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2007 - 20102
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Author: Jesto, George × Author: KAU × Type: Thesis ×
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    ThesisItemOpen Access
    Development and evaluation of different vaccines against duck pasteurellosis
    (Department of Dairy Science, College of Veterinary and Animal Sciences, Mannuthy, 2010) Jesto, George; KAU; Krishnan Nair
    This study was undertaken to develop biofilm vaccines against duck pasteurellosis using oil, saponin and aluminium hydroxide as adjuvants and to experimentally evaluate their immunogenicity in ducks. Identity of P. multocida serotype A: 1 (DP1) used for study was confirmed by biochemical tests and by PM-PCR and pathogenicity was established in Swiss albino mice before vaccine production. The LD50 (11 w) of the DP1 isolate determined was 10 CFU / bird and MDT was 23.75 h in 11 week old ducklings when a high dose of 3 X 10 6 CFU of P. multocida per bird was given. At 11 Weeks age MDT gradually increased as the dose of inoculum decreased. In 21 week old ducks, the LD50 (21w) of the isolate DP1 was estimated to be 3 ×108 CFU of P. multocida and it showed that the Kuttanad duck had decreased susceptibility to pasteurellosis with age. On light microscopic studies planktonic cells appeared to be Gram negative coccobacillary, while biofilm cells were Gram negative and pleomorphic. Electron microscopic studies revealed that P. multocida could form well differentiated classic biofilm and 0.32 per cent TSB media supplemented 0.5 per cent chitin seemed to be excellent medium for biofilm formation by P. multocida. Four different vaccines viz. OV, OBV, SV and SAV were prepared and all of them were found to be sterile and safe. The oil adjuvanted vaccines (OV and OBV) offered better protection compared to saponin and aluminium hydroxide adjuvanted vaccine groups (SV and SAV) following primary vaccination, up to seven weeks. The modified oil adjuvanted vaccine prepared was not only found to be homogenous, but also more efficient in stimulating a humoral immune response and hence may be recommended. The oil adjuvanation gave better protection than saponin and aluminium hydroxide adjuvanation. The SAV gave better protection than SV which might be due to the presence of aluminium hydroxide which potentiated the immunostimulating ability of saponin. The combined vaccine (SAV) although was found to be better than single vaccine (SV) they cannot be used as a substitute to oil adjuvanted vaccines. The booster vaccination was found to have added advantageous effect on protection and is a must, to prevent losses. Pasteurella biofilms although found to be weak in inducing a primary immune response had the potency to evoke a more powerful secondary response compared to planktonic cells. Vaccination done at six weeks age followed by booster vaccination at 16 weeks age seemed to be a better modification of existing schedule and may be recommended. In histopathological studies, lymphoid hyperplasia was observed in spleen in survived control birds and in SV and SAV vaccine groups that did not survive challenge test, which indicated the persistence of Pasteurella organisms through mild infection in them following experimental challenge. Lymphoid depletion was observed in caecal tonsil in experimental pasteurellosis as in spleen. As the survived vaccinated birds following challenge test showed normal intact caecal tonsil, the course of disease and lesions might be less prominent in vaccinated birds during infection process. The well developed bursa observed in OV and OBV birds that survived challenge test indicated that the humoral immune response was well induced in them compared to other groups. The designed primers E1 and E2 amplified the gene E and hence, this pair of primers could be used for the production of amplified Gene E sequences for further studies on recombinant ghost system. In conclusion, 0.32 per cent TSB media supplemented 0.5 per cent chitin seemed to be an excellent medium that support classical biofilm formation by P. multocida. Booster vaccination definitely had added advantageous effect on protection. Immunization at 6 weeks of age with OV followed by booster vaccination at 16 weeks age with OBV seemed to be a better modification of existing schedule and may be recommended. In histopathological studies, the lesions were less prominent in vaccinated birds than control birds which indicated that the vaccines were effective.
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    ThesisItemOpen Access
    Bacteria associated with respiratory infections in poultry
    (Department of Veterinery Microbiology, College of Veterinary and Animal Science, Mannuthy, 2007) Jesto, George; KAU; Krishnan Nair, G
    This study was undertaken to isolate and identify of bacteria from respiratory tract of poultry and to study the antibiogram of the isolates. Birds showing respiratory signs were sacrificed, postmortem examination was conducted and samples such as nasal, tracheal and air sac swabs and lungs were collected after taking all sterile precautions. A total of 105 samples were collected by sacrificing birds showing clinical signs. Isolation of causative bacteria was made by culturing on brain heart infusion agar, Mac Conkey agar and blood agar. For identification of isolates all the procedures were followed as described by Barrow and Feltham (1993). A total of 31 bacterial isolates were obtained from samples. A total of 12 Escherichia coli isolates were isolated and identified, 4 Pasteurella multocida isolates and 15 Staphylococcus sp. Isolates were isolated and identified biochemically. Out of 15 Staphylococcus sp. isolated and identified 11 isolates (73.33 per cent) were coagulase negative This result indicate that CoNS were more frequently isolated from staphylococcal infections although they do not possess the virulent coagulase activity. So importance must be given to CoNS also, as given to coagulase positive staphylococci and much study need to be diverted to find the virulence factors and role of them in producing bacterial infections in poultry. Multi drug resistance (resistance to at least three antimicrobials) was found among all E. coli isolates obtained in the study. Hence it may be concluded that the high level of resistance observed among poultry E coli isolates obtained in the study may be due to incorporation of antibiotics in feed as growth promoters. As 100 per cent sensitivity is shown to enrofloxacin and chloramphenicol by P. multocida isolates, these two drugs may be used for treating pasteurellois. Amoxycillin clavulanic acid (Ac) and cephalexin (Cp) was found to be the most effective antibiotic against Staphylococcus sp. in the study. The plasmid DNA content of the seven isolates of E. coli was analysed on agarose gel electrophoresis but correlation between the number of plasmids and antibiotic resistance could not be ascertained in this study. In conclusion, the results of this study provide evidence for significant antimicrobial resistance among bacterial isolates from birds. Long term prospective studies involving isolation, identification and antibiogram from more samples are required to identify novel pathogens causing respiratory disease in birds. Such studies provide data on temporal and spatial difference in antibiotic resistance patterns, which in turn helps the scientific community to design better disease control strategies.