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Environmental Science & Technology Oct 2023Opportunistic pathogens (OPs) are of concern in drinking water distribution systems because they persist despite disinfectant residuals. While many OPs garner protection...
Opportunistic pathogens (OPs) are of concern in drinking water distribution systems because they persist despite disinfectant residuals. While many OPs garner protection from disinfectants via a biofilm lifestyle, () also gains disinfection resistance by being harbored within free-living amoebae (FLA). It has been long established, but poorly understood, that grown within FLA show increased infectivity toward subsequent FLA or human cells (i.e., macrophage), via a process we previously coined "protozoan-priming". The objectives of this study are (i) to identify in a key genetic determinant of how protozoan-priming increases its infectivity, (ii) to determine the chemical stimulus within FLA to which responds during protozoan-priming, and (iii) to determine if more infectious forms of also exhibit enhanced disinfectant resistance. Using as a FLA host, the priming effect was isolated to 's locus, which is activated upon sensing elevated magnesium concentrations. Supplementing growth medium with 8 mM magnesium is sufficient to produce grown with an infectivity equivalent to that of grown via the protozoan-primed route. Both forms with increased infectivity (FLA-grown and Mg-supplemented) exhibit greater monochloramine resistance than grown in standard media, indicating that passage through FLA not only increases 's infectivity but also enhances its monochloramine resistance. Therefore, laboratory-based testing of disinfection strategies should employ conditions that simulate or replicate intracellular growth to accurately assess disinfectant resistance.
Topics: Humans; Legionella pneumophila; Magnesium; Water Microbiology; Disinfectants; Amoeba
PubMed: 37756220
DOI: 10.1021/acs.est.3c04013 -
Acta Tropica Nov 2023Acanthamoeba keratitis (AK) is an eye disease often occurring in contact lens wearers. AK treatment is prolonged and requires multiple drugs, which can lead to adverse...
Acanthamoeba keratitis (AK) is an eye disease often occurring in contact lens wearers. AK treatment is prolonged and requires multiple drugs, which can lead to adverse effects. Our study aimed to compare the in vitro activities and safety of Miltefosine with that of conventional antimicrobial agents used to treat AK. Acanthamoeba castellanii genotype T4 was obtained from a patient with keratitis and subjected to in vitro susceptibility testing with various antimicrobial agents, including Chlorhexidine (CHX), Pentamidine isethionate (PI)Polyhexamethylene biguanide (PHMB), and Miltefosine to assess their efficacy against Acanthamoeba trophozoites and cyst. The cytotoxicity of the agents was evaluated in Vero cells, and their selectivity indexes (SI) were calculated. Chlorhexidine exhibited the highest amoebicidal activity with the highest selectivity index against the trophozoite and cyst, ranging from 1.17 to 8.35. The selectivity index of PHMB is slightly comparable to Chlorhexidine, exhibiting significant anti-Acanthamoeba activity. On the other hand, Pentamidine isethionate and Miltefosine displayed low SI among the compounds. Pentamidine isethionate was effective at high concentrations, which was toxic. Miltefosine exhibited the lowest cytotoxicity; nevertheless, due to the lowest anti-Acanthamoeba activity presented a low selectivity against the parasite. Further studies on more clinical samples and prolonged incubation time should be done to investigate the effectiveness and toxicity of drugs in both in vitro and in vivo conditions.
