Drug Target Discovery Methods In Targeting Neurotropic Parasitic Amoebae.

Neurotropic parasitic amoebal infections have imposed an enormous challenge to chemotherapy in patients who fall victims to the infections caused by them. Conventional antibiotics that are given to treat these infections have a low patient compliance because of the serious adverse effects that are associated with their use. Additionally, the growing incidence of the development of drug resistance by the neurotropic parasites like Naegleria fowleri, Balamuthia mandrillaris, and Acanthamoeba spp has made the drug therapy more challenging. Recent studies have reported some cellular targets in the neurotropic parasitic Acanthamoeba that are used as receptors by human neurotransmitters like acetylcholine. This Viewpoint attempts to highlight the novel methodologies that use drug assays and structural modeling to uncover cellular targets of diverse groups of drugs and the safety issues of the drugs proposed for their use in brain infections caused by the neurotropic parasitic amoebae.

Planktonic free-living amoebae susceptibility to dental unit waterlines disinfectants.

A high diversity of microorganisms is encountered inside dental unit waterlines (DUWL). Among those the presence of free-living amoebae (FLA) appears currently underestimated, although human infections may occur due to contact with FLA-contaminated water during dental cares. In order to limit microbial DUWL contamination, disinfectants are provided by dental unit manufacturer, however, with limited documentation on their activities against FLA. The aim of this study was to evaluate the efficiency of three commercial DUWL disinfectants: the Calbenium© (Airel, Champigny-sur-Marne, France), the Oxygenal 6© (Kavo, Biberach, Germany) and the Sterispray© (Gammasonic, Billom, France), against two FLA species, i.e. Acanthamoeba castellanii and Vermamoeba vermiformis alone or co-cultured with Pseudomonas aeruginosa and Candida albicans at concentrations ranging from 0% to 5% (v/v). Results showed varied efficacies of disinfectants: the Oxygenal 6© did not exhibit FLA killing activity, while the Sterispray© and the Calbenium© displayed concentration- and species-dependent activities with a maximum eradication rates of 100% and 86%, and 79% and 97% for A. castellani and V. vermiformis, respectively. None of the disinfectants were able to totally eradicate FLA at concentrations recommended by manufacturers. Present results highlight unsatisfactory anti-FLA activities of 3 DUWL disinfectant preparations advocating deeper investigation of antimicrobial spectra of commercial disinfectants in use for DUWL maintenance.

Amebic meningoencephalitides and keratitis: challenges in diagnosis and treatment.

PURPOSE OF REVIEW: Acanthamoeba spp., Balamuthia mandrillaris, and Naegleria fowleri, although free-living amebae, also cause devastating diseases in humans leading to death. Acanthamoeba spp. and B. mandrillaris cause granulomatous amebic encephalitis, cutaneous and nasopharyngeal as well as disseminated infection. Acanthamoeba also causes a vision-threatening infection of the cornea, Acanthamoeba keratitis, principally in contact lens wearers. N. fowleri causes an acute, fulminating infection of the central nervous system, primary amebic meningoencephalitis, in healthy children and young adults who indulge in aquatic activities in fresh water. This review focuses on the recent developments in the diagnosis and treatment and clinical management of the diseases caused by these amebae. RECENT FINDINGS: Development of a multiplex real-time PCR test has made it possible to simultaneously detect all the three free-living amebae in a sample. It is a rapid assay with a short turn-around time of just 4-5 h. An early diagnosis would be helpful in initiating potentially effective treatment. A recent study reported exciting results indicating that loading of rokitamycin in chitosan microspheres improves and prolongs the in-vitro anti-Acanthamoeba activity of the drug. SUMMARY: Diagnoses of these infections are challenging and antimicrobial therapy is empirical, which often results in fatalities. Further research is needed to explore the possibility of a better drug delivery system that crosses the blood-brain barrier and effectively reach the central nervous system.

Evaluation of bithionol as a bath treatment for amoebic gill disease caused by Neoparamoeba spp.

This study examined the toxicity of bithionol to Atlantic salmon Salmo salar and rainbow trout Oncorhynchus mykiss in fresh- and seawater and the efficacy of bithionol as a 1h seawater bath treatment for amoebic gill disease (AGD). To examine toxicity, fish were bathed for 1, 3 and 6h in bithionol, an anti-protozoal at 0, 1, 5, 10, 25 and 35mgL(-1) with toxicity determined by time to morbidity. Efficacy was examined by bathing AGD-affected Atlantic salmon and rainbow trout for 1h at bithionol concentrations of 1-25mgL(-1). Efficacy was determined by examining gill amoeba counts and identifying percent lesioned gill filaments at 1 and 24h after bath exposure to bithionol. For both species, bithionol was determined to be toxic at 25 and 35mgL(-1) exhibiting median lethal times (LT50s) ranging from 21 to 84min. Morbidity occurred in the 5 and 10mgL(-1) treatments, however, due to sampling regime there were not enough fish available to calculate LT50s. Only bithionol at 1mgL(-1) was considered non-toxic with no signs of morbidity. Bithionol was more toxic in seawater than freshwater and had no acute effects on gill Na+/K+ ATPase and succinic dehydrogenase, or plasma osmolality and chloride concentration. Bithionol at 1mgL(-1) reduced percent lesioned gill filaments in Atlantic salmon and rainbow trout by 33 and 27 per cent, respectively, compared to the seawater control. Similarly, numbers of amoeba were reduced by 33 and 43 per cent for Atlantic salmon and rainbow trout, respectively, when compared to the seawater control. Furthermore, bithionol reduced percent lesioned gill filaments as much as did the current industry standard of freshwater. This study demonstrated that a 1h seawater bath containing 1mgL(-1) bithionol could be an improvement to the current method of treatment for AGD-affected Atlantic salmon and rainbow trout.

Effects of aqueous extracts from leaves and leaf litter on the abundance and diversity of soil gymnamoebae in laboratory microcosm cultures.

The distribution and abundance of microbiota in soil and litter may be significantly affected by the quality and quantity of localized patches of leaf organic matter. This study examined the relative effects of aqueous extracts of shed autumn leaves from American beech (Fagus grandifolia), sugar maple (Acer saccharum), red oak (Quercus rubra), and white oak (Quercus alba) on the density and diversity of gymnamoebae in laboratory cultures. Overall, the beech leaf extract produced the most growth of gymnamoebae followed by white oak with leaf extracts from maple and red oak producing least growth. Cultures using natural leaf litter from beneath beech trees had higher densities and diversity of gymnamoebae than leaf-litter cultures from a maple-oak stand. Soil microcosms confirmed that beech leaf extracts produced a higher density of gymnamoeba growth when added to soil cultures compared with maple and oak leaf extracts. Protein content, CHN (carbon and nitrogen content), and pH of the leaf extracts were assayed, but these alone were not sufficiently different to account for the effects. A dilution experiment indicated that some other concentration-dependent factor in the extract may produce the effects.