeba.

A comparison of the use of different swab materials for optimal diagnosis of amoebic gill disease (AGD) in Atlantic salmon (Salmo salar L.)

Routine gill swabbing is a non-destructive sampling method used for the downstream qPCR detection and quantitation of the pathogen Neoparamoeba perurans, a causative agent of amoebic gill disease (AGD). Three commercially available swabs were compared aiming their application for timelier AGD diagnosis (Calgiswab^® (calcium alginate fibre-tipped), Isohelix^® DNA buccal and cotton wool-tipped). Calcium alginate is soluble in most sodium salts, which potentially allows the total recovery of biological material, hence a better extraction of target organisms' DNA. Thus, this study consisted of (a) an in vitro assessment involving spiking of the swabs with known amounts of amoebae and additional assessment of retrieval efficiency of amoebae from agar plates; (b) in vivo testing by swabbing of gill arches (second, third and fourth) of AGD-infected fish. Both in vitro and in vivo experiments identified an enhanced amoeba retrieval with Calgiswab® and Isohelix® swabs in comparison with cotton swabs. Additionally, the third and fourth gill arches presented significantly higher amoebic loads compared to the second gill arch. Results suggest that limiting routine gill swabbing to one or two arches, instead of all, could likely lead to reduced stress-related effects incurred by handling and sampling and a timelier diagnosis of AGD.

Non-lethal loop-mediated isothermal amplification assay as a point-of-care diagnostics tool for Neoparamoeba perurans, the causative agent of amoebic gill disease

Neoparamoeba perurans is the causative agent of amoebic gill disease (AGD). Two loop-mediated isothermal amplification (LAMP) assays targeting the parasite 18S rRNA and the Atlantic salmon EF1α, used as internal control, were designed. The N. perurans LAMP assay did not amplify close relatives N. pemaquidensis and N. branchiphila, or the host DNA. This assay detected 10⁶ copies of the parasite 18S rRNA gene under 13 min and 10³ copies under 35 min. Five "fast-and-dirty" DNA extraction methods were compared with a reference method and further validated by TaqMan™ qPCR. Of those, the QuickExtract buffer was selected for field tests. Seventy-one non-lethal gill swabs were analysed from AGD-clinically infected Atlantic salmon. The pathogen was detected under 23 min in fish of gill score >2 and under 39 min for lower gill scores. About 1.6% of the tests were invalid (no amplification of the internal control). 100% of positives were obtained from swabs taken from fish showing gill score ˃3, but only ~50% of positives for lower gill scores. The present LAMP assay could be implemented as a point-of-care test for the on-site identification of N. perurans; however, further work is required to improve its performance for lower scores.

A colonic amoebic abscess mimicking colonic carcinoma

Amebiasis is one of the major causes of diarrhea in the developing countries and it can present with a wide range of gastrointestinal symptoms depending on the phase of infection. We described a case of 50 year-old male patient who presented with abdominal pain, diarrhea and vomiting. After right hemicolectomy for appendicular abscess with tumour over the ileum, histopathological examinations revealed numerous trophozoites of Entamoeba histolytica in a background of inflammations (Figure 1). Following resection of the ameboma, he received intravenous metronidazole treatment for total of two weeks duration.

Presence of Acanthamoeba in the ocular surface in a Spanish population of contact lens wearers

Pathogenic strains of Acanthamoeba are causative agents of a sight-threatening infection of the cornea known as Acanthamoeba keratitis (AK) which mainly affects contact lens wearers and it is commonly related to poor hygiene of contact lenses and their cases. Moreover, treatment of AK is complex due to the existence of a highly resistant cyst stage and if not diagnosed early has poor prognosis, leading to blindness and/or keratoplasty. Even though AK is increasing worldwide as well as awareness among patients and clinicians, it is still a poorly studied pathogen. Additionally, a remaining question to be answered is whether these opportunistic pathogens are present in the ocular surface of healthy contact lens wearers since they are the main group at risk.In order to carry out this study, sterile Schirmer strip tests were collected from a group of individuals all of them contact lens wearers who were attending a local ophthalmology clinic in Tenerife, Canary Islands, Spain. The collected samples (100 eyes of 50 patients) were cultured in 2% Non-Nutrient Agar (NNA) plates and positive plates (16) were then cultured in axenic conditions for further analyses. Molecular analysis classified all isolated strains belonged to Acanthamoeba genotype T4 and osmotolerance and thermotolerance assays revealed that all strains were potentially pathogenic. In conclusion, the ocular surface of contact lens wearers included in this study was colonized by potentially pathogenic strains of Acanthamoeba and should be considered as a risk for AK infection in this region and worldwide.

