Aeromonas Veronii Bv Research Articles

Türkiye'de Yetiştiriciliği Yapılan Levrek Balıklarında (Dicentrarchus labrax) Aeromonas veronii biovar veronii Enfeksiyonu

Fish in aquaculture systems are susceptible to infectious agents as they are kept in a densely populated and often physically restricted environment. Genus Aeromonas include well-known pathogens, and the member Aeromonas veronii has been reported to cause diseases in both humans and animals, either as primary infection or as mixed infection with other pathogens. This study describes a low mortality epizootic caused by Aeromonas veronii biovar veronii in European seabass (Dicentrarchus labrax) farmed in the Aegean Sea. The gills, kidneys and livers of moribund fish were pale. Erythema, haemorrhage and superficial ulcerative lesions were detected on the skin. In addition, petechial haemorrhage was observed on the tongue, maxilla, and operculum. The spleen was enlarged and multiple granulomas were detected in both the kidney and the spleen. Some fish had skin depigmentation, ecchymosis in the liver, and a bloody exudate in the abdominal cavity. The intestinal walls were lined with a clear yellowish fluid. Twenty-nine motile, Gram-negative bacterial isolates were obtained from the internal organs of diseased fish. According to morphology, biochemical properties and 16S rRNA gene sequencing results, all isolates were identified as Aeromonas veronii bv. veronii. All isolates were resistant to amoxicillin and ampicillin, and sensitive to oxytetracycline, enrofloxacin, ciprofloxacin, florfenicol, and flumequine.

Polyinfection in Fish Aeromoniasis: A Study of Co-Isolated Aeromonas Species in Aeromonas veronii Outbreaks.

We studied the phenotypic and genomic characteristics related to the virulence and antibiotic resistance of two Aeromonas strains, which were co-isolated before an outbreak of Aeromonas veronii among diseased seabass on Agathonisi Island, Greece, in April 2015. The first strain, AG2.13.2, is a potentially pathogenic mesophilic variant of Aeromonas salmonicida, and the second, AG2.13.5, corresponds to an Aeromonas rivipollensis related to A. rivipollensis KN-Mc-11N1 with an ANI value of 97.32%. AG2.13.2 lacks the type III secretion system just like other mesophilic strains of A. salmonicida. This characteristic has been associated with lower virulence. However, the genome of AG2.13.2 contains other important virulence factors such as type II and type VI secretion systems, and toxins such as rtxA, aerolysin aer/act, and different types of hemolysins. The strain also carries several genes associated with antibiotic resistance such as the tetE efflux pump, and exhibits resistance to tetracycline, ampicillin, and oxolinic acid. In an in vivo challenge test with gilthead seabream larvae, the A. veronii bv sobria strain AG5.28.6 exhibited the highest virulence among all tested strains. Conversely, both A. salmonicida and A. rivipollensis showed minimal virulence when administered alone. Interestingly, when A. veronii bv sobria AG5.28.6 was co-administered with A. rivipollensis, the larvae survival probability increased compared to those exposed to A. veronii bv sobria AG5.28.6 alone. This finding indicates an antagonistic interaction between A. veronii bv sobria AG5.28.6 and A. rivipollensis AG2.13.5. The co-administration of A. veronii bv sobria AG5.28.6 with Aeromonas salmonicida did not yield distinct survival probabilities. Our results validate that the primary pathogen responsible for European seabass aeromoniasis is Aeromonas veronii bv sobria.

Isolation, genetic characterization, and virulence profiling of different Aeromonas species recovered from moribund hybrid catfish (Clarias spp.).

