Amoebic Colonization in Humans: the Role of Zoonotic Transmission in Infection Ecology

Specific or non-specific cytolytic processes of free-living amoebae causing meningoencephalitis have been emphasized and the cytolytic ability related to hydrolases in Entamoeba sp. and Naegleria sp. has also been reported since the latter half of 1970's. However, no information on hydrolase activities in Acanthamoeba sp. is available. Hydrolases in Acanthamoeba culbertsoni, a pathogenic species of free-living amoebae, were assayed and compared with those in a non-pathogenic species, A. royreba. Pathogenicity of these two species was confirmed through experimental infection to BALB/c mice. Hydrolase activities and cytotoxic effects between pathogenic and non-pathogenic species were compared in the trophozoites cultured in CGV media and in CHO cell line, respectively. The results are summarized as follows: The mice infected with A. culbertsoni were all dead 15 days after nasal inoculation, and the mean survival time was 8.5 days. Also the mice infected with this pathogenic species mani fested typical meningoencephalitis, whereas the mice infected with A. royreba did not. Hydrolases detected both in the cell extracts and culture media were acid phosphatase, beta-N-acetyl galactosaminidase, beta-N-acetyl glucosaminidase, alpha-mannosidase, neutral proteinase and acid proteinase, all of which were detected with remarkably higher rate in A.culbertsoni than in A. royreba. A. culbertsoni revealed strong cytotoxicity for the target CHO cells, whereas A. royreba did not show any specific cytotoxicity. About 80% of the target cells mixed with A. culbertsoni were dead 48 hours after cultivation, and more than 95% of the target cells were dead 72 hours after cultivation. Hydrolase activities in A. culbertsoni cultured with the target cell line were assayed according to the culture time. The activities of acid phosphatase, beta-N-acetyl glucosaminidase, beta-N-acetyl glucosaminidase, alpha-mannosidase and acid proteinase in this pathogenic amoeba were detected higher in amoeba extracts than in culture media up to 120 hours after cultivation, but after 120 hours of cultivation those activities were detected higher in culture media than in the amoeba lysates. Neutral proteinase activity in A. culbertsoni increased more in EBSS medium than in the lysate specimens although the activity in the extracts was generally steady according to the cultivation time. Summarizing the above results, it is concluded that there were differences in hydrolase activities between pathogenic A. culbertsoni and non-pathogenic A. royreba, and that some hydrolase activities were detected remarkably higher in A. culbertsoni which revealed strong cytotoxicity to the target CHO cell line.

Species of small, free-living amoebae of the genera Naegleria and Acanthamoeba can cause fatal amoebic meningoencephalitis. Previous investigations have shown that pathogenic amoebae are associated with thermally altered water. Flow cytometric techniques for identifying species of pathogenic and nonpathogenic amoebae from such water have been developed, using immunofluorescence and fluorescein-bound concanavalin A. Flow cytometry is accomplished with a cytofluorograph, in which cells are dispersed in a suspended carrier liquid and passed in front of a focused argon ion laser beam. Cells are then distinguished by the degree of scattered light (size) or fluorescence. Flow cytometry techniques have proven efficient for environmental samples, as indicated by the identification of pathogenic Naegleria fowleri and nonpathogenic Naegleri gruberi and Acanthamoeba castellanii isolated from the Savannah River Plant in South Carolina. Cytofluorographic analysis of environmental samples has several advantages over the current methods of isolation and classification of free-living amoebae. With this system, it is possible to rapidly identify species and quantitate mixtures of pathogenic amoebae in environmental samples. Cytofluorographic analysis of amoebic isolates reduces the time presently required to screen environmental sites for pathogenic amoebae. The cytofluorograph permits detection and species identification of nonthermophilic Naegleria spp. and Acanthamoeba spp. that could not easily be isolated for species identification by conventional methods. Other advantages of flow cytometry over fluorescent microscopy include a high degree of statistical precision due to the large numbers measured, high immunofluorescent titers, and elimination of subjectivity and fluorescence fading.