Canine amoebic meningoencephalitis due to Balamuthia mandrillaris

A 1-year-old Siberian Husky dog with acute-onset of seizures, recumbency, paddling, and muscular fasciculations was autopsied. A locally extensive hemorrhagic and malacic focus was noted in the right cerebral frontal cortex, and severe necrotizing and hemorrhagic, neutrophilic meningoencephalitis was diagnosed microscopically. Amoebic trophozoites and cysts were identified within the affected cerebral parenchyma and confirmed by indirect immunofluorescence assay and real-time PCR as Balamuthia mandrillaris. B. mandrillaris is found in soil and water and the infection has been reported in both immunocompromised and immunocompetent humans and rarely in the dog.

Human infections caused by free-living amoebae

[b]Abstract Introduction[/b]. Among free-living amoebae that are widely distributed in nature only four genera/species are known as agents of human infections:[i] Acanthamoeba spp., Naegleriafowleri, Balamuthia mandrillaris[/i] and[i] Sappiniapedata[/i]. These amoebae are not well adapted to parasitism, and could exist in the human environment without the need for a host. Infections due to these amoebae, despite low morbidity, are characterized by relatively high mortality rate and pose serious clinical problems. [b]Objectve[/b]. This review study presents and summarizes current knowledge about infections due to pathogenic and opportunistic free-living amoebae focused on epidemiology, clinical manifestations, diagnosis and treatment based on global literature. [b]State of knowledge[/b]. All four genera have been recognized as etiologic factors of fatal central nervous system infections and other serious diseases in humans. [i]N. fowleri[/i] causes an acute fulminating meningoencephalitis in children and young adults. [i]Acanthamoeba spp[/i]. and [i]B.mandrillaris[/i] are opportunistic pathogens causing granulomatous amoebic encephalitis and disseminated or localized infections which could affect the skin, sinuses, lungs, adrenals and/or bones. [i]Acanthamoeba spp[/i]. is also the main agent of acute eye infection -[i] Acanthamoeba keratitis, [/i]mostly in contact lens wearers. However, there is only one recognized case of encephalitis caused by [i]S. pedata. [/i] [b]Conclusions[/b]. Amoebic diseases are difficult to diagnose which leads to delayed treatment, and result in a high mortality rate. Considering those issues, there is an urgent need to draw more attention to this type of diseases.

A rare case of cutaneous acanthamoebiasis in a renal transplant patient

A 35-year-old woman receiving immunosuppressionfor renal transplantation presented with a onemonthhistory of tender skin nodules on herbilateral upper extremities. A skin biopsy revealedgranulomatous inflammation in the deep dermisand the subcutaneous fat with foci of necrosis.Within the foci of necrosis were large histiocytoidstructures with prominent nuclei. Periodic acid-Schiffstain revealed a round organism with a thick capsule,consistent with amoebal trophozoites. Testing withthe Center for Disease Control revealed the organismto be Acanthamoeba. Despite antimicrobial therapy,the patient continued to develop subcutaneousnodules that extended to the lower extremities andtrunk and ultimately extended to the bone, causingacanthamoebal osteomyelitis. Throughout thehospital course, the patient remained neurologicallyintact without evidence of central nervousinvolvement. A diagnosis of isolated disseminatedcutaneous acanthamoebiasis secondary to iatrogenicimmunosuppression was made. Historically, mostcases of granulomatous amoebic encephalitisand cutaneous acanthamoebiasis have occurredin patients with HIV/AIDS. However, with the useof newer and more effective immunosuppressiveregimens, both are occurring more frequently inthe setting of iatrogenic immunosuppression. Therare and isolated cutaneous nature of this patient'spresentation makes this case unique.

