Etiology and epidemiological significance
The causative agent of the disease is Neisseria meningitidis. Morphologically, these are gram-negative diplococci that lack flagella (non-motile) and are strict aerobes. Cultivating them in laboratory conditions requires special nutrient media enriched with animal or human proteins.
The source of infection is sick individuals and asymptomatic carriers. Carriers play a key role in the spread of the pathogen. In the Russian Federation, between 1,000 and 6,000 cases of the disease are officially registered annually. However, the statistics predominantly capture severe generalized forms, whereas localized and mild variants often remain etiologically unverified.
On a global scale, meningococcus accounts for the vast majority of bacterial purulent meningitides. According to WHO data, the incidence ranges from 1 to 1,000 cases per 100,000 population depending on geography, season, and the current epidemiological situation.
Clinical presentation of generalized forms
Generalized meningococcal infection is distinguished by an extremely rapid, sometimes fulminant development. The typical clinical picture often manifests suddenly and is accompanied by the following syndromes:
- Intoxication syndrome: sharp weakness, chills, temperature elevation up to 39.5–40.0 °C, with the fever typically resistant to standard antipyretic drugs.
- General cerebral syndrome: intense, "bursting" headache, dizziness, as well as cerebral vomiting that does not bring relief to the patient.
- Meningeal syndrome: positive meningeal signs (nuchal rigidity, Kernig's sign), hyperesthesia, photophobia, and pain upon eye movement.
- Hemorrhagic syndrome (in meningococcemia): appearance of an asymmetric hemorrhagic rash (ranging from small petechiae to large elements of 1–2 cm). Initially, the exanthema localizes on the distal extremities (dorsal surface of the hands and feet) and over large joints, and as it progresses, it spreads to the trunk. The skin remains pale in this case.
Life-threatening complications
A physician of any specialty must be able to recognize early complications of the infection, as they rapidly lead to a fatal outcome. The most formidable conditions include:
- Infectious-toxic shock (ITS): characterized by rapidly progressing intoxication within the first day, spread of the hemorrhagic rash to the trunk, and manifestations of encephalopathy. An important diagnostic criterion is the shock index (the ratio of pulse rate to systolic blood pressure), for example, its elevation to 0.9 and above.
- Brain edema-swelling: naturally develops against the background of pronounced meningeal and general cerebral syndromes.
- Acute adrenal insufficiency.
- Acute renal failure (ARF).
Pre-hospital management and anti-epidemic measures
Upon suspicion of a generalized form, the patient is subject to emergency hospitalization in an infectious disease hospital. Transportation must be carried out by a physician-led emergency resuscitation team, as the patient's condition can critically deteriorate at any moment.
At the pre-hospital stage (especially with signs of ITS), parenteral administration of antibiotics (e.g., levomycetin) is indicated. This prescription must be performed strictly simultaneously with adequate anti-shock therapy, including the administration of glucocorticosteroids, to prevent a catastrophic drop in blood pressure due to the massive death of the pathogen and the release of endotoxin.
Anti-epidemic measures are immediately organized in the focus of infection:
- Medical observation is established for contacts for a period of 10 days (with mandatory thermometry and examination of the nasopharyngolarynx).
- Chemoprophylaxis of contacts is carried out.
Briefly: answers to topical questions
Which clinical forms belong to localized meningococcal infection?
Localized forms of meningococcal infection include meningococcal carriage and acute nasopharyngitis.
- Meningococcal carriage is a condition in which clinical symptoms are completely absent, and the diagnosis is established during the examination of contacts.
- Acute nasopharyngitis is a form accompanied by intoxication syndrome (adynamia, fever, weakness) and catarrhal syndrome (nasal congestion, pharyngeal mucosal hyperemia).
These forms most often proceed mildly and, as a rule, are not etiologically verified without targeted laboratory examination in the focus.
What are the clinical manifestations of acute adrenal insufficiency (Waterhouse-Friderichsen syndrome) in meningococcal infection?
The clinical manifestations of acute adrenal insufficiency (Waterhouse-Friderichsen syndrome) correspond to the picture of severe infectious-toxic shock (ITS) in the fulminant form of meningococcemia.
- Hemodynamic disorders — a sharp drop in blood pressure, thready pulse.
- Skin changes — rapid spread of the hemorrhagic rash, early appearance of cyanotic spots and ecchymoses.
- Neurological disorders — depression of consciousness, vomiting, pronounced meningeal syndrome.
- General toxic manifestations — hyperacute onset with high fever.
Without emergency care, the condition is characterized by an extremely unfavorable prognosis and rapid lethality.
Which specific drugs and in what dosages are used for chemoprophylaxis of contacts in the focus?
For the chemoprophylaxis of contacts in the focus, systemic antibacterial drugs in tablet form are used.
- Ciprofloxacin — prescribed at a dose of 500 mg orally once.
- Rifampicin — prescribed at a dose of 600 mg orally every 12 hours for 2 days.
These regimens are recommended for individuals over 18 years of age who have been in close contact with the patient and are prescribed taking into account possible contraindications.
What characteristic changes are found in the cerebrospinal fluid (CSF) in meningococcal meningitis?
In meningococcal meningitis, signs of purulent inflammation are detected in the cerebrospinal fluid.
- Macroscopic changes — CSF pressure is elevated, the fluid has a turbid, whitish color.
- Cytology — pronounced neutrophilic pleocytosis (from 500 to 1,000 or more cells in 1 µl, where 60–100% are neutrophils).
- Biochemistry — hyperproteinorrachia (increase in protein level to 2–8 g/l with cell-protein dissociation), decreased glucose concentration, and elevated lactate level.
- Microbiology — bacterioscopy of the sediment reveals gram-negative diplococci (intracellularly and extracellularly), and a positive Pandy test is detected.
Signs of ITS in meningococcemia can be remembered by the triad: "Rash on the trunk + Encephalopathy + Shock index > 0.8".
Class and exam questions
Is it permissible to administer antibiotics at the prehospital stage without corticosteroids?
No, in the presence of signs of infectious-toxic shock, parenteral administration of an antibiotic (e.g., levomycetin) should be carried out only simultaneously with anti-shock therapy with glucocorticosteroids.
What is the typical rash in meningococcemia?
This is an asymmetric hemorrhagic exanthema. Elements of various sizes (from 2 to 20 mm) appear first on the distal extremities and over the joints, and then may spread to the trunk.
What diseases require differential diagnosis?
First of all, differential diagnosis is carried out with meningitis of other etiology, leptospirosis, hemorrhagic fevers, and sepsis.
What else to study on this topic
- Pathogenesis of blood-brain barrier (BBB) breakthrough and mechanisms of cerebral hypertension development
- Mechanisms of DIC syndrome development in meningococcemia
- Algorithm of cytochemical and biochemical examination of cerebrospinal fluid (CSF) to confirm the diagnosis
- Classification of the pathogen: main serological groups and types of meningococcus
- Specific vaccine prophylaxis: indications and used drugs
Master the complete topic in the «Infectious Diseases» course
This is a summary. The course covers everything tested in classes and exams.
- Complete study guide on the topic "Meningococcal infection" and 3,312 more pages of the subject
- Assignments and quizzes after every topic — just like in a colloquium
- AI tutor answers questions on the topic anytime
- 41 video lessons on the subject
Other topics in the "Respiratory Infections" section
Prepared by WhiteCoat Pro faculty in accordance with the medical school curriculum. For educational purposes only.