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BackgroundAquatic opportunistic pathogen Aeromonas hydrophila, known to persist in low-nutrient chlorinated waters, can cause life-threatening infections. Two intensive care units experienced a cluster of Aeromonas infections following outdoor temperature spikes coinciding with recurrent plumbing issues, with fatalities due to severe underlying comorbidities co-occurring with extensively-drug resistant (XDR) Aeromonas.MethodsWe investigated this cluster using whole genome sequencing to assess genetic relatedness of isolates and identify antimicrobial resistance determinants. Three A. hydrophila were isolated from patients staying in or adjacent to rooms with plumbing issues during or immediately after periods of elevated outdoor temperatures. Sinks and faucets were swabbed for culture.ResultsAll A. hydrophila clinical isolates exhibited carbapenem resistance but were not genetically related. Diverse resistance determinants corresponding to extensively-drug resistant were found, including co-occurring KPC-3 and VIM-2, OXA-232, and chromosomal CphA-like carbapenemase genes, contributing to major treatment challenges. All 3 patients were treated with multiple antibiotic regimens to overcome various carbapenemase classes and expired due to underlying comorbidities. Environmental culture yielded no Aeromonas.ConclusionsWhile the investigation revealed no singular source of contamination, it supports a possible link between plumbing issues, elevated outdoor temperatures and incidence of nosocomial Aeromonas infections. The diversity of carbapenemase genes detected in these wastewater-derived Aeromonas warrants heightened infection prevention precautions during periods of plumbing problems especially with heat waves.

Pseudaminic acid is a non-mammalian sugar found in the surface glycoconjugates of many bacteria, including several human pathogens, and is a virulence factor thought to facilitate immune evasion. The final step in the biosynthesis of the nucleotide activated form of the sugar, CMP-Pse5Ac7Ac is performed by a CMP-Pse5Ac7Ac synthetase (PseF). Here we present the biochemical and structural characterization of PseF from Aeromonas caviae (AcPseF), with AcPseF displaying metal-dependent activity over a broad pH and temperature range. Upon binding to CMP-Pse5Ac7Ac, AcPseF undergoes dynamic movements akin to other CMP-ulosonic acid synthetases. The enzyme clearly discriminates Pse5Ac7Ac from other ulosonic acids, through active site interactions with side-chain functional groups and by positioning the molecule in a hydrophobic pocket. Finally, we show that AcPseF binds the CMP-Pse5Ac7Ac side chain in the lowest energy conformation, a trend that we observed in the structures of other enzymes of this class. [Display omitted] • Crystal structures of AcPseF in the Apo and product-bound states were determined • AcPseF displays metal-dependent activity over a broad pH and temperature range • Pse5Ac7Ac is positioned within a hydrophobic pocket in the AcPseF active site • AcPseF binds the CMP-Pse5Ac7Ac side chain in the lowest energy tg conformation Keenan, Cowan et al. determined crystal structures of the CMP-Pse5Ac7Ac synthetase, AcPseF, in the ligand-free and product-bound forms. They provide molecular-level insights into how a Pse5Ac7Ac-processing enzyme might recognize and discriminate Pse5Ac7Ac from other ulosonic acids, which may inform the development of novel chemical tools or even antimicrobial inhibitors. [ABSTRACT FROM AUTHOR]

Motile aeromonads are an opportunistic and heterogenic bacteria that cause motile Aeromonas septicemia (MAS) which is accompanied with variety of clinical signs and lesions in fish. It has been found that their outer membrane proteins (OMPs) are highly immunogenic and may be used as a vaccine candidate. The present study was undertaken to evaluate OMP protection against Aeromonas hydrophila (A. hydrophila) strain ATCC 7966 (A5 and A8) and A. hydrophila strain DSM 30,187 (A6). Pathogenicity tests revealed that out of 12 isolated strains, seven were highly pathogenic, three were moderate, and two were avirulent. SDS-PAGE analysis of OMPs showed several protein bands (7–22) of different molecular weights ranging from 14 to 346 kDa. The common protein band was 39 kDa. It seems that pathogenicity and the number of protein bands are related in the highly pathogenic strains. Challenged A. hydrophila for Nile tilapia (O. niloticus) previously actively immunized with OMPs (A4, A5, A6, A8, and A11) showed a significant increase in relative percent survival (RPS) ranging from 50 to 100%. Immunological parameters such as immunoglobulin M (IgM), antioxidants (SOD, GSH, and CAT), and nitric oxide (NO) and expression of pro-inflammatory cytokines, interleukin 1β (IL-1β), and tumor necrosis factor-α (TNFα) showed a significant increase in OMP-immunized fish. Challenged A. hydrophila for O. niloticus previously passively immunized with OMPs (A4, A5, A6, A8, and A11) in fish-raised sera showed a significant increase in RPS (20 to 100%) in the vaccinated groups. It is concluded that OMPs from Aeromonas spp. have been identified as suitable target for protection development, especially in the case of heterogenic bacteria. [ABSTRACT FROM AUTHOR]

Understanding the behavior of pathogenic bacterial groups from domestic wastewater in surface water is critical to improving sanitation risk assessment and supporting effective policy implementation. Despite their importance, their behavior in freshwater environments is not fully understood. This study examined the behavior of pathogenic bacterial groups frequently found in domestic wastewater–Aeromonas, Arcobacter, and Mycobacterium—in freshwater microcosms containing domestic wastewater with different initial ammonium-nitrogen (NH4+-N) concentrations (2, 5, and 15 mg N L−1). Digital polymerase chain reaction (dPCR) assays with propidium monoazide (PMA) pretreatment were used to evaluate the behavior of viable targeted bacteria. Aeromonas and Arcobacter decayed quickly after the experiment began, with typical first-order decay constants of 0.718 to 0.820 day−1 and 1.14 to 1.19 day−1, respectively. These rates were comparable or higher than those of Escherichia coli, an indicator of fecal contamination (0.586–0.680 day−1). Conversely, the abundance of Mycobacterium increased over the course of the 7-day experiment. The decay or growth of the target bacterial groups in the microcosms under aerobic conditions was not affected by varying NH4+-N concentrations. Sequencing of the near-full-length 16S ribosomal ribonucleic acid (16S rRNA) gene amplicons with PMA pretreatment revealed that the primary Aeromonas and Arcobacter populations in the initial microcosms were pathogenic species relatives. Conversely, the major Mycobacterium populations thriving in the microcosms were presumably uncultured species with low 16S rRNA gene sequence similarity (< 98.65%) to the cultured species. This study provides insights to improve sanitation risk assessment and promote suitable policy implementation. [ABSTRACT FROM AUTHOR]

Background Aeromonas virulence may not be entirely dependent on the host's immune status. Pathophysiologic determinants of disease progression and severity remain unclear. Methods One hundred five patients with Aeromonas infections and 112 isolates were identified, their clinical presentations and outcomes were analyzed, and their antimicrobial resistance (AMR) patterns were assessed. Two isolates (A and B) from fatal cases of Aeromonas dhakensis bacteremia were characterized using whole-genome sequencing. Virulence factor- and AMR-encoding genes from these isolates were compared with a well-characterized diarrheal isolate A. dhakensis SSU and environmental isolate Aeromonas hydrophila American Type Culture Collection_7966T. Results Skin and soft tissue infections, traumatic wound infections, sepsis, burns, and intraabdominal infections were common. Diabetes, malignancy, and cirrhosis were frequent comorbidities. Male sex, age ≥ 65 years, hospitalization, burns, and intensive care admission were associated with complicated disease. High rates of AMR to carbapenems and piperacillin-tazobactam were found. Treatment failure was observed in 25.7% of cases. Septic shock and hospital-acquired infections were predictors of treatment failure. All 4 isolates harbored assorted broad-spectrum AMR genes including blaOXA , ampC , cphA , and efflux pumps. Only clinical isolates possessed both polar and lateral flagellar genes, genes for various surface adhesion proteins, type 3 and 6 secretion systems and their effectors, and toxin genes, including exotoxin A. Both isolates A and B were resistant to colistin and harbored the mobile colistin resistance-3 (mcr-3) gene. Conclusions Empirical therapy tailored to local antibiograms may facilitate favorable outcomes, while advanced diagnostic methods may aid in identifying correct Aeromonas spp. of significant clinical importance. [ABSTRACT FROM AUTHOR]

