Search Results (638)

Malaria disease affects millions of people annually, making the Amazon Basin a major hotspot in the Americas. While traditional control strategies rely on physical and chemical methods, the Anopheles microbiome offers a promising avenue for biological control, as certain bacteria can inhibit parasite development and alter vector immune and reproductive systems, disrupting the transmission cycle. For this reason, this study aimed to explore the bacterial communities in An. darlingi and An. triannulatus s.l., including breeding sites, immature stages, and adults from San Pedro de los Lagos (Leticia, Amazonas) through next-generation sequencing of the 16S rRNA gene. The results revealed a higher bacterial genus richness in the L1–L2 larvae of An. triannulatus s.l. Aeromonas and Enterobacter were prevalent in most samples, with abundances of 52.51% in L3–L4 larvae and 48.88% in pupae of An. triannulatus s.l., respectively. In breeding site water, Verrucomicrobiota bacteria were the most dominant (52.39%). We also identified Delftia (15.46%) in An. triannulatus s.l. pupae and Asaia (98.22%) in An. darlingi, linked to Plasmodium inhibition, and Elizabethkingia, in low abundances, along with Klebsiella and Serratia, known for paratransgenesis potential. Considering the high bacterial diversity observed across the different mosquito life stages, identifying bacterial composition is the first step towards developing new strategies for malaria control. However, the specific roles of these bacteria in anophelines and the malaria transmission cycle remain to be elucidated. Full article

Bacterial sepsis caused by Aeromonas hydrophila (A. hydrophila) and infectious spleen and kidney necrosis virus disease (ISKNVD) caused by infectious spleen and kidney necrosis virus (ISKNV) frequently result in significant mortality among Chinese perch (Siniperca chuatsi). Co-infection of mandarin fish with A. hydrophila and ISKNV occurs from time to time. In this study, a visual detection method for ISKNV and A. hydrophila was developed, using loop-mediated isothermal amplification (LAMP) and pre-addition of hydroxynaphthol blue. Primers for amplifying LAMP in the same system were designed based on the conserved regions of the MCP gene of infectious spleen and kidney necrosis virus, as well as the hlyA gene of A. hydrophila. The results showed that this method amplified bright trapezoidal bands in the presence of only A. hydrophila or ISKNV and both, with sky blue for positive amplification and violet for negative amplification. There was no cross-reactivity with other pathogens, and fragments of 182 bp, 171 bp and 163 bp appeared after digestion of the A. hydrophila LAMP product and 136 bp, 117 bp and 96 bp appeared after digestion of the ISKNV LAMP product. This holds true even when both positive products are present simultaneously. The minimum detection limit of this method was 100 fg for A. hydrophila and 100 fg for ISKNV, and the minimum detection limit for the mixed template was 1 pg. Overall, this method has high sensitivity and specificity to rapidly detect and distinguish between the two pathogens. Full article

Aeromonas hydrophila presents a significant threat to global aquaculture due to its ability to infect freshwater and marine fish species, leading to substantial economic losses. Effective mitigation methods are essential to address these challenges. Vaccination has emerged as a promising strategy to reduce A. hydrophila infections; however, it faces several obstacles, including variability in immune responses, pathogen diversity, and environmental factors affecting vaccine efficacy. To enhance vaccine performance, researchers focus on adjuvants to boost immune responses and develop multivalent vaccines targeting multiple A. hydrophila strains. Tailoring vaccines to specific environmental conditions and optimizing vaccination schedules can further address the challenges posed by pathogen diversity and variable immune responses. This review provides an in-depth analysis of the immunological hurdles associated with A. hydrophila vaccine development. Current vaccine types—live attenuated, inactivated, subunit, recombinant, and DNA—exhibit diverse mechanisms for stimulating innate and adaptive immunity, with varying levels of success. Key focus areas include the potential of advanced adjuvants and nanoparticle delivery systems to overcome existing barriers. The review also highlights the importance of understanding host–pathogen interactions in guiding the development of more targeted and effective immune responses in fish. Complementary approaches, such as immunostimulants, probiotics, and plant-based extracts, are explored as adjuncts to vaccination in aquaculture health management. Despite notable progress, challenges remain in translating laboratory innovations into scalable, cost-effective solutions for aquaculture. Future directions emphasize the integration of advanced genomic and proteomic tools to identify novel antigen candidates and the need for industry-wide collaborations to standardize vaccine production and delivery. Addressing these challenges can unlock the potential of innovative vaccine technologies to safeguard fish health and promote sustainable aquaculture practices globally. Full article

