Johne's Disease: Experimental Infection in Mice With Studies on the Isolation and Cultivation of Mycobacterium johnei

Cameron, John (1954) Johne's Disease: Experimental Infection in Mice With Studies on the Isolation and Cultivation of Mycobacterium johnei. PhD thesis, University of Glasgow.

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Abstract

The methods for the isolation of Myco. johnei from intestinal mucosa and media for its cultivation are discussed; 30 bovine and 2 pigmented ovine strains of Myco. johnei have been isolated. A new method for the isolation of the organism from faeces has been devised. A vitamin-K compound was found to stimulate the growth of a strain of Myco. johnei not requiring the growth factor supplied by Myco. phlei. This compound did not support the growth of 3 typical strains of Myco. johnei requiring the growth factor. Other aspects of the metabolism of Myco. johnei were also investigated. The main object of this study was to reproduce Johne's disease in mice. For this purpose, 6 strains of Myco. johnei were inoculated as cultures: of these, 4 were virulent, one was avirulent, and one was tested only with what may have been sub-minimal inocula. Five strains were inoculated as suspensions of infected viscera: of these, 3 were virulent, and the virulence of the other 2 is as yet unknown. The infection was produced by the intraperitoneal and intravenous, but not by the oral route. Johne's disease in mice is characterised by a very long/ long incubation period - 8 to 16 months, depending on the size of the inoculum - at the end of which Myco. johnei appears in the faeces and rapidly increases in numbers as the infection progresses. The disease is almost asymptomatic, yet in some experiments the death-rate was very high. Although it was possible to produce the infection in approximately 14 months with 0. 5 mgm. dry weight of organisms, the use of larger doses shortened the incubation period. The shortest incubation period observed was 6 months. Post-mortem examination of infected mice reveals thickening of the intestine and enlargement of the mesenteric lymph glands; microscopically, innumerable organisms are seen in smears of the viscera. The lesions, infiltrated by macrophages packed with acid-alcohol-fast bacilli, and sometimes by giant cells, were found in the intestinal mucosa and submucosa, and in the mesenteric lymph glands, liver, and spleen; the intestinal lesions are a replica of those seen in cattle, although generally more extensive. Myco. johnei was re-isolated from the faeces and organs of experimentally infected mice, and the infection was reproduced by inoculation of the viscera of such animals. Of a total of 205 mice inoculated with cultures, 51 received sub-minimal inocula, 55 received the avirulent strain/ strain, and 55 were killed for histological examination within 4 weeks of inoculation. Of the remaining 46, 27 were killed after 9 months; of these 27, 11 had Myco. johnei in the faeces and 5 of the 11 examined histologically had lesions. Another 12 of the 46 had Myco. johnei in the viscera 12 to 16 months after inoculation and 11 of them, examined histologically, had lesions. The remaining 7 of the 46, still alive, have large numbers of Myco. johnei in the faeces. Of 54 mice inoculated with bovine intestinal mucosa, 7 died shortly after inoculation, 25 are in the incubation period, and 22 developed the infection. Of these 22, 12 are still alive and 10 are dead, of which 7, examined histologically, had lesions. Of 74 inoculated with mouse viscera, 12 died shortly after inoculation, 25 still alive have large numbers of Myco. johnei in the faeces, 18 are in the incubation period, 4, inoculated 11 months ago, probably received a sub-minimal dose, and 15 developed the infection. Of the 15, 7 examined histologically had lesions. Reasons are suggested for the failure of other workers to transmit Johne's disease to laboratory animals. The size of the inoculum, the length of the observation period, and differences in virulence of strains of Myco. johnei and in the susceptibility of animals, appear to be the main factors.

Item Type: Thesis (PhD)
Qualification Level: Doctoral
Keywords: Microbiology, Animal diseases
Date of Award: 1954
Depositing User: Enlighten Team
Unique ID: glathesis:1954-79139
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 05 Mar 2020 11:40
Last Modified: 05 Mar 2020 11:40
URI: http://theses.gla.ac.uk/id/eprint/79139

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