The high diversity of Aeromonas spp. results in various pathogenicity levels. This group of bacteria causes a serious disease named motile Aeromonas septicemia (MAS) in catfish (Clarias spp.). This study aimed to characterize the species and virulence gene diversity of Aeromonas spp. isolated from diseased catfish. Nine Aeromonas spp. were isolated from infected catfish cultivated in Java, Indonesia, and they were identified at the phenotypic and molecular levels (16S rDNA). The virulence genes assessed included aer/haem, alt, ast, flaA, lafA, and fstA. Phylogenetic analysis identified nine isolates of Aeromonas spp.: Aeromonas hydrophila (11.11%), Aeromonas caviae (11.11%), Aeromonas veronii bv. veronii (44.44%), and Aeromonas dhakensis (33.33%). Virulence genes, such as aer/haem, alt, ast, flaA, lafA, and fstA, were detected in all isolates at frequencies of approximately 100%, 66.67%, 88.89%, 100%, 55.56%, and 66.67%, respectively. This study is the first report on A. dhakensis recovered from an Indonesian catfish culture. Furthermore, our study revealed the presence of A. veronii bv veronii, a biovar that has not been reported before in Indonesia. This finding confirms that MAS was caused by multiple species of Aeromonas, notably A. dhakensis and A. veronii bv veronii, within Indonesian fish culture. The presence of these Aeromonas species with multiple virulence genes poses a significant threat to the freshwater aquaculture industry.

Development of autogenous vaccines for farmed European seabass against Aeromonas veronii using zebrafish as a model for efficacy assessment

Aeromonas veronii bv. sobria is an emerging pathogen for the European seabass cultured in the Aegean Sea (Mediterranean) causing significant problems in the Greek and Turkish aquaculture industry since no licensed vaccine is currently available for the disease. A bivalent vaccine was developed based on two phenotypically distinct strains of the pathogen, PDB (motile, pigment-producing strain) and NS (non-motile, non-pigment-producing). The two strains comprising the bivalent vaccine were evaluated as monovalent products in zebrafish before the seabass trials. Challenges using the homologous or the heterologous strain showed that both vaccines were protective with RPS values ranging between 66 and 100% in zebrafish. The bivalent vaccine was then tested in European seabass following dip or intraperitoneal administration. Efficacy was evaluated separately against both strains comprising the bivalent vaccine. Dip vaccination applied to juvenile seabass of 2.5 g average weight provided protection following challenge tests 30 days post vaccination only in one of the two strains tested (strain PDB, RPS: 88%). This was also the case in the injection vaccination of adult seabass of 60 g average weight where the vaccine was effective only against the PDB strain (RPS: 63%). High antibody titers against both strains were found at 30 and 60 days after intraperitoneal vaccination in the adult seabass. The use of zebrafish as a model for vaccine development for aquaculture species is discussed.

Dynamics, Diversity, and Virulence of Aeromonas spp. in Homestead Pond Water in Coastal Bangladesh.

Aeromonads are aquatic bacteria associated with frequent outbreaks of diarrhea in coastal Bangladesh, but their potential risks from environmental sources have remained largely unexplored. This study, over 2 years, examined homestead pond waters in the region for monthly dynamics and diversity of Aeromonas spp. The bacterial counts showed bi-modal annual growth peak, pre- and post-monsoon, strongly correlating (p < 0.0005) with temperature. Of 200 isolates characterized, Aeromonas veronii bv. sobria (27%) was predominant among co-existent Aeromonas schubertii (20%), Aeromonas hydrophila (17%), Aeromonas caviae (13%), and three more. PCR screening of virulence-related genes identified 15 genotypes (I to XV), however, enterotoxigenicity in animal model was observed for five genotypes, ca. 18% (nine of 50) strains, prevalent in A. veronii bv. sobria, A. hydrophila, and A. caviae. Pathogenic strains were distinguishable by possessing at least three of the major virulence genes: ascV, hlyA, ela, ast, and alt, together with accessory virulence factors. PFGE of XbaI-digested genomic DNA revealed high genetic diversity and distant lineage of potentially toxigenic clones. Therefore, along with increased global warming, Aeromonas spp. having multi-factorial virulence potential in coastal ponds that serve as drinking water sources pose a potential health risk, and underscores the need for routine monitoring.

Antibacterial Effects of Essential Oils of Seven Medicinal-Aromatic Plants Against the Fish Pathogen Aeromonas veronii bv. sobria: To Blend or Not to Blend?