Background/Objectives: Aeromonas hydrophila is a significant opportunistic pathogen with a broad host range. It produces a catecholate siderophore, amonabactin, during iron starvation, but the in vivo infection mechanism that involves amonabactin is unclear. This study aims to elucidate the role of amonabactin synthetase G (AmoG) in the pathogenicity of A. hydrophila and its impact on gut barrier function. Methods: ΔAmoG was generated by deleting the AMP-binding domain of AmoG in A. hydrophila CCL1. In vivo infection experiments were conducted to assess the mutant’s iron-chelating ability and pathogenicity. Complementation of ΔAmoG with AmoG (ΔAmoG-C) was performed to confirm the observed phenotypes. Transcriptomic and qRT-PCR analyses were used to investigate gene expression changes in infected fish. Goblet cell counts, tight junction expression, and D-lactic acid and LPS levels were measured to evaluate gut barrier function. Results: ΔAmoG exhibited impaired iron-chelating ability and reduced pathogenicity compared to wild-type CCL1. Complementation with AmoG restored virulence in ΔAmoG-C. Transcriptomic and qRT-PCR analyses revealed an elevated expression of Wnt/β-catenin pathway components and antimicrobial genes in ΔAmoG-infected fish. Further investigation indicated increased goblet cells and an enhanced expression of tight junctions, as well as lower D-lactic acid and LPS levels, in ΔAmoG-infected fish. However, gut permeability, bacterial load, and lethality did not significantly differ between CCL1, ΔAmoG, and ΔAmoG-C infections when the Wnt/β-catenin pathway was activated. Conclusions: AmoG plays a crucial role in A. hydrophila pathogenicity by modulating host Wnt/β-catenin signaling and gut mucosal barrier function. This study provides insights into the pathogenesis of A. hydrophila and potential therapeutic targets. Full article

Aeromonas veronii (A. veronii) is a ubiquitous bacterium in terrestrial and aquatic environments. It has a significant impact on animal and human health, with it becoming an emerging crucial pathogen worldwide. However, there have been no reports of mute swan infections. In the present study, after an observation of pathological changes, one bacterial strain isolated from a dead migratory mute swan was identified as A. veronii HNZZ-1/2022 based on its morphology, matrix-assisted laser desorption ionization–time of flight mass spectrometry (MALDI-TOF MS), and sequence analysis of the 16S rRNA and gyrB genes. To explore its pathogenicity, virulence gene detection and a gosling infection experiment were subsequently carried out, respectively. Six virulence genes for cytotonic enterotoxins (alt), lateral elastase (ela), lipase (lip), cytotoxic enterotoxin (act), aerolysin (aerA), and polar flagellin (fla) were present in the template DNA of A. veronii HNZZ-1/2022. Experimentally infected goslings exhibited hemorrhages of various different degrees in multiple organs. The half-maximal lethal dose (LD₅₀) value of A. veronii strain HNZZ-1/2022 was estimated to be 3.48 × 10⁸ colony forming units (CFUs) per mL for goslings. An antimicrobial susceptibility test showed that the A. veronii HNZZ-1/2022 strain was resistant to meropenem, ampicillin, and enrofloxacin. To date, this is the first report of A. veronii in migratory mute swans, thus expanding the currently known host spectrum. These results suggest that the migratory mute swan is a new host for A. veronii and demonstrate the need for extensive surveillance and research of A. veronii to minimize its transmission between animals, the environment, and humans. Full article

The cooperation between microalgae and bacteria can enhance the carbon fixation efficiency of microalgae. In this study, a microalgae-bacteria coexistence system under high-concentration CO₂ stress was constructed, and the bacterial community structure of the entire system was analyzed using the 16S rDNA technique. Microbacterium sp., Bacillus sp., and Aeromonas sp. were screened and demonstrated to promote carbon fixation in Chlorella vulgaris HL 01 (C. vulgaris HL 01). Among them, the Aeromonas sp. + C. vulgaris HL 01 experimental group exhibited the most significant effect, with an increase of about 24% in the final biomass yield and a daily carbon fixation efficiency increase of about 245% (day 7) compared to the control group. Continuous cultivation of microalgae and bacterial symbiosis showed that bacteria could utilize the compounds secreted by microalgae for growth and could produce nutrients to maintain the vitality of microalgae. Detection of extracellular organic compounds of microorganisms in the culture broth by excitation-emission matrix spectral analysis revealed that bacteria utilized the aromatic proteinaceous compounds and others secreted by C. vulgaris HL 01 and produced new extracellular organic compounds required by C. vulgaris HL 01. The metabolic organic substances in the liquids of the experimental groups and the control group were analyzed by liquid chromatography-mass spectrometry, and it was found that 31 unique organic substances of C. vulgaris HL 01 were utilized by bacteria, and 136 new organic substances were produced. These differential compounds were mainly organic acids and their derivatives, benzene compounds, and organic heterocyclic compounds, etc. These results fully demonstrate that the carbon fixation ability and persistence of C. vulgaris HL 01 are improved through material exchange between microalgae and bacteria. This study establishes a method to screen carbon-fixing symbiotic bacteria and verifies that microalgae and bacteria can significantly improve the carbon fixation efficiency of microalgae for high-concentration CO₂ through material exchange, providing a foundation for further research of microalgae-bacterial carbon fixation. Full article

