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Assam Agricultural University, Jorhat

Assam Agricultural University is the first institution of its kind in the whole of North-Eastern Region of India. The main goal of this institution is to produce globally competitive human resources in farm sectorand to carry out research in both conventional and frontier areas for production optimization as well as to disseminate the generated technologies as public good for benefitting the food growers/produces and traders involved in the sector while emphasizing on sustainability, equity and overall food security at household level. Genesis of AAU - The embryo of the agricultural research in the state of Assam was formed as early as 1897 with the establishment of the Upper Shillong Experimental Farm (now in Meghalaya) just after about a decade of creation of the agricultural department in 1882. However, the seeds of agricultural research in today’s Assam were sown in the dawn of the twentieth century with the establishment of two Rice Experimental Stations, one at Karimganj in Barak valley in 1913 and the other at Titabor in Brahmaputra valley in 1923. Subsequent to these research stations, a number of research stations were established to conduct research on important crops, more specifically, jute, pulses, oilseeds etc. The Assam Agricultural University was established on April 1, 1969 under The Assam Agricultural University Act, 1968’ with the mandate of imparting farm education, conduct research in agriculture and allied sciences and to effectively disseminate technologies so generated. Before establishment of the University, there were altogether 17 research schemes/projects in the state under the Department of Agriculture. By July 1973, all the research projects and 10 experimental farms were transferred by the Government of Assam to the AAU which already inherited the College of Agriculture and its farm at Barbheta, Jorhat and College of Veterinary Sciences at Khanapara, Guwahati. Subsequently, College of Community Science at Jorhat (1969), College of Fisheries at Raha (1988), Biswanath College of Agriculture at Biswanath Chariali (1988) and Lakhimpur College of Veterinary Science at Joyhing, North Lakhimpur (1988) were established. Presently, the University has three more colleges under its jurisdiction, viz., Sarat Chandra Singha College of Agriculture, Chapar, College of Horticulture, Nalbari & College of Sericulture, Titabar. Similarly, few more regional research stations at Shillongani, Diphu, Gossaigaon, Lakhimpur; and commodity research stations at Kahikuchi, Buralikson, Tinsukia, Kharua, Burnihat and Mandira were added to generate location and crop specific agricultural production packages.

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20161
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Subject: Veterinary Microbiology × Author: HAZARIKA, PARISHMITA × End date: 2019 × Thesis Type: M.V.Sc. ×
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    ThesisItemOpen Access
    IMMUNO PROTECTIVE POTENTIAL OF PARTIALLY PURIFIED TOXOIDS OF Clostridium difficile IN MICE
    (Assam Agricultural University, Khanapara,Guwahati, 2016-11) HAZARIKA, PARISHMITA; SHARMA, R. K.
    The present study was undertaken to characterize Clostridium difficile toxins, in respect to the influence of glucose and stages of growth (incubation period) on release of toxins, cytotoxic activities in Vero cells and the immune-protective potential of partially purified toxoids of C. difficile in mice. A total of 10 isolates of C. difficile from the repository of Department of Microbiology, College of Veterinary Science, Khanapara, Guwahati were revived and reconfirmed, based on morphological and staining characteristics, and molecular detection of gluD gene. Characterization of all the 10 isolates, in respect to certain virulence associated genes revealed presence of tcdA (toxin A) and tcdB (toxin B) genes in three strains of C. difficile each. Another three strains could reveal tcdA and tcdB together in the same isolate, while one strain was found to be negative for tcdA and tcdB gene.The protein concentration in the cell free supernatant of toxin A and toxin B positive isolate of C. difficile growth in nutrient media without addition of glucose was found to increase with advancement of growth phases and reached the highest conc. during the decline phase of 48 hr (5.24 µg/µl and 5.06 µg/µl, respectively). Similar trend of protein conc. was observed in the cell free supernatants of both the isolates, in presence of glucose in the nutrient media. However, the presence of glucose was found to suppress the protein conc. in the cell free supernatants of toxin A and toxin B of C. difficile (3.49 µg/µl and 3.99 µg/µl, respectively). The protein profile of toxin A positive C. difficile isolate, in presence of glucose could show 10 protein bands with mol. wt. ranging from 25 to 135 kDa, while the same isolates in absence of glucose in nutrient media revealed 16 protein bands within the range of 22.4 kDa and 100.0 kDa. Similarly, the isolate positive for toxin B revealed 8 protein bands of 35 to 135 kDa range in the cell free supernatant with addition of glucose, while the growth of the same isolate in nutrient media without glucose could exhibit 15 protein bands within the range of mol. wt. 20.0 to 135.0 kDa. Toxin A, B and AB of C. difficile were extracted in thioglycolate media without addition of glucose at 48 hr of incubation and were partially purified by ammonium sulphate precipitation. The partially purified toxins were found to be cytotoxic for Vero cells at two dilution (1:10 and 1:100). Among the three toxins, toxin B was found to be more prominent cytotoxic activities than the other two toxins, A and AB. Complete detoxification was confirmed by testing the monolayer of Vero cells for no cytopathic effect. The immune-protective efficacy of the three toxoid vaccine preparations were tested by immunization of groups of mice with challenge trial on 34th day of post immunization revealed variable protection level. The immunized groups of mice were found to have 100.0 percent protection against homologous challenge dose of 6.0x108CFU. However, the groups of mice, immunized with toxoid A and B could show 75.0 percent protection against challenge with 9.0x108CFU of homologous strains of C. difficile. On the other hand, the vaccine prepared from toxoid AB could confer only 25.0 percent protection in mice, following homologous challenge with 9.0x108CFU. The immunized affected mice, following challenge with 9.0x108CFU dose could show clinical symptoms, suggestive of intestinal disorder, with any mortality. All the affected immunized mice with clinical symptoms were found to recover by the end of the challenge study. The challenge trial with 6.0 x 108 and 9.0x108CFU / dose of homologous strain of C. difficile could produce 100.0 percent mortality in the mice of control group during 48 hr of post challenge observation. The affected mice of the control group revealed an initial development of clinical symptoms, suggesting intestinal infection during 24 hr of observation and all the clinically affected mice were died within 48 hr of challenge. Mortality in mice of control group due to inoculated strain of C. difficile was confirmed by re-isolation of the inoculated strains from the affected liver as well as haemorrhagic part of intestine and intestinal contents.