Amoebic gill disease increases energy requirements and decreases hypoxia tolerance in Atlantic salmon (Salmo salar) smolts

Globally, Atlantic salmon (Salmo salar Linnaeus) aquaculture is now routinely affected by amoebic gill disease (AGD; Neoparamoeba perurans). The disease proliferates throughout the summer and is implicated in decreasing tolerance of salmon to environmental perturbations, yet little empirical evidence exists to support these observations. Using salmon acclimated to 15 or 19 °C, our aim was to determine the effects of clinically light-moderate (industry-relevant) AGD on metabolism (ṀO_2rest and ṀO_2max), aerobic scope (ṀO_2max - ṀO_2rest), excess post-exercise oxygen consumption (EPOC), and hypoxia tolerance. An increase in ṀO_2rest (~8% and ~ 13% increase within the 15 and 19 °C acclimation groups, respectively) with increasing disease signs demonstrated an increase in baseline energy requirements as the disease progressed. Conversely, ṀO_2max remained stable at both temperatures (~364 mg O₂ kg^-1 h^-1), resulting in a decline in aerobic scope by 13 and 19% in the 15 and 19 °C groups, respectively. There was evidence of a decrease in hypoxia tolerance as the dissolved oxygen concentrations at loss of equilibrium increased by ~8% with more severe lesion coverage of the gills. These results suggest an increase in basal energy requirements and reduction in hypoxia tolerance as AGD proliferates, lending support to the idea that AGD reduces environmental tolerance. However, the lack of an effect of acclimation temperature indicates that the temperature-disease interaction may be more complicated than currently thought.

Immersion challenge of naïve Atlantic salmon with cultured Nolandella sp. and Pseudoparamoeba sp. did not increase the severity of Neoparamoeba perurans-induced amoebic gill disease (AGD)

Amoebic gill disease (AGD) is one of the main health issues impacting farmed Atlantic salmon. Neoparamoeba perurans causes AGD; however, a diversity of other amoeba species colonizes the gills and there is little understanding of whether they are commensal or potentially involved in different stages of gill disease development. Here, we conduct in vivo challenges of naïve Atlantic salmon with cultured Nolandella sp. and Pseudoparamoeba sp. to investigate their pathogenicity to Atlantic salmon gills. Additionally, we assessed whether the presence of Nolandella sp. and Pseudoparamoeba sp. influences the onset and/or severity of N. perurans-induced AGD. All three strains attached and multiplied on the gills according to qPCR analysis. Furthermore, minor gross gill lesions and histological changes were observed post-exposure. While N. perurans was found associated with classical AGD lesions, Nolandella sp. and Pseudoparamoeba sp. were not found associated with lesion sites and these lesions did not meet the expected composite of histopathological changes for AGD. Moreover, the presence of these non-N. perurans species did not significantly increase the severity of AGD. This trial provides evidence that cultured Nolandella sp. and Pseudoparamoeba sp. do not induce AGD and do not influence the severity of AGD during the early stages of development.

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.

Primary amoebic meningoencephalitis caused by Naegleria fowleri: an old enemy presenting new challenges

First discovered in 1899, Naegleria fowleri is a protist pathogen, known to infect the central nervous system and produce primary amoebic meningoencephalitis. The most distressing aspect is that the fatality rate has remained more than 95%, despite our advances in antimicrobial chemotherapy and supportive care. Although rare worldwide, most cases have been reported in the United States, Australia, and Europe (France). A large number of cases in developing countries go unnoticed. In particular, religious, recreational, and cultural practices such as ritual ablution and/or purifications, Ayurveda, and the use of neti pots for nasal irrigation can contribute to this devastating infection. With increasing water scarcity and public reliance on water storage, here we debate the need for increased awareness of primary amoebic meningoencephalitis and the associated risk factors, particularly in developing countries.