Pomacea canaliculata is an invasive species which has significantly impacted native ecosystems globally. The benthic worm Limnodrilus hoffmeisteri is essential for the stability of the native aquatic ecosystem, facilitating the nutrient cycle dynamics through bioturbation. Nevertheless, limited information exists regarding the impact of P. canaliculata on those key native benthic species. Present study evaluated the impacts of P. canaliculata on L. hoffmeisteri by exposing L. hoffmeisteri to P. canaliculata (PC group) and the native snail Bellamya aeruginosa (BA group), with a control group consisting of no snails (NS group). The survival rate of L. hoffmeisteri in the PC group persisted diminished over 14 days, with notable declines in the rates of successful food acquisition and aggregation, an increase in migration, and a decrease in swing frequency. Elevated oxidative stress levels were linked to these alterations in L. hoffmeisteri behavior. Additionally, the presence of P. canaliculata increased the abundance of intestinal pathogenic bacteria in L. hoffmeisteri, with Aeromonas being one of the most lethal. Experimental models of Aeromonas‐free P. canaliculata (AFPC), re‐infected AFPC (IPC), and Aeromonas (As) were established to illustrate the role of Aeromonas in the decline of L. hoffmeisteri. Similar patterns in L. hoffmeisteri survival, behavior, and oxidative stress were observed in As, IPC, and PC group; however, these effects were mitigated by the elimination of Aeromonas in the AFPC group. Furthermore, L. hoffmeisteri was fatally affected by the four Aeromonas strains that were obtained from P. canaliculata intestine. These findings indicate that P. canaliculata exerts a deleterious impact on L. hoffmeisteri, and Aeromonas colonizing in intestine plays an important role. This study reveals a novel invasion mechanism of P. canaliculata. [ABSTRACT FROM AUTHOR]

Polymyxin antibiotics B and colistin are considered drugs of last resort for the treatment of multi-drug and carbapenem-resistant Gram-negative bacteria. With the emergence and dissemination of multi-drug resistance, monitoring the use and resistance to polymyxins imparted by mobilised colistin resistance genes (mcr) is becoming increasingly important. The Aeromonas genus is widely disseminated throughout the environment and serves as a reservoir of mcr–3, posing a significant risk for the spread of resistance to polymyxins. Recent phylogenetic studies and the identification of insertion elements associated with mcr–3 support the notion that Aeromonas spp. may be the evolutionary origin of the resistance gene. Furthermore, mcr–3-related genes have been shown to impart resistance in naïve E. coli and can increase the polymyxin MIC by up to 64-fold (with an MIC of 64 mg/L) in members of Aeromonas spp. This review will describe the genetic background of the mcr gene, the epidemiology of mcr-positive isolates, and the relationship between intrinsic and transferable mcr resistance genes, focusing on mcr–3 and mcr–3-related genes. [ABSTRACT FROM AUTHOR]

Addressing the global antimicrobial resistance (AMR) crisis requires a multifaceted innovative approach to mitigate impacts on public health, healthcare and economic systems. In the complex evolution of AMR, biofilms and the acquisition of antimicrobial resistance genes (ARGs) play a pivotal role. Aeromonas is a major AMR player that often forms biofilm, harbors ARGs and is frequently detected in wastewater. Existing wastewater treatment plants (WWTPs) do not have the capacity to totally eliminate antimicrobial-resistant bacteria favoring the evolution of ARGs in wastewater. Besides facilitating the emergence of AMR, biofilms contribute significantly to biofouling process within the activated sludge of WWTP bioreactors. This paper presents the inhibition of biofilm formation, the expression of biofilm-linked genes and ARGs by phytochemicals andrographolide, docosanol, lanosterol, quercetin, rutin and thymohydroquinone. Aeromonas species were isolated and purified from activated sludge samples. The ARGs were detected in the isolated Aeromonas species through PCR. Aeromonas biofilms were quantified following the application of biocompounds through the microtiter plate assay. qPCR analyses of related genes were done for confirmation. Findings showed that the natural compounds inhibited the formation of biofilms and reduced the expression of genes linked to biofilm production as well as ARGs in wastewater Aeromonas. This indicates the efficacy of these compounds in targeting and controlling both ARGs and biofilm formation, highlighting their potential as innovative solutions for combating antimicrobial resistance and biofouling. [ABSTRACT FROM AUTHOR]

The widespread use of antibiotics in aquaculture has been associated with the development of multidrug resistance in the environment and in humans. This is also exacerbated by the application of high stocking densities in fish farming systems, including catfish (Clarias sp). This study aims to see the potential of Sargassum aquifolium extract, which is a brown macroalgae, as an antibacterial agent for fish disease, Aeromonas hydrophila. Previous studies have revealed the phytochemical profile of S. aquifolium extract, but its effectiveness as an antibacterial agent has not been studied. The ethanol extract concentrations used were 20%, 40%, 60%, 80%, and 100% with two repetitions. The MIC test method was carried out to determine the lowest concentration of S. aquifolium ethanol extract that could inhibit the growth of Aeromonas hydrophila bacteria, while the MBC test was carried out to determine the bactericidal properties against A. hydrophila bacteria. SEM analysis was carried out to determine the morphological damage to A. hydrophila bacterial cells that had been treated with S. aquifolium ethanol extract. Based on the results, it was revealed that S. aquifolium extract could inhibit the growth of A. hydrophila highest with a very strong category at a concentration of 100%. The MIC value of S. auifolium extract was shown at a concentration of 100% but did not cause bacterial cell death based on the MBC value and SEM observations. These findings indicate that S. aquifolium extract has the potential to inhibit the growth of A. hydrophila. Increasing in vivo parameters such as the immune system, production performance, and survival in catfish is still needed to strengthen these results. [ABSTRACT FROM AUTHOR]

This study investigates the hygiene status, behavioral practices, and handling of cutting boards for meat and vegetable processing in selected open markets in Benin City. Utilizing a structured questionnaire and laboratory analysis for Escherichia coli and Aeromonas, the research found prevalent Escherichia coli in all samples, with varying concentrations of Aeromonas, more pronounced in vegetable processing areas. Analysis of the questionnaire revealed that 30% of traders leave cutting boards uncovered, 88% clean them before use (52% with water and detergent), and 12% dust boards before use. Furthermore, 80% of meat sellers store leftover meat in refrigerators, while 68% of vegetable sellers store leftovers in the open market. The findings underscore the importance of proper hygienic practices in handling cutting boards to mitigate food contamination risks, urging awareness among traders regarding effective cleaning and storage procedures. [ABSTRACT FROM AUTHOR]

Aeromonas veronii, a threatening fish pathogen, is implicated in food-borne infections in humans, contributing to substantial economic losses in the aquaculture sector. To examine the occurrence, resistance profiles, 16SrRNA sequence analysis, virulence-determinant and resistance genes, and pathogenicity of A. veronii isolated from Nile tilapia (Oreochromis niloticus), almost 150 fish weighing 75 ± 10 g (apparently healthy; n = 50 and moribund fish; n = 100) were collected from commercial farms in Ismailia Governorate, Egypt. Subsequently, the clinical, post-mortem, and bacteriological examinations were carried out. The overall prevalence of A. veronii in the collected O. niloticus was 18.6% (28/150), where the pathogen was only detected in the moribund one. Phylogenetic analysis revealed that the tested isolate exhibited significant genetic identity with other strains from diverse locations and origins in China and Egypt. PCR showed that aerA (95.4%) was the most predominant virulence gene associated with A. veronii isolates retrieved from O. niloticus, followed by hly (80.3%), ast and ser (69.7% for each), and alt (50.1%). Moreover, 40.9% of the obtained isolates were extensively drug-resistant (XDR) to seven classes and inherited blaTEM, tetA, blaCTX-M, and sul1 genes. Besides, 6.1% of the recovered isolates were carbapenem-resistant and XDR to seven classes harboring blaTEM, blaNDM, blaCTX-M, sul1, and tetA genes. The cumulative mortality rate was 86.7% in the fish group injected with a virulent A. veronii strain at a concentration of 3 × 108 CFU/mL. Concisely, this study underscored the existence of XDR A. veronii in O. niloticus specifying a public health hazard. XDR A. veronii isolated from O. niloticus commonly inherited aerA, ast, ser, and alt virulence-determinant genes and blaTEM, sul1, blaCTX-M, and tetA resistance genes. [ABSTRACT FROM AUTHOR]

This study describes the identification and characterisation of a new mesophilic Aeromonas salmonicida strain, named HMes1 isolated from Atlantic salmon (Salmo salar L.) in Tasmania. Isolates were identified as Aeromonas salmonicida through phenotypic, phylogenetic and genetic characterisation. After characterisation, the diagnostic phenotypic identification system MicroSys A24 was updated and a new multiplex conventional PCR was developed to enable rapid and inexpensive identification of atypical A. salmonicida, and exclusion of the exotic strain, A. salmonicida ssp. salmonicida. [ABSTRACT FROM AUTHOR]

