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Effect of Oxytetracycline on Bacterial Load of Hypophthalmichthys Molitrix (silver Carp) Fish in Culture Pond of Mymensingh, Bangladesh

M.A. Kashem
Department of Fisheries Technology, Sylhet Agricultural University, Sylhet-3100, Bangladesh

M.N. Uddin
Department of Fisheries Technology, Bangladesh Agricultural University, Mymensingh-2202, Bangladesh

M.T. Hasan
Department of Aquaculture, Sylhet Agricultural University, Sylhet-3100, Bangladesh

S.M.I Khalil
Department of Fish Health Management, Sylhet Agricultural University, Sylhet-3100, Bangladesh

M.S. Reza
Department of Fisheries Technology, Bangladesh Agricultural University, Mymensingh-2202, Bangladesh

Abstract/ Executive Summary:

Investigation was conducted to assess the influence of antibiotic on bacterial flora of H. molitrix where other physicochemical parameters of culture ponds were suitable for microbes and fish. The experiments were performed from April to October, 2012 in the ponds of Faculty of Fisheries, Bangladesh Agricultural University, Mymensingh. Oxytetracycline (OTC) was used as an antibacterial agent, which is a broad spectrum antibiotic widely use in Bangladesh aquaculture. Pelleted feed with 2g/kg OTC was applied in culture ponds. Physicochemical parameters of water like temperature, pH, dissolved oxygen, alkalinity, ammonia and nitrate were recorded weekly 28.99 to 31.09°C, 7.58-7.95 ppm, 5.36-5.86 mg/L, 86.31-111.99 mg/L, 0.20-0.30 mg/L and 0.11-0.17 mg/L, respectively. All the parameters were in suitable range for fish culture. Total viable counts of bacteria (measured as colony-forming units) were in the range of 4.9±1.03×103- 5.75±1.0×103 cfu/mL in pond water, 5.62±1.0×107- 6.60±1.02×107 cfu/g in sediments, 7.94±1.01×106-9.12±1.0×106 cfu/g in gills, 5.12±1.05×107-6.60±1.01×107 cfu/g in intestinal contents of H. molitrix in control ponds respectively. After OTC treatment the bacterial range were 3.1±1.19×103-3.1±1.20×103 cfu/mL in water, 3.1±1.13×106-4.27±1.10×106 cfu/g in sediment, 3.16±1.29×105- 4.07±1.20×105 cfu/g in gill, 2.63±1.17×106-2.95±1.1×106 cfu/g in intestinal contents of H. molitrix treated ponds respectively, indicating reduction of overall bacterial load below 1 log in sediment, gills and intestinal contents of H. molitrix significantly. (P<0.05).

Keywords: Oxytetracycline (OTC) , Pelleted feed, H. molitrix, Bacterial load

Location: Faculty of Fisheries, BAU, Mymensingh.

Start Date: 00-04-2012

End Date: 00-10-2012

Program Area: Animal Health and Management

Commodity: Carp fish

Objectives:

1. To determine the bacterial load in water, sediments, gills and intestine of experimental M. molitrix before antibiotic treatments and after antibiotic treatments in ponds.

Methodology:

Experimental site: The experiment was conducted in three (3) earthen ponds of the Faculty of Fisheries, BAU, Mymensingh. The ponds were more or less similar in size (12×15 ft), depth, basin conformation, bottom-soil type and contour. Ponds were classified into two groups viz. (a) Control pond without antibiotic medicated diet fed (pond no.-3), (b) Oxytetracycline treated ponds (pond no.1 and pond 2). Pond-1 and 2 were designated as treatment-I and treatment-II where pelleted feed containing 2g/kg oxytetracycline was used for two weeks. The ponds were devoid of aquatic vegetations, well exposed to sunlight and completely free from flooding. Rain water and water from deep tube-well were the main sources of water in the experimental ponds during the study period. Physicochemical analysis: Physicochemical parameters were determined for each treatment on weekly basis between 9.00-10.00 hours.Water samples were collected from each pond from surface to a depth of 15-20 cm. On each sampling day, 250 mL water was collected carefully in a clean black plastic bottle with cap from each pond. Each bottle was then marked with respective pond number with three replicates. The physicochemical parameters eg. dissolved oxygen (DO), pH, total alkalinity, ammonia and nitrite-nitrogen and temperature were observed on the spot and were determined by using univesal pocket meters. Sampling for bacteriological analysis: For microbial investigations three samplings of water, sediment, gills and intestine of H. molitrix were done weekly in culture ponds before antibiotic treatment. After antibiotic treatment samplings were done every alternative day and means were taken. Pond water: 250 ml of water were collected in sterile glass bottles (15-20 cm depth) from three different locations. The three samples were combined to make a composite sample for bacteriological analysis in the laboratory. Aliquots of 0.1 mL of the serial dilutions were inoculated onto nutrient media in duplicate using the spread plate method as this medium recovered most of the bacteria. Sediment: Bottom sediment 10g were collected, with sterile glass bottles submerged to the bottom, from the same three locations in each pond. The sediment sample of 0.2 g was suspended in 1mL of sterile saline solution. 1 ml of the homogenate was serially diluted (10^-1 to10^-8) and treated as previously described for the water sample. Fish gills and intestine: For every sampling, three H. molitrix (80-140 g) from each pond were used for bacterial counts in fish organs (e.g gills and intestine). The fish were killed by pitching. Around 0.5-1 g each of gills and intestinal content were taken aseptically and homogenized separately in a mortar. Approximately 0.2 g of each homogenate was then putted in a tube containing 2 mL of sterile saline solution. 1 ml of each homogenate solution was serially diluted (to 10^-7) and treated in the same way as the pond water samples. Aerobic plate count (APC): All plates in duplicate on sterile petri dish were done for every dilution. From sample solution of different dilutions 0.1 mL samples were taken by a micropipette and transferred aseptically into the pre-prepared agar plates by raising the upper lid sufficient enough to enter the tips of the pipette. The samples were then spreaded homogenously and carefully by sterile flamed L-shaped glass rod throughout the surface of the media until the sample were dried out. For total heterotrophic aerobic bacterial counts of pond water, sediment, gills and intestine, all the inoculated plates were incubated at 28?C for 24-48 hrs. The colony-forming units (cfu) were counted under a Quebec darkfield colony counter (Leica, Buffalo. NY. USA) equipped with a guide plate ruled in square centimetres. Plates containing 30-300 colonies were used to calculate bacterial population results, recorded as cfu per unit of sample by using following formula: cfu /g = {(No. of colonies on petridish × dilution factor × wt. of total sample solution) ÷ wt. of fish sample in gm)}. Data analysis: Data were calculated by using simple MS office programme and SPSS software.

Source of Information: J. Agrofor. Environ. 7 (2): 183-187, 2013; ISSN 1995-6983

Article Link (Online Journal):

Funding Source:

Total Budget (Tk.) :

Achievement/Findings:

Total viable counts of bacteria (measured as colony-forming units) were in the range of 4.9±1.03×10³- 5.75±1.0×10³ cfu/mL in pond water, 5.62±1.0×10⁷- 6.60±1.02×10⁷ cfu/g in sediments, 7.94±1.01×10⁶-9.12±1.0×10⁶ cfu/g in gills, 5.12±1.05×10⁷-6.60±1.01×10⁷ cfu/g in intestinal contents of H. molitrix in control ponds respectively. After OTC treatment the bacterial range were 3.1±1.19×10³-3.1±1.20×10³ cfu/mL in water, 3.1±1.13×10⁶-4.27±1.10×10⁶ cfu/g in sediment, 3.16±1.29×10⁵ - 4.07±1.20×10⁵ cfu/g in gill, 2.63±1.17×10⁶-2.95±1.1×10⁶ cfu/g in intestinal contents of H. molitrix treated ponds respectively, indicating reduction of overall bacterial load below 1 log in sediment, gills and intestinal contents of H. molitrix significantly. (P<0.05).

Knowledge Management: Journal