Balamuthia mandrillaris meningoencephalitis associated with solid organ transplantation--review of cases

We report the first identified transmission of Balamuthia mandrillaris through solid organ transplantation. Kidneys were transplanted from a donor with presumptive diagnosis of autoimmune encephalitis. Shortly after, the recipients developed neurologic symptoms. Magnetic Resonance Imaging of the brain from the donor and both kidney recipients demonstrated multiple ring enhancing lesions with surrounding edema and adjacent leptomeningeal extension. In addition most of the lesions demonstrated signal changes suggesting central hemorrhagic foci. Specimens were tested locally and at the Centers for Disease Control and Prevention. Histopathology revealed B. mandrillaris in either brain tissue and/or cerebral spinal fluid in the donor and recipients.

[A case of pulmonary amebiasis]

A 57-year-old man was admitted to our hospital because of dyspnea and right abdominal pain. Chest X-ray radiogram showed right massive pleural effusion. Ultrasonic echogram of abdomen showed a unilocular liver cyst. He was treated with intravenous infusion of meropenem, and percutaneous pleural and liver drainage were performed. At the time of drainage, we injected contrast medium into the liver cyst and confirmed a fistula connecting to the right pleural space. Initially we made a diagnosis of bacterial empyema and liver abscess, yet there was no response to the initial treatment. Cultures of pleural effusion and liver abscess were confirmed to be negative. A few days after admission, the patient stated that he was a homosexual. Liver amebiasis and its perforation became the most likely diagnosis, and metronidazole was administered. On admission day 21, tests for anti-amebic antibody were positive. Finally he fully recovered. We must be aware of the rare pulmonary manifestation of amebiasis. We report this case and review the literature.

Free-living, amphizoic and opportunistic amebas

Amebas belonging to the genera Naegleria, Acanthamoeba and Balamuthia are free-living, amphizoic and opportunistic protozoa that are ubiquitous in nature. These amebas are found in soil, water and air samples from all over the world. Human infection due to these amebas involving brain, skin, lung and eyes has increased significantly during the last 10 years. The epidemiology, immunology, protozoology, pathology, and clinical features of the infections produced by these protozoa differ strikingly. Infection by the pathogenic Naegleria fowleri is acquired by exposure to polluted water in ponds, swimming pools and man-made lakes. Raised temperatures during the hot summer months or warm water from power plants facilitate the growth of N. fowleri. N. fowleri is a thermophilic ameba that grows well in tropical and subtropical climates. The CNS infection, called Primary Amebic Meningoencephalitis (PAM), produced by N. fowleri is characterized by an acute fulminant meningoencephalitis leading to death 3-7 days after exposure. Victims are healthy, young individuals with a history of recent water-related sport activities. The portal of entry is the olfactory neuroepithelium. The pathologic changes are an acute hemorrhagic necrotizing meningoencephalitis with modest purulent exudate, mainly at the base of the brain, brain-stem and cerebellum. Trophozoites can be seen within the CNS lesions located mainly around blood vessels. Thus far 179 cases have been reported; 81 in the USA alone. Balamuthia mandrillaris and several species of Acanthamoeba are pathogenic "opportunistic" free-living amebas which cause Granulomatous Amebic Encephalitis (GAE) in humans and animals. GAE is an infection, usually seen in debilitated, malnourished individuals, in patients undergoing immunosuppressive therapy for organ transplants and in Acquired Immunodeficiency Syndrome (AIDS). The granulomatous component is negligible, particularly in immunocompromised individuals. Pathologically these amebas produce a patchy, chronic or subacute granulomatous encephalitis with the presence of trophozoites and cysts. The portal of entry is probably through the respiratory tract or an ulceration of the skin reaching the CNS by hematogenous spread. As of October 1, 1996, 166 cases (103 due to Acanthamoeba and 63 due to Balamuthia) of GAE have been reported from around the world. Of these 103 cases due to Acanthamoeba (72 have been reported in the USA alone, > 50 in AIDS). It is well known that several species of Acanthamoeba can also produce, chronic sight threatening ulceration of the cornea called Acanthamoeba keratitis (AK), mostly in contact lens wearers or in individuals with minor corneal abrasions. Hundreds of cases of AK have been documented world wide.

