Gonococcal color and opacity variants: virulence for chicken embryos

Abstract

Previous studies have noted that the prevalence of certain gonococcal colony types is influenced by the physiological state of the human host. Consequently eight different gonococcal strains were passed on clear typing medium, and opaque (Op) and transparent (Tr) variants of heavily pilated (P++) bacteria were selected. P++Op and P++Tr were injected into 11-day-old chicken embryos, and the resulting mortality was determined. In every case the Tr variants were more lethal to the embryos than were the Op variants (P = 0.01). P++Tr were stable in vivo, but chicken embryos injected with P++Op strains developed bacteremia with P++Tr organisms. However, chicken blood was not bactericidal for either colonial variant. These results indicate that transparent pilated bacteria may be more virulent than opaque pilated bacteria and that in vivo selection of transparent forms occurs.

Effect of colony type and pH on surface charge and hydrophobicity of Neisseria gonorrhoeae

“…The results (Tables 1 and 2) demonstrate that the T1 and T2 variants were both more negatively charged and less liable to hydrophobic interaction than T3 and T4. The latter observation was sup- 21 (1) 37 (5) 16 (2) 44 (5) 24 (1) 38 (6) P-PEG 21 Table 1 as percentage of increase of material in T plus percentage of decrease of material in B compared to the partition in the basal system. ' Colony type.…”

“…In addition, the presence or absence in the outer membrane of a series of proteins, termed the "colony opacity-associated" (COA) proteins (26,27), seems also to influence the degree of virulence displayed by a particular strain. Recently it has been shown that piliated variants lacking the COA proteins are distinctly more virulent in an animal model than are piliated variants that possess them (24). Piliated variants, whether or not they possess the COA proteins, appear to be more virulent in these models than either of the nonpiliated variants.…”

Ability of Neisseria gonorrhoeae, Neisseria meningitidis, and commensal Neisseria species to obtain iron from transferrin and iron compounds

“…Although it is not possible to directly compare our results with those of Payne and Finkelstein (19, 20) and of Payne et al (21), the observed effects of iron on the virulence of gonococci in the chicken embryo model may have been influenced by factors other than the ability of the gonococcal isolates to scavenge iron. For instance, levels of available iron may have affected expression of outer membrane proteins (17) to a variable degree in different isolates, or other factors such as colony opacity (22) could have contributed to differences in virulence.…”

Intra-strain heterogeneity of gonococcal pili is related to opacity colony variance.

“…The Op organisms produce one or more additional protein(s) with apparent molecular weights ranging between 23,500-31,000 which are not found in Tr bacteria (13). Fourth, studies in the chicken embryo model indicate that P + T r bacteria are more virulent than P + O p organisms of the same strain (16). Because pili are suspected to be a virulence factor in gonococcal infections, it seemed appropriate to purify pili to determine if differences exist between pili obtained from Op and Tr bacteria.…”