Motile aeromonad septicemia (MAS), caused by the Aeromonas species, has been a serious problem in fish health management, particularly in Nile tilapia (Oreochromis niloticus). This study characterized an Aeromonas species isolated from farmed tilapia fingerlings in Binangonan, Rizal, Philippines, and tested for its pathogenicity in tank trials. The isolate, designated as Aeromonas veronii DFR01 (Diseased Fish Rizal), was identified based on 16S rRNA phylogenetic analysis, 16S rRNA homology, and MALDI-TOF mass spectrometry. Its biochemical profile was generated from API and Biolog Gen III systems. A median lethal dose of A. veronii DFR01 was determined to be 107 CFU/mL in tank trials and was utilized as a whole-cell inactivated antigen for oral vaccine development. The immunized tilapia fingerlings produced elevated levels of immunoglobulin M (IgM) in the blood as determined by an enzyme-linked immunosorbent assay (ELISA). There was a significant increase in IgM levels 14 days post-vaccination. A quantitative polymerase chain reaction (qPCR) showed increasing levels of IgM gene expression after vaccination until 38 days of culture. Vaccinated fish showed 25–35% cumulative mortality after the challenge, while non-vaccinated-challenged fish showed 75% mortality. The findings of this research suggest that the fish oral vaccine may prove beneficial for farmed tilapia populations. The vaccine elicited improved immune responses in the fish and resulted in higher survival rates.

Background: Diarrhoea is one of the main causes of mortalityand morbidity in childhood. Bacterial diarrhoea is a common disorder. Aeromonas species and Escherichia coli (E. coli) are some of the aetiological agents associated with diarrhoea in children. Objective: To determine the prevalenceof Aeromonas species and E. coli in the stool samples of primary school children as well as the antibiotic sensitivity pattern of the isolates. Methods: Stool samples were obtained from pupils (diarrhoeic and non- diarrhoeic) aged four to eighteen years in two primary schools in Ofada. The stool specimens were processed by standard microbiological methods and antibiotic susceptibility was determined using disc diffusion method. Results: Out of 104 stool samples, E. coli was isolated from seven (6.73%) stool samples while threestool samples yielded other pathogens such as Salmonella species, Shigella species, and Proteus vulgaris. Aeromonas spp was not isolated. Pathogenic E. coli was more prevalent among pupils aged 11 to 15 years. The susceptibility of E. coli to commonly used antibiotics (such as tetracycline and ampicillin) was < 30% compared to > 70% for Augmentin, ofloxacin and nalidixic acid. E. coli showed 100% susceptibility to only gentamicin. Conclusion: E. coli was the predominant bacterial agent isolated from stool samples of school children in Ofada, Ogun State. Gentamicin may be recommended as an effective antibiotic agent against E. coli diarrhoeal diseases in the population studied.

The study was to explore the effects of daily feeding frequency on the growth performance, feed utilization, digestive enzyme activity, and gut microbiota of large-mouth bass fry after domestication and feeding with a combination feed. The experiment selected 4 500 large-mouth bass with an initial weight of (0.65±0.01)g, randomly divided into five feeding frequency groups (1 to 5 meals/day), named F1 group, F2 group, F3 group, F4 group, and F5 group, with three replicates per group and 300 fish per replicate. The trial period was 30 days. The results showed that the final weight, specific growth rate, daily feeding rate, and condition factor of the fish in F1 group were significantly lower than those in the other groups (P<0.05), while the survival rates in F3 group and F4 group were significantly increased (P<0.05). The moisture content in the fish bodies of F1 group was increased (P<0.05), and the crude fat content was lower than that in the other groups (P<0.05). The intestinal protease activity in F1 group was significantly higher than in the other groups (P<0.05). The relative abundance of Aeromonas and Acinetobacter in the intestine of F1 group was significantly increased (P<0.05), while the relative abundance of Cetobacterium was significantly lower than in the other groups (P<0.05). The study indicates that based on growth performance and survival rate, the appropriate daily feeding frequency for large-mouth bass fry fed with compound feed is 3~4 meals per day. [ABSTRACT FROM AUTHOR]

In the present research, samples of Solea solea (Linnaeus) were randomly collected from Qarun Lake, Egypt, for routine parasitological, microbiological, and histopathological examinations. The parasitological analysis revealed that 6.70% of the examined samples were infested with the cymothoid isopod Livoneca redmanii. This parasite was isolated as females from the branchial cavity and as juveniles from the skin of the affected fish. Bacteriological examination identified Aeromonas species isolated from the gills, kidney, and liver of S. solea. Morphological, biochemical characterization, and molecular analysis confirmed the isolate as Aeromonas veronii. The isolated strain produced brown colonies on tryptic soy agar (TSA) supplemented with 3% NaCl. The drug susceptibility test indicated that Aeromonas veronii was sensitive to gentamicin, erythromycin, and trimethoprim/sulfamethoxazole, while exhibiting resistance to nalidixic acid, ampicillin, oxolinic acid, and tetracycline. Histopathological examination of the affected gills revealed edema, leukocyte infiltration, and hyperplasia of mucous cells. The infested skin exhibited sloughing and detachment of the lining epithelium, along with edema and degeneration of the muscles at the site of isopod attachment. [ABSTRACT FROM AUTHOR]

Motile aeromonad septicemia (MAS), caused by the Aeromonas species, has been a serious problem in fish health management, particularly in Nile tilapia (Oreochromis niloticus). This study characterized an Aeromonas species isolated from farmed tilapia fingerlings in Binangonan, Rizal, Philippines, and tested for its pathogenicity in tank trials. The isolate, designated as Aeromonas veronii DFR01 (Diseased Fish Rizal), was identified based on 16S rRNA phylogenetic analysis, 16S rRNA homology, and MALDI-TOF mass spectrometry. Its biochemical profile was generated from API and Biolog Gen III systems. A median lethal dose of A. veronii DFR01 was determined to be 107 CFU/mL in tank trials and was utilized as a whole-cell inactivated antigen for oral vaccine development. The immunized tilapia fingerlings produced elevated levels of immunoglobulin M (IgM) in the blood as determined by an enzyme-linked immunosorbent assay (ELISA). There was a significant increase in IgM levels 14 days post-vaccination. A quantitative polymerase chain reaction (qPCR) showed increasing levels of IgM gene expression after vaccination until 38 days of culture. Vaccinated fish showed 25–35% cumulative mortality after the challenge, while non-vaccinated-challenged fish showed 75% mortality. The findings of this research suggest that the fish oral vaccine may prove beneficial for farmed tilapia populations. The vaccine elicited improved immune responses in the fish and resulted in higher survival rates. [ABSTRACT FROM AUTHOR]

Horizontal gene transfer (HGT) is fundamental to microbial evolution and adaptation. When a gene is horizontally transferred, it may either add itself as a new gene to the recipient genome (possibly displacing nonhomologous genes) or replace an existing homologous gene. Currently, studies do not usually distinguish between "additive" and "replacing" HGTs, and their relative frequencies, integration mechanisms, and specific roles in microbial evolution are poorly understood. In this work, we develop a novel computational framework for large-scale classification of HGTs as either additive or replacing. Our framework leverages recently developed phylogenetic approaches for HGT detection and classifies HGTs inferred between terminal edges based on gene orderings along genomes and phylogenetic relationships between the microbial species under consideration. The resulting method, called DART , is highly customizable and scalable and can classify a large fraction of inferred HGTs with high confidence and statistical support. Our application of DART to a large dataset of thousands of gene families from 103 Aeromonas genomes provides insights into the relative frequencies, functional biases, and integration mechanisms of additive and replacing HGTs. Among other results, we find that (i) the relative frequency of additive HGT increases with increasing phylogenetic distance, (ii) replacing HGT dominates at shorter phylogenetic distances, (iii) additive and replacing HGTs have strikingly different functional profiles, (iv) homologous recombination in flanking regions of a novel gene may be a frequent integration mechanism for additive HGT, and (v) phages and mobile genetic elements likely play an important role in facilitating additive HGT. [ABSTRACT FROM AUTHOR]

The common use of antimicrobials in food-animal production can lead to drug residues in edible tissues for consumers. However, immunomodulators enhance immune responses and vaccine effectiveness. A new perspective explores bacterial extracellular bioactive molecules (EBMs) in food-animal production to modulate host immune responses, potentially transforming pathogen management and antimicrobial use. This study investigates the immunogenic potential of Aeromonas hydrophila-derived EBMs (Antigens) to enhance the immune system. Four Antigens were administered intraperitoneally to Oreochromis niloticus (Nile Tilapia). Antigens 2 and Antigens 3 boosted fish immune competence within 21 days. Remarkably, Antigens 3 induced robust immunity against A. hydrophila with a single dose, notably enhancing antibody-based immune responses. The increased antibody activity suggests Antigens 3 could be a vaccine candidate, promising further research and potential application in food-animal production to improve disease control. This study highlights immunomodulators' potential in reshaping disease management in the food-animal industry, emphasizing the benefits of focusing on bacterial EBMs to reduce reliance on antimicrobials and achieve sustainable disease prevention. [ABSTRACT FROM AUTHOR]

