Microbiological Profile of Meningoencephalitis Due to Pathogenic Free-Living Amoebae: A Case Series From Kerala, India

Background: Free-living amoebae (FLA) are environmental protozoa that cause rare but often fatal infections of the central nervous system (CNS), collectively manifesting as meningoencephalitis. Data from the Indian subcontinent remain limited. This case series describes the clinical profile, diagnostic challenges, treatment strategies, and outcomes of patients with FLA meningoencephalitis in Kerala, India. Methods: A retrospective observational study was conducted on 12 patients with microbiologically confirmed FLA meningoencephalitis managed at a tertiary care centre in Kerala between May 2024 and April 2025. Clinical features, laboratory findings, diagnostic modalities, treatment regimens, and outcomes were extracted from medical records and analysed descriptively. Results: Twelve patients (age range: 6-56 years; median: 32.5 years) were included, with a slight male predominance (58.3%). Over half of the patients resided in Malappuram district. The most common presenting symptoms were fever (91.7%), headache (83.3%), and altered mental status (50%). Cerebrospinal fluid (CSF) analysis showed elevated protein in 75%, reduced glucose in 83.3%, and pleocytosis (median cell count: 157 cells/mm3) with either neutrophilic or lymphocytic predominance. Motile trophozoites were detected on fresh CSF wet mount in all cases, while PCR confirmed FLA (Acanthamoeba spp.) in 41.7% of patients. All patients received combination antimicrobial therapy including amphotericin B, miltefosine, rifampicin, azithromycin, and fluconazole (with cotrimoxazole substituted for amphotericin B in children). Overall mortality was 41.7%. Conclusions: FLA meningoencephalitis often presents with non-specific neurological symptoms, making early recognition challenging. Rapid wet mount microscopy of fresh CSF is a pivotal diagnostic tool in resource-limited settings and facilitated early diagnosis in this series. Early initiation of multidrug therapy upon identification of FLA on wet mount microscopy has improved survival. Although mortality remains high, this outcome exceeds the global data reported for Acanthamoeba infections and reinforces the value of starting treatment promptly.