Diagnostic challenges in Balamuthia mandrillaris infections

Balamuthia spinosa n. sp. (Amoebozoa, Discosea) from the brackish-water sediments of Nivå Bay (Baltic Sea, The Sound) - a novel potential vector of Legionella pneumophila in the environment

We have found a new free-living amoeba species named Balamuthia spinosa n. sp. (Amoebozoa, Discosea) in the bottom sediments of the brackish-water Nivå Bay (Baltic Sea, The Sound). This species resembles members of the genus Stygamoeba morphologically and was (mis)identified as belonging to this genus during the initial investigation. However, SSU rRNA gene data show that it robustly groups with Balamuthia mandrillaris sequence among Acanthopodida and represents a new species of the genus Balamuthia. Fragments of Legionella pneumophila genome were found among the NGS contigs obtained from B. spinosa n. sp., suggesting that this species may be a vector of Legionella in the environment. We discuss a remarkable morphological and ultrastructural similarity between the genus Balamuthia and the genus Stygamoeba. In addition, our phylogenetic analysis based on the SSU rRNA gene sequences revealed a close relationship between the genera Stygamoeba and Vermistella. It is one more confirmation of the order Stygamoebida, which was formed basing on the morphological evidence. The position of these branches close to Thecamoebida clade is congruent with current phylogenomic data.

Detection of Naegleria fowleri, Acanthamoeba spp, and Balamuthia mandrillaris in Formalin-Fixed, Paraffin-Embedded Tissues by Real-Time Multiplex Polymerase Chain Reaction

OBJECTIVES

Pathogenic free-living amebae (FLAs) cause skin, ocular, and central nervous system (CNS) infections with significant morbidity and mortality. Diagnosis of FLA infections by pathologic examination of tissue sections can be aided using molecular assays. This study investigated the performance characteristics of a multiplex real-time polymerase chain reaction (PCR) assay (FLA-PCR) for detection and differentiation of FLAs in clinical specimens.

METHODS

FLA-PCR was performed on 39 human specimens comprising one cutaneous, 14 corneal, and 24 CNS formalin-fixed, paraffin-embedded (FFPE) tissues with a histopathologic diagnosis of FLA infection and four CNS FFPE tissues with inflammation but no evidence of FLAs. In addition, clinical specificity and assay limit of detection were determined.

RESULTS

FLA detection sensitivities ranged from 79% to 84% in FFPE tissues. No cross-reactivity was observed.

CONCLUSIONS

While sensitivity is limited, FLA-PCR assay may serve as a useful adjunct for detection or confirmation of FLA infections in FFPE tissues.

Detection of serum antibodies in children and adolescents against Balamuthia mandrillaris, Naegleria fowleri and Acanthamoeba T4

The presence of free-living amoebae of the genera Naegleria, Acanthamoeba and Balamuthia, which contain pathogenic species for humans and animals, has been demonstrated several times and in different natural aquatic environments in the northwest of Mexico. With the aim of continuing the addition of knowledge about immunology of pathogenic free-living amoebae, 118 sera from children and adolescents, living in three villages, were studied. Humoral IgG response against B. mandrillaris, N. fowleri and Acanthamoeba sp. genotype T4, was analyzed in duplicate to titers 1: 100 and 1: 500 by enzyme-linked immunosorbent assay (ELISA). Children and adolescents ages ranged between 5 and 16 years old, with a mean of 9 years old, 55% males. All tested sera were positive for the 1: 100 dilution, and in the results obtained with the 1: 500 dilution, 116 of 118 (98.3%) were seropositive for N. fowleri, 101 of 118 (85.6%) were seropositive for Acanthamoeba sp. genotype T4, and 43 of 118 (36.4%) were seropositive for B. mandrillaris. The statistical analysis showed different distributions among the three communities and for the three species of pathogenic free-living amoebae, including age. Lysed and complete cells used as Balamuthia antigens gave differences in seropositivity.

Isolation of Balamuthia mandrillaris from soil samples in North-Western Iran

Balamuthia mandrillaris is an opportunistic free-living amoebae (FLA) which has been reported as the causative agent of the fatal Balamuthia amoebic encephalitis (BAE). Currently, the transmission dynamics of this pathogen remain poorly understood although the organism has been associated with soils, and thus, soil exposure has been identified as a risk factor for this pathogenic amoeba. Nevertheless, environmental isolation of B. mandrillaris is a rare event and strains of this amoebic species have been isolated from soil and dust sources only in seven previous reports (Iran, Mexico, USA, Peru, Costa Rica, Guinea Bissau, and Jamaica). In Iran, a previous study reported the isolation of B. mandrillaris from dust collected in the city of Tehran and free of known infectious involvement. Therefore, in this work, 55 soil samples collected from public and recreational areas of East Azerbaijan, North-Western Iran, were investigated for the presence of this pathogen. Samples were cultured in 2% non-nutrient agar plates and were monitored for the presence of B. mandrillaris-like trophozoites and/or cysts. Those samples that were positive for these amoebae by microscopic criteria were then confirmed by PCR amplification and DNA sequencing of the mitochondrial 16S ribosomal DNA (rDNA) of B. mandrillaris. The obtained results revealed the presence of this emerging pathogen in 5 of 55 samples included in the study. Homology analysis of the obtained DNA sequences revealed high similarity with previously isolated strains from clinical and environmental sources. To the best of our knowledge, this is the first report on the isolation of B. mandrillaris from soil sources in Iran related to human activity and the second time that this pathogen is isolated from the environment in this country.