An unusual case of Acanthamoeba peritonitis in a malnourished patient on continuous ambulatory peritoneal dialysis (CAPD)

An unusual case of peritonitis in a 61-year-old patient is reported where culture for bacteria and fungi were negative. Acanthamoeba was isolated and the patient was treated with Ceftazidine, Cefazolin, Levofloxacin, Fluconazole and Rifampicin with regular haemodialytic support. The patient was completely cured of the infection and continuous ambulatory peritoneal dialysis (CAPD) fluid became clear after 2 weeks of treatment. Diagnosis and treatment of Acanthamoeba infections are difficult due to the rarity of the infections, lack of familiarity of most clinicians with disease syndromes, and limitations of therapeutics options. Even an experienced microbiologist can easily mistake the amoebae in ascitic fluid for peritoneal macrophages or lymphocytes.

Lawsuit against a dentist related to serious ocular infection possibly linked to water from a dental handpiece

This case report highlights the risks that may be associated with amoebae in the water of a dental unit. A woman with contact lenses visited her dentist for replacement of a bridge. During the treatment, a stream of water was directed from the handpiece into her right eye. Because of subsequent pain in the eye, the patient consulted several ophthalmologists, who discovered abrasive lesions of the cornea and inflammation. Despite antibacterial and anti-inflammatory treatments, the patient"s visual acuity declined gradually over a period of several days. A microbiological examination nearly 2 months later revealed amoebae in corneal samples. A lawsuit against the dentist was initiated. Although a causal relation with the dental treatment was rejected by the judge in this case, high numbers of amoebae in the water of dental units can present a risk if a patient with pre-existing corneal lesions is splashed. According to the precautionary principle, complete evidence of risk does not have to exist to institute measures to protect individuals and society from that risk. This case reinforces the importance of having patients wear safety glasses during dental treatments and of dental personnel draining the waterlines of dental units, as recommended by the Canadian Dental Association.

Rapidly fatal Acanthamoeba encephalitis and treatment of cryoglobulinemia

We describe a 66-year-old woman with therapy-refractory cryoglobulinemia treated with rituximab, plasmapheresis, and steroids; a case of fatal meningoencephalitis caused by Acanthamoeba spp. then developed. Such infections are rare and show an unusually rapid course (possibly related to rituximab).

Disseminated acanthamoeba infection in a renal transplant recipient: a case report

Acanthamoeba species are free-living amoebae that are the causative agents of chronic granulomatous meningoencephalitis, amoebic keratitis, pulmonary lesions, cutaneous lesions and sinusitis. Immunocompromised individuals are particularly susceptible to infections with Acanthamoeba, which can be disseminated at times. We herewith report the autopsy findings of disseminated Acanthamoeba infection in a 36-year-old female, a renal transplant recipient on immunosupressants for last four years. Central nervous system showed Acanthamoeba associated chronic granulomatous meningoencephalitis, with predominant perivascular infiltrate of amoebic cysts, trophozoites and inflammatory cells. Both lungs and pancreas also showed infiltration with Acanthamoeba.

A case of successful treatment of cutaneous Acanthamoeba infection in a lung transplant recipient

Acanthamoeba species are known to cause 2 well-described entities: (1) granulomatous amoebic encephalitis (GAE), which usually affects immunocompromised hosts, and (2) keratitis, which typically follows trauma associated with contamination of water or contact lenses. Less common manifestations include pneumonitis and a subacute granulomatous dermatitis. We describe a case of granulomatous dermatitis secondary to Acanthamoeba infection in a lung transplant recipient and a successful outcome following treatment with lipid formulation of amphotericin B and voriconazole. We believe this is the second case report describing disseminated Acanthamoeba infection in a lung transplant recipient. We also describe successful outcome with a combination of lipid formulation of amphotericin B and voriconazole, drugs that have not been previously reported to treat Acanthamoeba.

Transcriptome profiling the gills of amoebic gill disease (AGD)-affected Atlantic salmon (Salmo salar L.): a role for tumor suppressor p53 in AGD pathogenesis?

