VIRULENCE AND MOLECULAR CHARACTERIZATION OF AEROMONAS SPP. FROM FISH SAMPLES USING ARDRA TECHNIQUE (original) (raw)
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Biochemical and Molecular Characterization of Aeromonas Species Isolated from Fish
alexandria journal of veterinary sciences, 2018
In this study, a total of 150 Oreochromis niloticus (Nile tilapia) (90) and Ictalurus punctatus (Channel cat fish) (60) fish were collected randomly during an outbreak of disease mass mortalities from different fish farms in El Sharkia and El Ismailia governorate. Clinical signs and postmortem were recorded. Aeromonas veronii were isolated and presumptively identified using API20E system with recovery rate of 36.66% from total number of fish. The identification was confirmed for Aeromonas veronii biovar sobria by PCR and sequence analysis of 16s rRNA gene. The experimental infection was carried out by Aeromonas veronii biovar sobria isolate with 60 % of mortality rate. By antibiotic sensitivity test, Aeromonas veronii biovar sobria isolate was sensitive to Trimethoprim + Sulphamethoxazole and Erythromycin but it was resistant to Oxytetracyclin.
Zagazig Veterinary Journal, 2021
Aeromonads are halophilic, non-spore forming, Gram-negative rods which are ubiquitous in aquaculture and foodstuffs. Members of genus Aeromonas are abundant water inhabitant bacteria that were recovered from lakes, rivers, swamps, chlorinated water as well as food stuff as fish, meat, seafood, vegetables, and processed foods. Aeromonas species are opportunistic pathogens that affect many aquatic animals and human. These pathogens cause septicaemia, ulcerative and haemorrhagic diseases, and mortality in different fish species. They possess large number of virulence factors in addition to inherent resistance to various antimicrobials and ability to form biofilms with the help of quorum sensing. This review focuses on the pathogenic potentials of Aeromonas species which regarded as multifactorial and dependent on the presence of different virulence factors that enable bacteria to colonize, invade, and defeat the host's immune defences. This review also provides an update on the taxonomy, ecology, and control of Aeromonas infection in fishes.
Letters in Applied Microbiology, 2012
equally contributed to this study. Significance and impact on the study: Aeromonas species are widely distributed in aquatic environments and have considerable virulence potential. The aim of this study was to identify Aeromonas strains isolated from Accepted Article This article is protected by copyright. All rights reserved. healthy Northern snakehead, and to investigate if Aeromonas species isolated from healthy fish potential pathogenicity with special reference to virulence and epidemiology studies.
Aquaculture International, 2010
Heat-stable cytotonic enterotoxin gene (Ast) was detected by polymerase chain reaction (PCR) of twenty isolates of Aeromonas hydrophila isolated from various naturally infected fishes collected from both fresh and brackish water. These fishes were Nile tilapia and meagre, mullet and sea bream, respectively. Antibiotic susceptibility, pathogenic characteristics of these isolates and histopathological alterations of liver from experimentally infected tilapia fish with A. hydrophila which contained Ast gene were investigated. PCR technique for the detection of Ast as specific gene for A. hydrophila genomes showed that 90% of tested A. hydrophila (18/20) contained Ast gene, which is specific for A. hydrophila (SSU).The in vitro susceptibility of 18 strains of A. hydrophila (SSU) to 9 antibiotics was evaluated. Oxytetracycline only was an effective antibiotic for all tested isolates. On contrast, all these isolates were resistant to amoxicillin, ampicillin and penicillin. Pathogenicity assay in this study proved that 33.3% of the tested A. hydrophila (6/18) were pathogenic for tilapia in vitro with various levels of virulence where 2/6 were classified as strongly virulent according to the severity of mortality rate. Microscopically, A. hydrophila toxins apparently cause irreparable systemic damage to liver which leads to death.
Antibiotic resistance of pathogenic for fish isolates of Aeromonas spp
Bulgarian Journal of …, 2010
This study has determined and compared the antibiotic resistance towards various groups of antibiotics of 25 isolates from Aeromonas spp. with different origin. The strains have been isolated from drinking water and fish samples in Bulgaria, as well as from intensively bred trout fish in France, Sweden, Denmark, Spain, Scotland and England. The hemolytic activity of the isolates as regards sheep erythrocytes has been investigated in parallel. The Index of Resistance MAR has been calculated for each separate isolate. A wide antibiotic resistance of all clinic isolates has been determined. 60% of water isolates and 90% of clinical isolates possess a hemolytic activity. The presence in the environment of strains of Aeromonas spp. resistant to a wide group of antibiotics is a potential risk for the fishery farms. On the other hand, the results obtained give us grounds to accept the motile representatives of Aeromonas spp. as potential enteropathogens not only in our geographical region but also in Europe, as a whole.
