A woman treated successfully for gonorrhoea last year acquires culture-proven N. gonorrhoeae again from her partner despite having detectable antibodies against the organism after her previous episode. The property of Neisseria gonorrhoeae chiefly responsible for such recurrent infection and for the failure of vaccine development is:

• A Intracellular survival within neutrophils that shields it from antibody
• B Antigenic and phase variation of pili and Opa proteins through gene recombination ✓
• C Production of an antiphagocytic polysaccharide capsule like meningococci
• D Horizontal acquisition of beta-lactamase plasmids between strains

Explanation

Gonococci express pili (PilE) and opacity proteins (Opa) whose genes undergo extensive antigenic and phase variation through gene conversion with silent cassettes and slipped-strand mispairing of repeat tracts. Antibodies raised against one variant fail to recognize the new surface phenotype, so natural infection produces strain-specific, short-lived immunity and repeated infections are common. This same variation defeated pilus-based vaccine attempts. Gonococci lack a true capsule, and beta-lactamase plasmids affect drug resistance, not immune evasion.

Reference: Mims' Medical Microbiology and Immunology, 6th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.