Neisseria gonorrhoeae is a Gram-negative intracellular diplococcus, which infects epithelium particularly of the urogenital tract, rectum, pharynx and conjunctivae. Humans are the only host and the organism is spread by intimate physical contact. It is very intolerant to drying and although occasional reports of spread by fomites exist, this route of infection is extremely rare.

Clinical features

Up to 50% of women and 10% of men are asymptomatic. The incubation period is 2-14 days with most symptoms occurring between days 2 and 5. In men the most common syndrome is one of anterior urethritis causing dysuria and/or urethral discharge. Complications include ascending infection involving the epididymis or prostate leading to acute or chronic infection. In homosexual men rectal infection may produce proctitis with pain, discharge and itch.

In women the primary site of infection is usually the endocervical canal. Symptoms include an increased or altered vaginal discharge, pelvic pain due to ascending infection, dysuria, and intermenstrual bleeding. Complications include Bartholin’s abscesses and in rare cases a perihepatitis (Fitzhugh-Curtis syndrome) can develop. On a global basis GC is one of the most common causes of female infertility. Rectal infection, due to local spread, occurs in women and is usually asymptomatic, as is pharyngeal infection. Conjunctival infection is seen in neonates born to infected mothers and is one cause of ophthalmia neonatorum.

Disseminated GC leads to arthritis (usually monoarticular or pauciarticular) and characteristic papular or pustular rash with an erythematous base in association with fever and malaise. It is more common in women.

Diagnosis

N. gonorrhoeae can be identified from infected areas by culture on selective media with a sensitivity of at least 95%. Microscopy of Gram-stained secretions may demonstrate intracellular, Gram-negative diplococci, allowing rapid diagnosis. The sensitivity ranges from 90% in urethral specimens from symptomatic men to 50% in endocervical specimens. Nucleic acid amplification tests (NAATs) using urine specimens are non-invasive and highly sensitive, although may give false positive results. Microscopy should not be used for pharyngeal specimens. Blood culture and synovial fluid investigations should be performed in cases of disseminated GC. Coexisting pathogens such as Chlamydia, Trichomonas and syphilis must be sought.

Treatment

Treatment is indicated in those patients who have a positive culture for GC, positive microscopy or a positive NAAT. Epidemiological treatment is given to patients who have had recent sexual intercourse with someone with confirmed GC infection. Although N. gonorrhoeae is sensitive to a wide range of antimicrobial agents, antibiotic-resistant strains have shown a recent significant increase in the UK. Up to 10% of strains show resistance to penicillins and ciprofloxacin and over 40% resistance to tetracyclines. Immediate therapy based on Gram-stained slides is usually initiated in the clinic, prior to culture and sensitivity results. Antibiotic choice is influenced by travel history or details known from contacts.

Single-dose oral therapy with either cefixime (400 mg), ceftriaxone i.m. (250 mg) or spectinomycin 2 g i.m. (not generally available in the UK) successfully treats uncomplicated anogenital infection. Single-dose amoxicillin 3 g with probenecid 1 g, ciprofloxacin (500 mg) or ofloxacin (400 mg) are recommended for use in areas with low prevalence of antibiotic resistance.

Longer courses of antibiotics are required for complicated infections. There should be at least one follow-up assessment, and culture tests should be repeated at least 72 hours after treatment is complete. All sexual contacts should be examined and treated as necessary.

Although the history and examination will guide investigation, it must be remembered that multiple infections may coexist, some being asymptomatic. Full screening is indicated in any patient who may have been in contact with an STI.

In men:

• Urethral smears for Gram staining
• Urethral swabs for gonococcal culture and Chlamydia testing
• Two-glass urine test and urinalysis
• Rectal swabs for Gram staining and culture for N. gonorrhoeae and C. trachomatis
• Throat swab for culture for N. gonorrhoeae
• Blood for syphilis and HIV serology (with counselling).

In women:

• Smears from the lateral vaginal wall for Gram staining
• Vaginal swab for culture of Candida and Trichomonas
• A wet preparation is made from the posterior fornix for Trichomonas and for the potassium hydroxide test for bacterial vaginosis
• The pH of vaginal secretions using narrow-range indicator paper
• Endocervical smears and swabs for Gram staining, gonococcal culture and Chlamydia tests
• Urethral smears and swabs for Gram staining and gonococcal culture
• Rectal and throat swabs for N. gonorrhoeae and C. trachomatis, if indicated
• Urinalysis
• Cervical cytology
• Blood for syphilis and HIV serology (with counselling).

Additional investigations when indicated:

• Urine sample for nucleic acid amplification tests if available locally
• Blood for hepatitis B and C serology
• Swabs for HSV and Haemophilus ducreyi from clinically suspicious lesions into special media
• Smears and swabs from the subpreputial area in men with balanoposthitis (inflammation of glans penis and prepuce) for candidiasis
• Scrapings from lesions suspicious of early syphilis for immediate dark-ground microscopy
• Pregnancy testing
• Cervical cytology
• Stools for Giardia, Shigella or Salmonella from those practising oral/anal sex.