Challenging case of bacterial meningitis due to Moraxella osloensis diagnosed by 16s rRNA sequencing

Moraxella osloensis is a rare, Gram-negative, oxidase-positive coccobacillus that is infrequently identified as a pathogen in clinical diseases. It is usually opportunistic and associated with an immunocompromised host or the presence of invasive medical devices. Central nervous system infections caused by M. osloensis are extremely uncommon, with only a few cases documented in the literature.

We report the case of a 49-year-old female from Cameroon with a history of diabetes mellitus and osteoarthritis who presented in Qatar with a 10-day history of headache, fever, and vomiting. Her condition progressed to confusion and persistent fever. Cerebrospinal fluid (CSF) analysis revealed purulent leukocytosis with elevated protein and glucose levels, but cultures and Gram stain were negative-findings atypical for bacterial meningitis. Empirical treatment with ceftriaxone and acyclovir was initiated. Definitive identification of M. osloensis was achieved via 16S rRNA sequencing of the CSF. The patient received two weeks of targeted ceftriaxone therapy, resulting in clinical improvement and full recovery by Day 17 of hospitalization.

This case highlights the diagnostic challenges associated with atypical presentations of meningitis and underscores the limitations of conventional microbiological methods in detecting rare pathogens. M. osloensis may not be isolated by routine culture and is frequently misidentified. Molecular diagnostic techniques, such as 16S rRNA sequencing, play a crucial role in achieving accurate identification. Given the organism's potential for resistance and its association with invasive infections, prompt recognition and appropriate therapy are essential.

M. osloensis is a rare yet potentially serious cause of bacterial meningitis, particularly in immunocompromised patients. Molecular diagnostic techniques are indispensable for confirming the pathogen in culture-negative cases. Timely diagnosis and appropriate treatment can lead to favorable outcomes, as demonstrated in this report.