Background: Diarrheal illness is a prominent public health worry in developing countries, resulting in high mortality among children. Sociodemographic characteristics and geographic settings are the main effective factors for the increased incidence of childhood diarrhea. Aeromonas is a neglected organism capable of causing dysentery and diarrhea. The aim of this systematic review and meta-analysis was to determine the prevalence of Aeromonas as an agent in the causation of diarrhea in Asian children. Methods: We conducted a systematic review using Web of Science, PubMed, Wiley Online Library, Science Direct, and Google Scholar for peer-reviewed articles published between January 2000 and February 2023. We considered studies that found Aeromonas in diarrheal stool. A random-effects model was used to determine the pooled prevalence of Aeromonas. Results: Our search returned 2,057 articles, with 17 articles from seven Asian nations being included in the systematic review. The pooled prevalence of Aeromonas was 4.5% (95% confidence interval [CI]: 2.9%–6.8%), with heterogeneity (I2 = 96.85; p < 0.001). There was a greater prevalence in areas with high population living in poverty (12.2%; 95% CI: 5.8%–24%) and lower-middle-income countries (5.0%; 95% CI: 2.7%–9.0%). In addition, the prevalence of Aeromonas was greater in South Asia (10.0%; 95% CI: 5.6%–17.2%), in India (12.9%; 95% CI: 6.8%–23%), and in countries with open defecation rate of 5%–25% (11.3%; 95% CI: 6.3%–19.2%). Conclusion: The prevalence of Aeromonas-associated diarrhea in children in Asia estimated in the present study highlighted the high burden of Aeromonas in some parts of Asia. [ABSTRACT FROM AUTHOR]

Aeromonas veronii is an important pathogen found in various aquatic environments and products, posing a threat to public health. The Hanks‐like serine/threonine protein kinase is closely linked to the pathogenesis of pathogenic bacteria, but the exact role of YihE in A. veronii remains still unknown. To study the specific function of the YihE kinase, we constructed a knockout mutant of the yihE gene in A. veronii. The deletion of the yihE gene resulted in changes to the metabolism of L‐arginine‐AMC and acetic acid, as well as enhanced resistance to ampicillin and kanamycin in A. veronii. Additionally, the ΔyihE strain demonstrated a 1.4‐fold increase in biofilm formation ability and a 1.8‐fold decrease in adhesion and invasion to EPCs when compared to the wild‐type strain. A significant decrease in cytotoxicity was observed at 2 and 3 h post‐infection with EPCs compared to the wild‐type strain. Additionally, the deletion of the yihE gene was associated with a significant decrease in motility of the strain. Furthermore, the deletion of the yihE gene resulted in a 1.44‐fold increase in the LD50 of A. veronii in zebrafish. These findings offer valuable insights into the pathogenic mechanisms of A. veronii. [ABSTRACT FROM AUTHOR]

Simple Summary: An Aeromonas veronii strain, isolated from bronze gudgeon, was identified as a significant cause of morbidity and mortality. Through bacterial isolation, virulence gene analysis, and physiological characterization, we identified this bacterium as containing the act, alt, lip, LuxS, and ascV genes, which are distinct from those reported in infections of other aquatic animals. Designated as strain WH10, this is the first documented instance of Aeromonas veronii infecting bronze gudgeon. Our findings provide new insights into the mechanisms of bacterial transmission and underscore the necessity for further research into Aeromonas veronii pathogenesis. Aeromonas veronii, an opportunistic pathogen toward aquatic organisms, was identified as the causative pathogen (isolate WH10) in diseased bronze gudgeon via bacterial isolation, and morphological, physiological, biochemical, and molecular characterization. WH10 exerted its pathogenicity via five virulence genes, including those encoding cytotoxic enterotoxins (act and alt), lipase (lip), a quorum sensing-controlled virulence factor (LuxS), and a Type III secretion system inner membrane component (ascV). WH10 was shown to be sensitive to compound sulfamethoxazoles, cefothiophene, doxycycline, and sulfamethoxazole. Toward bronze gudgeon, WH10 had a median lethal dose (LD50) of 1.36 × 106 colony forming units/mL. Analysis of blood parameters of diseased fish revealed significant increases in monocytes and neutrophils, but decreased numbers of lymphocytes. Serum aspartate aminotransferase activity and triglyceride concentration were significantly higher in diseased fish than in healthy fish. The reverse was noted for alkaline phosphatase, total protein, albumin, total cholesterol, and glucose. Thus, Aeromonas veronii is implicated as the causative agent of the mass mortality observed in bronze gudgeon, warranting further investigations into the diagnosis, epidemiology, prevention, and treatment of this infectious disease. [ABSTRACT FROM AUTHOR]

Introduction: Aeromonas spp. are ubiquitous inhabitants of ecosystems, and many species are opportunistically pathogenic to humans and animals. Multidrug-resistant (MDR) Aeromonas species have been widely detected in hospitals, urban rivers, livestock, and aquatic animals. Results: In this study, we identified two Aeromonas isolates, namely Aeromonas veronii 0728Q8Av and Aeromonas caviae 1029Y16Ac, from coastal waters in Zhejiang, China. Both isolates exhibited typical biochemical characteristics and conferred MDR to 11 kinds of antibiotics, remaining susceptible to ceftazidime. Whole-genome sequencing revealed that both isolates harbored multiple antibiotic resistance genes (ARGs) and several mobile genetic elements (MGEs) on the chromosomes, each containing a resistance genomic island (GI), a typical class 1 integron, a transposon, and various insertion sequences (ISs). Most ARGs were situated within the multiple resistance GI, which contained a class 1 integron and a transposon in both Aeromonas isolates. Furthermore, a chromosomal mcr-3.16 gene was identified in A. veronii 0728Q8Av, while a chromosomal mcr-3.3 was found in A. caviae 1029Y16Ac. Both mcr-3 variants were not located within but were distanced from the multidrug resistance GI on the chromosome, flanking by multiple ISs. In addition, a mcr-3-like was found adjacent to mcr-3.16 to form a tandem mcr-3.16-mcr-3-like-dgkA structure; yet, Escherichia coli carrying the recombinants of mcr-3-like did not exhibit resistance to colistin. And an incomplete mcr-3-like was found adjacent to mcr-3.3 in A. caviae 1029Y16Ac, suggesting the possibility that mcr-3 variants originated from Aeromonas species. In vivo bacterial pathogenicity test indicated that A. veronii 0728Q8Av exhibited moderate pathogenicity towards infected ayu, while A. caviae 1029Y16Ac was non-virulent. Discussion: Thus, both Aeromonas species deserve further attention regarding their antimicrobial resistance and pathogenicity. [ABSTRACT FROM AUTHOR]

The study evaluated dietary supplementation with a feed additive composed of multi-strain Bacillus for Nile tilapia Oreochromis niloticus. In vitro and in vivo assays employing culture-based microbiological methods and metagenomics were performed. Additionally, the study assessed the haemato-immunology, intestinal microbiome, and growth performance of the animals. For this, 30 juvenile Nile tilapia were used in the in vitro assay and 180 (60 + 120) in the in vivo assays. In the in vitro assay, we found evidence of adhesion of the probiotic bacteria to the intestinal mucus of fish, corroborated in the 15-day in vivo assay, in which the count of B. licheniformis was significantly higher in fish fed with probiotic when compared to fish of the control group. Furthermore, in the 50-day in vivo trial, a metagenomic analysis provided evidence for the modulation of the intestine microbiome of Nile tilapia by dietary supplementation of the probiotic. In addition, there was an increase in species richness, higher abundance of potentially probiotic autochthonous species and a lower abundance of Aeromonas sp. when the animals were fed the supplemented diet. Finally, no significant differences were observed in growth performance and haemato-immunological analyses, suggesting no harm to fish health when the product was supplemented for 15 and 50 days. The in vitro results indicate that the multi-strain probiotics were able to adhere to the intestinal mucus of Nile tilapia. Additionally, a modulation of the intestinal microbiome was evidenced in the in vivo assay. [ABSTRACT FROM AUTHOR]

