Query: acanthamoeba

title: Acanthamoeba spp. as Agents of Disease in Humans
abstract: Acanthamoeba spp. are free living amebae that inhabit a variety of air, soil, and water environments. However, these amebae can also act as opportunistic as well as nonopportunistic pathogens. They are the causative agents of granulomatous amebic encephalitis and amebic keratitis and have been associated with cutaneous lesions and sinusitis. Immuno compromised individuals, including AIDS patients, are particularly susceptible to infections with Acanthamoeba. The immune defense mechanisms that operate against Acanthamoeba have not been well characterized, but it has been proposed that both innate and acquired immunity play a role. The ameba's life cycle includes an active feeding trophozoite stage and a dormant cyst stage. Trophozoites feed on bacteria, yeast, and algae. However, both trophozoites and cysts can retain viable bacteria and may serve as reservoirs for bacteria with human pathogenic potential. Diagnosis of infection includes direct microscopy of wet mounts of cerebrospinal fluid or stained smears of cerebrospinal fluid sediment, light or electron microscopy of tissues, in vitro cultivation of Acanthamoeba, and histological assessment of frozen or paraffin embedded sections of brain or cutaneous lesion biopsy material. Immunocytochemistry, chemifluorescent dye staining, PCR, and analysis of DNA sequence variation also have been employed for laboratory diagnosis. Treatment of Acanthamoeba infections has met with mixed results. However, chlorhexidine gluconate, alone or in combination with propamidene isethionate, is effective in some patients. Furthermore, effective treatment is complicated since patients may present with underlying disease and Acanthamoeba infection may not be recognized. Since an increase in the number of cases of Acanthamoeba infections has occurred worldwide, these protozoa have become increasingly important as agents of human disease.

title: Acanthamoeba: biology and increasing importance in human health.
abstract: Acanthamoeba is an opportunistic protozoan that is widely distributed in the environment and is well recognized to produce serious human infections, including a blinding keratitis and a fatal encephalitis. This review presents our current understanding of the burden of Acanthamoeba infections on human health, their pathogenesis and pathophysiology, and molecular mechanisms associated with the disease, as well as virulence traits of Acanthamoeba that may be targets for therapeutic interventions and/or the development of preventative measures.

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

title: Pathogenesis of Acanthamoeba infections.
abstract: Acanthamoeba are free living, harmless organisms, however, given the opportunity and the appropriate conditions, they can cause painful, sight threatening as well as fatal infections and, thus, are considered opportunistic pathogens. Acanthamoeba infections have become increasingly important in the past few years due to increasing populations of contact lens users and AIDS patients. The mechanisms associated with the pathogenesis of Acanthamoeba tend to be highly complex, depending on parasite, host and the environmental factors. Elucidation of the biochemical, cellular and molecular basis of the pathogenesis of diseases caused by Acanthamoeba may lead to the development of therapeutic interventions.

title: Acanthamoeba keratitis: the role of domestic tap water contamination in the United Kingdom.
abstract: The incidence of acanthamoeba keratitis (AK) in the UK is some 15 times that in the United States and seven times that in Holland. To investigate reasons for this higher frequency, a study of the role of domestic tap water as a potential source of AK was undertaken.  Tap outlets from the homes of 27 patients with culture proven AK were sampled and cultured for free living amoebae (FLA) For all Acanthamoeba isolates, mitochondrial DNA (mtDNA) restriction fragment length polymorphisms (RFLPs) and cytochrome oxidase (cox 1/2) sequence typing was performed to determine the similarity between corneal and tap water isolates.  FLA, including Acanthamoeba, were isolated from 24 (89% of 27 homes, and the presence within the homes varied significantly with tap water temperature and location: 19 (76% of 25 bathroom sink cold taps sampled compared with 6 (24% of 25 hot and 9 (47% of 19 kitchen cold taps compared with 3 (16% of 19 of hot kitchen taps. Acanthamoeba were isolated from 8 (30% of 27 homes (five bathroom sink cold taps, one cloakroom cold tap, one bath, and one bedroom sink mixer [hot/cold] taps) In six cases, identical Acanthamoeba mtDNA profiles were found for the clinical and home tap water isolates. In keeping with UK plumbing practice, 24 of 27 homes had internal roof water storage tanks to supply domestic taps, but the mains fed the kitchen cold tap.  Water storage tanks promote colonization of domestic water with FLA, including Acanthamoeba, and hence increase the risk of AK. This accounts for the significantly greater incidence of AK in the UK and supports advice to avoid using tap water in contact lens care routines.

title: Phylogenetic evidence for a new genotype of Acanthamoeba (Amoebozoa, Acanthamoebida)
abstract: Acanthamoeba are widespread free living amoebae, able to cause infection in animals, with keratitis and granulomatous encephalitis as major diseases in humans. Recent developments in the subgenus classification are based on the determination of the nucleotide sequence of the 18S rDNA. By this mean, Acanthamoeba have been clustered into 15 sequence types or genotypes, called T1 to T15. In this study, we analysed near full 18S rDNA of an Acanthamoeba recovered from an environmental sample and various unidentified Acanthamoeba sequences retrieved from GenBank. We provided phylogenetic evidence for a new genotype, which we proposed to name T16.

