Aeromonas Hydrophila Research Articles

The involvement of tumor necrosis factor receptor-associated factor 6 in regulating immune response by NF-κB at pre-molt stage of Chinese mitten crab (Eriocheir sinensis)

Molting is a crucial biological process of crustaceans. Crustaceans go through three separate stages throughout their molting process, including pre-molt, post-molt and inter-molt. However, the exact mechanism of immunological modulation during molting remains unclear. Tumor necrosis factor receptor-associated factor 6 (TRAF6) has been extensively documented to participate in immune defense. In the present study, a TRAF6 gene with two TRAF-type zinc finger domains was identified from Eriocheir sinensis (designed as EsTRAF6), and its role in regulating immune response during molting process was explored. The mRNA expression level of EsTRAF6 at pre-molt stage was higher than that at post-molt stage and inter-molt stage. After Aeromonas hydrophila stimulation, the expression levels of EsTRAF6, EsRelish and anti-lipopolysaccharide factors (ALFs) genes exhibited a considerable increase at three molting stages. Subsequently, the expression patterns of EsTRAF6 and EsRelish in response to the treatment with 20-hydroxyecdysone (20E) were examined. The mRNA expression of EsTRAF6 and EsRelish were significantly increased at 12 h after 20E injection. Additionally, the protein expression level of TRAF6 was also up-regulated in 20E group compared to control group. Furthermore, the role of EsTRAF6 in regulating the anti- ALFs expression at pre-molt stage post A. hydrophila stimulation was investigated. Following the inhibition of the EsTRAF6 transcript using RNAi or the injection of inhibitor (TMBPS), there was a notable decrease of the EsALF1, EsALF2 and EsALF3 transcripts. Moreover, a significant reduction in the phosphorylation level of NF-κB at pre-molt stage was observed after A. hydrophila stimulation in TRAF6-inhibited crabs. Collectively, our results suggest that EsTRAF6 could be induced by 20E and promoted the EsALFs expression by activating NF-κB at pre-molt stage, which provides a novel insight into the research of immune regulatory mechanism during the process of molting of crustaceans.

A proteomics and transcriptome analysis provides insight into the molecular mechanisms of tea tree oil against Aeromonas hydrophila

Aeromonas hydrophila is a widespread fish pathogen. However, due to the extensive use of antibiotics in aquaculture, this bacterium has developed drug resistance. In recent years, tea tree oil, extracted from Melaleuca alternifolia, has gained widespread application in antibacterial research. Nevertheless, the underlying mechanism of action of tea tree oil on A. hydrophila remains unclear. In this study, the inhibitory effect of tea tree oil on A. hydrophila was analyzed, and its mechanism of action was elucidated through a combination of transcriptome and proteome analyses. In the current work, tea tree oil (0.039 mg/mL) significantly inhibited the growth of A. hydrophila and changed the permeability of the cell membrane. A total of 109 differentially expressed genes (DEGs) were identified by the combined analysis of the transcriptome and the proteome, of which 46 were upregulated and 63 were downregulated. These co-regulated DEGs were primarily enriched in metabolic pathways such as bacterial chemotaxis, pyrimidine metabolism, and the two-component system. Simultaneously, it was found that the target proteins of tea tree oil, such as secB, yajC, rpsP, rplL, and rpsT were significantly downregulated. These findings suggested that the potential of tea tree oil as an alternative to antibiotics in inhibiting the growth of A. hydrophila. It provides new insights into the molecular mechanisms underlying the antimicrobial activity of tea tree oil against A. hydrophila.

Yorkie negatively regulates the Crustin expression during molting in Chinese mitten crab, Eriocheir sinensis

