The antibacterial effect of oxytetracycline (OTC) on bacterial load, pathogen and possible development of antibiotic resistance in intestinal flora of apparently healthy Nile tilapia (Oreochromis niloticus) was investigated under laboratory condition. OTC, a broad spectrum approved antibiotic widely used in aquaculture, was fed to Nile tilapia through medicated diet at a rate of 2 g/ kg of feed for consecutive 7 days in treatment 1 (T1) and 30 days in treatment 2 (T2). Changes in physico‐chemical parameters of water were also recorded where pH and dissolved oxygen influenced bacterial load and coliform count respectively. At the start of the experiment, initial bacterial load in fish intestine was 1.61 ± 2.25 × 1010 cfu/g, which after OTC treatment decreased significantly (p < .05) to 3.06 ± 2.08 × 108 cfu/g on day 7 and 3.45 ± 4.46 × 107 cfu/g on day 30 when compared with the control group. Among the 10 bacterial genera identified in the intestine, 4 potential public health concern bacteria viz., Salmonella, Escherichia, Enterobacter and Staphylococcaus were predominant. There was a sharp increase in bacterial load on day 18 in T2 that may be attributed to the development of antibiotic resistance in intestinal bacteria. Antibiotic susceptibility test for isolates against seven antibiotics: amoxycillin, ciprofloxacin, co‐trimoxazole, erythromycin, gentamicin, nitrofurantoin and tetracycline using disc diffusion method revealed significantly increased resistance of Gram‐negative rods (p < .05) that possibly caused increased frequency of OTC‐resistant microorganisms. In conclusion, short‐ and long‐term exposure to OTC treatment affected the distribution of bacterial genera including pathogens in the Nile tilapia gastrointestinal tract and concomitantly influenced their antimicrobial resistance.

The study was conducted to isolate the Dermatophilus species from the skin disease of cattle in and around BAU campus during the period from May 2008 to April 2009. A total of 105 skin diseased cattle head were examined where 68 were male and 37 were female ranging from 1 month to12 years of ages. 11 (10.476%) patients were found to have typical lesions of Bovine Dermatophilosis. The rural household farm, young, male and the indigenous cattle were more susceptible. The Dermatophilus species were found Gram positive, branching and filamentous typical form of mycelial elements in Giemsa's staining. It was less visible in Gram's staining. The isolated agents produced only acid from dextrose but did not produce acid and gas from lactose, mannitol, maltose and sucrose. The catalase and the urease test were positive but indole test was negative. β-hemolysis also appeared in early stage on blood agar. The isolated agents were more sensitive to Amoxicillin (70%) followed by Ampicillin (60%) and Cephalexin (60%). Kanamycin (10%) and Ciprofloxacin (10%) was the lowest sensitive to it.

Background and Objective: With changing pattern of culture practices in the coastal region of Bangladesh, the euryhaline giant freshwater prawn Macrobrachium rosenbergii has recently gained popularity among farmers of both semi-intensive and extensive culture systems to improve profitability. Since bacteria are the key player in aquaculture facilities governing health and quality of fish and prawn, comparative bacteriological analyses were undertaken to understand the suitable testing system of bacterial analysis for cultured freshwater prawn.Methodology: Both on-farm and laboratory conditions in low-resource settings were considered to monitor bacterial population in terms of bacterial count, gram staining and presence of enteric bacteria associated with prawn and its surrounding environment.Results: On-farm counting was about one log-unit lower total viable count in water, sediment and prawn samples compared to those of laboratory testing. The differences between on-farm and laboratory analysis probably occurred due to the time lapse during sample transportation. Study also showed that gram negative bacteria were dominant and enteric bacteria were present in both the prawn farms with more or less similar frequencies. Conclusion:It is concluded that the apparent difference in bacteriological condition of the two farms is possibly related to the differences in culture practices, environment and culture conditions and the study has recommended on-farm testing as an ideal bacteriological analysis method.

The study was performed with a view to isolate and identify a virulent strain of S. gallinarum and determine the purity, safety and efficacy of BIO-TYPHOID® vaccine. A total of 40 backyard layer chicken were used for this study where Group A was used for experimental vaccination, Group B kept as control and Group C was used for calculating virulent S. gallinarum challenge dose. Primary and secondary vaccination was carried out at 40 days and 110 days of age, respectively. Blood samples were collected to obtain the sera after vaccination from both vaccinated and unvaccinated control group and antibody titres were determined by Microplate agglutination test. The antibody titre increased in primary vaccination up to days 56 days post vaccination (DPV) and then decreased gradually. The highest antibody titre (Mean ± SE) 384.00 ± 42.67 was obtained at 91 DPV (21 days later of secondary vaccination) and maintained up to 98 DPV. Safety test was done by inoculating mice and purity test of the vaccine was done by inoculating on to Blood Agar media. The efficacy of BIO-TYPHOID® vaccine was recorded as 90% which was determined by challenge infection with 0.1 ml of 5x105 CFU virulent S. gallinarum. Results of this study revealed successful protections by BIO-TYPHOID® vaccine. Keywords: BIO-TYPHOID® vaccine; Chicken; Efficacy; Fowl Typhoid DOI: 10.3329/jbau.v7i2.4737 J. Bangladesh Agril. Univ. 7(2): 295-299, 2009

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