Background Water-associated bacterial infections cause a wide spectrum of disease. Although many of these infections are typically due to human host commensal Staphylococcal or Streptococcal spp, water exposure can result in infections with environmental gram negatives such as Vibrio spp, Aeromonas spp, Chromobacterium violaceum , and Shewanella spp (collectively VACS). Methods We performed a retrospective analysis of the epidemiology, clinical presentation, and outcomes of deep and superficial infections associated with VACS organisms in our health service between 1 January 2015 and 31 December 2023. Results We identified 317 patient episodes of infection with VACS organisms over this period. Of these, Aeromonas spp (63%) was the most common, followed by Vibrio spp (19%), Shewanella spp (13%), and C violaceum (5%). The majority were isolated from males (74.4%) and involved the lower limb (67.5%). Mild infections were more common than severe presentations, with only 15 (4.7%) admissions to the intensive care unit and 8 (2.5%) deaths. Colonization occurred in 6.9% of patients, in contrast to the perceived severity of some of these bacteria. Copathogens were common and included Staphylococcus aureus (48%) and enteric bacteria (57%). The majority of patients (60%) had no documented water exposure. Initial empiric antimicrobial therapy presumptively covered the susceptibilities of the isolated organisms in 47.3% of patients; however, a lack of VACS-covering empirical therapy was not associated with readmission. Conclusions The isolation of a VACS organism in our setting was often not associated with documented water exposure, which has implications for empiric antimicrobial therapy. Severe disease and death were uncommon. [ABSTRACT FROM AUTHOR]

Aeromonas spp. causes the human diseases including diarrhea, gastroenteritis, and bacteremia. Aeromonas spp. can be found in kitchen sponge, one of the reservoirs for food-borne bacterial pathogens. Virulence study of Aeromonas spp. in vivo in animal model is important since the animal model can mimic manifestasions in human infections. Omphisa fuscidentalis was chosen for alternative virulence model, since they are in the same taxonomical order with the well-known infections model, Galleria mellonella. Bacterial isolation and selection of kitchen sponge used Brain Heart Infusion agar and Endo Agar, respectively. Bacterial virulence of KS-1 was injected into Omphisa fuscidentalis larvae. Survival percentage and melanization score of infected larvae were evaluated. Hemolymph of larvae with melanization score of 1 and 4 were stained with Giemsa method to observe the hemocyte changes. Bacterial identification of isolate KS-1 based on 16S rRNA sequence resulted in 96.9% identity to Aeromonas spp. strain VS7. Isolate KS-1 injection to O. fuscidentalis revealed higher bacterial dosage resulting more severe symptoms to the larvae according to survival percentage and melanization score. However, statistical analysis showed evaluation of melanization score could distinguish larvae with 106 and 107 CFU/larva dosage injection, while evaluation of survival percentage could not. Hemocyte of larvae with melanization score 1 had larger and more cytoplasmic vacuolization than the score 4 (healthy larvae). Omphisa fuscidentalis is an alternative of insect model for bacterial infections with survival percentage and melanization score as the evaluation. Cytoplasmic vacuolization of hemocyte can be used as larvae's health indicator in a cellular level. [ABSTRACT FROM AUTHOR]

The goal of this investigation was to examine the occurrence and virulence features of the antibiotic-resistant fish-borne Aeromonas hydrophila that were isolated from fish sold in Aswan City, Egypt. A total of 125 fish samples (25 of each:the mullet, the saurus, the catfish, the Nile perch, and the Nile tilapia) were examined. The mean Aeromonas counts in the examined samples varied from 3.89± 0.35 logCFU/g in the Nile tilapia to 2.68± 0.13 log CFU/g in the Nile perch. 35.2% of the inspected samples had Aeromonas spp. and A.hydrophila as the majority, followed byA. sobria (11%), A. caviae (4%), and A.veronii (3.2%). Based on the species-specific 16S rRNA gene, it was found that 16 isolates were confirmed as A. hydrophila and possessed 62.5, 25, and 37.5% of the virulence genes for aerA, ahh1, and altA, respectively. Additionally, A. hydrophila exhibits varying levels of resistance to the most extensively verified antibacterial substances. Therefore, it is recommended that hygienic techniques be used upon handling, preparing, processing, and storing fish to improve its quality and reduce microbiological contamination with A.hydrophila. Additionally, it is crucial to motivate researchers to pursue non-antibiotic control strategies for this type of pathogen and other bacterial infections in farmed fish. [ABSTRACT FROM AUTHOR]

Aeromonas dhakensis is reported as an emerging pathogenic species within the genus Aeromonas and is widely distributed in tropical coastal areas. This study provided a detailed description and characterization of a strain of A. dhakensis (202108B1) isolated from diseased Ancherythroculter nigrocauda in an inland region of China. Biochemical tests identified the isolate at the genus level, and the further molecular analysis of concatenated housekeeping gene sequences revealed that the strain belonged to the species A. dhakensis. The isolated A. dhakensis strain was resistant to five antibiotics, namely, penicillin, ampicillin, clindamycin, cephalexin, and imipenem, while it was susceptible to or showed intermediate resistance to most of the other 15 tested antibiotics. The isolated strain of A. dhakensis caused acute hemorrhagic septicemia and tissue damage in artificially infected A. nigrocauda , with a median lethal dose of 7.76 × 104 CFU/fish. The genome size of strain 202108B1 was 5 043 286 bp, including 1 chromosome and 4 plasmids. This is the first detailed report of the occurrence of infection caused by an A. dhakensis strain causing infection in an aquaculture system in inland China, providing important epidemiological data on this potential pathogenic species. [ABSTRACT FROM AUTHOR]

Growing evidence suggests a close relationship between gut microbiota and infectious diseases. However, the specific role of gut microbiota in host-pathogen interactions during aquaculture-related infections remains poorly understood. This study investigated the diversity and composition of gut microbiota communities in Aeromonas veronii-infected Lateolabrax maculatus using high-throughput sequencing. The results revealed significant changes in the structure and composition of L. maculatus gut microbiota after A. veronii infection. Over time, Bacteroidetes and Firmicutes decreased significantly, while Proteobacteria increased significantly after A. veronii infection. Most intestinal bacteria showed a decline in abundance over time, with probiotics (such as Lactobacillus) experiencing a significant decrease and pathogens (such as Aeromonas) showing a significant increase. Conversely, no differences were observed in the structure and composition of gut microbiota between healthy L. maculatus and those infected with A. veronii after treatment with Lactobacillus plantarum; no changes in relative abundances of other bacterial phyla or genera except for Aeromonas. Furthermore, intestinal flora's structural diversity and composition differed significantly from untreated L. maculatus infected with A. veronii. These findings suggest alterations in the structure and composition of gut microbiota following A. veronii infection. L. plantarum can maintain a dynamic balance within the intestinal flora, reducing the potential risk of pathogen infections. [ABSTRACT FROM AUTHOR]

The study examined the impact of a diet enriched with nanosilver (AgNPs) on the specific immunity, tissue biopsy, and growth effectiveness of Labeo rohita infected with A. carviae. The fish were divided into four groups with replications, and three diets were prepared with AgNPs (0, 10, 15, and 20 µg AgNPs kg-1 diet) added. The fish in the 15µg kg-1 group showed improved growth rates and a 70% survival rate after being challenged with A. carviae. Antioxidant indices, as well as the non-specific immune response, provided notable variations in the inclusion values of AgNPs in the liver and gill. The supplementation of 15µgkg-1 AgNPs most effectively improved tissue damage caused by A. caviae exposure in immunoprotective organs. T3 had higher liver TNF-α transcription than other treatments, while T4 had the highest values for IL-10. The amount of IL-10 in kidneys, gills, and muscles was also higher in T3, T2 and T3 respectively. The research suggests that AgNPs can positively influence fish growth and manage A. caviae infections by boosting antioxidant status and immunity while causing minimal harm to the immunoprotective organs. [ABSTRACT FROM AUTHOR]

Bacteria of the genus Aeromonas are widely distributed in water bodies around the world. Some Aeromonas species have been identified as human pathogens causing intestinal and a variety of extraintestinal infections. In Germany, information on diseases caused by Aeromonas is rare, because Aeromonas infections are not notifiable in Germany. To address this information gap and gain better insights, a successful collaboration with human medical diagnostic laboratories within Germany was established and several Aeromonas isolates from diseased patients were sent to the Aeromonas laboratory of the German Federal Institute for Risk Assessment. 52 clinical Aeromonas isolates, of which anonymized patients’ data were available, were selected for further characterization by MALDI-TOF MS, biochemical testing, and whole genome sequencing (WGS). Nearly half of the isolates were from patients older than 60 years, whereas only four isolates were from patients aged up to 10 years. 30 isolates originated from stools of patients with diarrhea/(gastro-)enteritis and 22 strains were from patients with diverse extraintestinal infections, such as wound infection, septicemia, bursitis, abscesses, cholangitis, urinary tract infections, and pneumonia. Taxonomical identification revealed following predominant species: A. veronii biovar sobria (18 isolates), A. caviae (17 isolates), and A. hydrophila (nine isolates). Two A. salmonicida isolates and one isolate each of A. dhakensis, A. bestiarum, and A. encheleia were also identified. Three closely related intestinal isolates could not be assigned to a recognized Aeromonas species. The clustering of strains based on virulence factor profile resulted in a grouping that closely resembles the clustering of the phylogenetic tree suggesting that the profiles are specific for each species. Our study on clinical Aeromonas isolates characterizes for the first time human pathogenic strains isolated in Germany. These bacteria are important microorganisms within the One Health context because of their ubiquitous presence in the environment and as a cause of opportunistic infections in humans and animals. Infections caused by Aeromonas bacteria show a seasonality with increased infection rates in warmer periods. In view of climate change, Aeromonas bacteria are regarded as emerging pathogens and research is required to determine the reservoirs in One Health sources from which human infections may arise.