Molting is a key biological process of crustaceans, which is mainly regulated by 20-hydroxyecdyone (20E). The molting cycle could be divided into three main stages including pre-molt, post-molt and inter-molt stages. The mechanism of immune regulation during molting process still requires further exploration. Yorkie (Yki) is a pivotal transcription factor in the Hippo signaling pathway, and it plays an essential role in regulating cell growth and immune response. In the present study, a Yki gene was identified from Eriocheir sinensis (designed as EsYki), and the regulatory role of EsYki in controlling the expression of antimicrobial peptide genes throughout the molting process was investigated. The mRNA expression level of EsYki was higher at the pre-molt stage compared to the post-molt stage and inter-molt stage. Following the injection of 20E, there was a notable and consistent rise in the EsYki mRNA expression in haemocytes. The increase was observed from 3 h to 48 h with the maximum level at 12 h. And the phosphorylation of Yki in the haemocytes was also significantly up-regulated at 3 h post 20E injection. Moreover, the levels of EsYki mRNA expression at three molting stages were significantly increased post Aeromonas hydrophila stimulation. The maximum level was detected at post-molt stage following A. hydrophila stimulation, while the lowest level was observed at inter-molt stage. The expression pattern of EsCrus was in contrast to EsCrus. After EsYki mRNA transcripts were inhibited by Yki inhibitor (CA3), the mRNA expression levels of EsCrus1 and EsCrus2 following A. hydrophila stimulation were significantly elevated. Furthermore, the phosphorylation level of NF-κB was also increased following the inhibition of Yki. Collectively, our findings indicated that EsYki could be induced by 20E and has a suppressive effect on the expression of EsCrus via inhibiting NF-κB during molting process. This research contributes to the understanding of the immunological regulation mechanism during molting process in crustaceans.

<i>Citrus reticulata</i> flavonoids as a valuable source for reducing meat-borne <i>Aeromonas hydrophila</i>

Meat products are one of the nutritious diet options available to consumers. However, meat products have the potential to serve as a reservoir of food-borne infections, such as those caused by Aeromonas species, which pose a significant risk to public health. A total of 270 samples, 30 of each minced beef, meatball, beef burger, chicken nuggets, chicken pane, chicken burger, canned anchovy, canned mackerel, and canned sardine, were obtained from supermarkets in Aswan Province, Egypt, to analyze the occurrence and virulence features of Aeromonas hydrophila. Influence of Citrus reticulata peel extract on the A. hydrophila count and its virulence capacity after different marinating periods was also analyzed. The obtained results revealed that the Aeromonas counts ranged from 2.02±0.30 to 4.21±0.27 log10 CFU/g and 37% of the analyzed samples were contaminated with Aeromonas spp. The main strains discovered were A. hydrophila (13.3%), A. sobria (9.6%), A. caviae (7.4%), A. veronii (4%), and A. fluvialis (2.6%). It was found by polymerase chain reaction that all tested strains (n = 36) belonged to Aeromonas spp., and 89% were identified as A. hydrophila. In contrast, virulence genes aerolysin (aerA) and cytotoxic enterotoxin (act) were found in 61.1% and 50% of the tested isolates, respectively, with a wide range of antibacterial resistance. Additionally, the influence of Citrus reticulata peel extract on A. hydrophila counts at different marinating periods declined significantly with increased concentration without major changes in the sensory criteria.

Analysis of antibiotic resistant infections associated with hirudotherapy

ObjectiveGiven rising concern regarding antibiotic resistance, our objective was to evaluate antibiotic-resistant infections following leech therapy and to characterize the use of prophylactic antibiotics. MethodsAll reports of adverse events involving hirudotherapy (product code “NRN”) were retrieved from the U.S. Food and Drug Administration MAUDE database between 2012 and 2021. Antibiotic resistance was defined by bacterial culture or infection after antibiotic administration. ResultsNineteen cases of antibiotic resistance involving hirudotherapy were identified. Only three cases of antibiotic resistance were discovered on routine testing and the remaining 16 cases were associated with patient injury. Positive blood cultures or fever were present in 26.3 % (n = 5) of cases. Cultures of the infection grew Aeromonas hydrophilia (n = 13; 68.4 %), Vibrio vulnificus (n = 3; 15.8 %), Pseudomonas aeruginosa (n = 2; 10.5 %), and Proteus vulgaris (n = 1; 5.3 %). There were nine (47.4 %) multi-drug resistant infections. Infection was most commonly resistant to fluoroquinolones (n = 9; 47.4 %), trimethoprim-sulfamethoxazole (n = 9; 47.4 %) and ertapenem (n = 4; 21.1 %). ConclusionAntibiotic-resistant infections involving hirudotherapy are frequently resistant to multiple drugs, including fluoroquinolones and trimethoprim-sulfamethoxazole. Resistance to ertapenem, a drug of last resort, was also documented. The findings presented in this study support growing literature that the trend in multi-drug resistance is more severe than previously reported.

