Makindo Medical Notes.com

A non-blanching petechial rash is an ominous sign of meningococcaemia in an unwell patient

About

• Serious cause of Meningitis and Septicaemia
• Those with complement C8 and C9 deficiency are more susceptible

Epidemiology

• Over 13 serogroups - commonest are A,B,C W-135 and Y.
• In the UK mainly types B and C
• Affects either infant under 5 years or teenagers aged 15-19

Source

• Found in the nasopharynx of asymptomatic carriers

Characteristics

• N. meningitidis is a gram-negative Capsulated diplococcus
• The gram-negative cell wall contains lipopolysaccharide which is overproduced resulting in early DIC and petechiae and bruising
• The meningococcus can use both glucose and maltose

Virulence

• Can produce a polysaccharide capsule that blocks phagocytosis
• Lipopolysaccharide stimulates macrophages to release Cytokines
• Increased cytokines lead to septic shock (e.g. TNF-Alpha, IL-1, IFN-gamma)
• Meningococcal bacteria adhere to epithelium using pili. Also IgA protease
• The Bacteria have a rapid doubling time of the bacterium
• This causes the release of large amounts of endotoxin by a process known as blebbing.

Clinical

• Meningitis +/- accompanying meningococcal septicaemia
• Meningococcal septicaemia alone without evidence of meningitis.
• Adrenal haemorrhage (Waterhouse-Friderichsen syndrome).
• Multiorgan failure
• Disseminated intravascular coagulation
• Acute respiratory distress syndrome
• Purpura fulminans - cutaneous bleeding

Investigations

• Gram stain of CSF will show typical kidney-shaped gram-negative cocci within polymorphs
• Tests for meningococcal capsular antigen
• Oxidase positive
• Culture on chocolate agar with 5% CO₂
• Also use Thayer Martin media
• Carbohydrate fermentation - ferments glucose and maltose
• Polymerase chain reaction to detect meningococci in blood or CSF

Sensitivities

• Penicillin, Cefotaxime, Rifampicin, Ciprofloxacin

Management

• Prevention with a vaccine which covers the Y, W135, C and A serotype
• Antibiotic choice are
  • Ceftriaxone 2 g BD
  • Cefotaxime 2 g 6 hourly
  • Benzylpenicillin 2.4 g 4 hourly
• Vasopressor and aggressive fluid replacement
• Glucocorticoid therapy may be indicated e.g. adrenal haemorrhage (Waterhouse-Friderichsen syndrome).
• ? recombinant human activated protein C in sepsis
• Rifampicin for close contacts