1887

Abstract

Summary: Virulence of ) strains isolated from pigeons is associated with the presence of the extracellular proteins A, T1, T2 and T3. Based on the presence or absence of these proteins, six supernatant-phenotypes are distinguished. Experimental infection studies have indicated that strains belonging to the AT1, AT1, AT2 and AT3 groups are highly virulent for pigeons, strains belonging to the AT3 groups are moderately virulent and AT2 strains are of low virulence. In this study the surface structure of 15 pigeon strains representing high, moderate and low virulence supernatant-phenotypes was examined by electron microscopy. The presence of capsular material was determined by transmission electron microscopy after polycationic ferritin labelling and immunostabilization. Capsules from cells labelled with polycationic ferritin were usually thicker than those from cells exposed to antiserum. The capsule of the virulent strains had a regular, continuous appearance whilst irregularity of the capsule was a characteristic of the low virulence AT2 strains. Negative staining revealed the presence of fimbriae in all strains belonging to the high virulence AT1, AT1, AT2 and AT3 supernatant groups and in one strain of the moderately virulent AT3 group. The fimbriae were thin, flexible structures with a diameter of approximately 3-4 nm and a length of up to 700 nm. Fimbriae as described above were absent in two other AT3 strains examined and in the low virulence AT2 strains. Results from this study indicate that morphological differences in surface structure exist among virulent and low virulence pigeon strains, and that the capsule and/or fimbriae are possibly involved in virulence.

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/content/journal/micro/10.1099/13500872-145-2-335
1999-02-01
2019-11-18
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http://instance.metastore.ingenta.com/content/journal/micro/10.1099/13500872-145-2-335
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