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Isolation of Bacterial Fish Pathogen Aeromonas Hydrophila and Therapeutic Effects of Medicinal Plants on Its Invasion

Md. Tareq-Uz-Zaman
Department of Aquaculture, Bangladesh Agricultural University, Mymensingh-2200, Bangladesh

Md. Bazlur Rashid Chowdhury
Department of Aquaculture, Bangladesh Agricultural University, Mymensingh-2200, Bangladesh

Md. Rasheduzzaman Khan Dipu
Department of Aquaculture, Bangladesh Agricultural University, Mymensingh-2200, Bangladesh

Abstract/ Executive Summary:

Aeromonas hydrophila, a bacterial pathogen, was isolated form Pangasius hypophthalmus. For pathogenicity test, different doses were injected intramuscularly in Barbonymus gonionotus. Crude extracts were prepared from various parts Azadirachta indica, Curcuma longa, C. zedoaria, and Callotropis gigentia and applied to B. gonionotus for 7 days. Bath treatment was done up to their tolerance level and well ventilation was confirmed for aeration and 50% water was exchanged daily. Minimum inhibitory dose was detected as 7 mg/ml. High inhibitory effect was observed in case of A. indica and mixed extract of A. indica and C. gigentia. Both A. indica and C. gigentia showed the best result with 90-95% recovery of infected fish at a dose of 7 mg/l. C. zedoaria showed moderate to weak effect with 50-60% recovery at the same dose. The present study showed that medicinal plants would be an effective control measure against A. hydrophila.

Keywords: Fish pathogen, Fish disease, Therapeutic effect, Medicinal plant, Herbal plant, Aeromonas hydrophila

Location: BAU, Mymensingh

Start Date:

End Date:

Program Area: Pest Management

Commodity: Fish

Objectives:

The present study was undertaken to experimentally infected pangus fish, Pangasius hypophthalmus, with A. hydrophila and its control trial with a view to attain the collection and identification of virulent bacterial isolate, challenge test for pathogenicity evidence, artificial infection and therapeutic measures with medicinal plants and to examine therapeutic effect of medicinal plants on the experimental infection of fish under laboratory condition.

Methodology:

For isolation and experimental infection laboratory stock pathogens were used but due to their very low virulent characters, fresh isolates were collected from diseased wild and farmed P. hypophthalmus from “Valuka Fish Farm Project” for using in the study. Methods of bacterial isolation, their characterization and pathogenecity test were followed according to the method described by Barrow and Feltham (1993) and Chowdhury and Muniruzzaman (2002). At first glassware (Petri dishes, test tubes, L-sticks, mortar, conical flasks, vials, measuring cylinder etc.) were washed, dried and sterilized at 170°C for 1 hour by a dry sterilizer. The plastic materials were autoclaved at 121°C for 15 minutes. 0.85 g NaCl was poured into distilled water to make the volume 100 ml. This was called physiological saline (PS=0.85% NaCl). The preparation was mixed nicely by vortex mixer. All the PS were autoclaved at 121°C for 15 min and kept at 4°C for future use. Body cavities of the collected fish were opened by the help of sterilized scissors. After that sterile inoculating loop were used and samples collected. Sample were culture in TSA petridishes by sterile inoculating loops.Plate dilution technique was applied. TSA plates incubated at 25°C for 48 hours for colony appearances.After growing bacteria in an agar plate, carefully a single colony was taken by sterile inoculating loop and cultured in a agar plate and incubated at 25°C for 48 hours for colony appearances. Aeromonas bacteria was identified based on morphological, physiological and biochemical characters of the isolates. For bacterial suspension preparation 10 mg bacterial sample was added with 1 ml sterile PS in a sterile testtube and mixed nicely with rotator mixer. Bacterial suspension was prepared when the fish conditioning was confirmed and the fish were ready for injection. Apparently healthy Java barb (Barbonymus gonionotus), weighing 8-10 g, were collected. There were acclimatized in aquarium with aeration for two days and checked for any disease before exposing them to pathogenicity test. Three healthy fish against each bacterial pathogen were injected intramuscularly with 0.1 ml of bacterial suspension at the base of dorsal fin. Control fishes (three fish) received only sterile 0.85% PS and kept in an another aquarium. For experimental infection, three types of bacterial samples were used. Different doses like 10-1, 10-2, 10-3 and 10-4 were applied. All fishes died due injection with certain sign and symptoms. Re-isolation was done from dead fish. Medicinal plants were collected from the adjacent area of Bangladesh Agricultural University, Mymensingh. They were brought to the laboratory immediately after collection and preserved for using in the preparation of herbal extracts. The desired parts of plants were cut into small pieces which grinded by hammering. The large particulate from the extracts were screened out by passing through fine meshed cloth. The crude extracts were then preserved in the refrigerator at low temperature for future use in the efficacy test. Collected medicinal plants were applied against the bacterial fish pathogen, the effective plants were investigated to determine their minimum inhibitory dose (MID) that can inhibit the infectivity of bacterial pathogen. Two different doses, 8 mg/ml and 7 mg/ml of the plant extracts were applied.

Source of Information: J Fish 2(1): 76-79, Apr 2014

Article Link (Online Journal):

Funding Source:

Total Budget (Tk.) :

Achievement/Findings:

The present study was designed recover fresh isolate of Aeromonas pathogen and to examine the therapeutic effect of selected medicinal plants against common bacterial fish pathogen responsible for causing disease in cultured fishes. A total of three new bacterial isolates were recovered from naturally infected fish. Among them one isolate was detected as pathogenic, the rest two were non pathogenic. Selected new isolates showed high infectivity causing lesions on the body of the experimental fish. Basic results of this study regarding medicinal plants correspond with the works done by Muniruzzaman (2004) and Rahman (2005). The present study revealed that some medicinal plants have an important role to inhibit the growth of bacteria producing disease in fish. But the efficacy of the collected medicinal plants were found to be varied from species to species. All the medicinal plants in present study were found effective against the bacterial pathogen. Mixture of the A. indica and C. gigentia showed the highest effect against the bacterial pathogens tested. Individually C. gigentia and C. longa showed medium inhibitory response. Traditionally C. gigentia is used alone or with other medicinal plants to treat common diseases such as fevers, rheumatism, indigestion, cough, cold, eczema, asthma, elephantiasis, nausea, vomiting, diarrohea (Caius 1986). However, bacterial diseases by A. hydrophila could be reduced by the application of the medicinal plants extracts, used in present study.

Knowledge Management: Journal