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Frontiers in Veterinary Science 2021is a Gram-negative bacterium that is commonly distributed in aquatic surroundings and has been considered as a pathogen of fish, amphibians, reptiles, and mammals. In...
is a Gram-negative bacterium that is commonly distributed in aquatic surroundings and has been considered as a pathogen of fish, amphibians, reptiles, and mammals. In this study, a virulent strain GD18, isolated from grass carp (), was characterized to belong to a new sequence type ST656. Whole-genome sequencing and phylogenetic analysis showed that GD18 was closer to environmental isolates, however distantly away from the epidemic ST251 clonal group. The type VI secretion system (T6SS) was known to target both eukaryotic and prokaryotic cells by delivering various effector proteins in diverse niches by Gram-negative bacteria. Genome-wide searching and hemolysin co-regulated protein (Hcp) expression test showed that GD18 possessed a functional T6SS and is conditionally regulated. Further analysis revealed that VasH, a σ54-transcriptional activator, was strictly required for the functionality of T6SS in GD18. Mutation of H gene by homologous recombination significantly abolished the bactericidal property. Then the virulence contribution of VasH was characterized in both and models. The results supported that VasH not only contributed to the bacterial cytotoxicity and resistance against host immune cleaning, but also was required for virulence and systemic dissemination of GD18. Taken together, these findings provide a perspective for understanding the VasH-mediated regulation mechanism and T6SS-mediated virulence and bactericidal effect of .
PubMed: 34966816
DOI: 10.3389/fvets.2021.793458 -
Microorganisms Nov 2020Antimicrobial resistance (AMR) is one of the biggest challenges of the 21st century, and biofilm formation enables bacteria to resist antibiotic at much higher...
Antimicrobial resistance (AMR) is one of the biggest challenges of the 21st century, and biofilm formation enables bacteria to resist antibiotic at much higher concentrations than planktonic cells. Earlier, we showed that the Gram-negative RIT668 and RIT669 (closely related to NBRC 12681) from infected spotted turtles (), formed biofilms and upregulated toxin expression on plastic surfaces, and were predicted to possess multiple antibiotic resistance genes. Here, we show that they each resist several antibiotics in the planktonic phase, but were susceptible to neomycin, and high concentrations of tetracycline and cotrimoxazole. The susceptibility of their biofilms to neomycin and cotrimoxazole was tested using the Calgary device. For , the minimum inhibitory concentration (MIC) = 500-1000, and the minimum biofilm eradication concentration (MBEC) > 1000 μg/mL, using cotrimoxazole, and MIC = 32.3-62.5, and MBEC > 1000 μg/mL, using neomycin. For MIC = 7.8-15.6, and, MBEC > 1000 μg/mL, using cotrimoxazole, and MIC = 7.8, and MBEC > 1000 μg/mL, using neomycin. Both and activated an acyl homoserine lactone (AHL) dependent biosensor, suggesting that quorum sensing could mediate biofilm formation. Their multidrug resistance in the planktonic form, and weak biofilm eradication even with neomycin and cotrimoxazole, indicate that and are potential zoonotic pathogens, with risks for patients living with implants.
PubMed: 33212916
DOI: 10.3390/microorganisms8111805 -
BMC Microbiology Mar 2023Aeromonas hydrophila is an opportunistic pathogen. Thus, it has received significant attention mainly in the fish sectors with high production scales. Nile tilapia...
BACKGROUND
Aeromonas hydrophila is an opportunistic pathogen. Thus, it has received significant attention mainly in the fish sectors with high production scales. Nile tilapia broodstock confined in the environment of fish hatcheries can be stressed. Hence, they are vulnerable to A. hydrophila.
RESULTS
Sequencing of the gyr B gene revealed the presence of 18 different A. hydrophila strains (kdy 10,620-10,637), which were deposited in the NCBI under accession numbers ON745861-ON745878. The median lethal doses of the isolates ranged from 2.62 × 10 to 3.02 × 10 CFU/mL. Antibiotic resistant genes, sulfonamide (sul1) and tetracycline (tetA) were found in the eighteen isolates. Approximately 83.3% of A. hydrophila strains were sensitive to ciprofloxacin and florfenicol. Further, eight A. hydrophila strains had high MDR indices at 0.27-0.45. All isolates presented with hemolysin activity. However, only 72.22% of them had proteolytic activity, and only 61.11% could form biofilms. Bacterial isolates harbored different pattern virulence genes, the heat-stable cytotonic enterotoxin (ast), cytotoxic enterotoxin (act), and hemolysin (hly) genes were the most prevalent. Also, a trial to inhibit bacterial growth was conducted using titanium dioxide nanoparticles (TiO NPs) with three sizes (13, 32, and 123 nm). If A. hydrophila strains with a high MDR index were tested against TiO NPs (20 µg/mL) for 1, 12, and 24 h, those with a small size had a greater bactericidal action than large ones. Bacterial strains were inhibited at different percentages in response to TiO NP treatment.