Viral haemorrhagic fevers (VHFs), caused by filoviruses (e.g., Ebola virus, Marburg virus) and arenaviruses (e.g., Lassa virus, Machupo virus), represent a significant bioterrorism threat due to their zoonotic origins, high mortality rates, and severe clinical presentations. This review examines the potential use of VHFs as biological weapons, their zoonotic transmission dynamics, and implications for rural and agricultural health. A comprehensive review was conducted using electronic databases, including PubMed and Scopus, focusing on studies addressing VHFs in the context of bioterrorism and zoonotic disease transmission. Studies published between 2016 - 2024 were included, with search terms such as 'viral haemorrhagic fevers'', 'bioterrorism potential', and 'zoonotic transmission'. VHFs are zoonotic diseases transmitted to humans from animal reservoirs, primarily rodents and bats. Their pathogenicity, coupled with potential for engineered transmission, underscores their bioterrorism risk. Rural and agricultural communities face heightened exposure due to their proximity to these natural reservoirs. While these viruses are rare and unstable in natural settings, the prospect of their genetic manipulation or combination in order to create novel pathogens introduces new avenues for their potential use in bioterrorism. It is imperative to comprehensively understand their pathogenesis and to establish rigorous control and prevention measures to mitigate their impact on public health and safety. The ongoing vigilance and preparedness efforts are essential to counteract the potential threat posed by these agents in bioterrorism scenarios.

An increasing number of bacteria have been described as benefiting from interaction with free-living amoeba. The most common association between free-living amoeba and microorganisms is interaction of various non-pathogenic and pathogenic bacterial species with amoeba. Various pathogenic bacterial species have capacity to resist digestion by free-living amoeba, which has been observed by many researchers. Also, several of these pathogens are able to resist digestion by macrophages. In addition, free-living amoeba have been associated with several diseases in humans. Acanthamniioeba castella is an important predator of bacteria. It is a ubiquitous organism in water, soil, and air. Attention from a public health perspective is needed by investigation of interaction of foodborne pathogens and free-living amoeba. Bacteria can use free-living amoeba as reservoirs, mediators or vehicles, an infection route, “biological gym” and evolutionary crib or interaction may result in a close endosymbiotic relationship. The purpose of this review is to describe the interaction mechanisms between free-living amoeba and common bacteria species that survive in host cells.

In this study, 468 Listeria strains were checked for the presence of phosphatidylinositol-specific phospholipase C (PI-PLC) activity by using a simple assay that consisted of overlaying colonies formed on agar plates with L-alpha-phosphatidylinositol as substrate. In this assay, PI-PLC-active colonies show turbid halos around the colonies as a result of the release of insoluble diacylglycerol from the substrate. This activity was detected only in the pathogenic species Listeria monocytogenes and was not present in any of the 167 strains of Listeria seeligeri, Listeria welshimeri, Listeria innocua, Listeria murrayi, and Listeria grayi tested. Hence, screening for PI-PLC activity permits discrimination between pathogenic and nonpathogenic Listeria species. In particular, the hemolytic but nonpathogenic species L. seeligeri can now be separated from the hemolytic and pathogenic species L. monocytogenes and L. ivanovii. The use of this assay will improve the specific detection and/or isolation of pathogenic Listeria species from clinical samples or food enrichment cultures.