Lactobacillus delbrueckii ameliorates Aeromonas hydrophila-induced oxidative stress, inflammation, and immunosuppression of Cyprinus carpio huanghe var NF-κB/Nrf2 signaling pathway

Aeromonas hydrophila (A. hydrophila) is one of the most pathogenic disease-causing bacteria, and causes massive death of animals including fish. Thus, strategies are being sought to ameliorate the impact of A. hydrophila. In this study, we have evaluated the ameliorative potential of dietary Lactobacillus delbrueckii (L. delbrueckii). The fishes were divided into the control group, an A. hydrophila group (A. hydrophila), and an L. delbrueckii group (A. hydrophila + 1*107 CFU/g L. delbrueckii). The results showed that A. hydrophila increased reactive oxygen species (ROS) content. However, dietary supplementation with L. delbrueckii prevented oxidative damage caused by elevated levels of ROS. The toxic effects of A. hydrophila on superoxide dismutase (SOD) activity, glutathione-S-transferase (GST), glutathione peroxidase (GPx), and glutathione reductase (GR), along with the levels of glutathione (GSH), were mitigated by dietary L. delbrueckii (P < 0.05). Also, Dietary L. delbrueckii induced the expression of antioxidant-related genes (sod, cat, gpx, gst, NF-E2-related factor 2 (nrf2), Kelch-like-ECH-and associated protein 1a (keap1a)) in the intestine of fish (P < 0.05). Furthermore, L. delbrueckii increased A. hydrophila-induced lysozyme, ACP, C3, and C4 decline. The mRNA expression levels of interleukin 1β (il-1β), interleukin 8 (il-8), tumour necrosis factor α (tnf-α), and nuclear transcription factor-κB p65 (nf-κb p65) were significantly elevated by A. hydrophila. In contrast, the relative mRNA expression levels of inhibitor factor κBα (iκbα) in the intestine were decreased by A. hydrophila (P < 0.05). However, L. delbrueckii prevented A. hydrophila-induced the relative mRNA expression changes. These present results demonstrate that dietary L. delbrueckii alleviated A. hydrophila-induced oxidative stress, immunosuppression, inflammation, and apoptosis in common Cyprinus carpio.

Antibiotic-resistant bacteria contaminating leafy vegetables in Saudi Arabia’s eastern region

BackgroundFood-associated antibiotic-resistant bacteria can cause infections that may critically impact human health. The objectives of this study were to determine the microbial contamination level of green leafy vegetables and their antibiotic resistance pattern.MethodsSixty-three samples of leafy vegetables were collected from Dammam Central Fruit and Vegetables Market from January to June 2023. The vegetables included lettuce (Lactuca sativa), parsley (Petroselinum crispum), and watercress (Nasturtium officinale). Samples were tested by standard microbiological techniques for identification and antibiotic susceptibility testing.ResultEight types of bacteria belonging to six different genera were detected. Enterobacteriaceae family was represented by four genera: Klebsiella, Proteus, Morganella, and Enterobacter. The other two genera were Pseudomonas and Aeromonas. Enterobacter cloacae was the most abundant organism, followed by Pseudomonas putida and Aeromonas sobria. On the other hand, Morganella morganii, Aeromonas hydrophila, and Proteus mirabilis were the least abundant. The three vegetable types had different levels of bacterial contamination. All isolated organisms were sensitive to penicillin, cephalosporin, aminoglycoside, and fluoroquinolone. However, Klebsiella oxytoca, M. morganii, and K. pneumonia showed resistance to ampicillin. A. hydrophila, Morganella morganii, and E. cloacae showed resistance to amoxicillin. M. morganii and E. cloacae were found to be resistant to cefalotin. Moreover, A. hydrophila, M. morganii, and E. cloacae were resistant to cefoxitin. Again, A. hydrophila was found to be resistant to imipenem. Only M. morganii was resistant to Ciprofloxacin. Two isolates, P. mirabilis and M. morganii were resistant to tigecycline. Another two, M. morganii and P. mirabilis were resistant to Nitrofurantoin. Only M. morganii was found to be resistant to trimethoprim.ConclusionThis study aligns with the broad consensus in the literature about the significance of bacterial contamination in vegetables and the public health implications. The unique focus on antibiotic resistance patterns adds an essential dimension to the existing body of knowledge.