Development of different diagnostic techniques for Endolimax piscium (archamoebae) and their applicability in Solea senegalensis clinical samples

Systemic amoebiasis of sole is caused by Endolimax piscium, a cryptic parasitic archamoeba whose epidemiology and pathogeny are yet unknown. To establish reliable detection methods for this parasite, a battery of molecular diagnostic tools (ISH, PCR and qPCR) were developed and evaluated with a panel of clinical samples from symptomatic diseased fish and from apparently normal animals of different stocks. As there is neither enough background information on the epidemiology of the disease nor a validated reference method, comparison of tests used a composite reference method approach. The ISH technique was the most specific and sensitive in intestine samples and particularly useful as a reference confirmatory method, while the best method in muscle samples was qPCR. Application of the tests to asymptomatic fish demonstrated presence of parasites in a large proportion (>25%) of their intestines, suggesting that this is the point of entry of the amoebae and the initial stage in the development of the disease. The triggering factors that facilitate the breaching of the intestinal barrier by E. piscium, causing granulomatous lesions in other organs and systemic spreading, are not completely understood but our results point to the connective tissue as a preferential target for parasite development and migration.

Disseminated Acanthamoeba Infection Presenting With Cutaneous Lesions in an Immunocompromised Patient: A Case Report, Review of Histomorphologic Findings, and Potential Diagnostic Pitfalls

OBJECTIVES

Free-living amoebas are exceedingly rare causes of cutaneous infections and present unique diagnostic and therapeutic challenges. We describe a case of disseminated acanthamoebiasis with cutaneous manifestations and summarize additional diagnostic, prognostic, and therapeutic highlights.

METHODS

A 58-year-old man with relapsed chronic lymphocytic leukemia had several weeks of progressive, painful ulcerations on the forehead, arms, abdomen, and thighs. A biopsy was performed for histopathologic evaluation.

RESULTS

The biopsy specimen showed inflammatory infiltrate with abscess formation involving the epidermis, dermis, and subcutis. Scattered cells showed nuclei with a prominent central karyosome, dispersed chromatin, and either abundant foamy basophilic cytoplasm or two well-demarcated cytoplasmic walls. Acanthamoeba species was confirmed by polymerase chain reaction from the formalin-fixed, paraffin-embedded tissue.

CONCLUSIONS

Cutaneous lesions from acanthamoebiasis are exceptionally rare but should be included in the differential diagnosis of necrotic cutaneous lesions in immunocompromised patients. Although infrequently encountered, pathologists need to be aware of the morphologic features of free-living amoebas. Immunohistochemical and molecular studies can confirm the diagnosis. Multiagent treatment regimens, when initiated empirically, have been more successful than single-agent regimens, but infections involving the central nervous system are almost universally fatal.

Fatal primary meningoencephalitis caused by Naegleria fowleri

Naegleria fowleri is a free living parasite which habitats in fresh water reservoirs. It causes a fatal nervous system infection known as primary amoebic meningoencephalitis by invading through cribriform plate of nose and gaining entry into brain. We report a case of primary amoebic meningoencephalitis caused by Naegleria fowleri in Karachi, Pakistan, in a 42 years old male poultry farm worker having no history of swimming. Clinical course was fulminant and death occurred within one week of hospital admission. Naegleria fowleri was detected by wet mount technique in the sample of cerebrospinal fluid collected by lumbar puncture of patient. This is a serious problem and requires immediate steps to prevent general population to get affected by this lethal neurological infection.

Scrotal abscess, a rare case of extra intestinal amoebiasis

The majority of amoeba infection are asymptomatic, but clinically intestinal amoebiasis or extra intestinal amoebiasis may result. Genital amoebiasis is very rare manifestation of extra intestial amoebiasis, but a case of amoebic scrotal abscess, seen in Surabaya. The invasive form of Entamoeba histolytica trophozoite was seen in Giemsa stained aspirate of the abscess. In case of an abscess bacteria are primarly considered, but the case presented here shows that amoeba can be the cause, although very rarely. Thus when bacteriological diagnostics are negative amoeba should be considered, especially in case of brown-reddish colored and foul smelling pus.