Background: Aeromonas hydrophila is a key pathogen affecting freshwater fish, including Labeo rohita (rohu), causing significant aquaculture losses. This study explores the role of intimin and invasin, known virulence factors, in A. hydrophila pathogenesis using in silico methods. Methods: We analyzed the distribution of invasin and intimin across 53 A. hydrophila genomes and examined their physicochemical properties, secondary structures, and 3D models. Since crystal structures were unavailable, homology-based modeling was employed to study the structure of rohu β-integrins. In silico docking was performed to explore the interactions between intimin/invasin and β-integrins. Results: Our findings revealed that intimin and invasin were present in only 6 out of the 53 A. hydrophila strains examined, which were designated as hypervirulent strains. The transmembrane regions of intimin and invasin were modeled as β-barrels, a common feature of porins. The in silico docking experiments indicated the significant binding affinity of invasin and intimin with all the β-integrins of rohu fish, suggesting a critical role in host attachment and cellular internalization. Conclusions: This in silico study highlights the pivotal role of invasin and intimin in host tissue’s binding efficacy, offering valuable insights into the binding potential of A. hydrophila across various organs in rohu fish. Full article

Aeromonas species are enteropathogens that cause gastroenteritis with a unique three-peak infection pattern related to patient age. The contributions of individual Aeromonas species to age-related infections remain unknown. Multi-locus sequence typing (MLST) was performed to determine the species of Aeromonas strains from Australian patients with gastroenteritis. Public database searches were conducted to collect strains of enteric Aeromonas species, identified by either MLST or whole genome sequencing with known patient age. Violin plot analysis was performed to assess Aeromonas infection distribution across patients of different ages. Generalized additive model (GAM) analysis was employed to investigate the relationship between Aeromonas species and patient age. A total of 266 strains of seven Aeromonas species met the selection criteria, which were used for analyses. The violin plots revealed distinct patterns among individual Aeromonas species in relation to patient age. The GAM analyses identified a significant association between Aeromonas species and patient age (p = 0.009). Aeromonas veronii (153 strains) showed the highest probability of infection in most ages, particularly among young adults. Aeromonas caviae (59 strains) is more common in young children and adults over 60 years of age. The probability of infection for Aeromonas hydrophila (34 strains) and Aeromonas dhakensis (9 strains) was generally low, there was a slight increase in individuals aged 50–60 for A. hydrophila and over 60 years for A. dhakensis. These findings provide novel evidence of the varied contributions of different Aeromonas species to human enteric infections related to patient age, offering valuable insights for epidemiology and clinical management. Full article

A feeding trial was conducted for 120 days in a pilot field condition to evaluate ginger powder (GP; Zingiber officinale) as a feed supplement for Labeo rohita to improve immunity, blood metabolic profile, and resistance to Aeromonas hydrophila bacterial infection. The study was conducted following a complete randomized design in outdoor cemented tanks (20 m²) with a stocking density of 30 fish (average weight: 20.5 g) per tank. L. rohita fingerlings were divided into five groups and fed a diet with no GP supplementation (control diet; C) or a diet supplemented with 5 g (GP5), 10 g (GP10), 15 g (GP15), or 20 g (GP20) of GP per kg of the control diet. The results showed that fish well-being, determined by measuring the condition factor, remained higher than 1.0 for all the experimental groups. The condition factors of all the groups were not significantly different between the groups, suggesting GP had no negative impact on overall fish health. Immune responses significantly improved in the groups fed with diets supplemented with GP at doses of 10 to 15 g per kg of their diet, as seen in respiratory burst activity, total immunoglobulins, and lysozyme activity at 60 and 120 days. Blood metabolic variables, particularly the albumin level, tended to show some level of improvement in the GP15-fed group. However, the effect was not significant. Total protein and globulin levels and the albumin/globulin ratio were not significantly affected by dietary GP. Importantly, fish fed the GP15 diet showed the highest resistance to the A. hydrophila challenge. In conclusion, ginger powder holds promise as a health-promoting nutraceutical for farmed L. rohita, contributing to their sustainable farming. Full article