This study investigated the pathogenic mechanisms of Aeromonas veronii in macrophages. THP-1 derived macrophages were used as a human macrophage model and were treated with A. veronii strain AS1 isolated from intestinal biopsies of an IBD patient, or Escherichia coli strain K-12. RNA was extracted and subjected to RNA sequencing and comparative transcriptomic analyses. Protein levels of IL-8, IL-1β, IL-18, and TNFα were measured using ELISA, and apoptosis was assessed using caspase 3/7 assays. Both A. veronii AS1 and E. coli K-12 significantly upregulated the expression of many genes involving inflammation. At the protein level, A. veronii AS1 induced significantly higher levels of IL-8, TNFα, mature IL-18 and IL-1β than E. coli K-12, and led to greater elevation of caspase 3/7 activities. Both A. veronii AS1 and E. coli K-12 upregulated the expression of CASP5, but not other caspase genes. A. veronii AS1 significantly downregulated the expression of 20 genes encoding histone proteins that E. coli K-12 did not. The more profound pathogenic effects of A. veronii in inducing inflammation and apoptosis in macrophages than E. coli K-12, are consistent with its role as a human enteric pathogen. The upregulated expression of CASP5 and increased release of IL-1β and IL-18, support the role of CASP5 in activation of non-canonical inflammasome. The downregulation of histone genes by A. veronii suggests a unique impact on host cell gene expression, which may represent a novel virulence strategy. These findings advance the understanding of pathogenic mechanisms of the emerging human enteric pathogen A. veronii.

ABSTRACT Aquatic ecosystems serve as crucial reservoirs for pathogens and antimicrobial resistance genes, thus presenting a significant global health risk. Here, we investigated the phylogenomics of Aeromonas veronii from Lake Wilcox in Ontario. Among the 11 bacterial isolates, nine were identified as A. veronii. Notably, 67% of A. veronii isolates were potential human pathogens. Considerable genetic diversity was noted among the A. veronii isolates, suggesting the lake as a reservoir for multiple human pathogenic strains. Comparison of the A. veronii sequenced with global A. veronii genomes highlighted significant genetic diversity and suggests widespread dissemination of strains. All the isolates carried chromosomal genes encoding resistance to β-lactams. Although virulence gene content differed between human and non-human pathogenic strains, type III secretion systems was associated with human pathogenic isolates. The assessment of AMR genes in global isolates showed that β-lactam and tetracycline resistance genes were predominant. Although the machine learning-based pangenome-wide association approach performed did not yield any source-based genes, some genes were enriched in a few isolates from different sources. The mrkABCDF operon that mediates biofilm formation and genes encoding resistance to colistin, chloramphenicol, trimethoprim, and tetracycline were enriched in animal products, whereas macrolide resistance genes and Inc plasmid-types were linked to the aquatic environment. Novel biosynthetic gene clusters were identified, suggesting that A. veronii with varying pathogenic potential could produce unique secondary metabolites. There is a need for continuous tracking of pathogens in aquatic ecosystems to contribute to our understanding of their evolutionary dynamics and the ecological roles of their genetic elements.IMPORTANCELakes and other aquatic ecosystems can harbor harmful bacteria that can make people sick and resist antibiotics, posing a significant global health risk. In this study, we investigated Aeromonas veronii, a Gram-negative bacteria found in Lake Wilcox in Ontario. We used various techniques, including whole-genome sequencing (WGS), to analyze the bacteria and found that many of the isolates had the potential to cause human disease. We also discovered significant genetic diversity among the isolates, indicating that the lake may be a reservoir for multiple human pathogenic strains. All isolates carried genes that confer resistance to antibiotics, and some virulence genes were associated with human pathogenic isolates. This study highlights the importance of monitoring aquatic ecosystems for harmful bacteria to better understand their evolution, potential for human pathogenicity, and the ecological roles of their genetic elements. This knowledge can inform strategies for preventing the spread of antibiotic-resistant bacteria and protecting public health.

ABSTRACT Pomacea canaliculata is an invasive species which has significantly impacted native ecosystems globally. The benthic worm Limnodrilus hoffmeisteri is essential for the stability of the native aquatic ecosystem, facilitating the nutrient cycle dynamics through bioturbation. Nevertheless, limited information exists regarding the impact of P. canaliculata on those key native benthic species. Present study evaluated the impacts of P. canaliculata on L. hoffmeisteri by exposing L. hoffmeisteri to P. canaliculata (PC group) and the native snail Bellamya aeruginosa (BA group), with a control group consisting of no snails (NS group). The survival rate of L. hoffmeisteri in the PC group persisted diminished over 14 days, with notable declines in the rates of successful food acquisition and aggregation, an increase in migration, and a decrease in swing frequency. Elevated oxidative stress levels were linked to these alterations in L. hoffmeisteri behavior. Additionally, the presence of P. canaliculata increased the abundance of intestinal pathogenic bacteria in L. hoffmeisteri, with Aeromonas being one of the most lethal. Experimental models of Aeromonas‐free P. canaliculata (AFPC), re‐infected AFPC (IPC), and Aeromonas (As) were established to illustrate the role of Aeromonas in the decline of L. hoffmeisteri. Similar patterns in L. hoffmeisteri survival, behavior, and oxidative stress were observed in As, IPC, and PC group; however, these effects were mitigated by the elimination of Aeromonas in the AFPC group. Furthermore, L. hoffmeisteri was fatally affected by the four Aeromonas strains that were obtained from P. canaliculata intestine. These findings indicate that P. canaliculata exerts a deleterious impact on L. hoffmeisteri, and Aeromonas colonizing in intestine plays an important role. This study reveals a novel invasion mechanism of P. canaliculata.

Addressing the global antimicrobial resistance (AMR) crisis requires a multifaceted innovative approach to mitigate impacts on public health, healthcare and economic systems. In the complex evolution of AMR, biofilms and the acquisition of antimicrobial resistance genes (ARGs) play a pivotal role. Aeromonas is a major AMR player that often forms biofilm, harbors ARGs and is frequently detected in wastewater. Existing wastewater treatment plants (WWTPs) do not have the capacity to totally eliminate antimicrobial-resistant bacteria favoring the evolution of ARGs in wastewater. Besides facilitating the emergence of AMR, biofilms contribute significantly to biofouling process within the activated sludge of WWTP bioreactors. This paper presents the inhibition of biofilm formation, the expression of biofilm-linked genes and ARGs by phytochemicals andrographolide, docosanol, lanosterol, quercetin, rutin and thymohydroquinone. Aeromonas species were isolated and purified from activated sludge samples. The ARGs were detected in the isolated Aeromonas species through PCR. Aeromonas biofilms were quantified following the application of biocompounds through the microtiter plate assay. qPCR analyses of related genes were done for confirmation. Findings showed that the natural compounds inhibited the formation of biofilms and reduced the expression of genes linked to biofilm production as well as ARGs in wastewater Aeromonas. This indicates the efficacy of these compounds in targeting and controlling both ARGs and biofilm formation, highlighting their potential as innovative solutions for combating antimicrobial resistance and biofouling.