Topics: Chlorocebus aethiops; Animals; Humans; Acanthamoeba; Chlorhexidine; Trophozoites; Pentamidine; Vero Cells; Anti-Infective Agents; Acanthamoeba Keratitis; Cysts
PubMed: 37643658
DOI: 10.1016/j.actatropica.2023.107009 -
Global prevalence of free-living amoebae in solid matrices - A systematic review with meta-analysis.Acta Tropica Nov 2023The ubiquitous free-living amoebae (FLA) are microorganisms of significant medical, sanitary, and ecological importance. However, their characterization within solid... (Meta-Analysis)
Meta-Analysis Review
The ubiquitous free-living amoebae (FLA) are microorganisms of significant medical, sanitary, and ecological importance. However, their characterization within solid matrices such as soil, dust, sediment, mud, sludge, and compost remain to be systematized. In this study, we conducted a systematic review with meta-analysis to explore the global distribution of FLA in solid matrices. From the analysis of 104 out of 4,414 scientific articles retrieved from different databases, it was found that the general global prevalence of FLA in solid matrices was of 55.13% (95% confidence interval (CI) 49.32-60.94). Specifically, FLA prevalence was high in soil (72.40%, 95% CI 69.08-75.73), sediment (57.91%, 95% CI 50.01-65.81), mud (52.90%, 95% CI 24.01-81.78), dust (48.60%, 95% CI 43.00-54.19), and sewage sludge (40.19%, 95% CI 30.68-49.70). In aerosols it was comparatively lower (17.21%, 95% CI 12.76-21.66). Acanthamoeba spp. (52.23%) and Hartmanella/Vermamoeba spp. (36.06%) were found to be more prevalent, whereas Naegleria spp. (34.98%) and Balamuthia spp. (27.32%) were less prevalent. The distribution of the highest global prevalence values for species of Acanthamoeba spp., considering different publication periods of the studies, is as follows: A. hatchetti (51.46%), A. rhysodes (47.49%), A. polyphaga (36.37%), A. culbertsoni (34.31%), A. castellanii (34.21%), and A. lenticulata (32.82%). For other FLA species, the distribution is: Hartmannella/Vermamoeba vermiformis (91.57%), Naegleria fowleri (42.32%), Naegleria gruberi (32.39%), and Balamuthia mandrillaris (25%). The most prevalent Acanthamoeba genotypes were T4 (33.38%) and T3 (23.94%). Overall, the global prevalence of FLA in solid matrices is as high as or greater than that reported in water by previous systematic reviews. Thus, actions aimed at reducing exposure to FLA or exploring their ecological dynamics should consider not only water but also the various solid matrices. The finding outlined here can provide valuable insights for such actions, e.g., informing on the level of exposure to FLA, or on the microbial biodiversity of specific environmental compartments.
Topics: Animals; Amoeba; Prevalence; Sewage; Acanthamoeba; Coleoptera; Dust; Soil; Water
PubMed: 37633571
DOI: 10.1016/j.actatropica.2023.107006 -
Pathogens (Basel, Switzerland) Aug 2023spp. is the etiological agent of amoebic keratitis. In this study, the effect of taurine in physiological concentrations in tears (195 μM) on trophozoites of through...
spp. is the etiological agent of amoebic keratitis. In this study, the effect of taurine in physiological concentrations in tears (195 μM) on trophozoites of through the ex vivo amoebic keratitis model was evaluated. Trophozoites were coincubated with the Syrian golden hamster cornea () for 3 and 6 h. Group 1: Control (-). Corneas coincubated with amoebic culture medium and taurine. Group 2: Control (+). Corneas coincubated with trophozoites without taurine. Group 3: Corneas coincubated with taurine 15 min before adding trophozoites. Group 4: Trophozoites coincubated 15 min with taurine before placing them on the cornea. Group 5: Corneas coincubated for 15 min with trophozoites; subsequently, taurine was added. Results are similar for both times, as evaluated by scanning electron microscopy. As expected, in the corneas of Group 1, no alterations were observed in the corneal epithelium. In the corneas of Group 2, few adhered trophozoites were observed on the corneal surface initiating migrations through cell junctions as previously described; however, in corneas of Groups 3, 4 and 5, abundant trophozoites were observed, penetrating through different corneal cell areas, emitting food cups and destabilizing corneal surface in areas far from cell junctions. Significant differences were confirmed in trophozoites adherence coincubated with taurine ( < 0.05). Taurine does not prevent the adhesion and invasion of the amoebae, nor does it favor its detachment once these have adhered to the cornea, suggesting that taurine in the physiological concentrations found in tears stimulates pathogenic mechanisms of .
PubMed: 37624009
DOI: 10.3390/pathogens12081049 -
Microbiology (Reading, England) Aug 2023The predation and engulfment of bacteria by facilitates intimate interactions between host and prey. This process plays an important and underestimated role in the...
The predation and engulfment of bacteria by facilitates intimate interactions between host and prey. This process plays an important and underestimated role in the physiology, ecology and evolution of pathogenic bacteria. species can be reservoirs for many important human pathogens including is the leading cause of bacterial foodborne enteritis worldwide, despite being a microaerophile that is incapable of withstanding atmospheric levels of oxygen long-term. The persistence and transmission of this major pathogen in the natural environment outside its avian and mammalian hosts is not fully understood. Recent evidence has provided insight into the relationship of and spp. where are a transient host for this pathogen. Mutations to the flagella components were shown to affect interactions. Here, we show that the motility function of flagella is not a prerequisite for interactions and that specific -linked glycan modifications of the major flagellin, FlaA, are important for the recognition, interaction and phagocytosis by . Substitution of the -linked glycosylated serine 415 and threonine 477 with alanine within FlaA abolished interactions with and these mutants were indistinguishable from a Δ mutant. By contrast, mutation to serine 405 did not affect 11168H and interactions. Given the abundance of flagella glycosylation among clinically important pathogens, our observations may have a wider implication for understanding host-pathogen interactions.