Approximately 10 Streptomyces species cause disease on underground plant structures. The most economically important of these is potato scab, and the most studied of these pathogens is Streptomyces scabiei (syn. S. scabies). The main pathogenicity determinant of scab-causing Streptomyces species is a nitrated diketopiperazine, known as thaxtomin A (ThxA). In the pathogenic species Streptomyces turgidiscabies, ThxA biosynthetic genes reside on a mobile pathogenicity island (PAI). However, the mobilization of PAIs in other Streptomyces species remains uncharacterized. Here, we investigated the mobilization of the PAI of S. scabiei 87-22. Based on whole genome sequences, we inferred the evolutionary relationships of pathogenic Streptomyces species and discovered that Streptomyces sp. strain 96-12, a novel pathogenic species isolated from potatoes in Egypt, was phylogenetically grouped with nonpathogenic species rather than with known pathogenic species. We also found that Streptomyces sp. strain 96-12 contains a PAI that is almost identical to the PAI in S. scabiei 87-22, despite significant differences in their genome sequences. This suggested direct or indirect in vivo mobilization of the PAI between S. scabiei and nonpathogenic Streptomyces species. To test whether the S. scabiei 87-22 PAI could, indeed, be mobilized, S. scabiei 87-22 deletion mutants containing antibiotic resistance markers in the PAI were mated with Streptomyces diastatochromogenes, a nonpathogenic species. The PAI of S. scabiei was site-specifically inserted into the aviX1 gene of S. diastatochromogenes and conferred pathogenicity in radish seedling assays. Our results demonstrated that S. scabiei, the earliest described Streptomyces pathogen, could be the source of a PAI responsible for the emergence of novel pathogenic species.

Transcriptional response patterns of mud loach (Misgurnus mizolepis; Cypriniformes) hepcidin, a potential ortholog to human hamp1, in response to experimental challenges with non-pathogenic and pathogenic bacterial species were analyzed based on the semi-quantitative reverse transcription-PCR assay. Mud loach hepcidin transcripts were much more preferentially induced by pathogenic bacterial species (Edwardsiella tarda and Vibrio anguillarum) causing apparent pathological symptoms than by non-pathogenic species (Escherichia coli and Bacillus thuringiensis) displaying neither clinical signs nor mortality. However in overall, the induced amounts of hepcidin transcripts were positively related with the number of bacterial cells delivered in both pathogenic and non-pathogenic bacterial species. Inducibility of hepcidin transcripts were variable among three tissues examined (liver, kidney and spleen) in which kidney and spleen were more responsive to the bacterial challenge than liver. Time course expression patterns of hepcidin mRNAs after challenge were different between groups challenged with pathogenic and non-pathogenic species, although the overall pattern of hepcidin expression was in accordance with that generally observed in battery genes appeared during early phase of inflammation. Fish challenged with E. coli (non-pathogenic) showed the significant induction of hepcidin transcripts within 24 hr post injection (hpi) but the level was rapidly declined to the basal level either at 48 or 96 hpi. On the other hand, hepcidin transcript levels in E. tarda (pathogenic)-challenged fish were continuously elevated until 48 hpi, then downregulated at 96 hpi, although the level at 96 hpi was still significantly higher than control level observed in non-challenged fish. This expression pattern was consistent in all the three tissues examined. Taken together, our data indicate that hepcidin is tightly in relation with pathological and/or inflammation status during bacterial challenge, consequently providing useful basis to extend knowledge on the host defensive roles of hepcidin under infectious conditions in bony fish.

Entamoeba is a genus of gastrointestinal protozoon that is transmitted through contaminated food and water. This protozoon is commonly found in human and nonhuman primates. Contact between humans and Formosan rock macaques (Macaca cyclopis) has become more frequent due to food provisioning; accordingly, concerns regarding zoonotic pathogen transmission through the fecal-oral route have increased. For example, surveillance of intestinal parasites in wild Formosan rock macaques indicated that Entamoeba infection was the most prevalent type of intestinal parasite infection. The morphologies of pathogenic and nonpathogenic species are difficult to distinguish. In this study, we collected fecal samples from wild Formosan rock macaques in the Shoushan National Nature Park (Kaohsiung, Taiwan) and adopted both morphologic and molecular methods for Entamoeba species identification. In total, we collected 208 fecal samples with a 57.7% (120/208, 95% confidence interval: 50.9-60.4%) prevalence of Entamoeba infection. Four Entamoeba species were identified: three nonpathogenic species, Entamoeba coli (19%), Entamoeba chattoni (50%), and Entamoeba hartmanni (11%), and one potentially pathogenic species, Entamoeba nuttalli (20%). Our study revealed the risk of zoonotic transmission of these Entamoeba species to humans. To address relevant public health and wildlife conservation concerns, further research is required to fully understand the virulence of E. nuttalli isolated from Formosan rock macaques.

