Mycobacterium Tuberculosis, Herpes Simplex Virus Type 1 and Enterovirus in Clear Cerebrospinal Fluid Meningitis at Brazzaville University Hospital

Introduction: Clear cerebrospinal fluid (CSF) meningitis represents a major public health problem in resource‑limited countries. It is characterized by CSF pleocytosis with a macroscopically clear appearance, and its etiologies are mainly viral, tuberculous, or undetermined.Objective: This study aimed to analyze clear CSF samples from a cytological and biochemical perspective, identify the main pathogens, and assess the diagnostic yield of examinations performed at the Brazzaville University Hospital laboratory.Methods: An analytical cross‑sectional study with prospective data collection was conducted from April 1 to September 30, 2021, including all clear CSF samples received at the bacteriology‑virology‑immunology laboratory of CHU‑B. Analyses included cytology, biochemistry, and PCR detection of Mycobacterium tuberculosis, HSV‑1, and Enterovirus.Results: The frequency of clear CSF meningitis was 48.6%. Patients under 5 years accounted for 67.9% of cases, with a slight male predominance (sex ratio 1.03). Cytology showed a mean of 245 leukocytes/mm³, with lymphocytic predominance. Protein levels were elevated (2.02 g/L) in all cases, while hypoglycorrhachia was observed only in tuberculous meningitis. The pathogens identified were mainly Enterovirus (20.3%), followed by Mycobacterium tuberculosis (5.8%) and HSV‑1 (11.6%). A large proportion of cases (63.8%) remained of undetermined etiology. Diagnostic yield was higher among infants (