The Causes of Postoperative Meningitis: The Comparison of Gram-Negative and Gram-Positive Pathogens

To determine the microbiological etiology in critically ill neurosurgical patients with nosocomial meningitis (NM) and to show the impact of Gram-negative rods and the differences between patient characteristics and the clinical and prognostic measures in Gram-negative and Gram-positive meningitis.

In this prospective, single-center study, we reviewed all adult patients hospitalized during a 12-year period and identified pathogens isolated from post-neurosurgical cases of NM. Demographic, clinical, and treatment characteristics were noted from the medical records.

Of the 134 bacterial NM patients, 78 were male and 56 were female, with a mean age of 46±15.9 and a median age of 50 (18-80) years. One hundred and forty-one strains were isolated; 82 (58.2%) were Gram-negative, 59 (41.8%) were Grampositive. The most commonly isolated microorganism was Acinetobacter baumannii (34.8%). Comparison of mortality data shows that the patients who have meningitis with Gram-negative pathogens have higher mortality than with Gram-positives (p=0.034). The duration between surgery and meningitis was shorter in Gram-negative meningitis cases compared to others (p=0.045) but the duration between the diagnosis and death was shorter in Gram-positive meningitis cases compared to Gram-negatives (p=0.017). Cerebrospinal fluid protein and lactate levels were higher and glucose level was lower in cases of NM with Gram-negatives (p values were respectively, 0.022, 0.039 and 0.049).

In NM, Gram-negative pathogens were seen more frequently; A. baumanni was the predominant pathogen; and NM caused by Gram-negatives had worse clinical and laboratory characteristic and prognostic outcome than Gram-positives.