Neisseria meningitidis

Neisseria meningitidis CSF Gram 1000

Neisseria meningitidis, colloquially termed meningococcus, is a gram-negative bacterium predominantly recognized for inducing meningitis, a severe inflammation of the membranes that envelop the brain and spinal cord. Exclusive to human infections, it is noteworthy that there's no known animal reservoir for this bacterium. Moreover, it remains the sole bacterial agent known to trigger epidemics of meningitis.

Neisseria meningitidis

Meningococcal vaccination travel requirements map

Neisseria meningitidis Colonies growth on New York City Medium Agar

Clinical Presentations

Meningitis: Representing the most widely recognized manifestation of the infection, initial symptoms are typically non-specific. However, these can swiftly escalate to more alarming indications such as fever, headache, neck stiffness, progressing eventually to coma and potentially, death. With an estimated mortality rate at approximately 10%, any suspicion of meningitis mandates urgent medical attention, being classified as a medical emergency.

Septicaemia: Often termed "blood poisoning," this facet of the disease has been linked to fatalities, especially among infants. Despite potentially not manifesting the classic symptoms associated with meningitis, the emergence of a non-blanchable purpuric rash can easily be overlooked, bearing grave implications given its potential severity. Alarmingly, the mortality rate from septicaemia can escalate to around 50% within mere hours from its onset. The presence of a rash that fails to whiten under pressure (non-blanching) necessitates immediate hospital evaluation.

Waterhouse-Friderichsen syndrome: This is characterized by an acute, typically bilateral hemorrhage within the adrenal glands, resulting from severe infection.

In the UK, the established protocol entails that any General Practitioner doctor encountering a suspected case of meningococcal meningitis or septicaemia should promptly administer intravenous antibiotics (preferably benzylpenicillin), concurrently seeking hospital admission. Despite potentially hindering microbiological confirmation owing to premature treatment, this approach significantly reduces mortality.

It's vital to note that not every purpura-resembling rash signifies septicaemia. However, alternative causes, such as ITP, a platelet disorder, also necessitate swift medical investigation.

Strains

Several strains of meningococcus exist, with strains A, B, C, Y, and W135 being clinically the most significant:

• A - Predominantly found in sub-Saharan Africa; vaccination with the Men A&C vaccine is advised prior to traveling to this region.
• B - Considered the most virulent, it constitutes about 40% of UK cases. The evolving nature of this strain has impeded the development of a comprehensive vaccine. However, the MeNZB vaccine, targeting a specific strain of group B meningococcus, has been employed to curb an epidemic in New Zealand.
• C - Previously accounting for nearly 60% of UK cases, the rollout of a successful vaccination program for infants has seen a decline. While the unconjugated C component of Men A&C was ineffective for children under 2, the development of a conjugated version (Men C conj) has enhanced its efficacy in this demographic.
• W135 - A concern especially for those partaking in the annual pilgrimage to Mecca. Saudi Arabia mandates pilgrims on Hajj to provide proof of Men W135 vaccination.
• Y - Over the past ten years, serogroup Y has emerged as a causative agent in North America.

Risk Factors

Individuals with compromised immunity, such as those with nephrotic syndrome or post-splenectomy, are particularly vulnerable to meningococcal infections. For those with asplenia (absent or non-functional spleen), vaccination protocols are stringently adhered to.

Vaccines

Although 13 distinct types of Meningococcus bacteria exist, only five serogroups, namely A, B, C, Y, and W135, are responsible for nearly all human infections. Regrettably, an effective vaccine for Meningococcus B remains elusive.

• Polysaccharide vaccines
• Conjugate vaccines

See also

• Meningitis
• Meningococcemia

External links

• EpiscanGIS - Online Monitoring Invasive Meningococcal Disease in Germany
• Pathology of Meningococcal Infection

Neisseria meningitidis Resources
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