Comparative Studies on Antibacterial Potentials of Cassia fistula and Carica papaya Leaf Extract against Selected Fish Pathogens

Aim: To investigate the antibacterial efficacy of Cassia fistula and Carica papaya leaf extracts against selected fish pathogens such as Aeromonas hydrophila, Vibrio parahaemolyticus, Staphylococcus aureus, Proteus mirabilis and Micrococcus luteus, Study Design: To carry out the antibacterial sensitivity studies of C. fistula and C. papaya leaf extracts using one way analysis of variance. Place and Duration of Study: Department of Biological Sciences, Bells University of Technology, Ota, Ogun State, between November 2022-April, 2023 Methodology: Leaves were subjected to aqueous extraction, and concentrated at 500C in hot air oven. The extracts were screen for biomolecules responsible for antibacterial activities. Antibacterial sensitivity test was carried out on bacteria pathogens using agar well diffusion technique. Results: Results showed that C. fistula leaf extract was more effective against A. hydrophila (20.00b ± 2.31 mm) and P. mirabilis (17.00b ± 1.15 mm) than C. papaya leaf extract. (14.00c ± 2.31 mm and 15.00c ± 1.15 mm), while C. papaya was only effective against V. parahaemolyticus (17.50b ±1.73 mm) than C. fistula (15.50c ± 0.58 mm). The results depicted significant difference (P˂0.05) in the inhibition zone among A. hydrophila, V. parahaemolyticus and P. mirabilis, except S. aureus (12.50b ± 1.73 mm) and M. luteus (11.50b ± 0.58 mm) (P˃0.05). Minimum Inhibitory Concentrations and Minimum Bactericidal Concentrations confirmed that C. fistula was more effective on A. hydrophila than C. papaya at a lesser dose with a marked difference (P˃0.05). Conclusion: C. fistula leaf extract exhibited higher antibacterial efficacy than C. papaya, showing that it is more effective against all tested bacteria except V. parahaemolyticus. This implies that C. fistula is an excellent antibacterial agent with capacity to destroy a wide range of bacteria than C. papaya. Therefore, it can be used to treat fish diseases and pond water against bacteria pathogens, including multidrug resistant bacteria.

Effects of a Chinese herbal medicine mixture on growth performance, immune response, and gene expression in Chinese soft-shelled turtles (Pelodiscus sinensis)

Chinese herbal medicines (CHMs), known for their safety, low toxicity, and minimal impact on the environment, are often used as a natural feed additive in aquaculture to prevent or control diseases of aquatic animals. However, their effect on cell responses of Chinese soft-shelled turtle (Pelodiscus sinensis) remains unexplored. In this study, the extract mixed with four Chinese herbs of Astragalus membranaceus, Lycium barbarum, Rhizoma polygonati and Codonopsis pilosula in proportions (7:8:3:2) was used as a feed additive for 60 days to study their effects on the growth performance and immune response of P. sinensis in greenhouse mode. Results showed that the weight gain rate and the specific growth rate in the CHMs group were 46.63 % and 0.64 %, which were 1.13- and 1.15-fold of that in the control group, respectively. Besides, CHMs could significantly improve the survival rate by 76.94 % after artificial infection of Aeromonas hydrophila. The CHMs group also exhibited significant increases in the activities of total superoxide dismutase (27.76 %), catalase (41.28 %), glutathione peroxidase (14.62 %), and glutathione sulfur transferase (36.75 %) compared to the control group. Conversely, malondialdehyde concentration was reduced to 67.82 % of that in the control group. Moreover, the concentration of lysozyme and complement C3, as well as the activity of acid phosphatase, rose by 16.43 %, 24.30 %, and 27.68 %, respectively. Comparative transcriptome analysis revealed that growth, immunity, and lipid metabolism-related pathways are involved in the response to CHMs. Among these, the two pathways of the cell cycle and the cytokine-cytokine receptor interaction may play important roles in the growth and immunity of P. sinensis. SMOX, STAT3, and HMGCS1 may serve as key genes in CHMs-stimulated immune response in P. sinensis; GADD45B, ARG1, ACVR1C, and BMP7 may be crucial genes in promoting the growth of P. sinensis. This study provides a theoretical and practical basis for the green and efficient culture of P. sinensis.