Neoparamoeba spp. are amphizoic amoebae with the capacity to colonize the gills of some marine fish, causing AGD. Here, the gill tissue transcriptome response of Atlantic salmon (Salmo salar L.) to AGD is described. Tanks housing Atlantic salmon were inoculated with Neoparamoeba spp. and fish sampled at time points up to 8 days postinoculation (pi.). Gill tissues were taken from AGD-affected fish, and a DNA microarray was used to compare global gene expression against tissues from AGD-unaffected fish. A total of 206 genes, representing 190 unique transcripts, were reproducibly identified as up- or downregulated in response to Neoparamoeba spp. infection. Informative transcripts having GO biological process identifiers were grouped according to function. Although a number of genes were placed into each category, no distinct patterns were observed. One Atlantic salmon cDNA that was upregulated in infected gill relative to noninfected gill at 114 and 189 h pi. showed significant identity with the Xenopus, mouse, and human anterior gradient-2 (AG-2) homologs. Two Atlantic salmon AG-2 mRNA transcripts, designated asAG-2/1 and asAG-2/2, were cloned, sequenced, and shown to be predominantly expressed in the gill, intestine, and brain of a healthy fish. In AGD-affected fish, differential asAG-2 expression was confirmed in samples used for microarray analyses as well as in AGD-affected gill tissue taken from fish in an independent experiment. The asAG-2 upregulation was restricted to AGD lesions relative to unaffected tissue from the same gill arch, while p53 tumor suppressor protein mRNA was concurrently downregulated in AGD lesions. Differential expression of p53-regulated transcripts, proliferating cell nuclear antigen and growth arrest and DNA damage-inducible gene-45beta (GADD45beta) in AGD lesions, suggests a role for p53 in AGD pathogenesis. Thus AGD may represent a novel model for comparative analysis of p53 and p53-regulated pathways.

Disseminated Acanthamoebiasis after Lung Transplantation

Protozoan infections in organ transplant recipients are rare. We report a fatal case of disseminated acanthamoebiasis in a bilateral lung transplant recipient that presented with cutaneous lesions, respiratory failure, and seizures. Acanthamoeba infection may be identified in transplant recipients with exposure to water who develop non-healing cutaneous ulcers with granulomatous inflammation. Cutaneous lesions are the initial manifestation of infection and a harbinger of dissemination. Early institution of combination anti-microbial therapy is therefore necessary for effective treatment and prevention of lethal spread to the central nervous system.

Design and evaluation of a specific primer pair for the diagnosis and identification of Acanthamoeba polyphaga

Random amplified polymorphism DNA (RAPD) is a useful tool for species identification. The obtained band patterns can be used for specific primer pair design that may be useful for species diagnosis. In this study, a distinctive a 962-bp band in A. polyphaga band patterns was found, by using the OPC20 primer (ACTTCGCCAC). The DNA fragment was used to design a specific primer pair that was useful for the identification of different isolates as A. polyphaga species. A case of A. polyphaga in disseminated acanthamoebiasis affecting mesenteric nodes is also reported.

Molecular cloning and characterization of a cDNA encoding a laminin-binding protein (AhLBP) from Acanthamoeba healyi

Adherence of Acanthamoeba to host tissue is believed to be crucial in the establishment of amoebic keratitis or GAE. We have isolated a cDNA from a GAE-causing gymnoamoeba, Acanthamoeba healyi, encoding a protein that binds laminin by screening with a peptide G-specific DNA probe. The cDNA clone (AhLBP) was identified on the basis of sequence homology to the nonintegrin mammalian metastasis-associated 67-kDa laminin receptor (67-LR). The predicted amino acid sequence is 256 residues long with a calculated molecular mass of 28.2kDa and a theoretical pI of 5.48. Southern and Northern blot analyses suggested the gene as a single copy in A. healyi genome and expressed as a single transcript of approximately 1.0kb. Virulent strains of Acanthamoeba revealed higher level of the AhLBP mRNA expression than soil isolates. Specific binding of the purified recombinant protein to laminin was confirmed by sandwich Western blot. The polypeptide encoded by AhLBP shared substantial identity with the acidic class ribosomal proteins involved in protein synthesis. Therefore, the AhLBP may be multifunctional in A. healyi, acting as a laminin-binding molecule but also playing a role in cell division and growth. AhLBP-EGFP fusion protein expressed in A. healyi was localized mainly at the cell membrane and nucleus and at cytoplasm with lesser degree. N-terminal 64 amino acids were important for the localization at the cell membrane. This is the first description of a cDNA encoding a laminin-binding protein from protozoan parasites.