Despite progress achieved, there is limited available information about the antibacterial activity of constituents of essential oils (EOs) from different medicinal-aromatic plants (MAPs) against fish pathogens and the complex interactions of blended EOs thereof. The present study aimed to investigate possible synergistic antimicrobial effects of EOs from seven Greek MAPs with strong potential against Aeromonas veronii bv. sobria, a fish pathogen associated with aquaculture disease outbreaks. The main objective was to evaluate whether blending of these EOs can lead to increased antimicrobial activity against the specific microorganism. A total of 127 combinations of EOs were prepared and their effect on A. veronii bv. sobria growth was tested in vitro. We examined both the inhibitory and bactericidal activities of the individual EOs and compared them to those of the blended EOs. The vast majority of the investigated combinations exhibited significant synergistic and additive effects, while antagonistic effects were evident only in a few cases, such as the mixtures containing EOs from rosemary, lemon balm and pennyroyal. The combination of EOs from Greek oregano and wild carrot, as well as the combinations of those two with Spanish oregano or savoury were the most promising ones. Overall, Greek oregano, savoury and Spanish oregano EOs were the most effective ones when applied either in pure form or blended with other EOs.

Structural Studies of the Lipopolysaccharide of Aeromonas veronii bv. sobria Strain K133 Which Represents New Provisional Serogroup PGO1 Prevailing among Mesophilic Aeromonads on Polish Fish Farms

In the present work, we performed immunochemical studies of LPS, especially the O-specific polysaccharide (O-PS) of Aeromonas veronii bv. sobria strain K133, which was isolated from the kidney of carp (Cyprinus carpio L.) during an outbreak of motile aeromonad infection/motile aeromonad septicemia (MAI/MAS) on a Polish fish farm. The structural characterization of the O-PS, which was obtained by mild acid degradation of the LPS, was performed with chemical methods, MALDI-TOF mass spectrometry, and 1H and 13C NMR spectroscopy. It was revealed that the O-PS has a unique composition of a linear tetrasaccharide repeating unit and contains a rarely occurring sugar 2,4-diamino-2,4,6-trideoxy-D-glucose (bacillosamine), which may determine the specificity of the serogroup. Western blotting and ELISA confirmed that A. veronii bv. sobria strain K133 belongs to the new serogroup PGO1, which is one of the most commonly represented immunotypes among carp and trout isolates of Aeromonas sp. in Polish aquacultures. Considering the increase in the MAI/MAS incidences and their impact on freshwater species, also with economic importance, and in the absence of an effective immunoprophylaxis, studies of the Aeromonas O-antigens are relevant in the light of epidemiological data and monitoring emergent pathogens representing unknown antigenic variants and serotypes.

Evaluation of quorum-sensing inhibitory effects of extracts of three traditional medicine plants with known antibacterial properties.

Today an alternative approach to control bacterial infections is the use of natural and traditional plant compounds to interfere with their quorum-sensing (QS) systems. In this study, antibacterial and anti-QS sensing activity of Syzygium aromaticum, Dionysia revoluta Boiss. and Eucalyptus camaldulensis Dehnh. were evaluated. These plants are local to the Middle East region and have since ancient times been used for their antibacterial activity. Plant compounds were extracted with n-hexane, methanol and 96% ethanol mixed solvent. Antibacterial activity of this herbal extracts against five Gram-negative and Gram-positive bacteria were assessed. The effective sub–minimum inhibitory concentration (MIC) of this extract on bacterial QS systems were investigated by a violacein quantification assay in the Chromobacterium violaceum CV026 biosensor strain, inhibition of exogenously QS signal molecules in Aeromonas veronii bv. Sobria strain BC88 and Pseudomonas aeruginosa isolated from a patient with cystic fibrosis in vitro. Results found that Syzygium aromaticum 0.39 to 0.048 mg/mL, Dionysia revoluta Boiss. 3.1 to 0.39 mg/mL and E. camaldulensis 0.78 to 0.097 mg/mL showed anti-QS activities by reducing the violacein formation depletion of QS signals produced in A. veronii and P. aeruginosa at sub-MICs. Regarding the anti-QS effects of these herbal extracts, their effective components may be candidates for use in combating bacterial infections at sub-MICs.