title: Genotyping of Acanthamoeba isolates from clinical and environmental specimens in Iran.
abstract: In this study, 15 Acanthamoeba isolates from AK patients and 10 environmental samples (water, soil and animal origin samples) were classified at the genotype level based on the sequence analysis of the Diagnostic Fragment 3 (DF3) of Acanthamoeba small subunit rRNA gene. The obtained results revealed that most of these Acanthamoeba strains belonged to genotype T4 both in clinical and environmental samples. The presence T11 genotype in clinical samples was also revealed after the genotyping analysis and to our knowledge this is the first report of T11 genotype in Iran. Moreover, the isolation of T4 genotype from cow faeces in this study highlights a possible transmission of Acanthamoeba through animal faeces in Iran. Overall, the widespread distribution of pathogenic Acanthamoeba T4 across the environmental sources and the increasing number of contact lens wearers in Iran, demands more awareness within the public and health professionals as this pathogen is emerging as a risk for human health in Iran and worldwide.

title: The Occurrence Acanthamoeba (Free Living Amoeba) in Environmental and Respiratory Samples in Poland
abstract: Free living amoebae are amphizoic organisms living in soil, air, fresh and sea water. Species belonging to the genera Acanthamoeba, Naegleria and Balamuthia are human parasites, which may invade the central nervous system, lungs, adrenal glands, skin, eyes and lower jaw. In this paper, we examine the occurrence of potentially virulent strains of amoebae in water bodies of the West Pomeranian and Lubuskie voivodeships (north western Poland) and in biological material from patients with symptoms of pneumonia. We examined 45 natural water bodies (lakes, ponds, rivers, seas and lagoons) 39 artificial water bodies (swimming pools, firefighting and reservoirs fountains) and the water supply system in the city of Szczecin, and collected altogether 216 samples. We also examined biological material from 130 immunocompromised patients with atypical symptoms of pneumonia. From the collected environmental samples we isolated 110 strains of amoebae from the amphizoic group, 24 of which were thermophilic. Based on the morphological attributes of trophozoites and cysts, all the isolates were classified to the genus Acanthamoeba. Amoebae from the genus Acanthamoeba were also isolated from biological samples from patients with symptoms of pneumonia with secondary immune deficiencies. The presence of amoebae was determined in 2 samples of bronchoaspirate fluid taken from patients after chemotherapy and in 2 samples of bronchoalveolar lavage from patients with respiratory insufficiency. Molecular identification of the amoeabe isolated from biological samples confirmed their affinity to Acanthamoeaba genus, two of them classified as T4 genotypes. The two other sequences could not be classified to any known Acanthamoeba genotype. Thus there is a need for further investigation to establish Acanthamoeba genotype in biological material from patients with immunosuppression and pneumonia symptoms.

title: National Outbreak of Acanthamoeba Keratitis Associated with Use of a Contact Lens Solution, United States
abstract: Premarket standardized testing for Acanthamoeba spp. is warranted.

title: Patient characteristics, diagnosis, and treatment of non contact lens related Acanthamoeba keratitis
abstract: To review the clinical characteristics, diagnosis, and visual outcome in patients with non contact lens related Acanthamoebakeratitis and compare the findings with reported series of contact lens associated Acanthamoeba keratitis.  Medical and microbiology records of 39 consecutive patients with a diagnosis ofAcanthamoeba keratitis, at a tertiary eyecare centre in India between January 1996 and June 1998, were analysed retrospectively.  A majority of the patients presented with poor visual acuity and large corneal stromal infiltrates (mean size 38.20 (SD 26.18) mm) A predisposing factor was elicited in 19/39 (48.7% patients (trauma 15, dirty water splash three, leaf juice one) None of the patients had worn contact lenses. Most patients (26/39 (66.6% came from a low socioeconomic background. Complaint of severe pain was not a significant feature and radial keratoneuritis was seen in 1/39 (2.5% patients. A ring infiltrate was present in 41.1% of cases. A clinical diagnosis of fungal keratitis was made in 45% of the patients before they were seen by us. However, all patients were diagnosed microbiologically at our institute based on demonstration ofAcanthamoeba cysts in corneal scrapings (34/39) and/or culture of Acanthamoeba(34/39) Treatment with biguanides (PHMB, 15/38 (39.4% PHMB with CHx, 23/38 (60.5% one patient did not return for treatment) resulted in healing with scar formation in 27 out of 31(87.0% followed up patients (mean time to healing 106.9 days) Overall visual outcome was poor with no statistical difference between cases diagnosed within 30 days (early) or 30 days after (late) start of symptoms. The visual outcome in cases requiring tissue adhesive (five) and keratoplasty (three) was also poor.  This is thought to be the largest series of cases ofAcanthamoeba keratitis in non contact lens wearers. In such cases, the disease is advanced at presentation in most patients, pathognomonic clinical features are often not seen, disease progression is rapid, and visual outcome is usually poor. Possible existence of Acanthamoeba pathotypes specifically associated with non contact lens keratitis and unique to certain geographical areas is suggested.