Emergence of Balamuthia mandrillaris meningoencephalitis in India

We report two cases of fatal chronic meningoencephalitis caused by Balamuthia mandrillaris in immunocompetent men. Diagnosis of amoebic meningoencephalitis was made ante-mortem in one case and postmortem in another by histopathological examination and confirmed by demonstration of B. mandrillaris deoxyribonucleic acid (DNA) by polymerase chain reaction (PCR).

Management of granulomatous amebic encephalitis: Laboratory diagnosis and treatment

Granulomatous amebic encephalitis is a life-threatening central nervous system (CNS) infection caused by the free-living amoebae Acanthamoeba spp., Balamuthia mandrillaris and Sappinia pedata. The disease has a subacute to chronic onset affecting commonly the immunocompromised population with high mortality rate. The diagnosis of this disease entity requires high suspicion with appropriate sample collection and testing by the laboratory experts. Radiological investigations are nonspecific and commonly confused with CNS tuberculosis, neurocysticercosis, disseminated encephalomyelitis, viral encephalitis etc., delaying the accurate diagnosis of these cases. Early diagnosis plays a crucial role in the survival of these cases since appropriate management can be initiated. No single drug is effective; hence multiple antibiotics targeting various proteins or receptors are required for successful treatment. A combination of surgical and medical interventions involving multiple specialty experts is required to prevent death and morbidity in survivors.

An autopsy case of Balamuthia mandrillaris amoebic encephalitis, a rare emerging infectious disease, with a brief review of the cases reported in Japan

Balamuthia mandrillaris is an amoeba found in fresh water and soil that causes granulomatous amoebic encephalitis. We report herein an autopsy case of B. mandrillaris amoebic encephalitis, which was definitely diagnosed by PCR. An 81-year-old man, who had Sjögren's syndrome, manifested drowsiness 2 months before his death with progressive deterioration. Neuroimaging demonstrated foci of T2- and fluid-attenuated inversion recovery high and T1 low-intensity with irregular post-contrast ring enhancement in the cerebral hemisphere, thalamus and midbrain. Pathologically, multiple hemorrhagic and necrotic lesions were found in the cerebrum, thalamus, midbrain, pons, medulla and cerebellum, which were characterized by liquefactive necrosis, marked edema, hemorrhage and necrotizing vasculitis associated with the perivascular accumulation of amoebic trophozoites, a few cysts, and the infiltration of numerous neutrophils and microglia/macrophages. The trophozoites were ovoid or round, 10-60 μm in diameter, and they showed foamy cytoplasm and a round nucleus with small karyosome in the center. The PCR and immunohistochemistry from paraffin-embedded brain specimens revealed angioinvasive encephalitis due to B. mandrillaris. Human cases of B. mandrillaris brain infection are rare in Japan, with only a few brief reports in the literature.

Fatal Granulomatous Amebic Encephalitis Due to Balamuthia mandrillaris in New Mexico: A Case Report

Balamuthia mandrillaris is a free-living amoeba that can cause granulomatous amebic encephalitis (GAE). We report a case in an individual with a history of alcohol abuse, cocaine use, and ditch water exposure. This is the first reported case of GAE due to B mandrillaris in New Mexico.

The isolation of Balamuthia mandrillaris from environmental sources from Peru

Balamuthia mandrillaris is an opportunistic free-living amoeba that has been reported to cause skin lesions and the fatal Balamuthia amoebic encephalitis (BAE) in humans and other animals. Currently, around 200 human BAE cases have been reported worldwide, although this number is considered to be underestimated. The highest number of BAE cases has been reported in the American continent, mainly in the southwest of the USA. Peru seems to be another hotspot for BAE with around 55 human cases having been identified, usually involving cutaneous infection, especially lesions in the central face area. The isolation of Balamuthia from environmental sources has been reported on only three prior occasions, twice from Californian soils and once from dust in Iran and so it seems that this amoeba is relatively rarely encountered in samples from the environment. We investigated that possibility of finding the amoebae in soil samples from different regions where clinical cases have been reported in Peru. Twenty-one samples were cultured in non-nutrient agar plates and were checked for the presence of B. mandrillaris-like trophozoites and/or cysts. Those samples that were positive for these amoebae by microscopic criteria were then confirmed by PCR amplification and DNA sequencing of the mitochondrial 16S rDNA gene of B. mandrillaris. We have detected the presence of B. mandrillaris in four samples collected in the regions of Piura (3) and Lima (1) where infection cases have been previously reported. We hypothesize that B. mandrillaris is present in Peru in soil and dust which therefore constitutes a source of the infection for the BAE cases previously reported in this country. Further studies should be carried out in the area to confirm the generality of this finding.