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Clinical & Experimental Ophthalmology Jul 2022Globally, infectious keratitis is the fifth leading cause of blindness. The main predisposing factors include contact lens wear, ocular injury and ocular surface... (Review)
Review
Globally, infectious keratitis is the fifth leading cause of blindness. The main predisposing factors include contact lens wear, ocular injury and ocular surface disease. Staphylococcus species, Pseudomonas aeruginosa, Fusarium species, Candida species and Acanthamoeba species are the most common causal organisms. Culture of corneal scrapes is the preferred initial test to identify the culprit organism. Polymerase chain reaction (PCR) tests and in vivo confocal microscopy can complement the diagnosis. Empiric therapy is typically commenced with fluoroquinolones, or fortified antibiotics for bacterial keratitis; topical natamycin for fungal keratitis; and polyhexamethylene biguanide or chlorhexidine for acanthamoeba keratitis. Herpes simplex keratitis is mainly diagnosed clinically; however, PCR can also be used to confirm the initial diagnosis and in atypical cases. Antivirals and topical corticosteroids are indicated depending on the corneal layer infected. Vision impairment, blindness and even loss of the eye can occur with a delay in diagnosis and inappropriate antimicrobial therapy.
Topics: Acanthamoeba; Acanthamoeba Keratitis; Blindness; Corneal Ulcer; Eye Infections, Fungal; Humans
PubMed: 35610943
DOI: 10.1111/ceo.14113 -
Frontiers in Microbiology 2023is an opportunistic protozoa, which exists widely in nature and is mainly distributed in soil and water. usually exists in two forms, trophozoites and cysts. The... (Review)
Review
is an opportunistic protozoa, which exists widely in nature and is mainly distributed in soil and water. usually exists in two forms, trophozoites and cysts. The trophozoite stage is one of growth and reproduction while the cyst stage is characterized by cellular quiescence, commonly resulting in human infection, and the lack of effective monotherapy after initial infection leads to chronic disease. can infect several human body tissues such as the skin, cornea, conjunctiva, respiratory tract, and reproductive tract, especially when the tissue barriers are damaged. Furthermore, serious infections can cause keratitis, granulomatous amoebic encephalitis, skin, and lung infections. With an increasing number of infections in recent years, the pathogenicity of is becoming more relevant to mainstream clinical care. This review article will describe the etiological characteristics of infection in detail from the aspects of biological characteristic, classification, disease, and pathogenic mechanism in order to provide scientific basis for the diagnosis, treatment, and prevention of infection.
PubMed: 37089530
DOI: 10.3389/fmicb.2023.1147077 -
Parasitology Research Dec 2023The members of genus Acanthamoeba are the etiological agent of uncommon but severe or even fatal opportunistic infections in human beings. The presence of different... (Review)
Review
The members of genus Acanthamoeba are the etiological agent of uncommon but severe or even fatal opportunistic infections in human beings. The presence of different classes of intracellular and extracellular proteases including serine proteases, cysteine proteases, and metalloproteases has been well documented in environmental and clinical isolates of Acanthamoeba spp. However, the role of the proteolytic enzymes in physiological, biological, and pathological mechanisms of the amoeba remains partially investigated. Some attempts have been conducted using various methods to determine the profile of proteases (number, class, optimal conditions, and activity of the enzymes), and possible pathogenicity mechanism of the proteolytic enzymes (various protein substrate degradation, cytopathic effect on different cell lines). In some cases, it was attempted to correlate intracellular and extracellular protease profile with pathogenicity potential of strains. This review revealed that the protease profile of different strains of Acanthamoeba was extremely complex, therefore, further comprehensive studies with application of a combination of various methods may help to elucidate the role of the enzymes.
