Etiologic determination
Despite the major contribution of globally analyzing CSF and secondary parameters, particularly CSF lactate, the precise etiologic definition is of great importance in cases of acute meningitis. Such precise definition is not simple, as identification of the causative microorganism is often difficult. Moreover, there are limits to conventional microbiological methods. Bacterioscopy is poorly sensitive, and although bacterial cultures are more sensitive, they can delay diagnosis because of the time it takes for the bacteria to grow in culture media.
Targeted molecular detection methods are usually more sensitive than conventional microbiological methods. Panel-based molecular tests identify multiple pathogens in a single test. In 2015, the U.S. Food and Drug Administration authorized the first commercial multiplex detection system for infectious causes of community-acquired meningitis and encephalitis. This test, the BioFire FilmArray system, detects 14 bacterial, viral, and fungal pathogens in a turnaround time of about 1 hour, including S. pneumoniae, N. meningitidis, H. influenzae, S. agalactiae (i.e., group B Streptococcus), E. coli (serotype K1), L. monocytogenes, HSV-1, HSV-2, varicella-zoster virus (VZV), cytomegalovirus (CMV), human herpesvirus 6 (HHV-6), human parechovirus (HPeV), and Cryptococcus neoformans/gattii.
A meta-analysis of eight precise diagnostic studies evaluating the BioFire FilmArray system showed a high sensitivity of 90% (95% confidence interval, 86%-93%) and specificity of 97% (95% CI, 94%-99%). The FilmArray ME panel can halve the time to microbiological result, allowing for earlier discontinuation of antimicrobial agents and hospital discharge in cases of viral meningitis.
Conclusion
Acute community-acquired meningitis is usually the result of viral or bacterial infections. Given the low specificity of clinical symptoms and, very often, of the general laboratory panel findings, many patients are empirically treated with antibiotics. High-sensitivity and -specificity molecular techniques allow for rapid identification of the bacterial etiology (which requires antibiotic therapy) or the viral etiology of meningitis. The latter can be managed only with symptom-specific medications and does not usually require extended hospitalization. Therefore, these new techniques can improve the quality of care for these patients with viral meningitis.
A version of this article first appeared on Medscape.com.