Is the Public Transportation System Safe from a Public Health Perspective?

ABSTRACTInfluenza A viruses (IAV) in swine (IAV-S) pose serious risk to public health through spillover at the human-animal interface. Continued zoonotic transmission increases the likelihood novel IAV-S capable of causing the next influenza pandemic will emerge from this animal reservoir. Because current mitigation strategies are insufficient to prevent IAV zoonosis, we investigated the ability of swine vaccination to decrease IAV-S zoonotic transmission risk. We assessed postchallenge viral shedding in market-age swine vaccinated with either live-attenuated influenza virus (LAIV), killed influenza virus (KV), or sham vaccine (NV). We also assessed postchallenge transmission by exposing naive ferrets to pigs with contact types reflective of those experienced by humans in a field setting. LAIV and KV swine groups exhibited a nearly 100-fold reduction in peak nasal titer (LAIV mean, 4.55 log 50% tissue culture infectious dose [TCID50]/ml; KV mean, 4.53 log TCID50/ml) compared to NV swine (mean, 6.40 log TCID50/ml). Air sampling during the postchallenge period revealed decreased cumulative IAV in LAIV and KV study room air (LAIV, area under the concentration-time curve [AUC] of 57.55; KV, AUC = 24.29) compared to the NV study room (AUC = 86.92). Pairwise survival analysis revealed a significant delay in onset of infection among ferrets exposed to LAIV pigs versus NV pigs (rate ratio, 0.66; P = 0.028). Ferrets exposed to vaccinated pigs had lower cumulative virus titers in nasal wash samples (LAIV versus NV, P < 0.0001; KV versus NV, P= 0.3490) and experienced reduced clinical signs during infection. Our findings support the implementation of preexhibition influenza vaccination of swine to reduce the public health risk posed by IAV-S at agricultural exhibitions.IMPORTANCE Swine exhibited at agricultural fairs in North America have been the source of repeated zoonotic influenza A virus transmission, which creates a pathway for influenza pandemic emergence. We investigated the effect of using either live-attenuated influenza virus or killed influenza virus vaccines as prefair influenza vaccination of swine on zoonotic influenza transmission risk. Ferrets were exposed to the pigs in order to simulate human exposure in a field setting. We observed reductions in influenza A virus shedding in both groups of vaccinated pigs as well as the corresponding ferret exposure groups, indicating vaccination improved outcomes on both sides of the interface. There was also significant delay in onset of infection among ferrets that were exposed to live-attenuated virus-vaccinated pigs, which might be beneficial during longer fairs. Our findings indicate that policies mandating influenza vaccination of swine before fairs, while not currently common, would reduce the public health risk posed by influenza zoonosis.

Tests for potentially pathogenic amoebae were carried out on soil samples from the following sites: (i) farmlands fertilized with municipal sewage wastes, (ii) a stream receiving sewage effluent from a sludge lagoon, (iii) a ravine receiving storm runoff from a cattle farm, (iv) farmlands not fertilized with sewage wastes, and (v) a vegetated shoreline of a waterfront estate not used for farming or livestock production. Study sites were located on the eastern shore of Maryland, bordered to the north by Delaware and to the south by Virginia. Twenty-four species of soil amoebae, including five potentially pathogenic Acanthamoeba species (members of the family Acanthamoebidae), were identified. All of the sites yielded two or more of the potential pathogens.