Acanthamoeba castellani encephalitis following partially mismatched related donor peripheral stem cell transplantation

We describe a case of Acanthamoeba encephalitis in a 45-year-old Caucasian male with acute myelogenous leukemia, who was 140 days status post partially mismatched related donor peripheral blood stem cell transplant. The patient had been transplanted with a highly T-cell-depleted graft, and was not taking any immunosuppressive drugs, and had no history of graft-versus-host disease. He complained of nausea, vomiting, and occasional episodes of confusion; he also had a chronic cough since transplantation. Physical examination was unremarkable except for orthostatic hypotension. Neurologic examination was within normal limits. Laboratory values including electrolytes, white blood cells and platelet counts were normal. Computed tomographic scan of the brain showed a pansinusitis and a hyperdense lesion along the corona radiata suggestive of a fungal abscess. Magnetic resonance imaging showed multifocal areas with mass effect in the posterior fossa and parietal and occipital lobes. The patient had worsening respiratory failure and died three days after admission. At autopsy, specific immunofluorescent staining identified Acanthamoeba castellani in the brain and lungs.

Cannabinoid-mediated exacerbation of brain infection by opportunistic amebae

Recent reports indicate a higher frequency of brain infections with opportunistic amebae of the genus Acanthamoeba among immune compromised individuals, including AIDS patients. We have demonstrated, using a murine model of Granulomatous Amebic Encephalitis (GAE), that the major psychoactive and immune suppressive component in marijuana delta-9-tetrahydrocannabinol (THC) exacerbates infection by these amebae. Mice administered THC and infected with Acanthamoeba exhibited dose-related higher mortalities than infected vehicle controls. The greater severity of disease for THC-treated mice was accompanied by decreased accumulation of macrophage-like cells at focal sites of infection in the brain. Furthermore, THC administration resulted in decreased levels of mRNA for the pro-inflammatory cytokines interleukin-1 alpha, interleukin-1 beta, and tumor necrosis factor alpha for neonatal rat microglia co-cultured with Acanthamoeba. These results indicate a potential for marijuana to alter the capacity of brain macrophage-like cells to mount a full complement of immune responsiveness to brain infection by opportunistic amebae.

Presence of virulent strains of amphizoic amoebae in swimming pools of the city of Szczecin

The studies included 10 public indoor swimming pools and 3 public open-air swimming pools located in the city of Szczecin. In 2003, water samples were collected for detection of virulent amphizoic amoebae strains. In all pools, 16 strains of thermophilic Acanthamoeba spp. were isolated, 5 of which proved virulent for mice. No pathogenic strains were detected in the water sampled in the indoor swimming pools, and the virulent strains, AD 16, AD 148, AD 166, AM 17, and AM 148, were found only in the open-air swimming pools. The post-mortem studies of mice that had been inoculated with these strains revealed the amoebae invasions in brain, lungs, liver, kidneys, and spleen.

Present status of contact lens-induced corneal infections

This article addresses the spectrum of corneal infections associated with contact lens wear. The status of bacterial, fungal, and Acanthamoeba keratitis is discussed as well as diagnosis and treatment for these infections.

Is the intestinal tract a portal of entry for Acanthamoeba infection?

Acanthamoeba culbertsoni isolated from a water sample of El-Mahmoudia canal in Alexandria, was orally inoculated into a mouse model (200-400 amoebae/mouse) under different conditions. One week postinfection (P.I.), 20% of infected normoacidic mice and all animals received cimetidine or tetracycline prior to infection passed the parasite in their stools. One month P.I., 70% of cimetidine and 100% of tetracycline pretreated mice showed marked erosion in the intestinal mucosa and areas of necrosis with congestion in the brains, with trophozoites and cysts in both tissues. It is concluded that, normoacidic mice may be simply acting as paratenic hosts. In case of hypoacidity or altered normal flora, the intestinal tract was invaded by amoebae representing a new portal of entry for CNS infection.