Antimicrobial susceptibility in bacterial isolates from water and agricultural products of the Chanchán river, Chimborazo Province, Ecuador

Introduction: river contamination with pathogenic and multidrug-resistant microorganisms is a public health issue due to its impact on health and its potential to transmit infectious diseases. Objective: To determine the presence of multidrug-resistant bacteria in irrigation water samples and agricultural products from the Chachán River. Method: a descriptive, non-experimental study with a quantitative and cross-sectional approach was conducted. Water samples were collected from six different points, and pH and temperature were measured. Additionally, 13 agricultural product samples from the same points were analyzed. The identification and antimicrobial susceptibility testing of bacteria were performed using the VITEK2 system and amplification and sequencing of the 16S rRNA gene. Results: a total of 17 bacterial strains were isolated from the water samples, 16 of which (94 %) belonged to the order Enterobacterales, including Proteus mirabilis, Proteus vulgaris, Morganella morganii, and Citrobacter diversus. From the agricultural products, 24 bacteria were isolated, including species of Klebsiella, Stenotrophomonas maltophilia, and Enterococcus faecalis. Antimicrobial resistance was observed in various strains, notably P. mirabilis, C. diversus, and P. vulgaris with multiple resistances. Resistance was also identified in pathogenic strains such as Yersinia enterocolitica, Plesiomonas shigelloides, and Aeromonas hydrophila. Conclusions: the Chachan River and the agricultural products irrigated with its waters contain multidrug-resistant bacteria, posing a significant risk to public health. It is crucial to implement control and monitoring measures to reduce the spread of these pathogens and ensure food safety

Bacterial infection-biased abundance of proteins in the skin mucus of obscure puffer (Takifugu Obscurus)

The skin mucus of fish is equipped with immunological and antimicrobial peptides that confer protection against invading pathogens. The skin mucus has been studied in fish however information regarding its immunological roles in bacterial infection is rare. This study highlighted the proteins and peptides in the skin mucus of Obscure puffer Takifugu obscurus that quantitatively altered against Aeromonas hydrophila infection. We infected the fish through bath immersion, intraperitonially, and treated with PBS (control) then compared the level of proteins in the skin mucus among the groups using liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis. The Tandem Mass Tag (TMT) based quantification showed that 4896 proteins were Deferentially Quantified Proteins (DQPs), based on 19,751 unique peptides. Of which 170 were depleted (decreased in abundance) and 69 were abundant in comparison of Bath Treated (BT) vs Control (C) groups. Similarly, 76 DQPs were depleted and 70 were abundant in comparison of Treated (T) vs BT groups. Further, 126 DQPs were depleted, and 34 were abundant in comparison to T vs C groups. The DQPs we report were mostly immunological and were involved in unique biological functions and pathways. The interesting protein we report, where some of the proteins are for the first time in fish, shows the protein-rich structure of the mucus of fish, which may act as a biomarker to be targeted for bacterial disease therapy in fish and ultimately hint to the way of making resistance in fish against bacterial pathogens.

Effects of berberine hydrochloride on antioxidant response and gut microflora in the Charybdis japonica infected with Aeromonas hydrophila

This study used berberine hydrochloride to treat the Asian paddle crab, Charybdis japonica infected with the Gram-negative bacterium Aeromonas hydrophila at concentrations of 0, 100, 200 and 300 mg/L. The effect of berberine hydrochloride on the survival rate and gut microbiota of C. japonica was investigated. Berberine hydrochloride improved the stability of the intestinal flora, with an increase in the abundance of probiotic species and a decrease in the abundance of both pathogenic bacteria after treatment with high concentrations of berberine hydrochloride. Berberine hydrochloride altered peroxidase activity (POD), malondialdehyde (MDA), and lipid peroxidation (LPO) in the intestinal tract compared to the control. Berberine hydrochloride could modulate the energy released from the enzyme activities of hexokinase (HK), phosphofructokinase (PFK), and pyruvate kinase (PK) in the intestinal tract of C. japonica infected with A. hydrophila. Zona occludens 1 (ZO-1), Zinc finger E-box binding homeobox 1 (ZEB1), occludin and signal transducer, and activator of transcription5b (STAT5b) expression were also increased, which improved intestinal barrier function. The results of this study provide new insights into the role of berberine hydrochloride in intestinal immune mechanisms and oxidative stress in crustaceans.

Probiotic, fructooligosaccharide and yeast extract mixture improves gut health in rainbow trout, Oncorhynchus mykiss.

