Morphology: Gram-negative diplococcus (kidney-bean-shaped pairs), oxidase-positive. Fastidious — requires Thayer-Martin or chocolate agar with CO2.
Typical drugs
- #1Ceftriaxone— **CDC 2021: ceftriaxone 500 mg IM × 1** for uncomplicated GC (1 g if ≥150 kg). Higher dose / longer course for DGI, GC arthritis, meningitis.
- #2Doxycycline— Co-treatment if chlamydia co-infection not excluded. NOT GC monotherapy — emerging resistance.
- #3Azithromycin— No longer recommended for GC due to rising resistance. Reserved for true cephalosporin allergy in consultation with ID.
Empiric therapy when resistant
Ceftriaxone 500 mg IM is still highly effective for US isolates. For documented ceftriaxone-resistant GC (rare; growing concern globally), consult ID — options include gentamicin + azithromycin combo or higher-dose ceftriaxone.
Resistance mechanisms
altered-target
PBP2 mutations (penA) → reduced cephalosporin susceptibility
Example: Ceftriaxone MIC creep documented globally; some XDR strains resistant to all oral agents — IM ceftriaxone remains reliable in US.
Enzymatic degradation
Plasmid-mediated TEM-1 β-lactamase
Example: Penicillin no longer used for GC anywhere — uniformly resistant.
Resistance notes
Macrolide and fluoroquinolone resistance widespread — never use azithro or cipro monotherapy. β-lactamase universal — no penicillin. Cephalosporin resistance emerging in Asia, Europe.
Common syndromes
Pearls
Disseminated Gonococcal Infection (DGI): triad of (1) tenosynovitis, (2) dermatitis (pustular/hemorrhagic, painful), (3) polyarthralgia → progresses to monoarticular septic arthritis if untreated. Young, sexually active patient. Knee most common joint. Always co-treat chlamydia unless excluded by NAAT (doxycycline 100 mg PO BID × 7 days). Test for HIV/syphilis in any patient with GC. Sexual partners need empiric treatment.
References
- CDC Sexually Transmitted Infections Treatment Guidelines (2021)
- IDSA Septic Arthritis Practice Guidance (2013)