Acanthamoeba

BackgroundThe environment preferred by Acanthamoeba trophozoites and the mechanism by which the amebae enters the cornea are not yet fully understood. A better understanding of the pathogenesis of this disease may help with prevention and treatment.

Acanthamoeba is a recognized pathogen in the immunocompromised patient, commonly presenting as chronic or subacute encephalitis. However, cutaneous disease in the absence of CNS involvement is increasingly recognized, especially in the setting of chronic, nonhealing skin lesions in the patient with AIDS. We describe a patient with AIDS and cutaneous acanthamoebiasis and review our experience with treatment and diagnosis.

Purpose: To describe the outcome of a series of Acanthamoeba keratitis treated with a similar regimen. Meth-ods: All cases diagnosed with Acanthamoeba keratitis in a referral centre from June 1994 through June 1997 were included. Diagnosis of Acanthamoeba keratitis was ...

Bacterial resistance is critical for the selection of antibiotics in the treatment of infections, so it is vital to know its current status in our geographical area. To determine in vitro antibiotic susceptibility of bacterial isolates obtained from keratitis and intraocular infections. A retrospective study of microbiological tests in Fundación Oftalmológica de Santander (FOSCAL) was carried out between June, 2011, and January, 2012. A total of 92 samples were examined and 110 bacteria, 27 fungi and 12 free-living amoebae were identified. Polymicrobial infections constituted 50% of the total; 1.1%, 0%, 1.1%, 16.9%, 29.3% and 85% of Gram-positive bacteria were resistant to imipenem, moxifloxacin, gatifloxacin, levofloxacin, ciprofloxacin and tobramycin, respectively, while 0%, 8.3%, 0%, 0%, 18.2% and 27.3% of Gram-negative bacteria were resistant to imipenem, moxifloxacin, gatifloxacin, levofloxacin, ciprofloxacin and tobramycin, respectively. For methicillin-resistant coagulase-pos...

Acanthamoeba castellanii causes amoebic keratitis
which is a painful sight-threatening disease of the eyes.
Its eradication is difficult because the amoebas encyst making
it highly resistant to anti-amoebic drugs, but several
medicinal plants have proven to be more effective than the
usual therapy. This study aimed to evaluate the in vitro
amoebicidal activity of ethanol extracts of Arachis hypogaea
L. (peanut), Curcuma longa L. (turmeric), and Pancratium
maritimum L. (sea daffodil) on A. castellanii cysts.
Acanthamoeba were isolated from keratitic patients, cultivated
on 1.5% non-nutrient agar, and then incubated with
different concentrations of plant extracts which were further
evaluated for their cysticidal activity. The results showed
that all extracts had significant inhibitory effect on the
multiplication of Acanthamoeba cysts as compared to the
drug control (chlorhexidine) and non-treated control, and
the inhibition was time and dose dependent. The ethanol
extract of A. hypogaea had a remarkable cysticidal effect
with minimal inhibitory concentration (MIC) of 100 mg/ml
in all incubation periods, while the concentrations of 10 and
1 mg/ml were able to completely inhibit growth after 48 and
72 h, respectively. The concentrations 0.1 and 0.01 mg/ml
failed to completely inhibit the cyst growth, but showed
growth reduction by 64.4–82.6% in all incubation periods.
C. longa had a MIC of 1 g and 100 mg/ml after 48 and 72 h,
respectively, while the concentrations 10, 1, and 0.1 mg/ml
caused growth reduction by 60–90.3% in all incubation
periods. P. maritimum had a MIC of 200 mg/ml after 72 h,
while the 20-, 2-, 0.2-, and 0.02-mg/ml concentrations
showed growth reduction by 34–94.3% in all incubation
periods. All extracts seemed to be more effective than chlorhexidine
which caused only growth reduction by 55.3–
80.2% in all incubation periods and failed to completely
inhibit the cyst growth. In conclusion, ethanol extracts of A.
hypogaea, C. longa, and P. maritimum could be considered
a new natural agent against the Acanthamoeba cyst.

Knowledge of the prevalence of free-living amoebae (FLA) in US household water can provide a focus for prevention of amoeba-associated illnesses. Household water samples from two Ohio counties, collected and examined for amoebae during 1990–1992, were used to describe the prevalence of Acanthamoeba and other FLA in a household setting. Amoebae were isolated and identified by morphologic features. A total of 2,454 samples from 467 households were examined. Amoebae were found in water samples of 371 (79%) households. Sites most likely to contain amoeba were shower heads (52%) and kitchen sprayers (50%). Species of Hartmannella, Acanthamoeba, or Vahlkampfia were most common. Detection was higher in biofilm swab samples than in water samples. Detection of FLA and Acanthamoeba, at 79% and 51%, respectively, exceed estimates that have been published in previous surveys of household sources. We believe FLA are commonplace inhabitants of household water in this sample as they are in the environment.

Primary amebic meningoencephalitis and granulomatous amebic meningoencephalitis are central nervous system infections caused by free-living amebae. We describe the neuroimaging findings in 5 such cases on CT and MR imaging. A spectrum of findings was seen in the form of multifocal parenchymal lesions, pseudotumoral lesions, meningeal exudates, hemorrhagic infarcts, and necrosis in the brain. Familiarity with the imaging findings is important for the diagnosis and management of this nearly universally fatal disease.

Eighteen cases of Acanthamoeba-associated keratitis among contact lens wearers seen at the Department of Ophthalmology, Karl-Franzens-University, Graz, Austria, between 1996 and 1999 are reviewed. The amoebae were proven to be the causative agents in three patients. The aim of our study was to discriminate between clinically relevant and nonrelevant isolates and to assess the relatedness of the isolates to published strains. Altogether, 20 strains of free-living amoebae, including 15 Acanthamoeba strains, 3 Vahlkampfia strains, and 2 Hartmannella strains, were isolated from clinical specimens. The virulent Acanthamoeba strains were identified as A. polyphaga and two strains of A. hatchetti. To our knowledge this is the first determination of keratitis-causing Acanthamoeba strains in Austria. Clinically relevant isolates differed markedly from nonrelevant isolates with respect to their physiological properties. 18S ribosomal DNA sequence types were determined for the three physiologi...

Small free-living amebas belonging to the genera Acanthamoeba and Naegleria occur world-wide. They have been isolated from a variety of habitats including fresh water, thermal discharges of power plants, soil, sewage and also from the nose and throats of patients with respiratory illness as well as healthy persons. Although the true incidence of human infections with these amebas is not known, it is believed that as many as 200 cases of central nervous system infections due to these amebas have occurred worldwide. A majority (144) of these cases have been due to Naegleria fowleri which causes an acute, fulminating disease, primary amebic meningoencephalitis. The remaining 56 cases have been reported as due either to Acanthamoeba or some other free-living ameba which causes a subacute and/or chronic infection called granulomatous amebic encephalitis (GAE). Acanthamoeba, in addition to causing GAE, also causes nonfatal, but nevertheless painful, vision-threatening infections of the hu...