CONCLUSIONS
Nile tilapia broodstock, mortality is associated with different A. hydrophila strains, which harbored virulent and MDR genes. Furthermore, TiO NPs had bactericidal activity, thereby resulting in a considerable reduction in bacterial load.
Topics: Animals; Aeromonas; Cichlids; Hemolysin Proteins; Prevalence; Anti-Bacterial Agents; Aeromonas hydrophila; Enterotoxins; Fish Diseases; Gram-Negative Bacterial Infections
PubMed: 36959570
DOI: 10.1186/s12866-023-02827-8 -
International Journal of Molecular... Oct 2021is one of the most important aquatic pathogens causing huge economic losses to aquaculture. Linalool, a vital ingredient of a variety of essential oils, was proved as a...
is one of the most important aquatic pathogens causing huge economic losses to aquaculture. Linalool, a vital ingredient of a variety of essential oils, was proved as a good antimicrobial agent in our previous studies. However, the low solubility and volatility of Linalool obstruct its application in the field of aquatic drugs. Thus, in this study, Linalool nano-emulsion (LN) was prepared to solve these obstructions. We investigated the physicochemical properties, antibacterial activity, and mode of action of LN against LN with different medium chain triglycerides (MCT) concentrations were prepared by ultrasonic method. The results showed that the emulsion droplet size of LN was the smallest when MCT was not added to the formulation. Nano-emulsions are usually less than 500 nm in diameter. In our study, LN in this formulation were spherical droplet with a diameter of 126.57 ± 0.85 nm and showed good stability. LN showed strong antibacterial activity, the MIC and MBC values were 0.3125% / and 0.625% /, respectively. The bacterial population decreased substantially at 1 × MIC of LN. LN exhibited disruptive effect on cell membranes by scanning electron microscope (SEM) and transmission electron microscope (TEM). The present study provided a formulation of Linalool nano-emulsion preparation. Moreover, the good antibacterial activity of LN showed in our study will promote the application of Linalool for the control and prevention of in aquaculture.
Topics: Acyclic Monoterpenes; Aeromonas hydrophila; Anti-Infective Agents; Emulsions; Microbial Sensitivity Tests; Nanotechnology; Particle Size
PubMed: 34681662
DOI: 10.3390/ijms222011003 -
Frontiers in Microbiology 2023is a significant pathogen to freshwater farmed animals, and antibiotics are usually used to control the bacterial septicemia caused by . Due to the severe situation of...
is a significant pathogen to freshwater farmed animals, and antibiotics are usually used to control the bacterial septicemia caused by . Due to the severe situation of development and spread of antibiotic resistance, there are stricter restrictions on antibiotics used in aquaculture. To evaluate the feasibility of glycyrrhetinic acid β (GA) as an alternative therapy against bacterial infection, in this study, an isolated from diseased fish is used to test the antibacterial, anti-virulence activity and therapeutic effect of GA and , respectively. Results showed that GA did not affect the growth of , while it could down-regulate ( < 0.05) the mRNA expression of the hemolysis-related genes and A, and significantly inhibited ( < 0.05) hemolytic activity of . In addition, test showed that oral administration of GA was ineffective in controlling acute infections caused by . In conclusion, these findings suggested that GA was a potential anti-virulence candidate against , but the application of GA for the prevention and treatment of -related diseases was still a long way.
PubMed: 36846766
DOI: 10.3389/fmicb.2023.1043838 -
Frontiers in Microbiology 2023Motile septicemia (MAS) is a burden for striped catfish () farmers in Vietnam. MAS can be caused by several species of but is seen as the leading cause of MAS in...
INTRODUCTION
Motile septicemia (MAS) is a burden for striped catfish () farmers in Vietnam. MAS can be caused by several species of but is seen as the leading cause of MAS in aquaculture, but recent reports suggest that is also causing MAS.