In 2019, a disease outbreak struck a hybrid sturgeon farm (Huso dauricus ♀ × A. schrenckii ♂) in Tiantai, Zhejiang province, leading to the deaths of 8000 sturgeons. The sturgeons exhibited reduced appetite, lethargic and uncoordinated swimming, and physical signs such as reddish petechiae and ulcers on the body and fins. Hemorrhagic spots were observed on the kidneys, spleen, and gonads, alongside reddish intestines with hemorrhagic ascites in the abdominal cavity. ST-1902 was isolated and identified as Aeromonas hydrophila through physiological and biochemical characterization and 16S rDNA sequence analysis. The pathogenicity of ST-1902 was confirmed through a challenge test, with a median lethal dosage (LD50) of 7.9 × 10⁶ CFU/IND. Histopathological examination showed hyperplasia and neoplasm-like changes in the epicedial mesothelial tissues, enlarged and necrosis renal tissue, and serious hemosiderosis in spleen and gills. Virulent genes (Aer, Epa, Alt, Hly, and Act) were detected in ST-1902, corresponding to typical β-hemolysis, extracellular protease, and enterotoxin. Moreover, antimicrobial experiment detection indicated ST-1902 is sensitive to quinolones and phenicols but resistant to sulfamethoxazole, aminoglycoside antibiotics with Sul1, and Intl and Ant (3”)-I. These results suggest that A. hydrophila was the causative agent of the sturgeon disease and highlight the emerging threat it poses to the sturgeon industry. Full article

North American beavers (Castor canadensis) are semi-aquatic rodents recognized as keystone species because they increase the diversity of freshwater ecosystems. This study aimed to characterize the mortality and pathological findings in free-ranging beavers in California and, based on these results, identify potential threats to freshwater ecosystems. This study included 18 beavers submitted for postmortem examination at the California Animal Health and Food Safety Laboratory, UC Davis, between 2008 and 2024. Gross and microscopic examinations, and bacteriological, parasitological, immunohistochemical, and molecular techniques, were used as tools to diagnose the cause of death/reason for euthanasia and comorbidities in the beavers. Baylisascaris spp.-associated or -suspected encephalitis was the most prevalent (9/18, 50%) cause of mortality/reason for euthanasia, followed by bacterial infections in six individuals. In these six animals, bacterial bronchopneumonia was diagnosed in two (Staphylococcus aureus and a mix of Gram-negative and -positive bacterial infection) and Listeria monocytogenes encephalitis, bacterial myofascitis (Aeromonas bestiarum and Pasteurella multocida), bacterial encephalitis (Acinetobacter towneri), and tularemia (Francisella tularensis) were diagnosed in one beaver each. Three animals died or were euthanized due to non-infectious causes, including motor vehicle trauma, squamous cell carcinoma, and capture cardiomyopathy. Endoparasitism was the main comorbidity, including granulomatous hepatitis caused by a suspected capillarid species, cerebral toxoplasmosis, Giardia infection, gastric nematodiasis, and cecal trematodiasis. In California, beavers are exposed to various pathogens that represent threats to humans, domestic animals, and wildlife. Since the interspecies transmission of these pathogens occurs in rivers, streams, lakes, and ponds, we suggest that studying beaver health can reflect freshwater ecosystem health. This study also indicates that the translocation of beavers to new areas without consideration and/or mitigation represents a potential risk of pathogen introduction. Full article

