Pathogenicity of Aeromonas hydrophila isolated from diseased sharp teeth catfish, Clarias gariepinus, with special reference to the lethality of its extracellular products (original) (raw)
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Journal of Aquaculture Research and Development, 2014
Bacterial isolation Lesions from skin, fin and gill, were inoculated onto Trypticase Soy Agar (TSA) (Merk, Germany) and incubated aerobically at 28°C for 24 h. Then internal samples were acquired alike aseptically from the kidney, liver, spleen and the infected muscles. The plates were examined for bacterial growth. Dominant colonies were selected, re-streaked on Trypticase Soy Agar (TSA). Cultures were placed in 20% glycerol and supplemented in Trypticase Soy Broth (TSB) for storage at-80°C. Dominant colonies were selected for bacterial isolation to establish the optimal number of bacterial cells, and undergoing thorough purification procedure until pure colonies were established to be sure that dominant colonies were not contaminated.
Virulence of <i>Aeromonas hydrophila</i> Isolated from Fresh Water Catfish
Journal of Biosciences and Medicines
Background: A large proportion of Nigerians consume fish as the source of protein in their meals. This may be attributed to health factors, preference and affordability for low income earners. The incidence of Aeromonas hydrophila in fresh catfish may constitute a significant health risk to the consumer if there is a horizontal transfer to man as it has been reported to be pathogenic. This study examined the possibility of fresh water catfish being a reservoir of pathogenic Aeromonas hydrophila. Method: Aeromonas hydrophila was isolated from the different organs of fresh water catfish (Clarias gariepinus and Ictalurus punctatus) obtained from Kporoko river in Lokoja. Aeromonas hydrophila was identified using both phenotypic and genotypic methods. The pathogenic traits of the Aeromonas species such as biofilm formation, production of haemolysin, enterotoxin and enzymes were determined. Results: Aeromonas hydrophila occurred in all the examined fish organs (fish, liver, kidney, skin and gut) of Clarias gariepinus but occurred only in the skin, intestine, kidney and gut of Ictalurus punctatus examined, but the incidence of Aeromonas hydrophila was prevalent in the gut of all the fishes analyzed. All the Aeromonas isolates analysed in this study produced biofilm, haemolysins and lipase enzymes. They also produced enterotoxins with values ranging between 0.069-1.138. Conclusion: The occurrence of Aeromonas in fresh catfish possessing these pathogenic traits is of great public health significance to man as it indicates the likelihood of man being predisposed to toxigenicity when the toxin concentration reaches a lethal value. It is therefore recommended that the internal organs of fresh catfish be thoroughly cleaned and cooked before consumption.
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.
Toxicity of crude extracellular products of Aeromonas hydrophila in tilapia, Tilapianilotica
Letters in Applied Microbiology, 1997
A .H . K H AL IL A ND E. H . M AN S OU R. 1997. Extracellular products (ECP) secreted from Aeromonas hydrophila with haemolytic and proteolytic activity were studied with respect to temperature and time of incubation as well as the lethal toxicity on tilapia, Tilapia nilotica. The highest production of the haemolysin product was achieved when Aer. hydrophila was grown at 35°C for 30 h. Tilapia erythrocyte was found to be more susceptible than sheep erythrocyte for determining the haemolytic activity. The haemolytic activity against tilapia erythrocyte was completely inactivated after heating the ECP at 60°C for 10 min or 55°C for 15 min. The proteolytic activity was maximized when the bacterium was grown at 30°C for 36 h. Complete inactivation of the protease enzyme was performed after heating the ECP at 80°C for 10 min or 70°C for 15 min. Aeromonas hydrophila was found to produce haemolytic and proteolytic exotoxin lethal to tilapia (LD 50 2·1 × 10 4 cell/fish), as well as heat stable unknown virulent factors that were responsible for 20% mortality. The lethality of ECP was decreased by heating and completely inactivated by boiling at 100°C for 10 min.
