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 are possible.
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, spectinomycin 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 the pili.
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
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.
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.
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