NAEGLARIA FOWLERI: THE BRAIN EATING AMOEBA OR AN ENIGMA?

Naeglaria fowleri (N. fowleri), popularly known as the brain eating amoeba is the causative agent of the fulminant disease, primary amoebic meningoencephalitis (PAM). Although a rare disease, it is a threat to human health with a case fatality rate ranging from 95-99%. PAM cases have been reported from the United States of America, Australia, Europe and Asia. From 1962 to 2014, 133 people have been infected by N. fowleri in the USA, out of which only three have survived. None of the PAM cases reported in Pakistan so far has survived. This underscores the importance to identify factors, which have led to the failure in decreasing case fatality associated with N. fowleri despite major advances in medical technology, health care; and prevention and control strategies since the first reported case in 1965. We need to focus on eliciting risk factors of the disease prevalent in our part of the world, which are at variance with the developed world. A predominant number. of PAM cases in the West are reported in young males who had participated in recreational activities. However, majority of cases reported in Pakistan are also among young males but they were linked with the religious practice of ablution. What is required to better understand and hence manage this enigma is further research. Further research is to be conducted to discover potent antimicrobials, to test the effectiveness of the new transcribial device in managing PAM, and to identify host factors, which make an individual susceptible to N. fowleri. Investigation of environmental factors related to N. fowleri also needs to be done. Doing so is of paramount importance, as it will help identify the preventive strategies to be employed against N. fowleri.

Amebic meningoencephalitis

As the result of research by many workers, information as to the accurate diagnosis and possibly effective treatment has accumulated. While much more definitive academic investigation will aid in improving the results of medical management, the next objective should be the serious study of patients with suggestive histories and with acute and chronic respiratory ailments for the possible role of free-living amebas therein. The state of the art has reached the point where the two free-living amebic infections can probably be diagnosed by direct examination of exudates from the respiratory tract before the diseases become serious and beyond treatment. At present, the lack of effort to do this is as if one were trying to diagnose amebic dysentery histolytica in the diagnosis of entamebiasis. There is need for increased effort by local health officials, parents, clinicians and laboratory scientists to attempt to prevent the tragic consequences of naegleramebiasis by all possible means, at facilities near the patient's home. While the prospects of effectively handling the problem of acanthamoebiasis are less promising, earlier recognition of it in patients now known likely to develop such an infection might lead to better understanding the approaches to its treatment.

Primary Amoebic Meningoencephalitis

Primary amoebic meningoencephalitis due to free living amoeba, also called 'brain eating amoeba', Naegleria fowleri, was detected in retroviral disease patient of 40 years who has history of using well water. Patient was admitted with severe headache, fever intermittent, nausea, vomiting and slurring of speech. CT scan and MRI scan findings were normal. CSF examination showed increased protein, low sugar and predominant lymphocytes. CSF was negative for cryptococcal antigen but wet mount preparation showed highly motile free living amoeba Naegleria fowleri. Patient was put on Amphotericin B, Metronidazole, Rifampicin in addition to ART and ATT and other supportive medications. His headache was relieved and patient improved and was discharged on request. Earlier eight cases have been reported from India of which four cases survived the acute episode.

