Neisseria gonorrhoeae

1. NAAT (PCR) is the recommended optimal diagnostic method for both N. gonorrhoeae and C. trachomatis — directly from Felix Lai senior notes mirroring GC lecture content; antigen detection is NOT available for gonococcus ^[3].

2. Thayer-Martin agar is the selective medium for gonococcal culture; this allows antibiotic sensitivity testing, which is critical given emerging cephalosporin resistance ^[3][1].

3. Maltose fermentation negative is the single most tested biochemical discriminator: gonococcus ferments glucose only; meningococcus ferments glucose AND maltose ^[1][2].

4. Disseminated gonococcal infection (DGI) presents as either (a) the classic triad of tenosynovitis + dermatitis + polyarthralgia, or (b) purulent monoarthritis. This is the most common cause of septic arthritis in sexually active young adults ^[3][7][8].

5. Complement C5–C9 (terminal/MAC) deficiency predisposes to recurrent Neisseria infections — tested in immunodeficiency lectures and past papers ^[11].

6. PID management: IM ceftriaxone single dose → PO doxycycline course → PO metronidazole course. This covers gonococcus, Chlamydia, and anaerobes — directly examined in 2024 MCQ Q89 ^[6][9].

• Gonococcus vs Meningococcus: both are G−ve oxidase + diplococci. Discriminate by maltose (GC −, MC +), capsule (GC absent, MC present), and clinical context (STI vs meningitis/septicaemia).
• Gonococcal arthritis vs Reactive arthritis (Reiter's): DGI arthritis is caused by direct joint invasion with positive joint culture; Reiter's is a sterile, reactive arthritis following enteric (Shigella, Salmonella, Campylobacter) or chlamydial infection with the classic triad of urethritis + conjunctivitis + arthritis. The 2019 MCQ Q9 vignette (diarrhoea → arthritis + urethral discharge + red eyes) = Reiter's, NOT gonococcal arthritis ^[10].
• Gram stain in ♂ vs ♀: urethral swab Gram stain is sensitive in symptomatic males but NOT reliable in females — always use NAAT for females.
• Ophthalmia neonatorum: N. gonorrhoeae causes hyperacute purulent conjunctivitis (within days of birth); C. trachomatis causes conjunctivitis slightly later (5–14 days). In adults, fulminant purulent conjunctivitis should prompt swab culture for Neisseria spp ^[5].

2024 Fourth Summative MCQ Q89 ^[9]

"A 23-year-old woman was admitted to gynaecology ward for lower abdominal pain and fever. She was sexually active and had 3 sexual partners in the past 6 months. Physical examination revealed lower abdominal tenderness. There was foul smelling vaginal discharge on speculum examination and cervical excitation was present on bimanual examination. Which of the following is the MOST APPROPRIATE management?"

Options: A. Single dose IM ceftriaxone + course of PO doxycycline and metronidazole; B. Single dose PO azithromycin; C. Single dose PO metronidazole; D. IV ceftriaxone + PO doxycycline.

Correct answer: A. This is classic PID (cervical excitation = chandelier sign). Outpatient PID regimen = IM ceftriaxone (covers GC) + PO doxycycline (covers Chlamydia) + PO metronidazole (covers anaerobes). Option D (IV route) is reserved for severe/admitted PID with systemic toxicity; the question asks "most appropriate" and the standard first-line outpatient regimen is A.

2019 Fourth Summative MCQ Q9 ^[10]

"A 36-year-old man presented with subacute onset pain and swelling of his right knee. Four weeks prior to this, he experienced bouts of diarrhoea which took over a week to settle. Further inquiry revealed painless urethral discharge and pain and redness of his eyes."

Correct answer: G (Reiter's syndrome / reactive arthritis). This is NOT gonococcal septic arthritis. The triad of arthritis + urethritis + conjunctivitis following enteric infection is classic reactive arthritis. Discriminator: gonococcal arthritis would present acutely with purulent joint or the DGI triad (tenosynovitis, dermatitis, polyarthralgia), and would not follow diarrhoea.

No other past paper questions directly examining N. gonorrhoeae were identified in the indexed past paper context.