Topics: Humans; Acanthamoeba; Serine Proteases; Serine Endopeptidases; Acanthamoeba Keratitis; Cell Line
PubMed: 38063887
DOI: 10.1007/s00436-023-08059-z -
Cornea Aug 2019
Topics: Acanthamoeba; Acanthamoeba Keratitis; Cysts; Humans; Microscopy, Confocal
PubMed: 31058658
DOI: 10.1097/ICO.0000000000001988 -
Journal of Neurovirology Dec 2022The report of death of a person from amebic meningoencephalitis, the proverbial "brain-eating ameba," Naegleria fowleri, acquired in a state park lake in Iowa in July... (Review)
Review
The report of death of a person from amebic meningoencephalitis, the proverbial "brain-eating ameba," Naegleria fowleri, acquired in a state park lake in Iowa in July 2022 has once again raised the seasonal alarms about this pathogen. While exceptionally rare, its nearly universal fatality rate has panicked the public and made for good copy for the news media. This review will address free-living ameba that have been identified as causing CNS invasion in man, namely, Naegleria fowleri, Acanthamoeba species, Balamuthia mandrillaris, and Sappinia diploidea (Table 1). Of note, several Acanthamoeba spp. and Balamuthia mandrillaris may also be associated with localized extra-CNS infections in individuals who are immunocompetent and disseminated disease in immunocompromised hosts. These ameba are unique from other protozoa in that they are free-living, have no known insect vector, do not result in a human carrier state, and are typically unassociated with poor sanitation. Table 1 Free-living ameba that have been identified as causing CNS invasion in man, namely, Naegleria fowleri, Acanthamoeba species, Balamuthia mandrillaris, and Sappinia diploidea Entity Pathogenic ameba Predisposing disorders Portal of entry Incubation period Clinical features Radiographic findings CSF finding Diagnostic measures Primary amebic meningoencephalitis Naegleria fowleri; N. australiensis; N. italica Previously healthy children or young adults Olfactory epithelium 2-14 days (average 5 days) Headache, fever, altered mental status, meningeal signs; seizures Brain edema; meningeal enhancement; hydrocephalus; basal ganglia infarctions Increased opening pressure; neutrophilic pleocytosis (~ 1000 cells/cu mm); low glucose Brain biopsy, CSF wet prep, IIF culture or PCR Granulomatous amebic encephalitis Acanthamoeba spp.; Balamuthia mandrillaris; Sappinia diploidea Typically, immunocompromised individual Skin sinuses; olfactory epithelium respiratory tract Weeks to months Headache; altered mental status seizures, focal neurological findings Focal parenchymal lesions with edema; hemorrhagic infarctions; meningeal enhancement Generally, LP contraindicated; when performed lymphocytic pleocytosis; increased protein; low glucose Brain biopsy, CSF culture, wet prep, IIF, or PCR IIF indirect immunofluorescence, LP lumbar puncture, PCR polymerase chain reaction.
Topics: Child; Humans; Leukocytosis; Amebiasis; Amoeba; Acanthamoeba; Naegleria fowleri; Central Nervous System; Headache; Infarction; Glucose
PubMed: 36098909
DOI: 10.1007/s13365-022-01096-x -
Journal of Clinical Microbiology Jan 2022Infections caused by Naegleria fowleri, Acanthamoeba spp., and Balamuthia mandrillaris result in a variety of clinical manifestations in humans. These amoebae are found...
Infections caused by Naegleria fowleri, Acanthamoeba spp., and Balamuthia mandrillaris result in a variety of clinical manifestations in humans. These amoebae are found in water and soil worldwide. spp. and B. mandrillaris cause granulomatous amoebic encephalitis (GAE), which usually presents as a mass, while N. fowleri causes primary amoebic meningoencephalitis (PAM). spp. can also cause keratitis, and both spp. and can cause lesions in skin and respiratory mucosa. These amoebae can be difficult to diagnose clinically as these infections are rare and, if not suspected, can be misdiagnosed with other more common diseases. Microscopy continues to be the key first step in diagnosis, but the amoeba can be confused with macrophages or other infectious agents if an expert in infectious disease pathology or clinical microbiology is not consulted. Although molecular methods can be helpful in establishing the diagnosis, these are only available in referral centers. Treatment requires combination of antibiotics and antifungals and, even with prompt diagnosis and treatment, the mortality for neurological disease is extremely high.
Topics: Acanthamoeba; Amebiasis; Amoeba; Balamuthia mandrillaris; Humans; Naegleria fowleri
PubMed: 34133896
DOI: 10.1128/JCM.00228-21 -
Experimental Eye Research Jan 2021Acanthamoeba keratitis (AK) is a rare protozoal infection of the cornea. At least eight species of Acanthamoeba are known to cause this sight-threatening disease of the... (Review)
Review
Acanthamoeba keratitis (AK) is a rare protozoal infection of the cornea. At least eight species of Acanthamoeba are known to cause this sight-threatening disease of the ocular surface. Acanthamoeba spp. exist in a wide array of niches ranging from thermal springs to under ice and every conceivable habitat in between. Contact lens wear is the leading risk factor for AK and is practiced by over 30 million individuals in the United States, yet the incidence of AK is less than 33 cases per one million contact lens wearers. Serological studies have reported that 90%-100% of individuals with no history of AK possess antibodies specific for Acanthamoeba antigens indicating that exposure to this organism is commonplace, yet disease is remarkably rare. Animal studies have shed light on the pathobiology and immunobiology of AK and indicate that a constellation of factors including the ocular surface microbiome and the microbiome of Acanthamoeba itself contribute to the pathogenesis of AK. Interesting, secretory antibodies produced by the adaptive immune response can prevent the initiation of corneal infection, but once Acanthamoeba trophozoites breach the corneal epithelium the adaptive immune system is helpless in altering the course of AK. It has been almost 50 years since AK was first described, yet many questions remain unanswered about this curious and enigmatic disease of the ocular surface.
