ACUTE BACTERIAL MENINGITIS

ACUTE BACTERIAL MENINGITIS

Bacterial meningitis

What is bacterial meningitis?

Meningitis is an infection of the membranes (meninges) that protect the spinal cord and brain. When the membranes become infected, they swell and press on the spinal cord or brain. This can cause life-threatening problems. Meningitis symptoms strike suddenly and worsen quickly.

History:

¤ Increased risk with exposure to meningococcal meningitis or travel
to meningitis belt (sub-Saharan Africa), but most cases sporadic.

¤ Increased incidence with extremes of age, head trauma, immuno-suppression.

What are the causes of bacterial meningitis?

Several different bacteria can cause meningitis:

- Streptococcus pneumoniae

- Haemophilus influenzae

- Neisseria meningitidis

What are the symptoms of bacterial meningitis?

1- Painful, stiff neck with limited range of motion.

2- Headaches.

3- High fever.

4- Feeling confused or sleepy.

5- Bruising easily all over the body.

6- A rash on the skin.

7- Sensitivity to light.

8- Nausea

9- Vomiting

10- Prodromal upper respiratory tract infection progresses to stiff neck,fever, headache, vomiting, lethargy, photophobia, rigors, weakness,seizures (20–30%).

11- Fever, nuchal rigidity, signs of cerebral dysfunction; 50% with Neisseria meningitidis meningitis have an erythematous, macular rash that progresses to petechiae or purpura.

12- Cranial nerve palsies (III, VI, VII, VIII) in 10–20%.

13- Elderly may to have lethargy or obtundation without fever, +/-meningismus.

Tests:

Laboratory

¤ Basic Blood Tests:

° Elevated WBC

¤ Specific Diagnostic Tests:

° Blood cultures are often positive

° Typical cerebrospinal fluid (CSF) in bacterial meningitis (normal): opening pressure >180 mm H2O (50–150); color turbid (clear); WBC >1000/mm3 with polymorphonuclear cell predominance (5); protein >100 mg/dL (15–45); glucose <40 mg/dL (40–80); CSF/blood glucose ratio <0.4 (>0.6); Gram stain of CSF shows organisms in 60–90%.

° Culture of CSF is positive in 70–85%; community-acquired acute bacterial meningitis caused by Streptococcus pneumoniae, Neisseria meningitidis, Listeria monocytogenes, Haemophilus influenzae, Escherichia coli, group B streptococcus.

° Antigen testing for specific pathogens appropriate when a purulent CSF specimen has a negative Gram stain and culture, sensitivity 80%

¤ Other Tests:

° Patients with evidence of ICP such as coma or papilledema or focal neurologic findings (seizures, cranial neuropathies) should have a noncontrast CT scan prior to lumbar puncture (LP); begin antibiotics before CT scan

Differential diagnosis:

¤ Bacteremia, sepsis, brain abscess, seizure disorder, aseptic meningitis (CSF WBC usually 100–1000/mm3, eventually with lymphocyte predominance), skull fracture, chronic meningitis, encephalitis, migraine headache, rickettsial infection, drug reaction.

Management:

What to Do First

¤ Medical emergency: do not delay appropriate antibiotic therapy

¤ Quick neurologic exam looking for focality or evidence of increased ICP.

¤ Blood culture ×2

¤ If increased ICP or focality, start empiric antibiotics based on patient’s age and circumstances and send for CT of head without contrast

¤ If CT nonfocal and safe for LP, proceed to lumbar puncture.

¤ If neurologic exam normal, LP and base therapy on STAT Gram stain of CSF.

¤ If CSF consistent with bacterial meningitis and positive Gram stain, start specific antibiotics. If consistent with bacterial meningitis with a negative CSF Gram stain, start empiric antibiotics.

General Measures:

¤ Rigorous supportive care

¤ Dexamethasone IV before antibiotics and q6h × 2 d for children >1 mo and consider for adults with increased ICP or coma.

Specific therapy

Indications

¤ If strongly suspect meningitis, start IV antibiotics as soon as blood cultures drawn

Treatment options:

¤ Empiric antibiotics (1):

° Age 18–50: ceftriaxone or cefotaxime +/-vancomycin (2)

° >50 years: ampicillin + ceftriaxone or cefotaxime +/− vancomycin (2)

° Immunocompromised: vancomycin + ampicillin + cetazadime

° Skull fracture: ceftriaxone or cefotaxime +/− vancomycin (2)

° Head trauma, neurosurgery, CSF shunt: vancomycin + ceftazadime

¤ Positive CSF Gram stain in community-acquired meningitis.

° Gram-positive cocci: ceftriaxone or cefotaxime + vancomycin.

° Gram-positive rods: ampicillin or penicillin G +/− gentamicin

° Gram-negative rod: ceftriaxone or cefotaxime

(1) Modify antibiotics once organism and its susceptibility are known; organism must be fully sensitive to antibiotic used.

(2) If prevalence of third-generation cephalosporin-intermediate + resistant S. pneumoniae exceeds 5%, add vancomycin until organism proved susceptible; if intermediate or resistant to cephalosporins, continue vancomycin and ceftriaxone or cefotaxime for possible synergy; if penicillin-susceptible, narrow to penicillin G; if penicillin-non-susceptible. and cephalosporin-susceptible, narrow to third-generation cephalosporin

¤ If dexamethasone used with vancomycin, consider adding rifampin to increase vancomycin entry into CSF.

Follow-up

During Treatment
¤ Look for contiguous foci (sinusitis, mastoiditis, otitis media) or distant infection (endocarditis, pneumonia) with S pneumoniae

¤ Narrow coverage as culture results and susceptibility data allow

¤ If patient on adjunctive corticosteroids and not improving as expected, or if pneumococcal isolate, repeat LP 36–48 hours after starting antibiotics to document CSF sterility.

¤ Treat close contacts of patients with N meningitidis to eradicate carriage. If not treated with a third-generation cephalosporin, the patient should receive chemoprophylaxis as well.

complications and prognosis:

A- Complications:

¤ Seizures, coma, sensorineural hearing loss, cranial nerve palsies, obstructive hydrocephalus, subdural effusions, CSF fistula (especially likely with recurrent meningitis), syndrome of inappropriate
antidiuretic hormone

¤ Consider placing ICP monitoring device

¤ ICP >15–20, elevate head to 30 degrees, hyperventilate adults.