Aquaculture, 1987
In this study we have analysed the biochemical, enzymatic, and cell surface properties of 59 Aeromonas strains isolated from fish culture systems, with the aim of establishing the possible relationships among some of these phenotypic characters and pathogenicity. The cytotoxic activity of extracellular products was also evaluated. Virulence assays showed that 64.3% of the strains were pathogenic for fish. However, both pathogenic and non-pathogenic Aeromonas isolates were able to produce enterotoxins. The majority of the strains were proteolytic, amylolytic and produced DNAase. Nevertheless, elastase and staphylolytic activities were present only in A. hydrophilu. Although 96% of the isolates produced haemolysins, a clear specificity toward trout or human erythrocytes was not found in the pathogenic strains. Similarly there was no specificity in the haemagglutinating activity. Statistical analysis of the association between virulence and phenotypic traits revealed a positive relationship among virulence for fish and arabinose and sucrose fermentation, elastase and haemolysis of human erythrocytes. However, only the LDC test showed a significant relation with enterotoxin production. These findings suggest that different mechanisms are involved in the invasion by Aeromonas of their poikiIotherm and homeotherm hosts. Extracellular products of the Aeromonas strains displayed cytotoxicity on fish cell-lines regardless of the virulence capacities of the strains, which indicates that cytotoxic activity is not an adequate criterion of pathogenicity.
Systematic and Applied Microbiology, 2010
Phenotypicaly identified Aeromonas strains (n =119) recovered mainly from diseased fish were genetically re-identified and the concordance between the results was analysed. Molecular characterization based on the GCAT genus specific gene showed that only 90 (75.6%) strains belonged to the genus Aeromonas. The 16S rDNA-RFLP method identified correctly most of the strains with the exception of a few that belonged to A. bestiarum, A. salmonicida or A. piscicola. Separation of these 3 species was correctly assessed with the rpoD gene sequences, which revealed that 5 strains with the RFLP pattern of A. salmonicida belonged to A. piscicola, as did 1 strain with the pattern of A. bestiarum. Correct phenotypic identification occurred in only 32 (35.5%) of the 90 strains. Only 14 (21.8%) of the 64 phenotypically identified A. hydrophila strains belonged to this species. However, coincident results were obtained in 88% (15/17) of the genetically identified A. salmonicida strains. Phenotypic tests were re-evaluated on the 90 genetically characterized Aeromonas strains and there were contradictions in the species A. sobria for a number of previously published species-specific traits. After genetic identification, the prevailing species were A. sobria, A. salmonicida, A. bestiarum, A. hydrophila, A. piscicola and A. media but we could also identify a new isolate of the recently described species A. tecta. This work emphasizes the need to rely on the 16S rDNA-RFLP method and sequencing of housekeeping genes such as rpoD for the correct identification of Aeromonas strains.
International Journal of Aquaculture, 2013
During last decades there has been a continuous growth of aquaculture industries all over the world and taking into consideration the spurt in freshwater ornamental fish aquaculture and trade in Kerala, the present study was aimed to assess the prevalence of various motile Aeromonas spp. in fresh water ornamental fishes and associated carriage water. The extracellular virulence factors and the antibiogram of the isolates were also elucidated. Various species of motile aeromonads such as Aeromonas caviae, A. hydrophila, A. jandaei, A. schubertii, A. sobria, A. trota and A. veronii were detected. Aeromonas sobria predominated both fish and water samples. Extracellular enzymes and toxins produced by motile aeromonds are important elements of bacterial virulence. The production of extracellular virulence factors -proteases, lipase, DNase and haemolysin by the isolates were studied. All the isolates from both fish and water samples produced gelatinase and nuclease but the ability to produce lipase, caseinase and haemolysins was found to vary among isolates from different sources. Among the 15 antibiotics to which the isolates were tested, all the isolates were found to be sensitive to chloramphenicol, ciprofloxacin and gentamicin and resistant to amoxycillin. Local aquarists maintain the fish in crowded stressful conditions, which could trigger infections by the obligate/ opportunistic pathogenic members among motile aeromonads.
American Journal of Advanced Food Science and Technology, 2013
A total of 103 representative colonies from 53 healthy and diseased food fish samples were tested for the incidence of Aeromonas spp. Of which 57% of colonies were positive for Aeromonas spp. by the multiplex PCR (MPCR). On an average, the prevalence was found to be 66% with highest incidence in diseased fishes (76%). About 48% of healthy fish samples were observed to contain Aeromonas. The biomoleculoar identification revealed that the selected virulent hemolytic and enterotoxigenic genes appeared in four different patterns viz. alt; act//hlyA/aer; alt and act//hlyA/aer; ast, alt and act//hlyA/aer, among the MPCR positive isolates of Aeromonas spp. The overall prevalence of the toxin genes alt, act/hlyA/aer and ast among the MPCR positive Aeromonas isolates was found to be 89.8%, 72.9% and 20%, respectively. The biochemical confirmation of the MPCR positive Aeromonas isolates revealed different species in the tested samples belonging to A. hydrophila, A. sobria, A. caviae, A. jandaei, A. veronii, A. schubertii and A. trota and the dominant species was found to be A. hydrophila (48%).