Topics: Humans; Animals; Acanthamoeba castellanii; Campylobacter jejuni; Flagellin; Alanine; Polysaccharides; Mammals
PubMed: 37610804
DOI: 10.1099/mic.0.001386 -
International Journal of Molecular... Aug 2023Uncoupling proteins (UCPs) are mitochondrial inner membrane transporters that mediate free-fatty-acid-induced, purine-nucleotide-inhibited proton leak into the...
Uncoupling proteins (UCPs) are mitochondrial inner membrane transporters that mediate free-fatty-acid-induced, purine-nucleotide-inhibited proton leak into the mitochondrial matrix, thereby uncoupling respiratory substrate oxidation from ATP synthesis. The aim of this study was to provide functional evidence that the putative gene of the free-living protozoan amoeba, , encodes the mitochondrial protein with uncoupling activity characteristic of UCPs and to investigate its role during oxidative stress. We report the sequencing and cloning of a complete coding sequence, its phylogenetic analysis, and the heterologous expression of AcUCP in the strain Measurements of mitochondrial respiratory activity and membrane potential indicate that the heterologous expression of AcUCP causes AcUCP-mediated uncoupling activity. In addition, in a model of oxidative stress with increased reactive oxygen species levels (superoxide dismutase 1 knockout yeasts), AcUCP expression strongly promotes cell survival and growth. The level of superoxide anion radicals is greatly reduced in the Δ strain expressing AcUCP. These results suggest that AcUCP targeted to yeast mitochondria causes uncoupling and may act as an antioxidant system. Phylogenetic analysis shows that the UCP diverges very early from other UCPs, but clearly locates within the UCP subfamily rather than among other mitochondrial anion carrier proteins.
PubMed: 37569876
DOI: 10.3390/ijms241512501 -
Translational Vision Science &... Aug 2023To develop a feline model of acute Acanthamoeba keratitis using methods that replicate natural routes of infection transmission.
PURPOSE
To develop a feline model of acute Acanthamoeba keratitis using methods that replicate natural routes of infection transmission.
METHODS
Corneal Acanthamoeba castellanii inoculation was performed by three methods: topical inoculation with Acanthamoeba solution following corneal abrasion, placement of a contaminated contact lens for 7 days, and placement of a contaminated contact lens for 7 days following corneal abrasion. Sham inoculations with parasite-free medium and sterile contact lenses were also performed. Cats were monitored by ocular examination and in vivo corneal confocal microscopy for 21 days post-inoculation. Corneal samples were collected at intervals for microbiologic assessment, histopathology, and immunohistochemistry.
RESULTS
All cats in the corneal abrasion groups developed clinical keratitis. Clinical ocular disease was inconsistently detected in cats from the contaminated contact lens only group. Initial corneal lesions were characterized by multifocal epithelial leukocyte infiltrates. Ocular lesions progressed to corneal epithelial ulceration and diffuse stromal inflammation. After 14 days, corneal ulcerations resolved, and stromal inflammation consolidated into multifocal subepithelial and stromal infiltrates. Corneal amoebae were detected by culture, in vivo confocal microscopy, histopathology, and immunohistochemistry in cats with keratitis. Neutrophilic and lymphocytic keratoconjunctivitis with lymphoplasmacytic anterior uveitis were identified by histopathology. Coinfection with aerobic bacteria was detected in some, but not all, cats with keratitis. Ocular disease was not detected in the sham inoculation groups.
CONCLUSIONS
Feline Acanthamoeba keratitis is experimentally transmissible by contaminated contact lenses and topical inoculation following corneal epithelial trauma.
TRANSLATIONAL RELEVANCE
Experimentally induced acute Acanthamoeba keratitis in cats is clinically and histopathologically similar to its human counterpart.
Topics: Cats; Animals; Humans; Acanthamoeba Keratitis; Acanthamoeba castellanii; Cornea; Corneal Injuries; Inflammation
PubMed: 37566398
DOI: 10.1167/tvst.12.8.10 -
Molecular and Biochemical Parasitology Dec 2023Acanthamoeba are known to cause a vision threatening eye infection typically due to contact lens wear, and an infection of the central nervous system. The ability of...