METHODS
Here we investigated the bacterial etiology of MAS and compared the genomic features of and . We collected 86 isolates from diseased striped catfish fingerlings over 5 years from eight provinces in Vietnam. Species identification was done using PCR, MALDI-TOF and whole genome sequence (WGS). The MICs of commonly used antimicrobials was established. Thirty presumed isolates were sequenced for species confirmation and genomic comparison. A phylogenetic analysis was conducted using publicly available sequences and sequences from this study.
RESULTS
A total of 25/30 isolates were sequence type (ST) 656 and 5/30 isolates were ST 251. Our isolates and all publicly available isolates from Vietnam belonged to ST 251 and differed with <200 single nucleotide polymorphisms (SNP). Similarly, all isolates from Vietnam belonged to ST 656 and differed with <100 SNPs. The gene was found in 1/5 and 19/25 . All had an MIC ≤2 mg/L while 19/25 had MIC ≥8 mg/L for oxytetracycline. The gene was only found in (14/25) which showed a MIC ≥8 mg/L for florfenicol. Key virulence genes, i.e., /, and were present in all genomes, while was only present in .
DISCUSSION
This study confirms previous findings where was the dominating pathogen causing MAS and that the importance of has likely been overestimated. The differences in antimicrobial susceptibility between the two species could indicate a need for targeted antimicrobial treatment plans. The lipopolysaccharide regions and outer membrane proteins did not significantly differ in their immunogenic potentials, but it remains to be determined with experiments whether there is a difference in the efficacy of available vaccines against and .
PubMed: 37808293
DOI: 10.3389/fmicb.2023.1254781 -
Access Microbiology 2022Plant-based protein is being sought after as a substitute for fish meals (powdered fish) in tilapia feeds. This is to promote sustainable aquaculture, as fish meals...
Plant-based protein is being sought after as a substitute for fish meals (powdered fish) in tilapia feeds. This is to promote sustainable aquaculture, as fish meals contribute to the dwindling marine fish catch. is an edible weed that shows potential to improve the growth and immunity of Nile tilapia. However, most studies only consider the survivability of fish to evaluate the benefit of using plant-based feeds and do not necessarily elucidate whether a pathogen is affected . leaf meals (ASLMs) were used to determine effectiveness against (BIOTECH 10089) injected intraperitoneally into Nile tilapia. Formulated feeds with fish meals substituted with 50 % (ASLM) and 75 % (ASLM) leaves were fed to Nile tilapia challenged with . Then spleen and kidney tissue were collected and analysed 10 days post-injection for total plate count. The fish fed with ASLM appeared healthier than those fed with ASLM and those fed with control feeds. Fish fed with ASLMs had lower counts (=0.03). Phytochemical screening and antimicrobial activity determination for crude methanolic leaf (ASL) and ASLMs were also conducted to enhance the results. The metabolites present in the extracts were carbohydrates, amino acids and proteins, cardiac glycosides, saponins and terpenoids. The ASL and ASLM extracts had antimicrobial activity (MIC=115 mg ml). Overall, the study showed that ASLMs can make tilapia more resilient against infections. Fish meal substitution was best at 50 %. Higher substitution had unwanted effects (more bacterial counts), possibly due to antinutritional factors.
PubMed: 35355878
DOI: 10.1099/acmi.0.000305 -
Scientific Reports May 2023Aeromonas hydrophila is a ubiquitous fish pathogen and an opportunistic human pathogen. It is mostly found in aquatic habitats, but it has also been isolated from food...
Aeromonas hydrophila is a ubiquitous fish pathogen and an opportunistic human pathogen. It is mostly found in aquatic habitats, but it has also been isolated from food and bottled mineral waters. It causes hemorrhagic septicemia, ulcerative disease, and motile Aeromonas septicemia (MAS) in fish and other aquatic animals. Moreover, it might cause gastroenteritis, wound infections, and septicemia in humans. Different variables influence A. hydrophila virulence, including the virulence genes expressed, host susceptibility, and environmental stresses. The identification of virulence factors for a bacterial pathogen will help in the development of preventive and control measures. 95 Aeromonas spp. genomes were examined in the current study, and 53 strains were determined to be valid A. hydrophila. These genomes were examined for pan- and core-genomes using a comparative genomics technique. A. hydrophila has an open pan-genome with 18,306 total genes and 1620 genes in its core-genome. In the pan-genome, 312 virulence genes have been detected. The effector delivery system category had the largest number of virulence genes (87), followed by immunological modulation and motility genes (69 and 46, respectively). This provides new insight into the pathogenicity of A. hydrophila. In the pan-genome, a few distinctive single-nucleotide polymorphisms (SNPs) have been identified in four genes, namely: D-glycero-beta-D-manno-heptose-1,7-bisphosphate 7-phosphatase, chemoreceptor glutamine deamidase, Spermidine N (1)-acetyltransferase, and maleylpyruvate isomerase, which are present in all A. hydrophila genomes, which make them molecular marker candidates for precise identification of A. hydrophila. Therefore, for precise diagnostic and discrimination results, we suggest these genes be considered when designing primers and probes for sequencing, multiplex-PCR, or real-time PCR.
