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1. Experimental listeriosis was produced in healthy rabbits of either sex by inoculating various doses of live Listeria monocytogenes inoculum via three different routesx (oral, intravenous and intraperitoneal). 2. The experimental disease was established by several parameters such as clinical features, reisolation of L. monocytogenes from blood and different organs showing histopathological changes. The presence of L. monocytogenes was further confirmed by the immnofluorscence technique and also by the immunohistological (Peroxidase antiperoxidase) methods 3. It was observed that the disease was produced by all the three modes of inoculation. However, the intensity of clinical features was not similar 4. The lesions produced as a result of L. monocytogenes inoculation showed a dose dependent relationship, smaller doses either had no effect or little effect as compared to larger doses 5. The histopathological features in different organs were described in terms of intensity of lesions from 1+ to 4+ (1+ being minimal size of lesion and 4+ indicating a severe lesion). It was found that these hidtopathological features were also dose dependent 6. It was interesting to observe that all the organs did not show uniformity in the intensity of lesions. Further, it was noticed that lymphoid related organs such as liver, spleen etc. were mainly and prominently affected as compared to non lymphoid organs 7. Those organs which have the presence of mononuclear phagocytic system (MPS) cells such as liver, spleen, kidney, lung, adrenals, brain etc. were the main organs involved forming a lesion in the form of necrotic foci 8. No lesions were seen in testis, ovary and uterus (non-pregnant) 9. Histopathological lesions of variable degree were consistently observed in the liver and spleen of rabbits when inoculated with 4 different doses (1.2X103,1.2X105, 1.2X107, 1.2X109 per ml per animal) by three different routes (oral, intravenous, intraperitoneal). 10. No histopathological evidence of infection was observed in the intestine, ovary, testis and uterus by any route except that of stomach, which developed lesions after intravenous route 11. Hearts of rabbits infected orally did not show any lesion while inconsistent results were obtained with intravenous and intraperitoneal routes of inoculation 12. Smaller dose (1.2X103 per ml per animal) failed to produce signs of keratoconjunctivitis and mucopurulent discharge in the eyes while lung, kidney and brain exhibited variable histopathological evidence of infection 13. L. monocytogenes was isolated from the various organs of rabbits infected by different routes except after oral inoculation of 1.2X103/ml/animal 14. The hyper immunized rabbit showed variable histopathological lesions after challenge by the oral route, whereas after intravenous challenge the organs looked normal 15. Several time passaged culture of L. monocytogenes proved to be highly virulent as it is shown in the form of some aggressive lesions in organs such as liver 16. The phenomenon of monocytosis was also studied. It showed variation after different routes and doses 17. The monocyte count was high after intravenous inoculation specially with a higher dose followed by intraperitoneal and then oral inoculation 18. The normal unimmunized rabbit showed a raised monocyte count up to 15% in 72 hours post inoculation. The count then gradually decreased in 120 hours. The immunized rabbits with the heat killed cells showed a normal range of the monocyte count after challenge with the live cells 19. Several times mice pass aged culture of L. monocytogenes (LD50, 0.55X104) when injected into rabbits showed sever histopathological lesions in the liver 20. The present study using rabbit as a model for the study of the pathogenesis of listeriosis may be compared with that of mice used by earlier workers

Item Type:Thesis (PhD)
Uncontrolled Keywords:listeriosis, listeria monocytogenes inoculum, mononuclear phagocytic system, monocytosis, l. monocytogenes
Subjects:Biological & Medical Sciences (c) > Biological Sciences(c1) > Microbiology(c1.8)
ID Code:1190
Deposited By:Mr. Muhammad Asif
Deposited On:03 Jan 2007
Last Modified:04 Oct 2007 21:05

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