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Isolation and Identification of Aeromonas Hydrophila from Silver Carp and Its Culture Environment from Mymensingh Region

Dr. M. Mamnur Rashid
Professor
Department of Aquaculture, Bangladesh Agricultural University, Mymensingh-2202Bangladesh

M. F. Ali
Department of Aquaculture, Sheikh Fajilatunnesa Mujib Fisheries College, Melandah, Jamalpur

M. S. Hossain
Fisheries Unit-1,Sherpur, C.P. Bangladesh Co. Ltd. Uttara, Dhaka

Abstract/ Executive Summary:

The pathogenic bacteria, Aeromonas hydrophila from naturally infected silver carp, Hypophthalmichthys molitrix were isolated and identified from a fish farm in Mymensingh. Fish showed motile Aeromonas septicemia (MAS) like reddish head and anal region, pale body colour and external haemorrhages. Intestine, liver, kidney and environmental samples such as sediment, feed and water were inoculated onto the Aeromonas isolation medium (AIM) and TSA plates. The AIM colonies were undergone specific characterization for Aeromonas hydrophila. Quantitative studies of bacterial flora of fish on TSA plates showed that the total bacterial load in intestine, liver and kidney of the sampled fish, sediment, feed and water of the environment were 1.00 × 10⁵ to 1.50 × 10⁵CFU/g, 2.7 × 10²to 4.46 × 10⁴CFU/g, 1.00 × 10³to 2.17 × 10³ CFU/g, 1.90 × 10⁴CFU/g, 4.10 × 10³CFU/g and 2.50 × 10³CFU/ml, respectively. After isolation, A. hydrophila was finally identified by their specific morphological, physiological and biochemical characteristics. They were gram negative, rod shaped, motile bacteria that showed positive reaction for oxidase and catalase, fermented glucose and were resistant to vibriostatic agent 0/129. They showed positive result in esculin hydrolysis test.

Keywords: Aeromonas hydrophila, Silver carp, Hypophthalmichthys molitrix, MAS

Location: Mymensingh

Start Date: 00-00-2010

End Date: 00-00-2011

Program Area: Animal Health and Management

Commodity: Carp fish

Objectives:

1) To identity and isolate Aeromonas hydrophila from silver carp and its culture environment from Mymensingh region

2) To identify the disease condition and the associated pathogen

Methodology:

Diseased as well as apparently healthy fish were sampled. Environmental water, sediment and feed were also collected from the farm. Trypton soya agar (TSA, Oxoid) plates were used for total bacterial count and AIM, for isolation of Aeromonas like bacteria. TSA slants were used for stocking Aeromonas bacteria for further studies.The external lesions were plated onto the TSA and AIM plates. Decimal dilutions of intestine, liver and kidney samples were inoculated onto duplicate TSA plates for total bacterial count and onto AIM plates for specific Aeromonas isolation. All the plates were incubated at 25°C for 48 hrs for colony appearances. All the grown colonies of Aeromonas like bacteria from the streaked and spreaded plates of AIM were sub cultured onto TSA plates to obtain fresh 24 hrs culture and then undergone morphological characterization such as shape, size, Gram character, flagellation and motility test. Biochemical characters such as oxidase, catalase, oxidative-fermentative (OF), acid and gas production from sugars (glucose, lactose, maltose, sucrose and manitol), methyl-red, H₂S production, Voges-proskauer (VP), arginine hydrolysis, esculin hydrolysis and 0/129 test were done to confirm their generic and specific natures. Physiological characters were studied by observing the growth of each isolate at temperatures of 4, 37 and 40°C in different concentrations of NaCl as 0, 1, 2, 3.5 and 4% to confirm the identification of the A. hydrophila bacteria.

Source of Information: J. Bangladesh Agril. Univ. 11(2): 373–376, 2013, ISSN 1810-3030

Article Link (Online Journal):

Funding Source:

Total Budget (Tk.) :

Achievement/Findings:

As Aeromonas hydrophila is an ubiquitous bacterial pathogen it might cause serious losses to the intensive culture system of Bangladesh. The higher loads of A. hydrophila in different organs of MAS affected silver carp fish, sediment, feed and water of the environment strongly supported the ubiquitousness of the bacteria in Mymensingh region of Bangladesh. So, proper management practices should be taken to avoid such disease of culture fishes especially silver carp and to get rid of the infection by such serious bacterial pathogen like Aeromonas hydrophila by improving their culture strategy and culture ecosystem.

Knowledge Management: Journal