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Isolation of Some Emergent Bacterial Pathogens Recovered from Capture and Culture Fisheries in Bangladesh

M. M. M. Hossian
Department of Fisheries and Marine Bioscience, Jessore Science and Technology University,Jessore-7408, Bangladesh

S. Mondal
Department of Fisheries and Marine Bioscience, Jessore Science and Technology University,Jessore-7408, Bangladesh

A. S. M. Shadat Mondal
The WorldFish Centre, Dhaka, Bangladesh

M. B. R. Chowdhury
Department of Aquaculture, Faculty of Fisheries, Bangladesh Agricultural University, Mymensingh- 2202, Bangladesh

M. A. Rahman
Department of Fisheries and Marine Bioscience, Jessore Science and Technology University,Jessore-7408, Bangladesh

Abstract/ Executive Summary:

Twenty-five bacterial strains were isolated from different sources (culture ponds and lakes) in different geographical regions of Bangladesh, characterized for the investigated of potential virulence status of the six pathogenic bacterial isolates selected from those 25 isolates of Aeromonas and Pseudomonas bacterial pathogens in four types of water [viz., pond water, physiological saline (0.85%Nacl), distilled water and tap water] by injecting on silver barb (Barbodes gonionotus) with low to high doses (3-5 x 104 CFU/ml to 3-5 x 106 CFU/ml bacteria) for 10 days in vitro. All the isolates were found capable of producing disease with the exposure doses of 3-5 x 106 CFU/ml and 3-5 x 105 CFU/ml bacteria. Out of the six isolates P. fluorescens Pf-16, was detected as highly virulent. This pathogen produced 40% lesions with 30% mortality of the experimental fish when challenged at a minimum dose of 3-5 x 104 CFU/ml in pond water. No infection or mortality was observed in the test fish with challenged dose of 3-5 x 104CFU/ml in distilled water, physiological saline and tap water. A. hydrophila Ah-25 was detected as medium virulent. This pathogen successfully produced 30% lesions with 20% mortality of the experimental fish when challenged at a minimum dose of 3-5 x 104CFU/ml in pond water. No infection and mortality was observed of the test fish with challenge dose of 3-5 x 104 CFU/ml in distilled water, physiological saline and tap water. A. veronii biovar sobria A- 44 was detected as low virulent. This isolate successfully produced 50% lesions with mortality 40% of the experimental fish when challenged at a minimum dose of 3-5 x 105 CFU/ml. No infection and mortality was observed with challenged dose of 3-5 x 104 CFU/ml in the pond water, distilled water, physiological saline and tap water.

Keywords: Barbodes gonionotus, Pathogenic, water, virulence, challenge, lesion, mortality, infection

Location: The field laboratory of the Faculty of Fisheries, Bangladesh Agricultural University

Start Date: 00-00-2010

End Date: 00-00-2011

Program Area: Animal Health and Management

Commodity: Carp fish

Objectives:

1. To find out the virulence status of the isolated emergent bacterial pathogens in different types of water with respect to fish.

Methodology:

This study was conducted in the field laboratory of the Faculty of Fisheries, Bangladesh Agricultural University, capture and culture fisheries in different geographical regions of Bangladesh (2001 to 2002) to isolate the potential emergent fish pathogenic bacteria form diseases fish. Further pathogenic bacteria sample and the pathogenecity of the selected virulent pathogens as well as the comparative analysis of their growth and survival were performed from 2010 to 2011, under the collaborative work with The WorldFish Centre, Dhaka & Dept of Fisheries & Marine Bioscience, Jessore Science & Technology University, Jessore. Characterization of Aeromonas isolates: Live fish were killed with a sharp scalpel by cutting below the head. Bacterial samples were collected from lesions and kidney of the diseased fish. Inocula were aseptically streaked onto selective Aeromonas agar plates supplemented with ampicillin SR 136E (Oxoid) and incubated at 22⁰C for 48h. If bacteria grew on the selective media, single colonies were transferred onto tryptone soya agar (TSA) slants as pure cultures and were maintained at 4°C for further study. Primary characterization: Before characterization, pure stocks were sub-cultured onto TSA plates to obtain a fresh, 24-hour culture. Morphological characteristics of bacterial colonies (shape, size and colour) were recorded. The shape of an individual bacterium was determined by Gram’s staining method using a fresh 24- hour old culture. Motility test was performed by preparing a dilute suspension of fresh bacterial culture on a clean glass slide with a coverslip and observing on a television monitor attached to a binocular electric microscope. Pathogenic bacterial isolates: The six bacterial isolates which were analyzed for their virulence properties in four types of water. Virulence peculiarities of these pathogens were determined on the basis of doses, water types and challenged against the fish silver barb (Barbodes gonionotus). On the basis of the primary detection of the pathogenicity, six bacterial isolates (apparently high pathogenic) of different species were selected for detailed study of Virulence in different types of experimental waters these were Aeromonas hudrophila isolates Ah-25, Ah-31, Aeromonas veronii biovar sobria isolates A-45, A-44, Pseudomonas fluorescens isolate Pf-16. and Pseudomonas sp. isolate Ps-13. Healthy young sliver barb (Barbodes gonionotus) weighing 10-15 gm, were acclimatized for 3 days in aquarium condition and was checked for any diseases before injected to fish.

Source of Information: BANGLADESH RESEARCH PUBLICATIONS JOURNAL; ISSN: 1998-2003, Volume: 6, Issue: 1, Page: 77-90, September-October, 2011

Article Link (Online Journal):

Funding Source:

Total Budget (Tk.) :

Achievement/Findings:

No infection and mortality was observed of the test fish with challenge dose of 3-5 x 104 CFU/ml in distilled water, physiological saline and tap water. A. veronii biovar sobria A- 44 was detected as low virulent. This isolate successfully produced 50% lesions with mortality 40% of the experimental fish when challenged at a minimum dose of 3-5 x 105 CFU/ml. No infection and mortality was observed with challenged dose of 3-5 x 104 CFU/ml in the pond water, distilled water, physiological saline and tap water.

Knowledge Management: Journal