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Microorganisms Apr 2024Acanthamoeba keratitis (AK) is a rare but potentially sight-threatening corneal infection caused by the Acanthamoeba parasite. This microorganism is found ubiquitously... (Review)
Review
Acanthamoeba keratitis (AK) is a rare but potentially sight-threatening corneal infection caused by the Acanthamoeba parasite. This microorganism is found ubiquitously in the environment, often in freshwater, soil, and other sources of moisture. Despite its low incidence, AK presents significant challenges due to delayed diagnosis and the complex nature of therapeutic management. Early recognition is crucial to prevent severe ocular complications, including corneal ulceration and vision loss. Diagnostic modalities and treatment strategies may vary greatly depending on the clinical manifestation and the available tools. With the growing reported cases of Acanthamoeba keratitis, it is essential for the ophthalmic community to thoroughly understand this condition for its effective management and improved outcomes. This review provides a comprehensive overview of AK, encompassing its epidemiology, risk factors, pathophysiology, clinical manifestations, diagnosis, and treatment.
PubMed: 38674702
DOI: 10.3390/microorganisms12040758 -
BMJ Open Ophthalmology Apr 2024Microbial keratitis (MK) is a significant cause of blindness in sub-Saharan Africa. We investigated the feasibility of using a novel corneal impression membrane (CIM)...
OBJECTIVE
Microbial keratitis (MK) is a significant cause of blindness in sub-Saharan Africa. We investigated the feasibility of using a novel corneal impression membrane (CIM) for obtaining and processing samples by culture, PCR and whole-genome sequencing (WGS) in patients presenting with suspected MK in Malawi.
METHODS AND ANALYSIS
Samples were collected from patients presenting with suspected MK using a 12 mm diameter polytetrafluoroethylene CIM disc. Samples were processed using culture and PCR for , herpes simplex virus type 1 (HSV-1) and the bacterial 16S rRNA gene. Minimum inhibitory concentrations of isolates to eight antimicrobials were measured using susceptibility strips. WGS was used to characterise isolates.
RESULTS
71 eyes of 71 patients were included. The overall CIM isolation rate was 81.7% (58 positive samples from 71 participants). 69 (81.2%) of isolates were Gram-positive cocci. Coagulase-negative 31.8% and species 14.1% were the most isolated bacteria. Seven (9.9%) participants were positive for HSV-1. Fungi and were not detected. Moxifloxacin and chloramphenicol offered the best coverage for both Gram-positive and Gram-negative isolates when susceptibility was determined using known antimicrobial first quartile concentrations and European Committee on Antimicrobial Susceptibility Testing breakpoints, respectively. WGS identified known virulence genes associated with keratitis.
CONCLUSIONS
In a resource-poor setting, a CIM can be used to safely sample the cornea in patients presenting with suspected MK, enabling identification of causative microorganisms by culture and PCR. Although the microbiological spectrum found was limited to the dry season, these preliminary results could be used to guide empirical treatment.
Topics: Humans; Pilot Projects; Malawi; Male; Female; Adult; Middle Aged; Eye Infections, Bacterial; Young Adult; Bacteria; Microbial Sensitivity Tests; Cornea; Keratitis; Anti-Bacterial Agents; Aged; Polymerase Chain Reaction; Adolescent; Acanthamoeba; RNA, Ribosomal, 16S
PubMed: 38653537
DOI: 10.1136/bmjophth-2024-001682 -
Revista Argentina de Microbiologia Apr 2024Free-living amoebae (FLA) of the genus Acanthamoeba are ubiquitous and amphizoic protozoa that colonize aquatic and terrestrial habitats and can serve as reservoirs for...
Free-living amoebae (FLA) of the genus Acanthamoeba are ubiquitous and amphizoic protozoa that colonize aquatic and terrestrial habitats and can serve as reservoirs for other microorganisms. They are considered econoses that can cause severe and rare pathologies. Due to limited epidemiological data available, the objective of this study was to investigate the presence of Acanthamoeba in coastal wetlands of the southeast of Buenos Aires province and evaluate their association with bacteriological and environmental variables. From February 2021 to July 2022, 22 seawater samples were collected at different points along the coast of the city of Mar del Plata (Buenos Aires, Argentina). Environmental parameters were determined and physicochemical and bacteriological studies, morphological identification, cultures and molecular typification were conducted. Regardless of the environmental and bacteriological variables, the presence of Acanthamoeba spp. was molecularly confirmed in 54.54% of the samples, being the first report of these protozoa in seawater in Argentina.
PubMed: 38632019
DOI: 10.1016/j.ram.2024.02.006 -
Digital Journal of Ophthalmology : DJO 2024Laboratory confirmation is crucial for diagnosis and management of herpes simplex virus (HSV) keratitis. However, the sensitivity of polymerase chain reaction (PCR) in...
