Evaluation of the FilmArray Meningitis/Encephalitis Panel for Detection of Pathogenic Microorganisms in Cerebrospinal Fluid Specimens

Background: Infectious meningitis and encephalitis are neurological emergencies that necessitate rapid diagnosis and treatment. Prompt initiation of empirical antimicrobials is common practice in suspected cases. However, swifter denite diagnosis and an earlier start of denitive treatment may improve outcomes. We compared the BioFire FilmArray Meningitis/Encephalitis (ME) Panel, a multiplex polymerase chain reaction test, with conventional standard methods of diagnosing infectious meningitis and encephalitis. Subjects and methods: We retrospectively studied 20 patients in whom meningitis or encephalitis was diagnosed according to clinical symptoms and laboratory ndings between January 2018 and December 2019 at our institution. The results of pathogen diagnosis by the FilmArray ME Panel were compared with those of conventional methods. Results: The median age of the patients was 39 years (range, 23 to 85 years), and 13 (65%) were women. The FilmArray ME Panel identied the following pathogens: herpes simplex virus (HSV)-1 in two patients, HSV-2 in one, varicella-zoster virus (VZV) in four, Streptococcus pneumoniae in three, and Cryptococcus neoformans in one. This test detected additional pathogens in one patient with S. pneumoniae and in one with VZV, whereas the conventional methods did not. The median time to pathogen identication was 2 h with the FilmArray ME Panel but 4 days with conventional methods. Conclusion: Our ndings suggest that the FilmArray ME Panel can detect and identify the most common pathogens faster and more sensitively than can conventional methods. This new method would thus help improve clinical outcomes through denitive diagnosis and treatment. the of the of empirical therapy causative rapid start FilmArray Meningitis/Encephalitis (ME) Panel (BioFire is new molecular method of multiplex polymerase chain reaction (PCR) testing that can detect the 14 most common pathogens in central nervous system infections [3, 4]. In this study, we compared the performance of the FilmArray ME Panel with that of conventional methods for diagnosing infectious meningitis and encephalitis.


Introduction
Infectious meningitis and encephalitis are neurological emergencies that necessitate prompt diagnosis and treatment [1]. Conventional standard methods for the diagnosis of meningitis and encephalitis include lumbar puncture for cerebrospinal uid (CSF) Gram stain, CSF bacterial culture, testing for bacterial and fungal antigens, and viral polymerase chain reaction (PCR), as well as blood cultures [2]. Prompt initiation of empirical antimicrobial treatment is recommended [1]. If the diagnosis is established, the e cacy of treatment could be increased by the provision of empirical therapy targeting the causative organism. Although this medical treatment strategy is bene cial, more rapid de nite diagnosis and an earlier start of speci c treatment can result in a more favorable outcome.
The FilmArray Meningitis/Encephalitis (ME) Panel (BioFire Diagnostics, LLC, Salt Lake City, UT, USA) is new molecular method of multiplex polymerase chain reaction (PCR) testing that can detect the 14 most common pathogens in central nervous system infections [3,4]. In this study, we compared the performance of the FilmArray ME Panel with that of conventional methods for diagnosing infectious meningitis and encephalitis.

Patients And Methods
This study was a single-center, retrospective, observational study. Twenty patients in whom meningitis or encephalitis was diagnosed according to clinical symptoms and laboratory ndings between January 2018 and December 2019 were enrolled. We analyzed laboratory data from CSF specimens sampled by lumbar puncture and performed assays with the FilmArray ME Panel. The FilmArray ME Panel can identify six bacteria (Escherichia coli K1, Haemophilus in uenzae, Listeria monocytogenes, Neisseria meningitidis, Streptococcus agalactiae, and Streptococcus pneumoniae), seven viruses (herpes simplex virus types 1 [HSV-1] and 2 [HSV-2], varicella-zoster virus [VZV], cytomegalovirus, human herpesvirus 6, human parechovirus, and enterovirus), and one yeast group (Cryptococcus neoformans/gattii). The CSF specimens (total, approximately 200 µL) were subjected to FilmArray ME Panel testing and conventional testing (CSF Gram stain, CSF bacterial culture, tests for bacterial and fungal antigens, and viral PCR), and the results were compared.
This study was approved by the ethics committee of the Nihon University School of Medicine.

Results
The demographic characteristics and all test results for each patient are listed in Table 1. The median age of the patients was 39 years (range, 23 to 85 years), and 13 (65%) were women. The nal clinical diagnoses were aseptic meningitis in eight patients, bacterial meningitis in four, VZV meningitis in four, HSV meningitis in one, HSV encephalitis in two, and cryptococcal meningitis in one. The pathogens were identi ed by the FilmArray ME Panel in 11 patients (55%) and by conventional methods in 9 (45%). The FilmArray ME Panel identi ed HSV-1 in two patients, HSV-2 in one, VZV in four, S. pneumoniae in three, and C. neoformans in one. This test also detected additional pathogens in one case of S. pneumoniae infection (patient 4) and one case of VZV infection (patient 17), whereas the conventional methods did not. The FilmArray ME Panel yielded negative results (none falsely negative) for 9 (45%) of the 20 patients, and all these cases were also con rmed negative by conventional methods. The median time to pathogen identi cation was 2 h with the FilmArray ME Panel and 4 days with the conventional methods.

Discussion
The FilmArray ME Panel rapidly detected some of the most common pathogens causing meningitis and encephalitis. Although it is a qualitative test, it is more sensitive than the conventional methods.
Laboratory testing is essential for the de nitive diagnosis of infectious meningitis and encephalitis. The conventional methods have advantages and disadvantages. Although CSF Gram stain enables prompt diagnosis, diagnostic sensitivity depends on the organisms [2]. CSF culture for bacterial meningitis and PCR for viral encephalitis are considered the "gold standard" methods for diagnosis [5]; however, nal results of these testing are often not available for several days after specimen collection. Therefore, these conventional methods should be used with caution, and empirical antimicrobials must be administered promptly [1]. Because of the rapidity of the FilmArray ME Panel for diagnosing infectious meningitis and encephalitis, it enables early initiation of de nitive therapy and will contribute to better outcomes in patients with those diseases.
The FilmArray ME Panel has higher sensitivity than do the conventional methods [6]. It detected additional pathogens in two patients (one with S. pneumoniae infection and one with VZV infection), whereas the conventional methods did not. Because antiviral agents and antibiotics had been administered to these patients before CSF collection, the conventional methods could not always identify the causes. Meningitis and encephalitis are caused by various bacteria, viruses, and fungi; therefore, the great advantage of the FilmArray ME Panel is that it can detect and identify the 14 most common pathogens simultaneously with treatment. Moreover, treatment that is started before pathogen testing does not affect the performance of this test.
Rapid diagnosis by the FilmArray ME Panel was associated with shorter hospitalization and more effective choices of antibiotics [7]. In addition to shortening the time to de nitive diagnosis and treatment, this test also helped decrease the cost of healthcare because unnecessary antimicrobials were not administered [8,9]. Thus the FilmArray ME Panel would help improve clinical outcomes by shortening the time to de nitive diagnosis and enabling shorter antimicrobial treatment and shorter hospitalization [10].