Recent developments in amoebiasis:the Gal/GalNAc lectins of Entamoeba histolytica and Entamoeba dispar

Amoebiasis is responsible for 50000-100000 deaths annually. Invasive amoebic disease begins with the attachment of Entamoeba histolytica trophozoites to colonic mucin, a process mediated by the amoebic Gal/GalNAc lectin. The non-pathogenic counterpart, E. dispar, is morphologically identical but genetically distinct. Investigations comparing the Gal/GalNac lectin from these two organisms are under way.

Entamoeba histolytica cysteine proteinases with interleukin-1 beta converting enzyme (ICE) activity cause intestinal inflammation and tissue damage in amoebiasis

The protozoan parasite Entamoeba histolytica causes intestinal inflammation and ulceration. Amoebic trophozoites activate the transcription factor NF-kappa B in human intestinal epithelial cells, initiating an inflammatory response programme with resultant damage to the intestinal tissue. Amoebic cysteine proteinases have been proposed as important virulence factors for amoebiasis. To test the role of amoebic cysteine proteinases in the pathogenesis of amoebic colitis, human intestinal xenografts in SCID mice were infected with E. histolytica trophozoites expressing an antisense message to ehcp5. The cysteine proteinase-deficient amoeba failed to induce intestinal epithelial cell production of the inflammatory cytokines interleukin (IL)-1B and IL-8, and caused significantly less gut inflammation and damage to the intestinal permeability barrier. The critical role of amoebic cysteine proteinases in human gut inflammation and tissue damage may be explained by our discovery that amoebic cysteine proteinases possess IL-1B converting enzyme (ICE) activity. This ICE activity could contribute to intestinal inflammation by activating human pIL-1B released by damaged intestinal cells. These results demonstrate for the first time that amoebic cysteine proteinases are a key virulence factor in amoebic colitis, and provide a novel mechanism for their activity.

Acanthamoeba meningoencephalitis following autologous peripheral stem cell transplantation

Amoebic meningoencephalitis is an unusual complication of bone marrow transplantation. We report a case of Acanthamoeba meningoencephalitis in a patient with non-Hodgkin's lymphoma after autologous stem cell transplantation. Leg weakness, fever and urinary retention developed 69 days following transplantation. The patient then developed fever, generalized tonic clonic seizure, rapid deterioration of mental functions and hypercapneic respiratory failure. Magnetic resonance imaging demonstrated a ring enhancing lesion at the level of the thoracic spines 11 and 12. Examination of the cerebrospinal fluid revealed pleocytosis. Despite empiric therapy with broad-spectrum antimicrobial agents, the patient's condition worsened and she died 11 days following admission. Autopsy findings revealed a subacute meningoencephalitis secondary to Acanthamoeba culbertsoni.

Cerebral amebiasis in the acquired immunodeficiency syndrome

Rare cases of cerebral amebiasis have been described in AIDS patients. We report the case of a 46 year-old homosexual man with AIDS who developed an intermittent amnesia and a right palpebral ptosis. The cerebrospinal fluid contained 169 cells (75% lymphocytes). The patient died five days after hospitalization. Necropsy revealed thrombosis of small vessels of the periventricular regions as well as necrosis and hemorrhage of the periventricular tissue, cerebellum and brainstem. The inflammatory process was scarce and composed mainly of CD-68 positive macrophages. In these regions as well as in meninges there were many trophozoites of ameba of the Acanthamoeba group. Although cerebral amebiasis is rare even in AIDS, the clinician should be attentive to this diagnosis in patients with an insidious encephalitis and cerebral cognitive abnormalities, with or without focal motor signs.

