Makindo Medical Notes

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

About

• Meningococcaemia is a serious cause of meningitis and septicaemia.
• Patients with complement C8 and C9 deficiencies are more susceptible to infection.

Epidemiology

• There are over 13 serogroups of Neisseria meningitidis.
• The most common serogroups are A, B, C, W-135, and Y.
• In the UK, the most prevalent types are B and C.
• The disease typically affects infants under 5 years and teenagers aged 15-19 years.

Source

• Neisseria meningitidis is found in the nasopharynx of asymptomatic carriers.

Characteristics

• Neisseria meningitidis is a gram-negative, capsulated diplococcus.
• The gram-negative cell wall contains lipopolysaccharide (LPS), which is overproduced, leading to early disseminated intravascular coagulation (DIC) and the appearance of petechiae and bruising.
• This bacterium can utilize both glucose and maltose as a carbohydrate source.

Virulence Factors

• Produces a polysaccharide capsule that blocks phagocytosis, enhancing survival in the bloodstream.
• Lipopolysaccharide stimulates macrophages to release cytokines, contributing to septic shock (e.g., TNF-Alpha, IL-1, IFN-gamma).
• Meningococcal bacteria adhere to the epithelium using pili and produce IgA protease, helping them evade the immune system.
• The bacteria have a rapid doubling time, which leads to the release of large amounts of endotoxin by a process known as "blebbing."

Clinical Manifestations

• Meningitis, often accompanied by meningococcal septicaemia.
• Meningococcal septicaemia alone, without evidence of meningitis.
• Adrenal haemorrhage (Waterhouse-Friderichsen syndrome).
• Multiorgan failure and disseminated intravascular coagulation (DIC).
• Acute respiratory distress syndrome (ARDS).
• Purpura fulminans (severe cutaneous bleeding).

Investigations

• Gram stain of cerebrospinal fluid (CSF) shows typical kidney-shaped gram-negative cocci within polymorphonuclear leukocytes.
• Tests for meningococcal capsular antigen.
• Oxidase positive (helpful for identifying *Neisseria* species).
• Culture on chocolate agar with 5% CO₂ or on Thayer-Martin media.
• Carbohydrate fermentation: ferments both glucose and maltose.
• Polymerase chain reaction (PCR) to detect *Neisseria meningitidis* in blood or CSF.

Antibiotic Sensitivities

• Penicillin
• Cefotaxime
• Rifampicin
• Ciprofloxacin

Management

• Prevention: Vaccination covering serogroups Y, W-135, C, and A.
• Antibiotic Therapy:
  • Ceftriaxone 2 g twice daily.
  • Cefotaxime 2 g every 6 hours.
  • Benzylpenicillin 2.4 g every 4 hours.
• Vasopressor support and aggressive fluid replacement for patients with septic shock.
• Glucocorticoid therapy may be indicated in cases of adrenal haemorrhage (e.g., Waterhouse-Friderichsen syndrome).
• Rifampicin for prophylaxis in close contacts of affected individuals.
• ? Use of recombinant human activated protein C in sepsis (experimental).