Neisseria gonorrohoeae : General Overview,Sample Collection, Detection, Lab Diagnosis, Pathogenesis and Complications

Neisseria gonorrhoeae

  • Etiology of Gonorrhea
  • Greek (gonos – seed and rhoia- flow)
  • First described in urethral discharge by Neisser in 1879
  • Cultured by Bumm in 1985 and proved its pathogenecity by inoculating human volunteers
  • Resemble meningococci very closely in many properties


  • Endocervical swab (not vaginal swabs)
  •   Uretheral discharge,  urine (in males)
  •   Discharge after prosthetic massage,
  •   Conjunctival swab in case of opthalmia neonatrum
  • – Throat infection may also occurs, in such case throat swab
  • In DGI, specimen may include blood, swabs of skin lesions, urine

Sample collection

(A)Collection or urethral discharge from male:
  • Cleanse around the urethral opening using a swab moistened with sterile physiological saline.
  • Gently massage the urethra from downwards, using a swab, collect a sample of discharge.
  • Make a smear of the discharge on a microscope slide by gently rolling the swab on slide which will avoid damaging pus cells that contain the bacteria.
  • Note: Very few pus cells may be present if the patient has recently passed urine. Allow 2–4 hours after urination before collecting a specimen.
  • When culture is indicated, collect a sample of pus on a sterile cotton-wool swab.
  • To isolate from urine, early morning first voided urine sample is taken, centrifuge and take the sediments.
  • A rectal swab is required in case of homosexual patients.
(B) Collection of cervical specimens from female
  • Use a sterile vaginal speculum to examine the cervix and collect the specimen.
  • Moisten the speculum with sterile warm water, and pass so that cervix could be visualized properly. Do not lubricate the speculum with a gel that may be bactericidal.
  • Cleanse the cervix using a swab moistened with sterile physiological saline.
  • Pass a sterile cotton-wool swab 20–30 mm into the endocervical canal and gently rotate the swab against the endocervical wall.

Transport media:
  • Spot inoculation of sample on culture medium

If not possible,

  • Specimens should be collected on charcoal impregnated swab
  • –Transported to lab on Stuart’s transport medium
Gram Staining: Gram negative, bean shaped diplococcus, intracellular as well as extra cellular
  • Characteristic  intracellular gram negative diplococci  lying with polymorphoinuclear leukocytes and few extracellular  – positive
  • Aprrox. 95 % infected male yield positive result
  • Not reliable in women unless intracellular gram negative diplococci is seen as there are other bacteria with similar morpholgy which appear like Neisseria gonorrhoeae
Direct detection:
  • Direct detection in patient secretion can be done which avoids problems with transport.
  • Gonozyme test: polyclonal antibody test to detect gonococcal antigen by enzyme immunoassay.
  • Direct florescence test
  • Slide agglutination test
Culture the specimen
  • Modified New York City (MNYC)
  • Thayer Martin medium with VCN
  • Chocolate agar

-Incubation at 37°C for 24 hour in a moist atmosphere containing 5-10% CO2 by placing a damp piece of filter paper at the bottom of the jar.


– Inoculate the specimen on two plates of Blood agar and incubate one anaerobically and the other aerobically at 35–37°C overnight.

Colony characteristics:

  • small, round, translucent, convex colonies grow with finely granular surface after 24 hrs
  • After 48 hrs, colonies are larger with crenated margin and opaque raised center
  • On Thayer Martin medium, growth is slow

Kellogg divided gonococci into 4 types on the basis of coloial morphology, auto-agglutinability and virulence

Four types of colonies

–  T1, T2: virulent and contains pilli, small brown colonies

–  T3, T4: avirulent and nonpiliated, large granular, non pigmennted

-Test suspected colonies by touching with a cotton  bud soaked in oxidase reagent, contact area of bud turns purple within 5-15 Secs.

Biochemical reaction
  • Catalase ,Oxidase, Glucose: +ve
  •  Lactose, sucrose and maltose: -ve
Antibody detection in patients sera:
  • Complement Fixation test (CFT)

Beta lactamase testing:

  •  Inoculate the medium with several colonies of organisms and place 6 microgram of penicilln disc on the well, if ZOI is less than 20 mm after overnight incubation, test for beta lactamase by chromogenic cephalosporin method
  • -Nitocephin, a chromogenic cephalosporin is normally yellow and turns red when hydrolyzed.
  • -Inoculate 50µl of heavy suspension of bacteria into the well of a microtitre plate and add 10µl of nitrocephin solution
  • -Incubate 30 mins, observe for color change.

Sensitivity to physical and chemical agents 

  • Verile fragile organism
  • Readily killed by drying, soap and water and many other cleaning or antiseptic agents
  • May remain viable for a day in pus contaminating linen or fabrics
  • Cutured gonococci dies in 3-4 days at room temperature
  • Stored for several months by harvesting the isolate into 1 ml trypone soya broth containing 6% lactose at -20°C or -70°C


  • Venereal disease transmitted by sexual contact
  • Incubation peroiod – 2-8 days
  • Confined to mucus secreting epithelial cells
  • Pili mediates the adhesion og gonococci to the urethra or mucosal surface
  • Cocci penetrates through the intercellular space and reach subepithelial connective tissue by the 3rd day after infection
  • Penetrate columnar epithelial cells. Stratified squamous epithelium is resistant
  • Attack mucous membrane of genitourinary tract, eye, rectum and throat producing acute suppuration followed by chronic inflammation and fibrosis

Disease in men

  • Acute urethritis (most common clinical presentation in male few days after unprotected sexual intercourse)
  • Dysuria and purulent penile discharge
  • Infection may extend to prostate, seminal vessicle and epididymus
  • Chronic urethritis may lead to stricture formation
  • Infection may spread to periurethral tissue causing abcesses and multiple draining sinuses

Disease in woman

  • Endocervix is the primary site of infection and extends to urethra and vagina giving rise to mucopurulent discharge
  • Vaginal epithelium are resistant to infection in adults but severe vulvovaginitis may occur in prepubertal girls
  • Asymptomatic carriage in woman is common (rare in man)
  • Symtomatic patients commonly experience vaginal discharge, dysuria and abdominal pain

Non-gonococcal urethritis in men

  • Chlamydia trachomatis is a common cause of non-gonococcal urethritis (NGU), particularly in men.
  • A presumptive diagnosis of NGU can be made when a urethral smear contains 5 or more pus cells and no intracellular Gram negative diplococci (or more than 15 pus cells in a first voided urine specimen from a male patient).

Binod G C

I'm Binod G C (MSc), a PhD candidate in cell and molecular biology who works as a biology educator and enjoys scientific blogging. My proclivity for blogging is intended to make notes and study materials more accessible to students.