2017
The present study was carried out to evaluate the comparative capability of producing infections and causing mortality of the experimental Magur (Clarias batrachus) with motile Aeromonas species. A total of 200 apparently healthy C. batrachus were acclimatized to the laboratory conditions for experimental study. Nine different groups (each group consisting of 20 fish) of healthy C. batrachus was injected with nine motile Aeromonas isolates (A. hydrophila-3, A. sobria-3 and A. caviae-3). Experimental C. batrachus were infected with motile A. hydrophila, A. sobria and A. caviae to groups 1-3, 4-6 and 7-9, respectively while group 10 was injected with sterile physiological saline (0.85% NaCl) and served as the control. The selected motile bacterial species via intramuscularly were injected at the rate of 4.5 × 10 5 cfu/fish for pathogenicity study on C. batrachus and monitored up to two weeks. The highest clinical infections were noticed 90% in group-3 whereas only 35% in group-8 within the experimental period. After two weeks of the experiment, the cumulative mortality rate was also found highest (60%) in group-3 but lowest (15%) in group-9 while no infection or mortality showed in group-10 (control group). The development of infection and mortality to the injected C. batrachus was associated more severely by Aeromonas hydrophila than A. sobria and A. caviae used in this study. However, the isolates motile Aeromonas species could serve as the primary cause of skin lesions as well as mortality in cultured C. batrachus. 1. Introduction Among the different air-breathing catfishes, Magur (Clarias batrachus) is very popular and highly valuable fish species in Bangladesh. It is not only recognized for its delicious taste and market value but it is also considered as a medicinal fish and traditionally remained a strike among the pregnant & lactating mothers, the elderly and children. It is prescribed prophylactically to the anemic & malnourished individuals as well as for the convalescent of the patients due to the nutritional superiority (Debnath, 2011). It is a very hardy fish that can survive for quite a few hours outside the water due to presence of accessory respiratory organs. C. batrachus was abundantly available in open water of Bangladesh but presently, it is threatened due to over exploitation and various ecological changes in its natural habitat. Although, the appropriate breeding, nursing and rearing technology of fry and fingerlings of C. batrachus had been developed by Bangladesh Fisheries Research Institute (BFRI) in few years ago but various diseases of this fish causes huge economic losses because of their high mortality under farming conditions.
Veterinary Record, 2009
The distribution of antigen and pathological changes induced by an experimental infection with Aeromonas hydrophila strain KJ99, and its extracellular products, were studied in two species of fish. The microorganism was disseminated systemically and the haemodynamic and tissue changes were similar to those observed in septicaemia of mammals. Intussusception, degeneration and necrosis of the nervous plexus and muscular layers of the gastrointestinal tract were common findings.
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.
Fish Pathology, 1981
A total 291 strains of motile members of the genus Aeromonas were classified according to the taxonomic scheme proposed by . Forty three were indetified as A. hydrophila biovar hydrophila, 9 as A. hydrophila biovar anaerogenes, and 52 as A. sobria. The remaining 187 strains could not be identified. Thirty seven (86%) of 43 A. hydrophila biovar hydrophila, 3 (33 %) of 9 A. hydrophila biovar anaerogenes, 32 (62 %) of 52 A. sobria, and 65 (35%) of the 187 unidentified originated from fishes.
FEMS microbiology letters, 2016
The aim of this study was to understand the pathogenesis of motile aeromonas septicemia caused by an emergent, high virulentA. hydrophila(vAh) in channel catfish,Ictalurus punctatus Adipose fin clipped catfish were challenged with vAh using a waterborne challenge method and the distribution of vAh over a time course was detected and quantified using real-time polymerase chain reaction (qPCR). The results showed that 77.8% of fish died within 48 h post challenge with mean-day to death of 1.5 days. At 2 h post challenge, vAh (inferred from genomic DNA copies or genome equivalents) was detected in all external and internal tissues sampled. Gill had the highest vAh cells at 1 h post challenge. Spleen harbored the most vAh cells among internal organs at 4 h post challenge. The tissues/organs with most vAh cells detected at 8 h post challenge were adipose fin, blood, intestine, kidney and skin while liver showed the highest vAh cells at 24 h post challenge. These results suggest that vAh ...
2022
Pangasius catfish, Pangasius nasutus, is a promising candidate for aquaculture due to its high market value. However, the presence of pathogenic bacteria in Aeromonas hydrophila is a major concern in P. nasutus farming in this country. This study determines the pathogenicity of A. hydrophila in P. nasutus. A total of 80 P. nasutus juveniles were intraperitoneally injected with 0, 10 3 , 10 5 , and 10 7 CFU mL-1 of A. hydrophila and monitored until 240 hr. The infected moribund fish's kidneys, livers, and spleens were collected for histopathological analysis. The LD 50-240hr value was found at 0.8 × 10 4 CFU/ml of A. hydrophila. The percentage of mortality in 0, 10 3 , 10 5 , and 10 7 CFU/ml infected groups were found to be at 0, 40, 60, and 90%, respectively. The infected fish showed congestion at the base of the fin, ascites, enlarged gall bladder, and swollen spleen. It is the earliest report on A. hydrophila's pathogenicity in high-value native fish, P. nasutus.