Virulence of South African isolates of Haemophilus paragallinarum. Part 3: Experimentally produced NAD-independent isolate

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Authors

Taole, M.
Albertyn, J.
Van Heerden, E.
Bragg, R.R. (Robert Richard)

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Published jointly by the Agricultural Research Council, ARC-Onderstepoort Veterinary Institute and the Faculty of Veterinary Science, University of Pretoria.

Abstract

A NAD-dependent isolate 46 (C-3) of Haemophilus paragallinarum, which was previously demonstrated to be of high virulence, was transformed to NAD independence using a plasmid isolated from a naturally occurring NAD-independent isolate of H. paragallinarum. The transformation was performed by two different methods and the identity of all of the isolates, before and after transformation was confirmed using a H. paragallinarum-specific PCR test. The transformed NAD-independent serovar C-3 isolate and the wild-type serovar C-3 isolate were used to experimentally infect vaccinated layer chickens. It was shown that the transformation to NAD independence significantly altered the virulence of the serovar C-3 isolate that was used in the transformation experiment. The mechanisms responsible for a decrease in virulence are not clear, but may be related to the pathology of the transformed isolate in the sinus of the chickens.

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The articles have been scanned in colour with a HP Scanjet 5590; 600dpi. Adobe Acrobat v.9 was used to OCR the text and also for the merging and conversion to the final presentation PDF-format.

Keywords

Veterinary medicine, Haemophilus paragallinarum, Infectious coryza, NAD dependent, NAD independent, Transformation

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Citation

Taole, M, Albertyn, J, Van Heerden, E & Bragg, RR 2002, 'Virulence of South African isolates of Haemophilus paragallinarum. Part 3: Experimentally produced NAD-independent isolate’. Onderstepoort Journal of Veterinary Research, vol. 69, no. 3, pp. 189-196.