BACKGROUND
Laboratory confirmation is crucial for diagnosis and management of herpes simplex virus (HSV) keratitis. However, the sensitivity of polymerase chain reaction (PCR) in keratitis is low (25%) compared with that of mucocutaneous disease (75%). We developed an educational intervention aimed at improving the diagnostic yield of PCR.
METHODS
The medical records of keratitis cases seen at the emergency department of a London tertiary ophthalmic referral hospital over two distinct periods, before and after an educational program on swab technique, were reviewed retrospectively.
RESULTS
A total of 252 HSV cases were included. Increases in the laboratory-confirmed diagnosis of HSV-1 were observed, in both first presentations (11.1%-57.7%) and recurrent cases (20%-57.6%). The rate of positive HSV-1 PCR in eyes with an epithelial defect increased from 19% pre-intervention to 62% post intervention. Notably, 3% were positive for varicella zoster virus DNA, and there was a single case of keratitis.
CONCLUSION
Our results suggest that, with proper swabbing technique, PCR may be more sensitive than previously reported.
Topics: Humans; Pilot Projects; Retrospective Studies; DNA, Viral; Keratitis, Herpetic; Herpesvirus 1, Human; Polymerase Chain Reaction; Herpes Simplex
PubMed: 38601900
DOI: 10.5693/djo.01.2024.01.002 -
Frontiers in Cellular and Infection... 2024Amoebae are micropredators that play an important role in controlling fungal populations in ecosystems. However, the interaction between fungi and their amoebic...
Amoebae are micropredators that play an important role in controlling fungal populations in ecosystems. However, the interaction between fungi and their amoebic predators suggests that the pressure from predatory selection can significantly influence the development of fungal virulence and evolutionary processes. Thus, the purpose of this study was to investigate the adaptation of saprotrophic strains during their interactions with . We conducted a comprehensive analysis of survival after co-culture by colony counting of the yeast cells and examining yeast cell phenotypic and genetic characteristics. Our results indicated that exposure to amoebae enhanced the survival capacity of environmental and induced visible morphological alterations in , particularly by an increase in filamentation. These observed phenotypic changes were closely related to concurrent genetic variations. Notably, mutations in genes encoding transcriptional repressors ( and ), recognized for their negative regulation of filamentous growth, were exclusively identified in amoeba-passaged isolates, and absent in unexposed isolates. Furthermore, these adaptations increased the exposed isolates' fitness against various stressors, simultaneously enhancing virulence factors and demonstrating an increased ability to invade A549 lung human epithelial cells. These observations indicate that the sustained survival of under ongoing amoebic predation involved a key role of mutation events in microevolution to modulate the ability of these isolates to change phenotype and increase their virulence factors, demonstrating an enhanced potential to survive in diverse environmental niches.
Topics: Humans; Candida albicans; Virulence; Amoeba; Ecosystem; Virulence Factors; Mutation; Phenotype
PubMed: 38550616
DOI: 10.3389/fcimb.2024.1367656 -
PloS One 2024Acanthamoeba castellanii is infected with diverse nucleocytoplasmic large DNA viruses. Here, we report the co-isolation of 12 viral strains from marine sediments in...
Acanthamoeba castellanii is infected with diverse nucleocytoplasmic large DNA viruses. Here, we report the co-isolation of 12 viral strains from marine sediments in Uranouchi Inlet, Kochi, Japan. Based on the morphological features revealed by electron microscopy, these isolates were classified into four viral groups including Megamimiviridae, Molliviridae, Pandoraviridae, and Pithoviridae. Genomic analyses indicated that these isolates showed high similarities to the known viral genomes with which they are taxonomically clustered, and their phylogenetic relationships were also supported by core gene similarities. It is noteworthy that Molliviridae was isolated from the marine sediments in the Japanese warm temperate zone because other strains have only been found in the subarctic region. Furthermore, this strain has 19 and 4 strain-specific genes found in Mollivirus sibericum and Mollivirus kamchatka, respectively. This study extends our knowledge about the habitat and genomic diversity of Molliviridae.
Topics: Japan; Phylogeny; Virion; Viruses; Acanthamoeba castellanii; Genome, Viral
PubMed: 38547190
DOI: 10.1371/journal.pone.0301185 -
Microorganisms Mar 2024spp [...].
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PubMed: 38543631
DOI: 10.3390/microorganisms12030581 -
Microorganisms Mar 2024The genus comprises free-living amoebae distributed in a wide variety of environments. These amoebae are clinically significant, causing opportunistic infections in...
