Gonococcal color and opacity variants: virulence for chicken embryos

Area of Science:

• Microbiology
• Bacteriology
• Infectious Diseases

Background:

• Gonococcal colony type prevalence is influenced by host physiology.
• Neisseria gonorrhoeae exhibits opaque (Op) and transparent (Tr) colony variants.
• Pilated (P++) bacteria are relevant for gonococcal virulence.

Purpose of the Study:

• To compare the virulence of opaque and transparent pilated gonococcal variants.
• To investigate in vivo stability and transformation of gonococcal colony types.

Main Methods:

• Eight gonococcal strains were cultured and variants selected: heavily pilated opaque (P++Op) and heavily pilated transparent (P++Tr).
• Bacterial variants were injected into 11-day-old chicken embryos.
• Embryo mortality and bacteremia were assessed. Chicken blood bactericidal activity was tested.

Main Results:

• Transparent variants (P++Tr) were significantly more lethal to chicken embryos than opaque variants (P++Op) (P = 0.01).
• P++Tr remained stable in vivo, while P++Op strains led to bacteremia with P++Tr organisms in chicken embryos.
• Chicken blood did not exhibit bactericidal activity against either variant.

Conclusions:

• Transparent pilated gonococci exhibit higher virulence than opaque pilated gonococci.
• In vivo selection favors the transparent morphotype, indicating its greater adaptability and pathogenicity.