Meningitis aguda

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ACUTE MENINGITIS
Karen L. Roos ABSTRACT
Acute meningitis is most often caused by bacteria or viruses. As soon as the diagnosis is suspected, and prior to head computed tomography and spinal fluid analysis, empiric therapy is initiated. An increasing number of polymerase chain reaction assays on cerebrospinal fluid are available, and this, in combination with serological assays, has greatlyimproved the ability to identify the meningeal pathogen. In this chapter, the epidemiology, clinical presentation, diagnosis, and treatment of acute meningitis are reviewed.

KEY POINTS:

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The first step in the management of acute bacterial meningitis is to obtain blood cultures and initiate adjunctive and antimicrobial therapy. The choice of antibiotic for empiric antimicrobial therapy isbased on the possibility that a penicillin- and cephalosporinresistant strain of Streptococcus pneumoniae is the causative organism of the meningitis.

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OVERVIEW Acute meningitis refers to a syndrome of fever, headache, and meningismus associated with a cerebrospinal fluid (CSF) pleocytosis due to infection and inflammation in the subarachnoid space. Bacteria or viruses most often cause acutemeningitis. Acute meningitis is differentiated from chronic meningitis by the duration of the signs and symptoms. Chronic meningitis refers to a syndrome of fever, headache, and meningismus of greater than 4 weeks’ duration associated with a CSF pleocytosis. Acute bacterial meningitis is now a disease predominately of young adults and older adults rather than of infants and young children due tothe profound reduction by vaccination in the incidence of invasive infections caused by Haemophilus influenzae type b. The most common causative organisms of bacterial meningitis in adults aged 15 to 50 years are Streptococcus pneumoniae and Neisseria meningitidis. The most common organisms causing meningitis in adults older than 50 years are S. pneumoniae and enteric gram-negative bacilli; however,meningitis caused by Listeria monocytogenes and H. influenzae is increasingly recognized. The viruses that cause acute meningitis are the nonpolio enteroviruses

(coxsackieviruses A and B, echoviruses, and the viruses identified by numbers [ie, enteroviruses 68 to 71]), arthropod-borne viruses, herpes simplex virus type 2 (HSV-2), EpsteinBarr virus, human immunodeficiency virus type 1 (HIV-1),and varicella-zoster virus. Less commonly, lymphocytic choriomeningitis virus, mumps virus, and adenovirus cause meningitis. The first step in the management of the patient with fever, headache, and stiff neck is to obtain blood cultures and initiate antimicrobial and adjunctive therapy. The choice of antibiotic for empiric antimicrobial therapy is based on the possibility that a penicillin- andcephalosporinresistant strain of S. pneumoniae is the causative organism of the meningitis and on the patient’s age and any associated conditions that may have predisposed the patient to meningitis. Empiric therapy of bacterial meningitis in neonates younger than 1 month should include a combination of ampicillin and cefotaxime. Empiric therapy in infants older than 1 month and in children andadults up to age 50 should include a combination of either a third- or fourth-generation cephalosporin plus vancomycin. Empiric therapy of bacterial meningitis in adults older than 50 years and in the immunocompromised patient should

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" ACUTE MENINGITIS

KEY POINTS:

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The mostcommon causative organisms of bacterial meningitis in adults aged 15 to 50 years are S. pneumoniae and Neisseria meningitides. Several factors predispose to pneumococcal meningitis including a complement deficiency, hypogammaglobulinemia, splenectomy, head trauma, CSF leak, alcoholism, diabetes, and sickle cell disease.

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include a combination of a third- or fourth-generation cephalosporin plus...
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