Structure of the O-specific polysaccharide of Aeromonas veronii bv. sobria strain Pt393 isolated from rainbow trout (Oncorhynchus mykiss), which contains a rarely occurring sugar 4-acetamido-4,6-dideoxy-d-galactose, tomosamine

The O-specific polysaccharide (OPS) was isolated from the lipopolysaccharide of Aeromonas veronii bv. sobria strain Pt393, which is pathogenic to the rainbow trout (Oncorhynchus mykiss), after mild acid hydrolysis followed by GPC. The high-molecular-weight OPS fraction was studied with chemical methods, mass spectrometry, and 1H and 13C NMR spectroscopy techniques, including 2D 1H,1H COSY, TOCSY, NOESY, 1H-detected heteronuclear 1H,13C HSQC, and HMBC experiments. It was found that the O-specific polysaccharide was built of a tetrasaccharide repeating unit composed of α-GalpNAc, α-FucpNAc, β-QuipNAc, and α-Fucp4NAc (4-acetamido-4,6-dideoxy-d-galactose, tomosamine) residues. The following structure of the OPS of A. sobria strain Pt393 was established:→4)-α-d-GalpNAc-(1 → 3)-α-l-FucpNAc-(1 → 3)-β-d-QuipNAc-(1 → 3)-α-d-Fucp4NAc-(1→

Evaluation of intraepithelial lymphocytes, goblet cells and immunoglobulin genes in the intestinal mucosal tissue of Pelodiscus sinensis after challenge with Aeromonas veronii bv. sobria and lipopolysaccharide

Pelodiscus sinensis, which is a high-value commercial freshwater species, frequently suffers from infectious diseases induced by various pathogens. The mucosa has been confirmed to contribute to host protection, which is the first line of defence against invading pathogens, including bacteria. This study was conducted to evaluate the intestinal mucosal immunity of P. sinensis against Aeromonas veronii bv. sobria and lipopolysaccharide (LPS) infection. A significant increase in the number of intraepithelial lymphocytes (IEL) and goblet cells was observed from 12 h after challenge with A. veronii bv. sobria and LPS (P < 0.01), and the peak was observed at 48 h. The expression of immunoglobulin M (IgM) mRNA also increased between 12 h and 24 h and then decreased until 96 h. Across the experiment, the expression of IgM mRNA in the challenge groups was significantly higher than that in the control group, except at 48 h (P < 0.01), and then declined until 96 h. In contrast, the expression of IgD mRNA had no significant differences compared with the control group. This result showed that the IEL, goblet cells and IgM in P. sinensis were involved in the intestinal mucosal immunity against A. veronii bv. sobria and LPS infection.

Involvement of bacterial quorum sensing signals in spoilage potential ofAeromonas veroniibv.veroniiisolated from fermented surimi

This study characterized the spoilage potential of the N-acyl homoserine lactone (AHL)-producing strain, Aeromonas veronii bv. veronii, isolated from fermented surimi, and investigated the effects of exogenous AHLs on its spoilage characteristics. The strain showed a strong ability of producing total volatile base nitrogen (TVB-N) and putrescine, and four types of AHLs, including N-butanoyl-L-homoserine lactone (C4-HSL), N-hexanoyl-L-homoserine lactone (C6-HSL), N-heptanoyl-L-homoserine lactone (C7-HSL), and N-octanoyl-L-homoserine lactone (C8-HSL), were identified from the supernatant by LC–MS/MS. Concentrations of AHLs reached the maximum value as the cells entered stationary phase contents and then decreased rapidly with the increasing pH. C8-HSL was found to be dominant with contents of 1,536.33 ng/mL and exogenous C8-HSL was most effective in promoting bacterial growth, biofilm formation, swimming motility, production of TVB-N and putrescine, and relative genes expression. The results indicated the involvement of AHL-based quorum sensing system in the regulation of spoilage potential of Aeromonas spp. Practical applications The results of the present study found that Aeromonas veronii bv. veronii was capable of producing four types of AHLs, which were considered to be involved in the regulation of spoilage potential of the strain. This would enrich the understanding of quorum sensing system in Aeromonas and give clue for new strategy of controlling food spoilage in food industry.