Acanthamoeba are known to cause a vision threatening eye infection typically due to contact lens wear, and an infection of the central nervous system. The ability of these amoebae to switch phenotypes, from an active trophozoite to a resistant cyst form is not well understood; the cyst stage is often resistant to chemotherapy, which is of concern given the rise of contact lens use and the ineffective disinfectants available, versus the cyst stage. Herein, for the first time, a range of raloxifene sulfonate/sulfamate derivatives which target nucleotide pyrophosphatase/phosphodiesterase enzymes, were assessed using amoebicidal and excystation tests versus the trophozoite and cyst stage of Acanthamoeba. Moreover, the potential for cytopathogenicity inhibition in amoebae was assessed. Each of the derivatives showed considerable anti-amoebic activity as well as the ability to suppress phenotypic switching (except for compound 1a). Selected raloxifene derivatives reduced Acanthamoeba-mediated host cell damage using lactate dehydrogenase assay. These findings suggest that pyrophosphatase/phosphodiesterase enzymes may be valuable targets against Acanthamoeba infections.
Topics: Animals; Acanthamoeba castellanii; Raloxifene Hydrochloride; Sulfonic Acids; Trophozoites; Alkanesulfonates; Phosphoric Diester Hydrolases
PubMed: 37562558
DOI: 10.1016/j.molbiopara.2023.111582 -
Diagnostic Microbiology and Infectious... Oct 2023Acanthamoeba keratitis is a devastating infectious disease of the cornea caused by an opportunistic amoeba, Acanthamoeba castellanii. It is poorly recognized, and...
Acanthamoeba keratitis is a devastating infectious disease of the cornea caused by an opportunistic amoeba, Acanthamoeba castellanii. It is poorly recognized, and diagnostic delays can lead to irreversible damage to the vision. The gold standard for diagnosis has been a sample culture that lasts approximately 2 weeks. Nevertheless, the essence of time has led to the need for an accurate and fast technique to detect A. castellanii from a sample. We developed both traditional and quantitative real-time-PCR-based methods to detect A. castellanii in less than 3 hours and with the sensitivity of one amoeba. Diagnostic laboratories can select the best-suited method for their purposes from 2 comparable methods. The correct treatment can be initiated from the emergency room when the diagnosis has been made quickly within a few hours, hence saving the patient from long-term complications.
Topics: Humans; Acanthamoeba castellanii; Rapid Diagnostic Tests; Acanthamoeba Keratitis; Cornea; Real-Time Polymerase Chain Reaction
PubMed: 37506594
DOI: 10.1016/j.diagmicrobio.2023.116014 -
BMC Microbiology Jul 2023Acanthamoeba castellanii is a free-living protist that feeds on diverse bacteria. A. castellanii has frequently been utilized in studies on microbial interactions....
BACKGROUND
Acanthamoeba castellanii is a free-living protist that feeds on diverse bacteria. A. castellanii has frequently been utilized in studies on microbial interactions. Grazing bacteria also exhibit diverse effects on the physiological characteristics of amoebae, such as their growth, encystation, and cytotoxicity. Since the composition of amoebae amino acids is closely related to cellular activities, it can indicate the overall responses of A. castellanii to various stimuli.
METHOD
A. castellanii was exposed to different culture conditions in low-nutrient medium with heat-killed DH5α to clarify their effects. A targeted metabolomic technique was utilized to evaluate the concentration of cellular amino acids. The amino acid composition and pathways were analyzed by two web-based tools: MetaboAnalyst and Pathview. Then, long-term exposure to A. castellanii was investigated through in silico and in vitro methods to elucidate the homeostasis of amino acids and the growth of A. castellanii.
RESULTS
Under short-term exposure, all kinds of amino acids were enriched in all exposed groups. In contrast to the presence of heat-killed bacteria, the medium exhibited obvious effects on the amino acid composition of A. castellanii. After long-term exposure, the amino acid composition was more similar to that of the control group. A. castellanii may achieve amino acid homeostasis through pathways related to alanine, aspartate, citrulline, and serine.
DISCUSSION
Under short-term exposure, compared to the presence of bacteria, the type of medium exerted a more powerful effect on the amino acid composition of the amoeba. Previous studies focused on the interaction of the amoeba and bacteria with effective secretion systems and effectors. This may have caused the effects of low-nutrient environments to be overlooked.
CONCLUSION
When A. castellanii was stimulated in the coculture system through various methods, such as the presence of bacteria and a low-nutrient environment, it accumulated intracellular amino acids within a short period. However, different stimulations correspond to different amino acid compositions. After long-term exposure, A. castellanii achieved an amino acid equilibrium by downregulating the biosynthesis of several amino acids.
Topics: Acanthamoeba castellanii; Escherichia coli; Coculture Techniques; Amino Acids; Acclimatization; Hot Temperature; Culture Media
PubMed: 37495951
DOI: 10.1186/s12866-023-02942-6