The COVID-19 pandemic has left an indelible mark on the physical, social, economic, political, and spiritual life and well-being of individuals, communities, institutions, and systems. The disruptive effects of this global crisis call for a deeper reflection and understanding of both the public health and biblical perspectives on pandemics to guide future physical, social, economic, political, and mental responses to future pandemics. This article utilizes basic epidemiological questions of who, what, where, when, why, and how, and explores their interactions with the CELEBRATIONS principles of Choice, Exercise, Liquid, Environment, Belief, Rest, Air, Temperance, Integrity, Optimism, Nutrition, Social Support, and Services. By exploring the nexus between these two perspectives, the authors propose unique biblical concepts that contribute to understanding the COVID-19 pandemic and go beyond the public health perspective.

Cryptococcus neoformans and Cryptococcus gattii are highly virulent species that cause diseases, such as meningoencephalitis and pulmonary infections. The CAP59 gene predominantly determines the virulence of the pathogenic species. This study aimed to examine CAP59 in both pathogenic and non-pathogenic species. This study identified Cryptococcus species through extensive literature, retrieved sequences from UniProt, explored protein families utilizing InterPro, motif analysis by MEME, multiple sequence alignment using Clustal Omega, performance of the phylogenetic analysis with MEGA, modeled protein structures with MODELLER, and separately visualized pathogenic and non-pathogenic structures in PyMOL. Motif analysis showed four conserved regions between the pathogenic and non-pathogenic sequences. Moreover, multiple sequence alignment revealed that pathogenic CAP59 gene sequences lacked a significant portion, compared to non-pathogenic ones, with several mutations in the gene sequence of pathogenic species CAP59 at highly conserved regions. The phylogenetic analysis and pairwise distance matrix revealed that Cryptococcus amylolentus is closely related to pathogenic species. Predicted CAP59 protein structures were superimposed to show structural differences between pathogenic and non-pathogenic species. In conclusion, the results suggested that non-pathogenic species may have evolved into pathogenic species since the CAP59 gene sequences of the non-virulent species were longer than those of the virulent species sequences. It implies that the virulent sequences may have lost that region at some point in evolution, which additional research on capsule formation-related genes can further corroborate.

In the NHS, criteria for the selection and purchase of medical devices tend to be restricted to concerns about any risks to patients and/or staff during clinical practice, and the purchase price. In addition, the basis for taking many of these decisions about purchase may be only that of personal opinion, anecdote or limited information. We report on the application of life-cycle assessment (LCA) to a particular medical device — the suction receptacle — as a case-study to determine the potential of LCA to improve the range and quality of information available for decision-making, and act as a framework for a more holistic approach. Using LCA, substantial environmental and economic burdens were found to be associated with the different product systems in use (durable versus disposable devices). We discuss the ways in which various stakeholders in the healthcare sector could use this information, at both a strategic and operational level. We also outline possible future developments of LCA that would support healthcare managers in the drive towards evidence-based decision-making.

Background: despite multimillion-dollar investments in sports facilities, there is little information on their contribution to energy expenditure of the population. In this study, participation in 71 physical activities (PAs) and 31 different types of spaces was examined. Objectives: to evaluate which types of spaces are more effective from a public health perspective. Methods: a cross-sectional sample was designed, stratified and proportional to the adult population of Gran Canaria (n = 3,000, ≥ 18 years). PA was evaluated using a validated questionnaire. The spaces used were grouped into two categories: public open spaces and sport facilities. Descriptive statistics and multiple logistic regression were used to analyze the data. Results: the open public spaces accumulated a volume of hours for PA between 1.6 and 28.4 times higher than the sport facilities depending on the socio-demographic group analyzed. The indoor sport facilities were the ones that expressed the greatest associative strength with the achievement of PA recommendations (OR = 5.45, 95 % CI: 4.01; 7.40). Conclusion: a dilemma was posed from a public health perspective because the urban open public spaces reached more population and supported most of the population's energy expenditure, particularly in the groups with the highest health risk, but the indoor sport facilities were the ones that best contributed to achieving a healthy level of physical activity. This study suggests changes in the polices of construction and management of sport facilities and open public spaces to increase PA in groups at higher health risk.