Topics: Animals; Humans; Aeromonas hydrophila; Virulence; Polymorphism, Single Nucleotide; Virulence Factors; Aeromonas; Fishes; Fish Diseases; Gram-Negative Bacterial Infections
PubMed: 37173388
DOI: 10.1038/s41598-023-34887-1 -
Viruses Nov 2022is a zoonotic pathogen and an important fish pathogen. A new lytic phage, Ahy-yong1, against multi-antibiotic-resistant pathogen was isolated, identified, and...
is a zoonotic pathogen and an important fish pathogen. A new lytic phage, Ahy-yong1, against multi-antibiotic-resistant pathogen was isolated, identified, and tentatively used in therapy. Ahy-yong1 possesses a head of approximately 66 nm in diameter and a short tail of approximately 26 nm in length and 32 nm in width. Its complete dsDNA genome is 43,374 bp with a G + C content of 59.4%, containing 52 predicted opening reading frames (ORFs). Taxonomic analysis indicated Ahy-yong1 as a new species of the genus of the family of the class. Ahy-yong1 was active only against its indicator host strain among the 35 strains tested. It is stable at 30-40 °C and at pH 2-12. phage Ahy-yong1 revealed an effective biofilm removal capacity and an obvious protective effect in brocade carp ( Koi). The average cumulative mortality for the brocade carp in the blank groups intraperitoneally injected with PBS was 1.7% ± 2.4%;for the control groups treated with (10 CFU/fish) via intraperitoneal injection, it was 100.00%;and for the test group I, successively treated with (10 CFU/fish) and phage Ahy-yong1 (10 PFU/fish) via intraperitoneal injection witha time interval of 2 hours, it was only 43.4% ± 4.7%. Furthermore, the cumulative mortality of the test group II, successively treated with phage Ahy-yong1 (10 PFU/fish) and (10 CFU/fish), was only 20.0% ± 8.2%, and that of the test group III, simultaneously treated with phage Ahy-yong1 (10 PFU/fish) and (10 CFU/fish), was only 30.0% ± 8.2%. The results demonstrated that phage Ahy-yong1 was very effective in the therapies against A18, prophylaxis was more effective than rescue, and earlier treatment was better for the reduction of mortality. This study enriches knowledge about phages.
Topics: Animals; Aeromonas hydrophila; Aeromonas; Carps; Bacteriophages; Caudovirales
PubMed: 36423108
DOI: 10.3390/v14112498 -
Antibiotics (Basel, Switzerland) May 2021and are major public health problems and the main cause of bacterial disease in Nile tilapia (). This study was conducted to determine the prevalence, antibiotic...
and are major public health problems and the main cause of bacterial disease in Nile tilapia (). This study was conducted to determine the prevalence, antibiotic resistance and some virulence genes of both and isolates from Nile tilapia. From Manzala Farm at Dakahlia governorate, 250 freshwater fish samples were collected. The confirmed bacterial isolates from the examined Nile tilapia samples in the study were 24.8% (62/250) for and 19.2% (48/250) for . multiplex PCR, revealing that the gene was found in 46.7% (29/62) of isolates, while the and virulence genes were found in 17.2% (5/29). Meanwhile, 39.5% (19/48) of isolates had the gene and 10.5% (2/19) had the and virulence genes. The Multiple Antibiotic Resistance indices of and were 0.587 and 0.586, respectively. In conclusion, alternative non-antibiotic control strategies for bacterial infections in farmed fish should be promoted to avoid multidrug-resistant bacteria. Therefore, it is suggested that farmers should be skilled in basic fish health control and that molecular detection methods are more rapid and cost-effective than bacteriological methods.
PubMed: 34070815
DOI: 10.3390/antibiotics10060654