Molecular characterization of Acanthamoeba strains isolated from domestic dogs in Tenerife, Canary Islands, Spain

The present study describes two cases of Acanthamoeba infections (keratitis and ascites/peritonitis) in small breed domestic dogs in Tenerife, Canary Islands, Spain. In both cases, amoebic trophozoites were observed under the inverted microscope and isolated from the infected tissues and/or fluids, without detecting the presence of other viral, fungal or bacterial pathogens. Amoebae were isolated using 2 % non-nutrient agar plates and axenified for further biochemical and molecular analyses. Osmotolerance and thermotolerance assays revealed that both isolates were able to grow up to 37 °C and 1 M of mannitol and were thus considered as potentially pathogenic. Moreover, the strains were classified as highly cytotoxic as they cause more than 75 % of toxicity when incubated with two eukaryotic cell lines. In order to classify the strains at the molecular level, the diagnostic fragment 3 (DF3) region of the 18S rDNA of Acanthamoeba was amplified and sequenced, revealing that both isolates belonged to genotype T4. In both cases, owners of the animals did not allow any further studies or follow-up and therefore the current status of these animals is unknown. Furthermore, the isolation of these pathogenic amoebae should raise awareness with the veterinary community locally and worldwide.

[Fatal encephalitis caused by a parasite]

BACKGROUND

Encephalitis caused by a free-living amoeba is relatively rare and usually fatal. This is because the diagnosis is often made late and treatment is difficult.

CASE DESCRIPTION

A 41-year-old patient with a previous history including kidney transplant was admitted with clinical symptoms of encephalitis. Brain imaging showed a number of hypodense regions, which were possibly abscesses. Although an infectious cause seemed probable, even the most extensive antimicrobial treatment was ineffective. The cause was not found until 2 months after the patient's death: infection with Balamuthia mandrillaris. A PCR test was used to detect this amoeba.

CONCLUSION

This case study describes the first patient in the Netherlands to be diagnosed with granulomatous amoebic encephalitis caused by B. mandrillaris. An amoeba may be the cause of encephalitis with either a fulminant course or with a gradual increase of symptoms, without conventional anti-infective therapy being effective.

Twenty years of acanthamoeba diagnostics in Austria

Acanthamoebae are the causative agents of an often seriously progressing keratitis (AK) occurring predominantly in contact lens wearers and can cause several disseminating infections potentially resulting in granulomatous amoebic encephalitis (GAE) in the immunocompromised host. Our institution is the Austrian reference laboratory for Acanthamoeba diagnostics and the aim of this study was to give an overview of proven cases of Acanthamoeba infections in Austria during the past 20 yr. All samples of patients with suspected AK or GAE were screened for Acanthamoeba spp. by culture and/or PCR and the detected amoebae were genotyped. Altogether, 154 cases of AK and three cases of GAE were diagnosed. Age of the AK patients ranged from 8 to 82 yr (mean 37.8) and 58% of the patients were female. Approximately 89% of the AK patients were contact lens wearers, almost all cases were unilateral and 19% of the patients required a keratoplasty. Age of the GAE patients ranged from 2 to 25 yr (mean 14.7), all were HIV-negative, but two were severely immunosuppressed at the time of diagnosis. The predominant genotype in the AK cases was T4, other genotypes found were T3, T5, T6, T10 and T11. The three GAE cases involved genotypes T2, T4 and T5.

[The current view of the diagnosis and management of amebiasis in the light of the authors own case reports]

This comprehensive review is focused on a serious protozoan disease, amebiasis. This disease is caused by the human parasite Entamoeba histolytica (E. histolytica), the second leading cause of mortality due to protozoan disease worldwide (the leading cause is malaria). The incidence of amebiasis in the Czech Republic is very low, but it may be underreported as the disease often escapes diagnosis. Intestinal colonisation by E. histolytica may be asymptomatic. The clinical picture ranges from diarrhea to colitis or fulminant colitis when the parasite progresses to the trophozoite stage. Secondary dissemination in the blood or lymph system may induce systemic signs of the disease. Liver abscess is the most common extraintestinal form of amebiasis. The diagnosis of intestinal amebiasis is based on the clinical picture and parasitological examination of the stool. To diagnose extraintestinal amebiasis, serology tests are used to detect antibodies in the blood. Recently, molecular methods have been increasingly used for the detection of the nucleic acids of the pathogen in biological specimens. The first line therapy for amebiasis are 5-nitroimidazole drugs, currently available in the Czech Republic. However, surgical intervention should also be considered in patients with a severe course of the disease. Included in the review are the case reports of patients with severe concomitant intestinal and extraintestinal amebiasis.