N.meningitides featured in Question 10 from the second paper of 2002: "Outline the diagnostic features, complications and treatment of patients with meningococcal sepsis." It also appeared in the ABG interpretation scenario for Question 3.1 from the second paper of 2015, where the trainees were expected to identify the meningococcaemia on the basis of "fever, headache and a widespread rash". The patient also had a horrific blood gas with features of hypoadrenalism, consistent with Waterhouse-Friedrichsen syndrome.
A good NEJM review article is available which covers this territory well. It is the source for most of the information offered in the summary below. If one wished to cultivate an intimate acquaintance with N.meningitides, one may consider reading Rouphael and Stephens' massive opus from 2012.
- Gram-negative aerobic diplococcus
- An encapsulated organism, resistant to opsonization- its capsule protects it against complement-mediated bacteriolysis and phagocytosis by neutrophils, Kupffer cells, and spleen macrophages.
- A fastidious bacterium: it dies within hours on extracorporeal surfaces.
- A well-adapted human pathogen: its transferrin-binding proteins steal iron from the human host.
- It readily invades the meninges, and many patients with menigococcal sepsis will also have meningitis.
- It is virtually defenceless against antibiotics. Antibiotic resistance to anything except for sulfonamides is very rarely seen. Usually, straightforward benzylpenicillin is enough.
Defence against N.meningitides:
- Antibody-mediated immunity is the most potent defence
- The peak incidence of the disease occurs in the first year of life
(following the loss of maternal antibody)
- Progressively less common throughout childhood
- Extremely rare in immunocompetent adults
- Becomes more common in the post-splenectomy state
Diagnostic features of meningococcal sepsis
- Abrupt onset of high fever
- Myalgias, arthralgias, headache, decreased level of consciousness
- Petechial or purpuric rash
- Digital ischaemia
- progression to purpura fulminans (this is one of the differentials for purpura fulminans)
- Hypotension and shock
- Characteristic severe myocardial depression
- Blood or CSF cultures positive for N.meningitidis
- PCR of peripheral blood (apparently, it is useful for diagnosis of meningococcal disease)
Complications of meningococcal sepsis
- Septic shock
- Acute adrenal haemorrhage (Waterhouse-Friedrichsen syndrome)
- Multiorgan system failure
Management of meningococcal sepsis
- Most strains are susceptible to penicillin.
- The Sanford Guide recomends ceftriaxone 2g bd or benzylpenicillin 2.4g q4h
- Chloramophenicol is an alternative, but apparently there has gradualyl been a worldwide development of resistance (and, worldwide there has been a gradual resistance developing to the use of chloramphenicol, as it is a dangerous drug perhaps better suited as a chemotherapy agent for haematological malignancy).
- Supportive management consists of vasopressor support and fluid resuscitiation, with correction of DIC-associated coagulopathy
- Corticosteroids may be useful if meningitis is present, but in the absence of meningitis they are not indicated except as management of relative adrenal insufficiency.
- Plasma exchange may improve survival if commenced early, but the evidence for it is not robust.