BACKGROUND Increased levels of cerebrospinal fluid (CSF) 14-3-3 proteins have been reported in acute bacterial meningitis. We tested the hypothesis that CSF 14-3-3 protein levels are substantially increased in acute bacterial meningitis and decreased after anti-microbial therapy, and that CSF 14-3-3 protein levels can predict treatment outcomes. METHODS We examined serial pan-CSF 14-3-3 (14-3-3-P) protein and five major isoform (beta, gamma, epsilon, eta, zeta) levels in 29 adult community-acquired bacterial meningitis (ACABM) patients. The CSF 14-3-3 protein levels were also evaluated in 12 aseptic meningitis patients during the study period. RESULTS All of the meningitis patients had a positive result on admission. Levels of CSF 14-3-3 protein in ACABM cases were significantly increased initially, and substantially decreased thereafter. Most of those who survived (survivors = 25 and non-survivors = 4) had nearly cleared their 14-3-3 protein from the CSF before discharge. Conversely, patients who died never cleared their CSF 14-3-3 protein. The median value of CSF 14-3-3-P and 14-3-3 gamma, 14-3-3 eta and 14-3-3 epsilon isoforms on admission in the bacterial meningitis group were 173.7, 137.7, 42.2 and 9.1, respectively, which were statistically significant than those of the aseptic meningitis group (48.4, 39.6, 2.5 and 0, respectively). Stepwise logistic regression analysis showed only CSF 14-3-3 gamma isoform on admission was independently associated with outcome (P = 0.05, OR = 0.991). CONCLUSIONS Serial 14-3-3 protein gamma isoform actually meets the major requirements for outcome prediction in the treatment of ACABM patients. Assay of the 14-3-3 protein gamma isoform should be added as a neuro-pathologic marker among the panel of conventional CSF parameters.