FilmArray Meningitis/Encephalitis Panel Accelerates Central Nervous System Infection Diagnosis and Reduces Empirical Acyclovir Use: A Japanese Prospective Study

Background Central nervous system (CNS) infections are medical emergencies with high morbidity and mortality, where delayed or inappropriate therapy worsens outcomes. Conventional cerebrospinal fluid (CSF) diagnostics are limited by low sensitivity after antibiotic exposure and long turnaround times. The FilmArray Meningitis/Encephalitis (ME) Panel provides multiplex molecular detection of 14 pathogens within ~1 h. Although widely evaluated internationally, no prospective studies in adult populations have been reported from Japan. Methods We conducted a prospective before-and-after study at two tertiary care centers in Japan. Adults (≥15 years) hospitalized with meningitis, meningoencephalitis, or myelitis and CSF pleocytosis (≥5 cells/μL) were included. The preintervention cohort (September 2018–March 2021, n = 101) underwent conventional diagnostics, whereas the postintervention cohort (April 2021–October 2023, n = 105) received ME Panel testing in addition to standard methods. Primary outcomes were pathogen detection rate and time to pathogen identification; the secondary outcome was empirical antimicrobial duration. Between-cohort differences were assessed using the Mann–Whitney U test for continuous variables and Fisher’s exact test for categorical variables. Results Demographics and etiologies were comparable between cohorts. Overall pathogen detection rates were similar (27.7% vs. 28.6%, p > 0.999). However, the ME Panel significantly shortened median time to pathogen identification from 79.0 h (48.0–168.0) to 3.4 h (1.2–5.8) ( p < 0.001). The panel detected all pathogens identified conventionally and additionally identified enterovirus and Streptococcus pneumoniae, with no false negatives. Among patients with unknown etiology, empirical acyclovir use declined significantly, from 6.0 days (3.8–8.3) to 4.0 days (0–6.5) ( p = 0.049), while antibacterial use remained unchanged. Conclusions The FilmArray ME Panel markedly accelerated pathogen identification while preserving diagnostic accuracy, supporting earlier acyclovir discontinuation and improved antimicrobial stewardship. This study provides the first prospective evidence of its clinical utility for adult CNS infections in Japan.