The present study investigated the effects of a feed additive (FA) containing a probiotic consortium, fructooligosaccharide and yeast extract on growth performance, humoral immune responses, hepatic antioxidant parametersand intestine digestive enzymes, morphology and transcripts in rainbow trout, Oncorhynchus mykiss. The fish were reared for 8 weeks, feeding on diets containing 0 (CNT), 0.3 (0.3FA), 1 (1FA)and 2 (2FA) g/kg FA. The results showed that fish growth parameters were significantly and quadratically related to FA levelsand FA treatments had better growth performance than CNT treatment. Intestinal amylase activity significantly increased in 2FA, whereas, intestinal protease activity increased in all FA treatments. Intestinal villus length and muscular layer thickness significantly increased in 0.3FA treatment. Blood leucocyte and lymphocyte counts, plasma lysozyme activityand hepatic glutathione content significantly increased in 0.3FA and 1FA treatments; whereas hepatic malondialdehyde significantly decreased in these treatments. Blood neutrophil and monocyte counts significantly increased in 0.3FA treatment, while plasma alternative complement activity significantly increased in 1FA treatments. Plasma bactericidal activities against Aeromonas hydrophila, Yersinia ruckeriand Streptococcus iniae, and intestinal expression of heat shock protein 70 and beta-defensin significantly increased in all FA treatments. The abundance of A. hydrophila, Y. ruckeriand S. iniae in fish gut significantly decreased in 0.3FA treatment; these bacteria were absent in the intestines of 1FA and 2FA treatments. The present results suggest that dietary 0.3-1 g/kg of FA can significantly improve growth performance, immune response, intestinal healthand hepatic antioxidant capacity in rainbow trout.

Discovery of Ll-CATH: a novel cathelicidin from the Chong’an Moustache Toad (Leptobrachium liui) with antibacterial and immunomodulatory activity

BackgroundCathelicidins are vital antimicrobial peptides expressed in diverse vertebrates, crucial for immunity. Despite being a new field, amphibian cathelicidin research holds promise.ResultsWe isolated the cDNA sequence of the cathelicidin (Ll-CATH) gene from the liver transcriptome of the Chong’an Moustache Toad (Leptobrachium liui). We confirmed the authenticity of the cDNA sequence by rapid amplification of cDNA ends and reverse transcription PCR, and obtained the Ll-CATH amino acid sequence using the Open Reading Frame Finder, an online bioinformatics tool. Its translated protein contained a cathelin domain, signal peptide, and mature peptide, confirmed by amino acid sequence. The comparative analysis showed that the mature peptides were variable between the amphibian species, while the cathelin domain was conserved. The concentration of Ll-CATH protein and the expression of its gene varied in the tissues, with the spleen showing the highest levels. The expression levels of Ll-CATH in different tissues of toads was significantly increased post infection with Aeromonas hydrophila. Chemically synthesized Ll-CATH effectively combated Proteus mirabilis, Staphylococcus epidermidis, Vibrioharveyi, V. parahaemolyticus, and V. vulnificus; disrupted the membrane of V. harveyi, hydrolyzed its DNA. Ll-CATH induced chemotaxis and modulated the expression of pro-inflammatory cytokine genes in RAW264.7 macrophages.ConclusionsThis study unveiled the antibacterial and immunomodulatory potential of amphibian cathelicidin, implying its efficacy against infections. Ll-CATH characterization expands our knowledge, emphasizing its in a bacterial infection therapy.

The effect of selenium on the intestinal health of juvenile grass carp based on the ERS-autophagy pathway

Selenium (Se), a trace element, is vital for the maintenance of cellular redox balance, thyroid hormone metabolism, inflammation, and immunity. Aeromonas hydrophila (A. hydrophila) is a common Gram-negative conditional pathogenic bacterium in fish culture, posing a serious threat to intensive aquaculture. Our study investigated the influence of dietary Se on the intestinal immune function of grass carp (Ctenopharyngodon idella) and the related regulatory mechanisms. The 2160 healthy juvenile grass carp (9.76 ± 0.005 g) were randomly assigned to 6 test groups of 6 replicates each, and fed graded selenomethionine (0.05, 0.20, 0.40, 0.61, 0.77, 0.98 mg Se/kg diet) for 70 days and then injected with A. hydrophila for a 6-day attack test. The results indicated that appropriate Se levels (0.40 mg/kg diet) alleviated intestinal damage caused by A. hydrophila and increased intestinal immune substances C3 and C4 levels as well as the activity of acid phosphatase (ACP) and lysozyme (LZ) (P > 0.05). Appropriate levels of Se (0.40 mg/kg-0.61 mg/kg diet) decreased intestinal pro-inflammatory cytokines (IFN-γ2, IL-6, IL-12p35, IL-17 A F and IL-17D) mRNA levels (P > 0.05) and increased intestinal anti-inflammatory factors (TGF-β1, IL-4/13A, IL-4/13B, IL-10 and IL-22) mRNA levels (P > 0.05) in juvenile grass carp. Further studies revealed that Se (0.40 mg/kg-0.61 mg/kg diet) inhibited intestinal endoplasmic reticulum stress (ERS)-related signaling pathway. Furthermore, we found that appropriate levels of Se (0.40 mg/kg-0.61 mg/kg diet) inhibited intestinal autophagy in juvenile grass carp, which may be related to ULK1, Beclin 1, ATG5, ATG12, LC3, and P62. In conclusion, appropriate levels of Se can alleviate intestinal inflammation and inhibit ERS and autophagy in juvenile grass carp. A quadratic regression analysis of intestinal ACP and LZ also indicated that the Se requirements of juvenile grass carp were 0.59 and 0.51 mg/kg, respectively.