Intragastric immunization of rats with Entamoeba histolytica trophozoites induces cecal mucosal IgE, eosinophilic infiltration, and type I hypersensitivity

We have investigated the role of IgE in the local immunity of intestinal amebiasis, a parasitic infection known to induce specific antibody-forming cells (AFC) and IgA antibodies in rodents and humans. We found that intragastric immunization of rats with glutaraldehyde-fixed Entamoeba histolytica trophozoites significantly increased antiameba AFC in the Peyer's patches and spleen and that the lamina propria of the cecum from immunized animals was infiltrated by eosinophils armed with IgE antibodies. Morphometric analysis showed that IgE-containing cells and eosinophils were nearly three times more abundant in the cecum of immunized rats. Antigenic challenge with amebal lysates provoked an increase in the short-circuit current and in the transepithelial potential difference in Ussing-chambered cecum preparations from immunized rats. Although eosinophilia and the increase of IgE are common consequences of infection by parasitic worms, our results indicate that local immunity in intestinal amebiasis also involves IgE deposition, eosinophil infiltration, and type I hypersensitivity, which may explain some symptoms of amebic dysentery such as colic, abdominal tension, tenesmus, and bloody stools.

Amebic keratitis in a wearer of disposable contact lenses due to a mixed Vahlkampfia and Hartmannella infection

PURPOSE

To support the hypothesis that Acanthamoeba is not a unique cause of amebic keratitis, we report a case of amebic keratitis in which viable Acanthamoeba could not be isolated from corneal tissue. Vahlkampfia and Hartmannella, two other genera of free-living ameba, were isolated, however, using prolonged culture.

METHODS

A 24-year-old wearer of soft contact lenses had keratitis. Extensive histologic and microbiologic investigations were performed on corneal scrape, biopsy, and keratoplasty tissue. Contact lenses, storage case, and the home water supply, where contact lens hygiene was practiced, were examined for the presence of micro-organisms.

RESULTS

No viruses, pathogenic bacteria, or fungi were detected from corneal tissue samples. Amebae were observed using light and electron microscopy, but these could not be unequivocally classified using immunocytochemical staining. Viable Vahlkampfia and Hartmannella, but no Acanthamoeba, were isolated from the corneal biopsy sample. Indirect immunofluorescence with a range of polyclonal rabbit antisera raised against axenically cultivated stains of the three amebal genera was unhelpful because of cross-reactivity. A diverse range of micro-organisms was present within the storage case, including the three amebal species. Amebic cysts also were associated with the contact lens.

CONCLUSION

A mixed non-Acanthamoeba amebic keratitis has been identified in a wearer of soft contact lenses where lack of storage case hygiene provided the opportunity for the free-living protozoa Vahlkampfia and Hartmannella to be introduced to the ocular surface. When Acanthamoeba-like keratitis occurs, but where Acanthamoeba cannot be isolated using conventional laboratory culture methods, alternate means should be used to identify other amebae that may be present. Polyclonal immunofluorescent antibody staining was unreliable for generic identification of pathogenic free-living amebae in corneal tissue.

Acanthamoeba meningoencephalitis after bone marrow transplantation

Two patients presented with fever and nodular pulmonary infiltrates 9 and 6 months after marrow transplantation for leukemia. The second patient also had painful subcutaneous nodules that subsequently ulcerated. Both had a history of sinusitis and both had recently been treated with corticosteroids. During treatment with antibacterial and antifungal antibiotics, they developed rapid mental deterioration, coma and/or seizures. CT findings included hydrocephalus with extensive cortical and periventricular hypodensities in the first patient, and hydrocephalus with a cerebellar hemorrhage and edema in the second patient. Cerebrospinal fluid had a low glucose and elevated protein levels with few erythrocytes and little or no pleocytosis. Despite therapy with broad-spectrum antibiotics, including coverage for opportunistic infections, both patients died. Autopsy revealed Acanthamoeba species causing necrotizing meningoencephalitis, pneumonitis and adrenalitis in the first patient and causing necrotizing meningoencephalitis and dermatitis in the second patient. While these are the only reported cases of disseminated Acanthamoeba infection in marrow transplant recipients, a review of the literature suggests that this organism may be a new cause of opportunistic infections.

Amebic abscess of the spleen complicated by metronidazole-induced neurotoxicity: case report

We describe a patient with a liver abscess due to Entamoeba histolytica, in whom metronidazole therapy (total dose, 21 g over 14 days) was complicated by reversible deafness, tinnitus, and ataxia and who relapsed 5 months later with a splenic abscess. Two courses of tinidazole (the second in combination with percutaneous aspiration of the abscess) were required to achieve cure.