Qianwen Zhang,1,&ast; Shengcen Zhang,1,&ast; Binbin Xu,1 Luyan Dong,1 Zhichang Zhao,2 Bin Li1 1Department of Clinical Laboratory, Fujian Medical University Union Hospital, Fujian, 350001, People’s Republic of China; 2Department of Pharmacy, Fujian Medical University Union Hospital, Fuzhou, Fujian, People’s Republic of China&ast;These authors contributed equally to this workCorrespondence: Bin Li, Department of Clinical Laboratory, Fujian Medical University Union Hospital, Fujian, 350001, People’s Republic of China, Email leonlee307@hotmail.com Zhichang Zhao, Department of Pharmacy, Fujian Medical University Union Hospital, Fuzhou, Fujian, People’s Republic of China, Email slip2046@126.comBackground: Hospital wastewater (HWW) promotes the spread of carbapenem resistance genes (CRGs). Aeromonas carry a large number of CRGs in HWW, they may play a role as a suitable reservoir for CRGs, while resistomes in HWW are still poorly characterized regarding carbapenem resistant Aeromonas. Thus, the aim of the study was to evaluate the molecular epidemiological characteristics of carbapenem resistant Aeromonas in HWW.Methods: A total of 33 carbapenem resistant Aeromonas were isolated from HWW. Antimicrobial susceptibility testing and polymerase chain reaction (PCR) were used to assess the antimicrobial resistance profiles. Molecular typing was performed using enterobacterial repetitive intergenic consensus PCR (ERIC-PCR) and multilocus sequence typing (MLST). The horizontal transmission mode of blaKPC was explored through conjugation and transformation experiments. The stability of blaKPC-IncP-6 plasmids was assessed through plasmid stability and in vitro competition test. The PCR mapping method was used to investigate the structural diversity of blaKPC.Results: The detection rates of blaKPC and cphA in Aeromonas were 97.0% and 39.4% respectively. Aeromonas caviae were grouped into 13 clusters by ERIC-PCR and 12 STs by MLST. Aeromonas veronii were grouped into 11 clusters by ERIC-PCR and 4 STs by MLST. 56.3% blaKPC were located on mobilizable IncP-6 plasmids. blaKPC-IncP-6 plasmid showed high stability and low cost fitness.Conclusion: Carbapenem resistant Aeromonas from HWW mainly carried blaKPC, which exhibited great structural diversity. Aeromonas might serve as reservoirs for blaKPC and blaKPC might spread mainly through transformation in HWW.Keywords: hospital wastewater, carbapenem resistance, Aeromonas, IncP-6, blaKPC

Abstract Aim Diarrhea is a common disease in immunocompromised patients and can be associated with greater morbidity and even mortality. Therefore, the present study was designed to determine the prevalence of Aeromonas spp., Campylobacter spp., and C. difficile among immunocompromised children. Methods This study was conducted on 130 stool samples from patients with diarrhea who had defects in the immune system and were referred to Hazrat Masoumeh Children’s Hospital in Qom. Demographic information, clinical symptoms, immune status, and duration of chemotherapy were also recorded for each child. DNAs were extracted from the stool, and then direct PCR assays were done by specific primers for the detection of Aeromonas spp., Campylobacter spp., and toxigenic C. difficile, including tcdA/B and cdtA/B genes. Co-infection in patients was also evaluated. Results 60.8% and 39.2% were male and female, respectively, with a m ± SD age of 56.72 ± 40.49 months. Most cases of immunocompromised states were related to Acute Lymphocytic Leukemia (77.7%) and Non-Hodgkin Lymphoma (14.6%). 93.1% of patients were undergoing chemotherapy during the study. Among patients, most clinical symptoms were related to bloody diarrhea (98.5%) and fever (92.3%). Based on PCR, 14.6, 9.2, and 1.5% were positive for Aeromonas spp., C. difficile, and C. jejuni, respectively. Among the C. difficile-positive cases, the tcdA gene was only detected in one patient. In total, three co-infections were identified, which included Aeromonas spp./C. difficile (tcdA +), C. jejuni/C. difficile, and C. jejuni/Aeromonas spp. Conclusions This is the first study in Iran to investigate the simultaneous prevalence of some pathogens in immunocompromised children with diarrhea. Because Aeromonas spp., Campylobacter spp., and C. difficile are not routinely detected in some laboratories, infections caused by them are underappreciated in the clinic. Our results showed that these pathogens are present in our region and can cause gastroenteritis in children, especially those with underlying diseases. Therefore, increasing the level of hygiene in some areas and controlling bacterial diarrheal diseases should be given more attention by health officials.

Abstract Background The population structure and the correlation between antimicrobial resistance (AMR) phenotypes and genotypes in Aeromonas species isolated from patients with gastroenteritis are not well understood. The aims of the study were to: (1) investigate the antimicrobial susceptibility profiles of Aeromonas species isolated from patients with gastroenteritis; (2) explore the relationship between AMR genes and resistance phenotypes; and (3) describe the population structure of these isolates and provide evidence of transmission events among them. Methods This microbiological survey was performed at the Microbiology Laboratory of the Emek Medical Center in Afula, Israel. Cultivation of Aeromonas was attempted from stool samples that tested positive by PCR. Antimicrobial susceptibility testing (AST) was performed using the Sensititre GN3F microdilution panel. Whole genome sequencing (WGS) was done using the Illumina NextSeq500/550 system. Phylogenetic studies involved multi-locus sequence typing (MLST) and core genome (cg) MLST. Resistance mechanisms were identified using the Comprehensive Antibiotic Resistance Database and compared with the AST results. Results The study included 67 patient-unique isolates. The species that were identified included A. caviae (n = 58), A. dhakensis (n = 3), A. media (n = 2), A. veronii (n = 2) and A. hydrophila (n = 2). Isolates were almost uniformly susceptible to amikacin, gentamicin, aztreonam, cefepime, ceftazidime, ciprofloxacin and meropenem. All isolates with the exception of 1–2 isolates were resistant to ampicillin, cefazolin and ampicillin-sulbactam which was compatible with the presence of the bla OXA genes. Variable resistance rates were observed to cefuroxime, cefoxitin, ceftriaxone, piperacillin-tazobactam that were not correlated with the presence of other β-lactamase genes. Resistance to tetracycline and trimethoprim-sulfamethoxazole correlated with the presence of tetA and sul1, respectively. The population structure of A. caviae was highly diverse with the minority of the isolates (16/57) clustering into six defined sequence types. A cgMLST-based distance of four genes was found in one pair of isolates, suggesting common source transmission. Conclusions A. caviae is the dominant species related to gastroenteritis and is characterized by a diverse population structure, with almost no evidence for common-source transmission. Resistance rates to most antimicrobial agents were low and partially matched with the presence of resistance genes.

Knowledge of the insect microbiota remains largely unexplored. The intestinal microbiome of Marchalina hellenica (Gennadius, 1883) (Hemiptera, Margarodidae) was determined in the current study. This species is the main source of pine honey production. A pool of 100 samples were selected, representing the distribution of M. hellenica in the province of Mugla, Turkey. API Staph tests were used to assess Gram-positive bacteria, while API 20NE and API 20E tests were used to assess Gram-negative bacteria. As a result, 33 Gram-negative and 15 Gram-positive isolates were obtained from samples collected from 44 different locations. Among Gram-positive, 14 out of 15 belonged to Staphylococcus spp. Among Gram-negative, 22 out of 33 belonged to Aeromonas spp. This is the first study intended to determine the intestinal microbiome of M. hellenica. [ABSTRACT FROM AUTHOR]

Although the genus Aeromonas inhabits the natural environment, it has also been isolated from hospital patient specimens as a causative agent of Aeromonas infections. However, it is not known whether clinical strains live in the natural environment, and if these strains have acquired antimicrobial resistance. In this study, we performed the typing of flagellin A gene (flaA) of clinical and environmental strains of Aeromonas hydrophila and A. veronii biovar sobria using Polymerase Chain Reaction (PCR) assay with newly designed primers. Detection rates of the clinical and environmental flaA types of A. hydrophila were 66.7% and 88.2%, and the corresponding rates for A. veronii biovar sobria were 66.7% and 90.9%. The PCR assays could significantly discriminate between clinical and environmental strains of both species in approximately 4 h. Also, among the 63 clinical Aeromonas strains used, only one extended-spectrum β-lactamase-producing bacteria, no plasmid-mediated quinolone resistance bacteria, and only four multidrug-resistant bacteria were detected. Therefore, the PCR assays could be useful for the rapid diagnosis of these Aeromonas infections and the monitoring of clinical strain invasion into water-related facilities and environments. Also, the frequency of drug-resistant Aeromonas in clinical isolates from Okinawa Prefecture, Japan, appeared to be low. [ABSTRACT FROM AUTHOR]

