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Infection with Neisseria gonorrhoeae, a Gram-negative diplococcus,
is most common in individuals between 15 and 35 years of
age. It is almost exclusively spread by sexual contact.
The organism adheres to the genitourinary epithelium via pili, then
invades the epithelial layer and provokes a local acute inflammatory
response. Variation in the proteins of the pili means that
infection does not provide protection against re-infection, therefore
infections with another strain of different antigenic structure
- Acute painful urethritis and urethral discharge.
- Female infection (cervicitis) is often asymptomatic or associated
with vaginal discharge.
- Pelvic inflammatory disease (PID) may develop (see
Urinary and genital infections
- Pharyngeal infection causes sore throat.
- Rectal infection causes a purulent proctitis.
- Infection can be complicated by bacteraemia, septic or reactive
arthritis of the large joints, or pustular rashes.
- Late complications include female infertility and male urethral
The optimal diagnostic technique is a nucleic acid amplification
test (NAAT) on urethral or vaginal swabs, or urine. Positive
samples are then cultured for susceptibility testing.
Treatment and Prevention
Treatment must be given before susceptibility results are available
and is based on the known susceptibility patterns found at the
clinic, as emergence of resistance is a problem. Ceftriaxone
or fluoroquinolones may be used. Gonorrhoea can be
prevented by avoiding sexual contact with individuals at high risk
and using effective barrier contraception. Contacts of infected
individuals should be traced and treated. At present vaccine development
is precluded by the antigenic variation that occurs within
Carriage of Neisseria meningitidis
(meningococcus) is common;
actual disease only develops in a few individuals. Infection is most
common in the winter, with epidemics occurring every 10-12
years. In Africa, severe epidemics of group A infection occur in
the 'meningitis belt' where the incidence can rise to 1000 cases per
100 000 each year. Most invasive infections are caused by serogroups
A, B or C. Group B infection is now the commonest, as
the incidence of group C infection has reduced in communities
where vaccination has become routine. A group A vaccination
programme is being implemented in Africa.
Pathogenesis and Clinical features
Diagnosis and Treatment
- An antiphagocytic polysaccharide capsule that allows survival
in the bloodstream.
- Lipo-oligosaccharide activates complement and stimulates
cytokine release, which leads to shock and disseminated intravascular
- The organism hijacks the β2-adrenoreceptor to cross the brain
- Meningococci cross mucosal epithelium by endocytosis.
Meningococcal meningitis is characterized by fever, neck stiffness
and reduced consciousness. The petechial rash, a sign of
septicaemia, may be present without other signs of meningitis.
Septic or reactive arthritis may develop.
The diagnosis is usually made clinically and confirmed by culture
of blood, aspirate from the rash and CSF. Rapid antigen detection
or NAAT on CSF and blood are sensitive and reliable.
Infection is life-threatening and rapidly progressive; treatment
should not await laboratory confirmation or hospitalization.
Intravenous benzylpenicillin (intramuscular in the community
setting) is the antibiotic of choice, but there have been reports of
meningococci with reduced susceptibility in other countries and
cefotaxime is an alternative. Treatment does not eradicate carriage
so the patient should be given 'prophylaxis' following recovery.
- A protein-conjugated serogroup C vaccine is more than 90%
efficient and has vastly reduced the incidence where it has been
- An effective vaccine against serogroup B is not available,
although a vaccine based on membrane proteins specific for epidemic
strains has shown promise.
- Close contacts of patients with meningococcal meningitis should
be given 'prophylaxis' with rifampicin or ciprofloxacin.
This Gram-negative coccobacillus is usually a commensal of the
upper respiratory tract. It is associated with otitis media, sinusitis
and lower respiratory tract infection in children or patients with
chronic pulmonary disease. It usually produces β-lactamase.