First isolation and characterization of the pathogenic Aeromonas veronii bv. veronii associated with ulcerative syndrome in the indigenous Pelophylax ridibundus of Al-Ahsaa, Saudi Arabia

Virulent microbial pathogen infections are the main cause for amphibian decline worldwide. In the present study, a bacterial strain named RDL-2, which was isolated from the skin of infected Pelophylax ridibundus larvae, was cultured and then phenotypically and biochemically characterized using scanning electron microscopic observations and the API20E strip and Biolog Gen III MicroPlate system. The 16S rRNA gene sequence of this strain was also obtained and used in strain identification and phylogenetic analysis. Healthy P. ridibundus larvae were challenged with RDL-2 and monitored to determine clinical signs consistent with the disease. Strain RDL-2 was identified as Aeromonas veronii based on its phenotypic and biochemical characteristics and on 16S rRNA gene sequence and phylogenetic analysis: RDL-2 was gram-negative, rod-shaped, and reacted positively for 69 (73%) of the 94 traits analysed; its 16S rRNA gene sequence displayed the highest homology to that of A. veronii bv. veronii (99.9%). Koch's postulates were fulfilled confirming that A. veronii is the causal agent of ulcerative syndrome. Thus, this study is the first to report A. veronii as a marsh frog pathogen in the Al-Ahsaa region. The aetiology of A. veronii as a potential poikilothermic pathogen shown here will expedite the development of diagnostic tests and methods for eradicating ulcerative syndrome.

Aeromonas and Plesiomonas species from scarlet ibis (Eudocimus ruber) and their environment: monitoring antimicrobial susceptibility and virulence.

The present study aimed at evaluating the role of captive scarlet ibises (Eudocimus ruber) and their environment as reservoirs of Aeromonas spp. and Plesiomonas spp., and analyzing the in vitro antimicrobial susceptibility and virulence of the recovered bacterial isolates. Thus, non-lactose and weak-lactose fermenting, oxidase positive Gram-negative bacilli were recovered from cloacal samples (n=30) of scarlet ibises kept in a conservational facility and from water samples (n=30) from their environment. Then, the antimicrobial susceptibility, hemolytic activity and biofilm production of the recovered Aeromonas spp. and Plesiomonas shigelloides strains were assessed. In addition, the virulence-associated genes of Aeromonas spp. were detected. Ten Aeromonas veronii bv. sobria, 2 Aeromonas hydrophila complex and 10 P. shigelloides were recovered. Intermediate susceptibility to piperacillin-tazobactam and cefepime was observed in 2 Aeromonas spp. and 1 P. shigelloides, respectively, and resistance to gentamicin was observed in 4 P. shigelloides. The automated susceptibility analysis revealed resistance to piperacillin-tazobactam and meropenem among Aeromonas spp. and intermediate susceptibility to gentamicin among P. shigelloides. All Aeromonas isolates presented hemolytic activity, while 3 P. shigelloides were non-hemolytic. All Aeromonas spp. and 3/10 P. shigelloides were biofilm-producers, at 28°C, while 10 Aeromonas spp. and 6/10 P. shigelloides produced biofilms, at 37°C. The most prevalent virulence genes of Aeromonas spp. were asa1 and ascV. Scarlet ibises and their environment harbour potentially pathogenic bacteria, thus requiring monitoring and measures to prevent contamination of humans and other animals.

Virulence and antimicrobial susceptibility of clinical and environmental strains of Aeromonas spp. from northeastern Brazil.

The aims of the present study were to isolate and identify clinical and environmental strains of Aeromonas spp. by means of biochemical tests and the automated method VITEK 2 and to investigate the presence of the virulence genes cytotoxic enterotoxin (act), hemolysin (asa-1), and type III secretion system (ascV), and also the in vitro antimicrobial susceptibility of the strains. From the clinical isolates, 19 Aeromonas hydrophila, 3 Aeromonas veronii bv. sobria, and 1 Aeromonas caviae were identified, while from the environmental strains, 11 A. hydrophila, 22 A. veronii bv. sobria, 1 A. veronii bv. veronii, and 1 A. caviae were recovered. The gene act was detected in 69.5% of clinical isolates, asa-1 in 8.6%, and ascV in 34.7%. In the environmental strains, the detection rates were 51.4%, 45.7%, and 54.2% for the genes act, asa-1, and ascV, respectively. Resistance to amoxicillin-clavulanate and piperacillin-tazobactam was observed in 15 and 3 clinical strains, respectively, and resistance to ceftazidime, meropenem, imipenem, ciprofloxacin, and trimethoprim-sulfamethoxazole was observed in 1 strain for each drug. Resistance to amoxicillin-clavulanate and piperacillin-tazobactam was detected in 17 and 1 environmental strain, respectively. Higher resistance percentages were observed in clinical strains, but environmental strains also showed this phenomenon and presented a higher detection rate of virulence genes. Thus, it is important to monitor the antimicrobial susceptibility and pathogenic potential of the environmental isolates.