Contact lenses and bacterial infections

Research has shown that although rare, contamination of contact lenses with Acanthamoeba and other organisms after cleansing can cause severe ocular morbidity. The author reviews the research data, and offers recommendations for appropriate use of cleansing solutions.

Culture isolation of Acanthamoeba species and leptomyxid amebas from patients with amebic meningoencephalitis, including two patients with AIDS

Acanthamoeba species and leptomyxid organisms are free-living amebas that cause meningoencephalitis, primarily in immunocompromised patients. We report the isolation and culture of Acanthamoeba species and leptomyxid amebas from four patients with fatal amebic meningoencephalitis. Acanthamoeba species were cultured from brain abscess specimens from three immunocompromised patients (including two patients with AIDS). In the case of the fourth patient, who had no identifiable immunodeficiency, leptomyxid amebas were cultured from a specimen from a subcutaneous nodule and were identified in amebic granulomas in brain tissue by the indirect immunofluorescence test. Persons with advanced infection due to the human immunodeficiency virus may be at increased risk for amebic meningoencephalitis, but the diagnosis should be considered in the differential diagnosis of any immunocompromised patient with cerebral abscesses.

Leptomyxid ameba, a new agent of amebic meningoencephalitis in humans and animals

Amebae belonging to the order Leptomyxida are regarded as innocuous soil organisms incapable of infecting mammals. We report here the isolation of a leptomyxid ameba from the brain of a pregnant baboon (Papio sphinx) that died of meningoencephalitis at the San Diego Zoo Wild Animal Park. By using rabbit anti-leptomyxid serum in the immunofluorescence assay, we have identified the leptomyxid ameba in the brain sections of a number of human encephalitic cases from around the world as well as a few cases of meningoencephalitis in animals in the United States, which suggests that the leptomyxid amebae are potential etiologic agents of fatal meningoencephalitis in humans and animals.

Altered neutrophils in mice immune to experimental Naegleria amoebic meningoencephalitis

Naegleria fowleri is the cause of primary amoebic meningoencephalitis in man. The mouse is considered to be a suitable experimental model for this disease. The data presented shows that blood neutrophils from N. fowleri immune mice (immunised) that had received a 'recall' amoeba antigen had altered responses compared with those from similarly treated normal mice. The neutrophils from immune animals showed increased basal levels of oxygen-dependent respiratory activity, measured by the chemiluminescence response. These neutrophils also showed increased responses to formyl-L-methionyl-L-leucyl-L-phenylalanine (fMLP), phorbol myristate acetate (PMA), and opsonized N. fowleri. The results are consistent with previous data suggesting that the neutrophil (and its activation) is important in defence against N. fowleri.

Ocular disease from wearing contact lenses. A potentially devastating complication

Because of the continued popularity of contact lenses in the United States, ocular inflammatory diseases are being encountered with increasing frequency by both ophthalmologists and primary care physicians. Distinction between minor noninfectious inflammation and serious, sight-threatening infection is crucial to the proper management of these patients. Symptoms of infectious keratitis are pain and loss of vision. Signs include infiltration or loss of clarity of the cornea, eyelid swelling, and purulent discharge. If an infectious process is suspected, the patient should be referred to an ophthalmologist immediately. If this is not possible, the contact lens should be removed and a culture performed, if possible. Aminoglycoside antibiotic drops should be applied frequently until ophthalmologic consultation is obtained. Patients should be reminded of the need for strict adherence to disinfection techniques and avoidance of homemade saline preparations. They should also be told to discontinue use of contact lenses at the first sign of ocular irritation or inflammation and to report to their physician if inflammation persists.

Association of amoebae and actinomyces in an intrauterine contraceptive device user

A patient wearing an intrauterine contraceptive device (IUD) was diagnosed as being colonized by Actinomyces and amoebae by examination of a routine Papanicolaou smear. The patient received vaginal treatment with metronidazole, which temporarily eliminated the protozoa; however, it was necessary to remove the IUD to definitively eradicate the microorganisms. Follow-up Papanicolaou smears taken after removal of the IUD have been normal and free of both microorganisms.