Introduction
- Gonorrhea is a common sexually transmitted bacterial infection.
- It is caused by Neisseria gonorrhoeae.
- The organism is a Gram-negative diplococcus and appears as paired kidney-shaped cocci under the microscope.
- Gonorrhea mainly infects the mucous membranes of:
- Genital tract
- Rectum
- Pharynx
- Conjunctiva
- The infection spreads mainly through sexual contact.
- It can affect both males and females.
- Many infected females may remain asymptomatic, which increases transmission in the community.
- Untreated gonorrhea may lead to serious complications such as:
- Pelvic Inflammatory Disease
- Infertility
- Epididymitis
- Ophthalmia Neonatorum
- Laboratory diagnosis is important because symptoms may resemble other genital infections.
Causative Organism
Neisseria gonorrhoeae belongs to the genus Neisseria.
Morphological Characteristics
- Gram-negative diplococcus
- Kidney-shaped cocci arranged in pairs
- Non-motile
- Non-spore forming
- Non-capsulated
- Usually intracellular within polymorphonuclear leukocytes
- Outer membrane containing lipooligosaccharide
- Pili for attachment
- Outer membrane proteins for adhesion
These structures are important for virulence and survival in host tissues.
Habitat and Reservoir
The organism commonly colonizes mucous membranes lined by columnar or transitional epithelium.
Common sites of habitat
- Urethra
- Endocervix
- Rectum
- Pharynx
- Conjunctiva
- In males, the urethra is the most common site of infection.
- In females, the endocervix is the principal site of colonization.
- Extra-genital sites such as rectum and pharynx may also serve as reservoirs, especially in asymptomatic carriers.
Because many infected individuals remain asymptomatic, they continue to act as an important source of transmission in the community.
Mode of Transmission
Gonorrhea spreads mainly through direct contact with infected mucosal secretions.
Main mode of transmission
- Sexual contact
Types of sexual transmission
- Vaginal intercourse
- Anal intercourse
- Oral sexual contact
- The infection spreads when gonococci come into contact with susceptible mucosal surfaces.
- Transmission is efficient because the organism adheres rapidly to epithelial cells.
Vertical transmission
- Infection may pass from infected mother to newborn during childbirth.
This may lead to Ophthalmia Neonatorum in newborn babies.
- The organism does not usually spread through casual contact because it survives poorly outside the body.
Pathogenesis
Pathogenesis begins when Neisseria gonorrhoeae enters susceptible mucosal surfaces and attaches to epithelial cells.
Step 1: Adhesion to Mucosal Cells
The organism uses pili and outer membrane proteins to attach firmly to epithelial cells.
Important structures involved
- Pili
- Outer membrane proteins
- Adhesins
These help bacteria resist mechanical washing by urine and secretions.
Step 2: Penetration of Epithelium
After attachment, gonococci penetrate between epithelial cells and enter subepithelial tissue.
- The organism multiplies locally.
- Tissue invasion begins at the mucosal surface.
Step 3: Inflammatory Response
The body responds by attracting neutrophils to the site of infection.
Result
- Purulent discharge develops
- Large numbers of intracellular gonococci appear inside neutrophils
Step 4: Tissue Damage
The organism produces endotoxin-like lipooligosaccharide, which causes inflammation and local tissue injury.
Effects
- Redness
- Swelling
- Pain
- Mucosal damage
Important Virulence Factors
- Pili for adhesion
- Por proteins for invasion
- Opa proteins for close attachment
- Lipooligosaccharide for inflammation
- IgA protease for immune evasion
These factors help the organism survive and persist in host tissues.
Spread of Infection
If untreated, infection may spread upward.
In males
- Epididymis
- Prostate
In females
- Uterus
- Fallopian tubes
Clinical Features
Clinical Features in Males
In males, urethral infection is the most common presentation.
Common symptoms
- Burning sensation during urination
- Purulent urethral discharge
- Urethral irritation
- Increased frequency of urination
- Thick
- Yellow or greenish
- Purulent
Complications in males
- Epididymitis
- Prostatitis
- Urethral stricture
- Infertility
Clinical Features in Females
In females, symptoms are often mild or absent.
Common symptoms
- Vaginal discharge
- Dysuria
- Lower abdominal pain
- Intermenstrual bleeding
Important point
- Many females remain asymptomatic, which increases spread of infection.
Major complication
Pelvic Inflammatory Disease
This may lead to:
- Tubal infertility
- Chronic pelvic pain
- Ectopic pregnancy
Extra-genital Infection
Rectal infection
- Rectal pain
- Discharge
- Irritation
Pharyngeal infection
- Sore throat
- Often asymptomatic
Eye infection
Ophthalmia Neonatorum occurs in newborns.
Laboratory Diagnosis
Laboratory confirmation is essential because symptoms may resemble other genital infections.
Specimens Collected
- Urethral swab
- Endocervical swab
- Rectal swab
- Pharyngeal swab
- Conjunctival swab
- First void urine
Direct Microscopy
Gram Staining
This is the most important rapid test in symptomatic males.
Findings
- Gram-negative intracellular diplococci inside polymorphonuclear leukocytes
Neisseria gonorrhoeae appears as paired kidney-shaped cocci.
- Rapid diagnosis
- Highly useful in acute male urethritis
Culture
Culture is important for confirmation and antibiotic sensitivity testing.
Culture medium used
Thayer–Martin agar
Incubation conditions
- 35–37°C
- 5–10% carbon dioxide
Colony appearance
- Small
- Smooth
- Transparent colonies
Biochemical Identification
Oxidase test
- Positive
Sugar fermentation
- Glucose positive
- Maltose negative
Molecular Diagnosis
NAAT (Nucleic Acid Amplification Test)
This is highly sensitive and widely used.
Advantages
- Detects asymptomatic infection
- Highly specific
- Can use urine sample