Occurrence and Virulence Characteristics of Aeromonas Species in Meat, Milk and Fish in India

AbstractAeromonas‐induced gastroenteritis is common in India. The incidence of Aeromonas in meat, milk and fish in Kolkata, India and their enterotoxic potentiality have been evaluated here. Aeromonas contamination was detected in all or most of the meat and fish with average load of 1.1 × 102, 3.5 × 103, 1.1 × 103, 2.1 × 103 and 1.6 × 104 cfu/g of red meats, chicken, Indian major carps, tilapia and shrimp, respectively; the levels were at least one order higher on fish skin and meat surface. Aeromonas was also detected in milk and ready‐to‐eat foods. About 59% of the isolates were β‐hemolytic, and 66–92% of them produced phospholipase, caseinase and enterotoxicity. Fish and shrimp isolates produced significantly higher levels of gelatinase (102.73–120.6 U/mL), hemolysin (causing &gt;80% erythrocyte lysis) and enteric fluid accumulation (0.86–0.89 mL/cm ileum length) compared with those from meat and milk indicating their serious pathogenic potentiality. Phenotypically, 43.2, 12.2 and 12.2% of β‐hemolytic strains were identified as recognized human pathogenic species, viz. Aeromonas hydrophila, Aeromonas caviae and Aeromonas veronii bv. sobria, respectively, which also expressed higher levels of virulence factors than other Aeromonas species detected. The ubiquitous presence of enterotoxigenic Aeromonas in different raw as well as ready‐to‐eat foods poses serious threat to human health.Practical ApplicationsUbiquitous presence of enterotoxigenic Aeromonas hydrophila, Aeromonas caviae and Aeromonas veronii bv. sobria in raw and ready‐to‐eat meat, milk and fish poses a serious human health risk in Indian subcontinent. Heavy bacterial load, combined with higher expression of virulence factors by the isolates, makes fish and shellfish as the most potential sources of Aeromonas infection. Different Aeromonas spp. differed in quantitative expression of different virulence factors. Qualitative and quantitative expression studies showed low positive correlations among gelatinase, hemolysin and ileal enterotoxicity, suggesting requirement of studying multiple virulence factors for identifying the virulent strains. A higher distribution of the bacterium on meat or fish surface and in unhygienically processed or stored food items indicates that adoption of standard practices of cleaning and sanitation would substantially improve safety of food products.

Attenuated virulence of pigment-producing mutant of Aeromonas veronii bv. sobria in HeLa cells and Nile tilapia (Oreochromis niloticus)

Aeromonas species are potential water/foodborne pathogens, whereas Aeromonas veronii bv. sobria is one of the most virulent species to human and fish. Most current experimental evidence has publicized that suicide plasmid dependent IS1-element untargeted integration into A. veronii bv. sobria ATCC 9071T strain was recently used to generate brown pigment-producing and spontaneous pelleting (BP+SP+) mutant. Current study was conducted to compare virulence of wild-type ATCC 9071T strain and its BP+SP+ mutant with respect to cytotoxicity in HeLa cells and lethality in Nile tilapia. It was found that the cytotoxicity of wild-type ATCC 9071T strain to HeLa cells has reached 75% versus 50% for the cytotoxicity of BP+SP+ mutant. Further, the median lethal dose (LD50) of wild-type ATCC 9071T strain in Nile tilapia was 8.25 Log10 colony-forming units (CFU)/ml, compared to 9.16Log10CFU/ml for the LD50 of BP+SP+ mutant. Thus, current study supports the notion that non pigment-producing Aeromonas strains are more virulent than pigment-producing ones.