To investigate the effect of tannic acid (TA) on the growth, disease resistance, and intestinal health of Chinese soft-shelled turtles, individual turtles were fed with 0 g/kg (CG), 0.5 g/kg, 1 g/kg, 2 g/kg, and 4 g/kg TA diets for 98 days. Afterwards, the turtles’ disease resistance was tested using Aeromonas hydrophila. The results showed that 0.5–4 g/kg of dietary TA increased the growth performance and feed utilization (p < 0.05), with 2.38 g/kg being the optimal level for the specific growth rate (SGR). The addition of 0.5–4 g/kg of TA in diets increased the mucosal fold height and submucosa thickness of the small intestine, which reached a maximum of 2 g/kg. The addition of 0.5–2 g/kg of TA effectively reduced the cumulative mortality that had been induced by A. hydrophila, with the 2 g/kg dosage leading to the lowest mortality. Additionally, 1–4 g/kg of TA improved the T-SOD, CAT, and GSH-Px activities during infection, while 2 g/kg of dietary TA enhanced the richness and diversity of the microbiota, for example, by increasing Actinobacteria but inhibiting Firmicutes. The transcriptome demonstrated that the predominant differentially expressed genes (DEGs) in TA2 were mainly enriched in the PPAR signaling pathway (Acsl5, Apoa2, Apoa5, Fabp1, Fabp2, and Fabp6); in glycine, serine, and threonine metabolism (Chdh, Gatm, and Shmt1); and in steroid biosynthesis (Cel, Hsd17b7, Soat2, and Sqle). The main differentially expressed metabolites (DEMs) that were discovered by means of metabolome analysis included cholylhistidine, calcipotriol, 13-O-tetradecanoylphorbol 12-acetate, and hexahomomethionine in CG vs. TA2. Integrative analyses of two omics revealed that 2 g/kg of TA mitigated inflammation by activating the PPAR signaling pathway and regulating the lipid metabolism via multiple pathways, such as steroid biosynthesis and α-linolenic acid metabolism. In general, the inclusion of 2 g/kg of TA in turtle diets can optimally promote growth and bacterial resistance by maintaining intestinal health and improving antioxidant capacity. Full article

Investigating human pathogens in wastewater is crucial for identifying and predicting potential occupational health risks faced by wastewater treatment plant (WWTP) workers. This study aimed to determine the occurrence and levels of Legionella pneumophila, Mycobacterium spp., Arcobacter butzleri, and Aeromonas hydrophila in untreated municipal wastewater. Grab influent, activated sludge, and secondary settling tank (SST) effluent samples were collected bi-weekly over 6 months from 5 WWTPs in Tshwane, South Africa. Mycobacterium spp., A. butzleri, and A. hydrophila were detected using quantitative PCR (qPCR), while Legionella was detected using both a culture method and qPCR. The four pathogens were identified in most samples at varying levels. Legionella pneumophila had a positivity rate of 92%, ranging from 2 to 5.4 log₁₀ MPN/100 mL. Detection rates of Legionella spp., L. pneumophila, and L. pneumophila serogroup 1 were 97%, 75%, and 69%, respectively, with up to 5.3 log₁₀ gene copies (GC)/mL. Importantly, this study demonstrates molecular typing of L. pneumophila serogroup 1 in wastewater, a topic that has been rarely documented. Mycobacterium spp. were detected in all samples at varying levels (log₁₀ GC/mL) in influent (2.8–7.6), activated sludge (4.8–8.9), and SST effluent (3.8–8.9) samples. Arcobacter butzleri and A. hydrophila were detected in 96% and 82% of the samples, respectively, with GC levels in influent, activated sludge, and SST effluent ranging from 0.8 to 6.6, 1.5 to 6.5, and 0.7 to 6.6 log₁₀ GC/mL for A. butzleri, and similar levels for A. hydrophila. These findings underscore the presence of respiratory and enteric pathogens at various treatment points, suggesting potential occupational exposure for WWTP workers. This emphasises the need for microbiological risk assessments (RAs) or reviewing existing RAs and implementing necessary control measures to protect WWTP workers. Full article

The grass carp (Ctenopharyngodon idella) is highly susceptible to infections caused by Aeromonas species, particularly A. hydrophila and A. veronii. However, the immunological mechanisms underlying co-infection by these pathogens remain largely uncharted. This study investigated the pathogenesis and host immune response in grass carp following concurrent infection with A. hydrophila and A. veronii. Mortality was observed as early as 24 h post-infection, with cumulative mortality reaching 68%. Quantitative analysis demonstrated significantly elevated bacterial loads in hepatic tissue at 3 days post-infection (dpi). Histopathological evaluation revealed severe hepatic lesions characterized by cellular necrosis, cytoplasmic vacuolization, and hemorrhagic manifestations. Comparative transcriptomic analysis of hepatic tissues between co-infected and control specimens identified 868 and 411 differentially expressed genes (DEGs) at 1 and 5 dpi, respectively. Gene ontology and KEGG pathway analyses revealed significant enrichment of immune-related genes primarily associated with Toll-like receptor signaling and TNF signaling cascades. Notably, metabolic pathways showed substantial suppression while immune responses were significantly activated after infected. These findings provide novel insights into the host–pathogen interactions during Aeromonas co-infection in grass carp, which may facilitate the development of effective prevention and control strategies. Full article