Neisseria gonorrhoeae file
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Neisseria gonorrhoeae (Gonococcus)
N.
gonorrhoeae causes the sexually
transmitted disease gonorrhoea.
The
gonococcus was first described by
Neisser in 1879 in gonorrheal pus.
Gonococci
resemble meningococci very
closely in many properties.
MORPHOLOGY:
Gram negative diplococci with adjacent sides
concave, being typically kidney shaped.
They are usually found with in the
polymorphs.
They possess pili on their surface.
CULTURE & CULTURAL CHARACTERISTICS:
Gonococci are fastidious organisms do not grow on
ordinary culture media.
They are aerobic but may grow anaerobically also.
The optimum temperature for growth is 35-36°C &
optimum pH is 7.2-7.6.
It is essential to provide 5-10% CO2.
Media used:
a) Non selective media: Chocolate agar,
Mueller-Hinton agar.
b) Selective media: Thayer Martin medium
with antibiotics (Vancomycin, Colistin &
Nystatin.
Colony morphology: Colonies are small,
round, translucent, convex or slightly
umbonate with finely granular surface &
lobate margins.
Biochemical reactions:
1)
Oxidase test: Positive
2)
Ferments only glucose
but not maltose.
PATHOGENICITY:
Source of infection:
1. Asymptomatic carriers
2. Patients
Mode of infection:
1. Venereal infection (sexual contact)
2. Nonvenereal infection
Antigenic structure & virulence factors:
1. Pili: They help in adherence of bacteria to host
epithelial cells & they are antiphagocytic.
2. Lipooligosaccharide: Endotoxic.
3. Outer membrane proteins: 3 types
a) Protein I (por)- it is a porin & helps in adherence.
b) Protein II (opa)- helps in adherence.
c) Protein III (rmp)- it is associated with protein I.
4. IgA1 protease: Splits & inactivates IgA.
Antigenic structure & virulence factors
Mechanism of pathogenesis:
Gonococci adhere to epithelial cells of urethra or
other mucosal surface through pili
Cocci penetrate through the intercellular space
They reach the sub epithelial connective tissue &
causes inflammation
Leads to clinical manifestations
Incubation period: 2-8 days.
Disease:
A) In men:
The disease starts as an acute urethritis with a
mucopurulent discharge
The infection extends to the prostate, seminal
vesicles & epididymis
In some it may become chronic urethritis leading to
stricture formation
The infection may spread to the periurethral tissues,
causing abscesses & multiple discharging sinuses
(Watercan perineum)
B) In women:
The initial infection is urethritis & cervicitis but vaginitis
does not occur in adult female (vulvovaginitis can
occur in prepubertal girls)
The infection may extend to Bartholin’s glands,
endometrium & fallopian tubes causing
Pelvic Inflammatory Disease (PID)
Rarely peritonitis may develop with perihepatic
inflammation (Fitz-Hugh-Curtis syndrome)
C) In both the sexes: Proctitis, pharyngitis,
conjunctivitis, bacteraemia which may lead to
metastatic infection such as arthritis,
endocarditis, meningitis, pyemia & skin rashes.
D) In neonates: Opthalmia neonatorum (a
nonvenereal gonococcal conjunctivitis in the
newborn) results from direct infection during
passage through birth canal.
LABORATORY DIAGNOSIS:
Specimens collected:
A) In men:
a) Acute infection- Urethral discharge
b) Chronic infectioni)
Morning drop
ii)
Discharge collected after prostatic massage
iii) Centrifuged deposit of urine
B) In women:
i)
ii)
Urethral discharge
Cervical swabs
C) In both the sexes: Blood, CSF, synovial fluid,
throat swab, rectal swab & material from skin
rashes.
Transport: If there is delay in processing than the
specimens should be sent in “ Stuart’s medium”.
Methods of examination:
A) Direct microscopy:
1. Gram staining:
Smear provides a
presumptive
evidence
of gonorrhea in men.
Gram negative
diplococci are found.
But it is unreliable
in women.
2. Immunofluorescence:
B) Culture:
Media used:
Colony morphology:
Gram’s smear:
Reveals Gram negative
cocci in pairs with
adjacent sides concave.
Biochemical reactions:
C) Serology:
Complement fixation test,
Precipitation,
Passive agglutination,
Immunofluorescence,
Radioimmunoassay.
TREATMENT:
Previously
Penicillin was drug of choice but
resistance developed rapidly.
Penicillin
resistant is due to production of
penicillinase enzyme & the strains are called
as penicillinase producing Neisseria
gonorrhoeae (PPNG).
Now
Ceftriaxone or Ciprofloxacin plus
Doxycycline or Erythromycin is useful.
EPIDEMIOLOGY:
Gonorrhoea
is an exclusively human disease.
The
only source of infection is a human
carrier or less often a patient.
Asymptomatic
carriage in women makes them
a reservoir to spread infection among their
male contact.
Gonorrhoea
is an venereal disease (STD).
PROPHYLAXIS:
Early
detection of cases,
Tracing
Health
of contacts,
education,
General
measures,
Vaccination
has no role in prophylaxis.
NONGONOCOCCAL (NONSPECIFIC) URETHRITIS
Urethritis due to causative agents other than
gonococcus.
Etiology:
a) Bacteria- Chlamydia trachomatis
Mycoplasma urealyticum
Ureaplasma urealyticum
b) Parasites- Trichomonas vaginalis
c) Viruses- Herpes simplex
Cytomegalovirus
d) Fungi- Candida
NGU can be a part of Reiter’s syndrome- a clinical
condition characterized by urethritis, arthritis &
conjunctivitis.
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