Growth performance, mucosal immunity and disease resistance in goldfish (Carassius auratus) orally administered with Escherichia coli Strain Nissle 1917.

The current research aimed to shed light on the efficacy of Escherichia coli strain Nissle 1917 (EcN) on goldfish (……) growth, gut immunity, morphology, bacterial nutritional enzyme activity and resistance to Aeromonas hydrophila infection. Fish fed with EcN at 106, 107 and 108CFU/g feed for 80days showed an enhancement in growth better than control fish. The gut innate immunity in terms of lysozyme activity, immunoglobulin and total protein levels was increased in the treatment fish with the best result being observed in fish fed EcN at 108CFU/ g. In addition, an increase was noted in the upregulation of immune-relevant genes, namely lysozyme, interleukin-1β, inducible nitric oxide synthase and tumor necrosis factor α of fish intestine. A marked surge in the number of proteolytic and heterotrophic bacteria was noted in the gut of fish nourished with the probiotic. Histological studies exhibited an improvement in the intestinal absorption surface area, intraepithelial lymphocyte count and goblet cell density. Significantly higher survival rate was obtained in fish fed EcN at 108CFU/g compared with the fish fed with the basal diet. These data exhibited the beneficial effect of EcN on goldfish growth, digestive enzymes, intestine heterotrophic bacteria and resistance against Aeromonas hydrophila challenge. This study confirmed the favorable outcomes resulting from the administration of EcN at108 CFU/g.

Effect on growth, gonad development, health and disease resistance against Aeromonas hydrophila of Origanum minutiflorum essential oil in Cyprinus carpio

This study investigated the effects on growth performance, histopathology, intestinal histomorphology, antioxidant activity, serum biochemical parameters, and disease resistance against A. hydrophila of carp fed with oregano essential oil (EO). Fish (13.54±0.24 g) were fed with experimental diets containing 1.0 and 3.0 mL kg−1 oregano EO for 60 days. At the end of the experiment, no significant difference was found among the growth performances of fish fed with oregano EO supplemented diets (p>0.05). However, dietary administration of 3.0 mL kg−1 oregano EO had significantly increased survival rates of common carp post-challenged with A. hydrophila (p < 0.05). In addition, goblet cells number and villi length in the intestine were increased in fish fed with oregano EO diets (p < 0.001). Also, no pathological findings were observed in hepatopancreas, gonads and intestines in fish fed with oregano EO. Fish fed with a diet containing 3.0 mL kg−1 oregano EO showed higher catalase activity (CAT) than the other experimental groups (p < 0.05). Superoxide dismutase (SOD), melondialdehyde (MDA), total protein, albumin, AST, ALT and ALP levels were similar in oregano EO supplemented groups compared to the control (p > 0.05). Number of mature oocytes in female ovaries caused a slight increase in fish fed with oregano EO. Adding oregano EO to common carp diet showed improved intestinal histomorphology and increased the survival against the A. hydrophila. Therefore, O. minutiflorum EO can be used as a health promoter for carp.

Tad pili contribute to the virulence and biofilm formation of virulent Aeromonas hydrophila.

