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Pathogenicity of Aeromonas Sobria to Thai Silver Barb (bar Bodes Gonionotus Bleeker) and Its Sensitivity to Some Antibiotic Agents

M.A. Sarker
Department of Aquaculture, Bangladesh Agticultural University, Mymensingh 2002, Bangladesh

M.B.R. Chowdhury
Department of Aquaculture, Bangladesh Agticultural University, Mymensingh 2002, Bangladesh

M.N. Uddin
1Department of Fisheties Technology, BA U, Mymensingh

M.G.A. Sarker
Department of Aquaculture, Bangladesh Agticultural University, Mymensingh 2002, Bangladesh

Abstract/ Executive Summary:

Five isolates of Aeromonas sobria, collected from the diseased fish were selected for detection the pathogenicity following water-born infection method on silver barbs (Barbodes gonionotus) at the selected exposure dose 2.5 x 108 CFU/ml which was standardized by preliminary test. In the experimental condition lesion and mortality were found in fishes. Among the isolate, Assm Ass19, Ass31 and Ass36 were successfully infected 20-60% fishes. Another isolate Ass20 was found non-pathogenic. Drug sensitivity test was performed by six antibiotics viz. Oxytetracycline, Oxolinic acid, Chloramphenicol, Stilphamethozazole, Streptomycin, Erythromycin. All the isolates showed variable reaction patterns to antibiotics. Most of the isolates were found sensitive to Oxytetracycline (OT), Oxolinic acid (OA) and Chloramphenicol (C) but resistance to Erythromycin and Sulphamethoxazole (SXT). Isolate Ass31 found resistant to Oxolinic acid.

Keywords: Aeromonas sobria, Pathogenicity, Sensitivity, B. gonionotus

Location: BAU

Start Date: 00-06-1997

End Date: 00-12-1997

Program Area: Animal Health and Management

Commodity: Carp fish

Objectives:

To evaluate the pathogenicity of Aeromonas sobria to silver barb (Barbodes gonionotus).

Methodology:

Isolation of bacterial isolates - Some Aeromonad isolates were collected from the ulcer affected different fish species of different water bodies during June to December'97. After collection the fish samples were immediately brought to the laboratory. A selective media Aeromonas Agar Base (Oxoid) supplemented with amphecillin. SR 136 E was used for isolation of Aeromonads isolates. It was found to be suitable for specific culture of Aeromonads. Swabs were taken from the lesions kidney and liver of the the affected fish and stricked on the plate containing Aeromonas selective agar by sterile inoculating loop and subsequently pure culture were obtained on TSA media using conventional separation techniques. Identification of Aeromonas sobria - Primary characterization were carried out. For species level identification of A. sobria biochemical tests were performed and finally confirmed. Pathogenicity test for A. sobria isolates - Five Aeromonas sobria isolates selected to investigate the pathogenic power to fish. The study was performed by water born infection method. The experiment was conducted in the wet laboratory of the Faculty of Fisheries, Bangladesh Agricultural University, Mymensingh. Healthy young silver barb collected from an experimental pond under Fisheries Faculty were selected for pathogenicity test. These were further acclimatized to aquarium conditions before use in the experiment. The fish was a exotic carp, Barbodes gonionotus weighing 10-15 gm. Isolates were cultured on the TSA medium by spreading method and incubated at 25°C for 24 h. The stock suspension of bacteria was prepared in sterile tap water with required amount of bacteria. In 30 1 capacity aquarium, 15 1 of bacterial suspension was prepared in the tap water with the stock suspension in such way that the bacterial density became 2.5 X 108 CFU/ml. This exposure dose of bacteria was selected by a preliminary experiment. Five fishes were exposed to bacterial suspension in aquarium under aerated condition at room temperature (water temperature ranged 24-27 °C). After 24 h of exposure 80% of the bacterial suspension was exchanged with tap water and from the following day 60% of water was exchanged at every 24 h of experimental period. The experimental period was 15 days. Two replications were set up for the same isolate and the experiments were repeated for confirmation of infection, and thus in total 20 fish were used for single species against the individual bacterial isolate. For each set of experiment control fish were maintained in the same way. Aeration system was controlled by air pump. No feed was applied during the experimental period. The appearance of lesion and mortality of experimental fish confirmed the infection. The pathogen was confirmed by reisolation of bacteria from the exposed fish. In the experimental condition radish zone appeared on the body surface, tail region, lower jaw and fin base of the fish. Then it terns in to dip hemorhagic lesion and died. Some time fishes were died with out appearing any lesion on the body surface. For these case internal infection was found. Experimental fish with lesion or died fishes were collected with the sterile forcep and container. Then isolation was done by the previous way. Antibiotic sensitivity test - Sensitivity test were performed by disc dispenser method. The drug discs (Oxoid Ltd.) were Oxytetracycline (30 J.Lg/disc), Chloramphenicol (30 J.Lg/disc), Streptomycin (10 J.Lg/disc) and Oxolinic acid (2 J.Lg/disc) were used to observed the resistance pattern of A. sobria isolates.

Source of Information: Bangladesh J. Fish. Res., 4(2): 165-170, 2000

Article Link (Online Journal):

Funding Source:

Total Budget (Tk.) :

Achievement/Findings:

In the present study, the selected Aeromonas sobria isolates under Aeromonad genus were capable of producing ulcerative disease.

Knowledge Management: Journal