bacterial meningitis

bacterial meningitis
Field	Infectious disease, Neurology

bacterial meningitis. It is a severe inflammatory condition affecting the protective membranes surrounding the brain and spinal cord, known collectively as the meninges. This medical emergency is primarily caused by the invasion of bacterial pathogens into the central nervous system, leading to rapid symptom onset and high mortality if untreated. Key causative agents include *Neisseria meningitidis*, *Streptococcus pneumoniae*, and *Haemophilus influenzae* type b, with global incidence influenced by factors like vaccination programs and geographical region.

Signs and symptoms

Classic symptoms often develop rapidly over hours and include severe headache, high fever, and neck stiffness, a triad known as meningismus. Patients may exhibit altered mental status, photophobia, and nausea or vomiting. In severe cases, signs of systemic infection such as a characteristic petechial rash are common, particularly with infection by *Neisseria meningitidis*, which can rapidly progress to Waterhouse-Friderichsen syndrome. Infants may present with nonspecific symptoms like bulging fontanelle, irritability, and poor feeding.

Causes and transmission

The disease is caused by bacterial invasion of the meninges, most frequently by *Streptococcus pneumoniae* and *Neisseria meningitidis* in adults and adolescents. Other significant pathogens include *Haemophilus influenzae* type b, *Listeria monocytogenes*, and Group B *Streptococcus*, particularly in neonates and the elderly. Transmission typically occurs through direct contact with respiratory secretions or droplets from infected individuals, as seen in settings like college dormitories or military barracks. The bacteria colonize the nasopharynx, cross the blood-brain barrier, and incite a potent inflammatory cascade within the subarachnoid space.

Diagnosis

Definitive diagnosis requires analysis of cerebrospinal fluid obtained via lumbar puncture. CSF findings typically show elevated white blood cell count with neutrophil predominance, low glucose levels, and high protein concentration. Gram staining and culture of the CSF are critical for identifying the causative organism. Additional diagnostic tools include blood cultures, PCR assays for bacterial DNA, and neuroimaging techniques like computed tomography to assess for complications such as brain swelling or hydrocephalus before performing a lumbar puncture.

Prevention

Primary prevention relies on vaccination. Key vaccines include the meningococcal conjugate vaccine against *Neisseria meningitidis* serogroups A, C, W, and Y, the serogroup B vaccine, the pneumococcal conjugate vaccine against *Streptococcus pneumoniae*, and the *Haemophilus influenzae* type b vaccine. Prophylactic antibiotics, such as rifampin, ciprofloxacin, or ceftriaxone, are recommended for close contacts of individuals infected with *Neisseria meningitidis* or *Haemophilus influenzae*. Public health measures in outbreak settings, like those implemented by the CDC or WHO, are also crucial.

Treatment

Empiric intravenous antibiotic therapy must be initiated immediately, often before confirmatory diagnostic results. Standard regimens include a third-generation cephalosporin like ceftriaxone or cefotaxime combined with vancomycin to cover resistant *Streptococcus pneumoniae*; ampicillin is added for coverage of *Listeria monocytogenes* in specific populations. Adjunctive therapy with dexamethasone is recommended, particularly for suspected *Streptococcus pneumoniae* meningitis, to reduce neurological sequelae. Supportive care in an intensive care unit addresses complications like septic shock, SIADH, or seizures.

Prognosis

Outcomes vary significantly based on the causative pathogen, timeliness of treatment, and patient age. Even with appropriate therapy, mortality remains substantial, exceeding 10% for *Streptococcus pneumoniae* meningitis and lower for *Neisseria meningitidis*. Survivors are at risk for long-term neurological deficits, including hearing loss, cognitive impairment, motor disabilities, and seizure disorders. Factors associated with poor prognosis include advanced age, comorbid conditions, delayed antibiotic administration, and the presence of bacteremia or coma at presentation. Follow-up often involves specialists in neurology and rehabilitation.

Category:Infectious diseases Category:Neurological disorders