The genus comprises free-living amoebae distributed in a wide variety of environments. These amoebae are clinically significant, causing opportunistic infections in humans and other animals. Despite this, limited data on sequence types and alleles are available in Italy. In the present study, we analyzed all sequences deposited from Italy with new positive clinical samples from symptomatic AK cases, to provide an overview of the genetic variants' spatial patterns from different sources within the Italian context. A total of 137 sequences were obtained. Six sequence types were identified: T2/6, T3, T4, T11, T13, and T15. Only T4 and T15 were found in both sources. The T4 sequence type was found to be the most prevalent in all regions, accounting for 73% (100/137) of the Italian samples analyzed. The T4 sequence type demonstrated significant allelic diversity, with 30 distinct alleles from clinical and/or environmental samples. These outcomes enabled a better understanding of the distribution of isolates throughout Italy, reaffirming its well-recognized ubiquity. isolates analysis from keratitis, together with the environmental strains monitoring, might provide important information on different genotypes spreading. This might be useful to define the transmission pathways of human keratitis across different epidemiological scales.
PubMed: 38543595
DOI: 10.3390/microorganisms12030544 -
Microorganisms Feb 2024Free-living amoebae (FLA) are widely distributed protozoa in both natural and artificial environments such as drinking water. In addition to the ability of all FLA to...
Free-living amoebae (FLA) are widely distributed protozoa in both natural and artificial environments such as drinking water. In addition to the ability of all FLA to transport various pathogenic microorganisms, certain species, such as spp. or , have intrinsic pathogenic abilities and cause severe cerebral infections. Previous work has shown an enrichment of FLA cysts in biofilm developed in upper levels of Drinking Water Storage Towers (DWSTs), suggesting that differences in densities of FLA cysts may play a role in their unequal distribution in the water column. To evaluate this hypothesis, a model of a water column was created for this study and used to analyze the vertical distribution of cysts of the FLA , , and from 0 to 23 weeks. Interestingly, our data showed that the cysts of both and were enriched in upper water levels during their aging. However, cysts were equally distributed in the water column during the entire study. These results show that, in addition to the role of water level variation in the DWST, some FLA cysts can become less dense during their aging, which contributes to their enrichment in upper water and therefore biofilm levels.
PubMed: 38543525
DOI: 10.3390/microorganisms12030474 -
PLoS Neglected Tropical Diseases Mar 2024Acanthamoeba keratitis (AK) is a corneal sight-threatening infection caused by the free-living amoebae of the genus Acanthamoeba. Early and appropriate treatment...
BACKGROUND
Acanthamoeba keratitis (AK) is a corneal sight-threatening infection caused by the free-living amoebae of the genus Acanthamoeba. Early and appropriate treatment significantly impacts visual outcomes. Mucoadhesive polymers such as chitosan are a potential strategy to prolong the residence time and bioavailability of the encapsulated drugs in the cornea. Regarding the recent administration of miltefosine (MF) for treating resistant AK, in the present study, we synthesized miltefosine-loaded chitosan nanoparticles (MF-CS-NPs) and evaluated them against Acanthamoeba.
METHODOLOGY/PRINCIPAL FINDINGS
Chitosan nanoparticles (CNPs) were prepared using the ionic gelation method with negatively charged tripolyphosphate (TPP). The zeta-potential (ZP) and the particle size of MF-CS-NPs were 21.8±3.2 mV and 46.61±18.16 nm, respectively. The release profile of MF-CS-NPs indicated linearity with sustained drug release. The cytotoxicity of MF-CS-NPs on the Vero cell line was 2.67 and 1.64 times lower than free MF at 24 and 48 hours. This formulation exhibited no hemolytic activity in vitro and ocular irritation in rabbit eyes. The IC50 of MF-CS-NPs showed a significant reduction by 2.06 and 1.69-fold in trophozoites at 24 and 48 hours compared to free MF. Also, the MF-CS-NPs IC50 in the cysts form was slightly decreased by 1.26 and 1.21-fold at 24 and 48 hours compared to free MF.
CONCLUSIONS
The MF-CS-NPs were more effective against the trophozoites and cysts than free MF. The nano-chitosan formulation was more effective on trophozoites than the cysts form. MF-CS-NPs reduced toxicity and improved the amoebicidal effect of MF. Nano-chitosan could be an ideal carrier that decreases the cytotoxicity of miltefosine. Further analysis in animal settings is needed to evaluate this nano-formulation for clinical ocular drug delivery.
Topics: Animals; Rabbits; Drug Carriers; Chitosan; Acanthamoeba; Nanoparticles; Phosphorylcholine
PubMed: 38527059
DOI: 10.1371/journal.pntd.0011976