Ocular Microbiology and Immunology Group
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2026 OMIG Abstract

POSTER PRESENTATION


Clinical and Genomic Profile of Neisseria meningitidis in Primary Meningococcal Conjunctivitis

Gerardo Ortega, Ana L. Melendez, and Paulo J. M. Bispo

Department of Ophthalmology, Mass Eye and Ear, Harvard Medical School, Boston, Massachusetts

Purpose: Primary meningococcal conjunctivitis (PMC) is a form of hyperacute bacterial conjunctivitis caused by Neisseria meningitidis that can progress to invasive meningococcal disease. While recent outbreaks have prompted genomic characterization of PMC-associated strains, the genomic profiles of N. meningitidis isolates from sporadic, non-outbreak PMC cases in the U.S. remain largely undescribed. We characterized the demographic and clinical features of PMC cases alongside the antimicrobial susceptibility and genomic profiles of N. meningitidis isolates from PMC.

Methods: Between 2014 and 2026, 8 non-duplicate N. meningitidis isolates were collected at Mass Eye and Ear from ocular infections, all presenting with PMC. We completed a retrospective chart review of clinical data for all patients. Six of the 8 isolates were available for antimicrobial susceptibility testing by broth microdilution and whole genome sequencing. Sequence types (STs) were obtained from PathogenWatch and clonal complexes (CCs) from PubMLST. We used ResFinder and CARD database to predict the resistomes of the isolates. Meningotype was used for in silico typing of serogroups and surface protein markers.

Results: The mean age of the PMC patients was 42.8 + 25.9 years. The average best corrected visual acuity at presentation recorded for 87.5% (7/8) of the patients was 0.23 + 0.12 (logMAR) and 0.02 + 0.04 after treatment, recorded for 50% of the patients. 75% (6/8) of the patients received a combined systemic and topical antibiotic treatment at presentation, with azithromycin + ceftriaxone (n=4) or ceftriaxone or penicillin alone (n=2) used systemically. None of the cases progressed to systemic disease. 50% (3/6) of the isolates carried the penA gene with F504L, A510V, and N512Y mutations, with 2 of these isolates demonstrating intermediate resistance to both ampicillin and penicillin. Three isolates were resistant to bactrim and one to ciprofloxacin. All were susceptible to azithromycin, ceftriaxone, chloramphenicol, and minocycline. The isolates clustered within three different CCs including CC198 (n=2, ST823), CC269 (n=2, ST467), CC41/44 (n=1, ST2578), and one was non-typeable. All 6 isolates were capsule null and had highly diverse surface protein (PorA, FetA, and PorB) types.

Conclusions: In this series of sporadic PMC cases, the N. meningitidis population was genetically diverse and unencapsulated, indicating potential selective pressure for capsule absence in non-outbreak related conjunctivitis as seen with other encapsulated pathogens (e.g., S. pneumoniae). While these non-hypervirulent strains can cause PMC, they did not demonstrate potential to progress to invasive diseases in our cohort. Resistome analysis demonstrated that these strains do not carry a large repertoire of antimicrobial resistance genes, which aligns with their multidrug susceptibility profiles, and favorable clinical outcomes when treated with first-line therapies.