Suicide Plasmid-Dependent IS1-Element Untargeted Integration into Aeromonas veronii bv. sobria Generates Brown Pigment-Producing and Spontaneous Pelleting Mutant

Foodborne Gram-negative pathogens belonging to the genus Aeromonas are variable in harboring insertion sequence (IS) elements that play an important role in the generation of dysfunctional relatives of known genes. Using suicide plasmids carrying an IS1-element, untargeted integration is a common problem during experimental trials to generate specific mutations by homologous recombination. In this work, different strains of Aeromonas veronii bv. sobria (AeG1 and ATCC 9071T), A. hydrophila ATCC 19570, and A. sobria ATCC 43979T are examined for acquisition of IS1-element from pYAK1 suicide plasmid. It was found that untargeted integration of IS1-element is encountered only in ATCC 9071T strain. Such untargeted integration generates a novel brown pigment-producing and spontaneous pelleting (BP(+)SP(+)) mutant. Furthermore, BP(+)SP(+) mutant strain secretes significantly higher quantity of PilF homologous protein than the wild-type strain and displays an enhanced protein tyrosine phosphorylation activity. Thus, current work shows that Aeromonas spp. strains are variable in their susceptibility for suicide plasmid-dependent IS1-element untargeted integration as well as the susceptible strain is changed to mimic pigment-producing and spontaneous pelleting strains that are naturally occurring among heterogeneous group of foodborne aeromonads.

Structural analysis of the O-specific polysaccharide from the lipopolysaccharide of Aeromonas veronii bv. sobria strain K49

The O-specific polysaccharide obtained by mild-acid degradation of the lipopolysaccharide from Aeromonas veronii bv. sobria strain K49 was studied by sugar and methylation analyses along with 1H and 13C NMR spectroscopy. The sequence of the sugar residues was determined using 1H,1H NOESY and 1H,13C HMBC experiments. The O-specific polysaccharide was found to be a high molecular mass polysaccharide composed of repeating units of the structure:→2)-β-d-Quip3NAc-(1→3)-α-l-Rhap-(1→3)-α-l-Rhap-(1→2)-α-l-Rhap-(1→3)-α-d-FucpNAc-(1→ESI MS confirmed the pentasaccharide structure of the repeating unit, as the molecular mass peaks seen in the spectrum differed by 812.34u, a value corresponding to the calculated molecular mass of the O-unit.

Characterization of pathogenic Aeromonas veronii bv. veronii associated with ulcerative syndrome from Chinese longsnout catfish (Leiocassis longirostris Günther)

273 bacterial strains were isolated from 20 Chinese longsnout catfish samples. The biochemical characteristics of all strains conformed to the species description of Aeromonas veronii bv. veronii on the basis of Vitek GNI+ card. Furthermore, 16S rDNA, gyrB and rpoD sequences of the representative strain PY50 were sequenced and showed high similarity with A. veronii bv. veronii in Genbank. Antibiotic-resistance of the representative strain PY50 was assessed by the Kirby-Bauer disk diffusion method, and the results showed it was susceptible and moderately susceptible to 13 and 4 of the 21 antimicrobial agents tested. Extracellular products of strain PY50 contained gelatinase, lecithinase, elastase, most of lipase and lipopolysaccharide. Virulence of strain PY50 and extracellular products to Chinese longsnout catfish were also tested, and LD50 were about 3.47×10(4) CFU per fish and 11.22 μg per fish in intraperitoneal injection respectively. This is the first report that A. veronii bv. veronii was the pathogenic agent of ulcerative syndrome in Chinese longsnout catfish.

Characterization of pathogenic Aeromonas veronii bv. veronii associated with ulcerative syndrome from chinese longsnout catfish (Leiocassis longirostris Günther).

273 bacterial strains were isolated from 20 Chinese longsnout catfish samples. The biochemical characteristics of all strains conformed to the species description of Aeromonas veronii bv. veronii on the basis of Vitek GNI+ card. Furthermore, 16S rDNA, gyrB and rpoD sequences of the representative strain PY50 were sequenced and showed high similarity with A. veronii bv. veronii in Genbank. Antibiotic-resistance of the representative strain PY50 was assessed by the Kirby-Bauer disk diffusion method, and the results showed it was susceptible and moderately susceptible to 13 and 4 of the 21 antimicrobial agents tested. Extracellular products of strain PY50 contained gelatinase, lecithinase, elastase, most of lipase and lipopolysaccharide. Virulence of strain PY50 and extracellular products to Chinese longsnout catfish were also tested, and LD50 were about 3.47×104 CFU per fish and 11.22 μg per fish in intraperitoneal injection respectively. This is the first report that A. veronii bv. veronii was the pathogenic agent of ulcerative syndrome in Chinese longsnout catfish.