Type IV pili (T4P) are versatile proteinaceous protrusions that mediate diverse bacterial processes, including adhesion, motility, and biofilm formation. Aeromonas hydrophila, a Gram-negative facultative anaerobe, causes disease in a wide range of hosts. Previously, we reported the presence of a unique Type IV class C pilus, known as tight adherence (Tad), in virulent Aeromonas hydrophila (vAh). In the present study, we sought to functionalize the role of Tad pili in the pathogenicity of A. hydrophila ML09-119. Through a comprehensive comparative genomics analysis of 170A. hydrophila genomes, the conserved presence of the Tad operon in vAh isolates was confirmed, suggesting its potential contribution to pathogenicity. Herein, the entire Tad operon was knocked out from A. hydrophila ML09-119 to elucidate its specific role in A. hydrophila virulence. The absence of the Tad operon did not affect growth kinetics but significantly reduced virulence in catfish fingerlings, highlighting the essential role of the Tad operon during infection. Biofilm formation of A. hydrophila ML09-119 was significantly decreased in the Tad operon deletant. Absence of the Tad operon had no effect on sensitivity to other environmental stressors, including hydrogen peroxide, osmolarity, alkalinity, and temperature; however, it was more sensitive to low pH conditions. Scanning electron microscopy revealed that the Tad mutant had a rougher surface structure during log phase growth than the wildtype strain, indicating the absence of Tad impacts the outer surface of vAh during cell division, of which the biological consequences are unknown. These findings highlight the role of Tad in vAh pathogenesis and biofilm formation, signifying the importance of T4P in bacterial infections.

Assessment of carbapenem resistance and carbapenemase genes in wastewater from cattle slaughterhouses: Implications for environmental antibiotic resistance surveillance

The objectives of the study were to determine the prevalence of carbapenem-resistant Gram-negative bacteria and assess the potential risks associated with cattle slaughterhouse wastewater. A total of 270 wastewater samples were collected from 10 different cattle slaughterhouses for microbiological analysis. Conventional culture methods were employed, followed by disc diffusion, the Modified Carbapenem Inactivation Method (mCIM), and the Modified Hodge Test (MHT) to identify carbapenem resistance. The Vitek® 2 compact system was used for species identification and antibiotic susceptibility profiling. Conventional and quantitative PCR (qPCR) were performed to detect specific carbapenemase genes (blaKPC, blaNDM, and blaOXA-48). Among the collected 72 carbapenem-resistant isolates, one Pseudomonas fluorescens, one Aeromonas hydrophila, and two Aeromonas sobria exhibited resistance to meropenem. Additionally, six P. fluorescens and two A. hydrophila isolates demonstrated intermediate resistance to meropenem. Furthermore, five carbapenem-resistant isolates were identified as Stenotrophomonas maltophilia, known to be inherently resistant to most antibiotics. Ten different antibiotics were evaluated in the antibiotic resistance panel and all Aeromonas isolates were found to be resistant to cefazolin and one A. hydrophila was detected as multi-drug resistant. The revealed data indicates that slaughterhouse wastewater can serve as a reservoir for antibiotic-resistant opportunistic pathogens. However, it may not pose a substantial risk for the distribution of carbapenemases, thereby mitigating concerns related to potential public health and environmental hazards associated with this aspect of slaughterhouse operations. This study contributes to understanding of antibiotic resistance in livestock-related environments and underscores the importance of continued monitoring and surveillance.

Synthesis of Zinc Nanoparticles in Hibiscus sabdariffa Plant Extract and Investigation of Its Antimicrobial Properties

Background: The use of nanotechnology in various biomedical and pharmaceutical fields is expanding rapidly. Objectives: The aim of this study was to synthesize zinc nanoparticles using Hibiscus sabdariffa plant extract and investigate their antimicrobial properties. Methods: In this experimental study, the aqueous extract of sour tea was mixed with a 0.1 M zinc sulfate solution at a 1:1 ratio and allowed to react for 15 minutes at room temperature to produce nanoparticles. The synthesis of zinc oxide nanoparticles was confirmed using spectrophotometric methods, measuring the average diameter of nanoparticles, X-ray diffraction, and scanning electron microscopy (SEM). The minimum inhibitory concentration (MIC) of the zinc oxide nanoparticles was then measured against standard strains. Results: The results showed that the largest inhibition zone diameter was observed at a concentration of 1024 μg/mL against Listeria monocytogenes, while the smallest inhibition zone was observed against Aeromonas hydrophila. At a concentration of 512 μg/mL, an inhibition zone of 10 mm was developed against two strains: Vibrio cholerae and Escherichia coli. Conclusions: Based on the results of this study, zinc oxide nanoparticles, along with the sour tea aqueous extract and zinc sulfate, exhibited antibacterial properties. However, the most pronounced antimicrobial effects were observed with the zinc oxide nanoparticles.