Biofilm formation in broiler drinking water systems is a public health concern. Bacterial detachment from the pipes into the drinking water subsequently increases the risk of waterborne transmission and has detrimental effects on animal and human health. The study evaluated the antimicrobial effectiveness of plasma‐activated water bubbles (PAWBs) recirculated under different flow regimes against the mixed‐species biofilms of Salmonella Typhimurium ATCC13311 and Aeromonas australiensis 03‐09 grown on the inner surfaces of polyvinyl chloride (PVC) pipes. A benchtop pipeline model representing broiler drinker lines was developed to compare the biofilm inactivation efficacy of PAWB recirculated at different flow rates, corresponding to Reynold's number of 1000, 2500, and 4000. The synergistic mechanical and oxidative recirculation using PAWB resulted in a higher biofilm inactivation from the pipe walls as compared to recirculation using distilled water alone. Apart from the flow regimes, various parameters including the volume of PAWB circulated, the concentration of the major plasma reactive species, and treatment time affected the susceptibility of the mixed‐species biofilms to PAWB treatment. Under all tested conditions, the bacterial cells were below the detection limit of 1 log CFU/mL in water after PAWB treatments. A better understanding of the hydrodynamic variations prevalent in the drinking water system is important for designing an effective disinfection protocol using PAWB. The results obtained from the study provide important information on the use of PAWB for biofilm control strategies. [ABSTRACT FROM AUTHOR]

Microplastics (plastic particles < 5 mm) are ubiquitous pollutants that have the ability to carry microbiota, including pathogens. Microbial adhesion is usually a sign of pathogenicity; thus, we investigated the adherent microbiota found on 4 mm nylon strips, which were ingested and excreted by wild fish specimens. Retention times were recorded and the polymer analysis of the excreted samples was performed, which showed no signs of degradation, nor did their controls, represented by the nylon strips submerged in the same water tanks. Both the ingested samples and controls presented pathogens in large quantities. Following Matrix-Assisted Laser Desorption/Ionization Time-Of-Flight identification, the dominant genus was represented by Aeromonas, revealing the fact that nylon microplastics can serve as undegradable physical carriers for this pathogen, among others, in the aquatic environment. [ABSTRACT FROM AUTHOR]

Aeromonas trota is sensitive to most antibiotics and the sole species of this genus susceptible to ampicillin. This susceptibility profile could be related to its inability to acquire exogenous DNA. In this study, A. trota isolates were analyzed to establish their capacity to incorporate foreign DNA. Fourteen strains were identified as A. trota by multilocus phylogenetic analysis (MLPA). Minimal inhibitory concentrations of antibiotics (MIC) were assessed, confirming the susceptibility to most antibiotics tested. To explore their capacity to be transformed, A. trota strains were used as recipients in different horizontal transfer assays. Results showed that around fifty percent of A. trota strains were able to incorporate pBAMD1-2 and pBBR1MCS-3 plasmids after conjugal transfer. In all instances, conjugation frequencies were very low. Interestingly, several isoforms of plasmid pBBR1MCS-3 were observed in transconjugants. Strains could not receive pAr-32, a native plasmid from A. salmonicida. A. trota strains were unable to receive DNA by means of electroporation, natural transformation or vesiduction. These results confirm that A. trota species are extremely refractory to horizontal gene transfer, which could be associated to plasmid instability resulting from oligomerization or to the presence of defense systems against exogenous genetic material in their genomes. To explain the poor results of horizontal gene transfer (HGT), selected genomes were sequenced and analyzed, revealing the presence of defense systems, which could prevent the stable incorporation of exogenous DNA in A. trota. [ABSTRACT FROM AUTHOR]

Objective: During Egypt's hot summer season, Aeromonas veronii infection causes catastrophic mortality on Nile Tilapia Oreochromis niloticus farms. Egypt is ranked first in aquaculture production in Africa, sixth in aquaculture production worldwide, and third in global tilapia production. This study aimed to investigate, at the molecular level, the early innate immune responses of Nile Tilapia to experimental A. veronii infection. Methods: The relative gene expression, co‐expression clustering, and correlation of four selected immune genes were studied by quantitative real‐time polymerase chain reaction in four organs (spleen, liver, gills, and intestine) for up to 72 h after a waterborne A. veronii challenge. The four genes studied were nucleotide‐binding oligomerization domain 1 (NOD1), lipopolysaccharide‐binding protein (LBP), natural killer‐lysin (NKL), and interleukin‐1 beta (IL‐1β). Result: The four genes showed significant transcriptional upregulation in response to infection. At 72 h postchallenge, the highest NOD1 and IL‐1β expression levels were recorded in the spleen, whereas the highest LBP and NKL expression levels were found in the gills. Pairwise distances of the data points and the hierarchical relationship showed that NOD1 clustered with IL‐1β, whereas LBP clustered with NKL; both genes within each cluster showed a significant positive expression correlation. Tissue clustering indicated that the responses of only the gill and intestine exhibited a significant positive correlation. Conclusion: The results suggest that NOD1, LBP, NKL, and IL‐1β genes play pivotal roles in the early innate immune response of Nile Tilapia to A. veronii infection, and the postinfection expression profile trends of these genes imply tissue‐/organ‐specific responses and synchronized co‐regulation. Impact statementWe tracked the early responses of four innate immunity genes (NOD1, LBP, NKL, and IL‐1β) in the spleen, liver, gills, and intestine of Nile Tilapia for up to 72 h after infection with Aeromonas veronii. The gene expression trends and the specific tissue/organ responses revealed a dynamic and coordinated co‐regulation. These findings provide valuable preliminary insights into the intricate immune mechanisms underlying the response of Nile Tilapia to A. veronii infection and may extend to other similar gram‐negative bacterial pathogens. [ABSTRACT FROM AUTHOR]

Aeromonas dhakensis is increasingly recognised to be an important pathogen responsible for disease losses in warm-water aquaculture and, similar to several other Aeromonas species, it can infect humans. Knowledge of A. dhakensis is accumulating, but this species remains relatively under-investigated compared to its close relative, Aeromonas hydrophila. The significance of A. dhakensis may have been overlooked in disease events of aquatic animals due to issues with reliable identification. Critical to appreciating the importance of this pathogen is the application of dependable molecular tools that enable accurate identification and discrimination from A. hydrophila and other motile aeromonads. This review aims to synthesise the key literature on A. dhakensis, particularly with relevance to aquaculture, including knowledge of the bacterium derived from disease case studies in aquatic hosts. Identification methods and strain phylogeny are discussed, with accurate detection important for prompt diagnosis and for distinguishing strains with heightened virulence. Increasing evidence suggests that A. dhakensis may be more virulent than A. hydrophila and correct identification is required to determine the zoonotic risks posed, which includes concerns for antibiotic-resistant strains. This review provides an impetus to improve species identification in the future and screen strain collections of presumptive Aeromonas spp. retrospectively to reveal the true prevalence and impact of A. dhakensis in aquaculture, the environment, and healthcare settings. [ABSTRACT FROM AUTHOR]

The genus Aeromonas includes well-known pathogenic species for fishes and humans that are widely distributed in the aquatic environment and foods. Nowadays, one of the main issues related to wild Aeromonas isolates is their identification at the species level, which is challenging using classical microbiological and biomolecular methods. This study aims to test MALDI-TOF MS technology in the identification of Aeromonas strains isolated from n. 60 retail sushi and sashimi boxes using an implemented version of the SARAMIS software V4.12. A total of 43 certified Aeromonas strains were used to implement the SARAMIS database by importing the spectra obtained from their identification. The original SARAMIS version (V4.12) failed to recognize 62.79% of the certified strains, while the herein-implemented version (V4.12plus) allowed the identification of all the certified strains at least to the genus level with a match of no less than 85%. Regarding the sushi and sashimi samples, Aeromonas spp. was detected in n. 18 (30%) boxes. A total of 127 colonies were identified at the species level, with A. salmonicida detected as the most prevalent species, followed by A. bestiarum and A. caviae. Based on the results of the present study, we could speculate that MALDI-TOF technology could be a useful tool both for the food industry to monitor product contamination and for clinical purposes to make diagnoses effectively and quickly. [ABSTRACT FROM AUTHOR]

This study was conducted to determine the effect of vitamin C supplementation on the survival rate and histopathological changes of gills and kidneys of tilapia infected by Aeromonas hydrophila. Three doses of vitamin C were tested (150; 300; and 450 mg/kg) with two control groups. Tilapia with uniform size (average weight of 14 grams) as the criteria for inclusion were randomly distributed in five ponds with 15 tilapia fish per pond. Tilapia was fed with hands until full for two weeks. Tilapia was then infected with A. hydrophila to find out the survival rate and histopathological changes of gills and kidneys at the end of the experimental period or 7 days after infection. The supplementation of 150 mg/kg vitamin C in feed increased Tilapia's survival rate (%) by 86.67% or higher than other treatment and control groups. The damage to gills in terms of lamella separation was found in all treatment groups and kidneys. The results found that the supplementation of 150 mg/kg vitamin C in feed increased survival rate but did not give effective protection on gills and kidneys. [ABSTRACT FROM AUTHOR]