[Spontaneous meningitis caused by gram-negative bacilli]

Abstract

Objective: To analyze the causative factors, clinical and microbiological characteristics, and prognosis in spontaneous meningitis caused by Gram-negative rods in adult patients.

Methods: Descriptive and retrospective study of all clinical records and microbiological findings in patients diagnosed of meningitis by Gram-negative bacilli, from 1973 to 1995, at Fundación Jiménez Díaz.

Results: Twenty patients had spontaneous meningitis caused by Gram-negative bacilli (2.1% of all diagnosed meningitis during this period). Fourteen patients were older than 65 years (range: 36-81; p < 0.05). Ninety-five percent of cases had an extranosocomial origin (p < 0.001). Ninety percent of patients had some underlying disease (p < 0.001). Twelve patients were immunosuppressed. Seven patients had changes in the urinary tract or repeated UTI infections. The most common clinical symptoms were a decrease in consciousness level, fever, and neck stiffness. Cerebrospinal fluid (CSF) in 18 patients showed cellular and biochemical changes. The CSF smear revealed the presence of Gram-negative bacilli in 15 patients. E. coli was the microorganism recovered most frequently. Immunosuppression (p < 0.05), septic shock (p < 0.001) and antimicrobial therapy not including a third generation cephalosporin (p < 0.01) were independently associated with mortality.

Conclusions: Spontaneous meningitis by Gram-negative bacilli is an uncommon infection. It occurs mainly in immunosuppressed patients older than 65 years or with changes in the urinary tract. It usually has an extranosocomial origin. The investigation of CSF is a highly effective for diagnosis. Therapy with third generation cephalosporins has notably improved its prognosis.