Topics: Acanthamoeba; Acanthamoeba Keratitis; Animals; Antibodies, Protozoan; Contact Lenses; Cornea; Eye Infections, Parasitic; Humans; Risk Factors
PubMed: 33221372
DOI: 10.1016/j.exer.2020.108365 -
International Microbiology : the... Aug 2021Acanthamoeba keratitis is a sight-endangering eye infection, and causative organism Acanthamoeba presents a significant concern to public health, given escalation of...
Acanthamoeba keratitis is a sight-endangering eye infection, and causative organism Acanthamoeba presents a significant concern to public health, given escalation of contact lens wearers. Contemporary therapy is burdensome, necessitating prompt diagnosis and aggressive treatment. None of the contact lens disinfectants (local and international) can eradicate Acanthamoeba effectively. Using a range of compounds targeting cellulose, ion channels, and biochemical pathways, we employed bioassay-guided testing to determine their anti-amoebic effects. The results indicated that acarbose, indaziflam, terbuthylazine, glimepiride, inositol, vildagliptin and repaglinide showed anti-amoebic effects. Compounds showed minimal toxicity on human cells. Therefore, effects of the evaluated compounds after conjugation with nanoparticles should certainly be the subject of future studies and will likely lead to promising leads for potential applications.
Topics: Acanthamoeba Keratitis; Acanthamoeba castellanii; Acarbose; Antiprotozoal Agents; Carbamates; Cell Line; Contact Lens Solutions; Contact Lenses; HaCaT Cells; Humans; Indenes; Inositol; Nanoparticles; Piperidines; Sulfonylurea Compounds; Triazines; Vildagliptin
PubMed: 33754231
DOI: 10.1007/s10123-021-00171-3 -
Journal of Basic Microbiology Apr 2024Free-living amoebae of the genus Acanthamoeba are infected by various bacteria in nature, and thus bacteria can protect themselves from adverse environmental conditions....
Free-living amoebae of the genus Acanthamoeba are infected by various bacteria in nature, and thus bacteria can protect themselves from adverse environmental conditions. Contrary to this ameba-bacteria relationship whether Acanthamoeba has antibacterial effects on bacteria is the different aspect of the relationship between these microorganisms. In this study, we investigate various Acanthamoeba strains have antibacterial effects on various Staphylococcus strains. Three environmental Acanthamoeba strains, isolated from various aquatic environments in Turkey, and Acanthamoeba castellanii ATCC 50373 standard strains were used in the study. The antistaphylococcal effect of cell-free supernatant (CFS) obtained from these amoebae against 12 different Staphylococcus bacteria was investigated by colony counting method. In addition, the pathogenicity of the tested Acanthamoeba strains was determined using osmotolerance and thermotolerance tests. CFSs obtained from Acanthamoeba were found to have varying degrees of antistaphylococcal effects on various Staphylococcus strains (0%-100%). It was determined that the CFS of the standard Acanthamoeba strain showed 100% inhibitory effect against one clinical methicillin-resistant Staphylococcus aureus strain (M2). Also, CFS of Ugöl strain showed 99.97% inhibitory effect against one clinical methicillin-sensitive Staphylococcus epidermidis strain (L3). It was determined that all Acanthamoeba isolates had no pathogenic potential. According to the results, it has been observed that Acanthamoeba produces antibacterial substance(s) against Staphylococcus bacteria and that the ameba-bacteria relationship may also result in the detriment of the bacteria. Furthermore, the current study indicates that new and natural antimicrobial agents from Acanthamoeba can be used as an alternative to infections caused by Staphylococcus.
Topics: Staphylococcus; Methicillin-Resistant Staphylococcus aureus; Acanthamoeba castellanii; Anti-Infective Agents; Anti-Bacterial Agents; Bacteria
PubMed: 38416601
DOI: 10.1002/jobm.202300551 -
International Journal of Molecular... Jan 2021Free-living amoebas, including spp., are widely distributed in soil, water, and air. They are capable of causing granulomatous amebic encephalitis, pneumonia,... (Review)
Review
Free-living amoebas, including spp., are widely distributed in soil, water, and air. They are capable of causing granulomatous amebic encephalitis, pneumonia, keratitis, and disseminated acanthamoebiasis. Despite low occurrence worldwide, the mortality rate of spp. infections is very high, especially in immunosuppressed hosts. infections are a medical problem, owing to limited improvement in diagnostics and treatment, which is associated with incomplete knowledge of pathophysiology, pathogenesis, and the host immune response against spp. infection. The aim of this review is to present the biochemical and molecular mechanisms of spp.-host interactions, including the expression of Toll-like receptors, mechanisms of an immune response, the activity of metalloproteinases, the secretion of antioxidant enzymes, and the expression and activity of cyclooxygenases. We show the relationship between spp. and the host at the cellular level and host defense reactions that lead to changes in the selected host's organs.
Topics: Acanthamoeba; Amebiasis; Brain; Humans; Immunity; Immunocompromised Host; Lung; Toll-Like Receptors
PubMed: 33514026
DOI: 10.3390/ijms22031261