Oral Presentation 25th International Pathogenic Neisseria Conference 2026

Increasing antimicrobial resistance in Neisseria meningitidis: Ciprofloxacin resistance, macrolide non-susceptibility, and outbreak of a multi-drug-resistant strain in the United States (139142)

Rebecca L. Howie 1 , Rebecca L. Howie 1 , Shalabh Sharma 1 , Sara L. Eisen 2 , Bikash Bogati 2 , Brittney Z. Thomas 2 , Rui Xu 2 , Sandip Shrestha 1 , Basanta Wagle 3 , Vishakh Walia 3 , Carolyn Wiest 2 , Daya Marasini 1 , Amy Rubis 4 , Matthew Keller 1
  1. Meningitis, Pertussis, and Diphtheria Laboratory Branch, Centers for Disease Control and Prevention, Atlanta, GA, United States
  2. Contractor for CDC, Applied Science Research and Technology, Smyrna, GA, United States
  3. Contractor for CDC, Great Hill Solutions, Chantilly, VA, United States
  4. Meningitis, Pertussis, and Diphtheria Epidemiology Branch, Centers for Disease Control and Prevention, Atlanta, GA, United States

Background: Neisseria meningitidis (Nm) causes invasive disease with high morbidity and mortality, even with rapid administration of appropriate antibiotics. Historically, few of the Nm isolates collected in the United States have been resistant to antimicrobials. All U.S. isolates collected from 2012-2016 and submitted to CDC were susceptible to cefotaxime, ceftriaxone, meropenem, rifampin, minocycline, and azithromycin and less than 1% were resistant to penicillin, ampicillin, ciprofloxacin, or levofloxacin.1 The report of Nm serogroup Y (NmY) with resistance to penicillin and ciprofloxacin (“dual-resistant”)2 heralded a new chapter in Nm antimicrobial resistance in the United States.

Methods: Since the 2019 emergence of dual-resistant Nm, CDC has performed whole-genome sequencing (WGS) on all invasive Nm isolates received for surveillance. WGS analysis included determination of serogroup, sequence type (ST), and clonal complex (CC); additionally, screening was performed for genes known to confer antimicrobial resistance. Antimicrobial susceptibility testing by broth microdilution was conducted for all NmY isolates, and for any isolates predicted to be resistant by WGS.

Results: Compared to <1% ciprofloxacin-resistant Nm reported in the U.S. in 20161, resistance reached >10% for Nm isolates collected 2019-2024 and submitted to CDC, which was primarily driven by the dual-resistant NmY CC23 ST-3587 strain. Serogroup switching from Y to serogroups B and W was indicated among dual-resistant ST-3587 isolates, previously reported3. Decreased susceptibility to azithromycin from a minimum inhibitory concentration encompassing 90 percent of isolates (MIC90) < 0.25 µg/mL to MIC90 =2 µg/mL in genogroup Y was followed by the emergence of non-susceptibility in a new strain, ST-1466. Finally, a previously unrecognized serogroup B strain with multi-drug resistance to rifampin and ciprofloxacin and non-susceptibility to cefotaxime caused a U.S. outbreak in 2024-2025.

Discussion: Antimicrobial resistance prevalence in Neisseria meningitidis has increased in the past ten years, and resistance to additional drugs and new patterns of resistance continue to emerge. Ongoing surveillance for antimicrobial resistance in N. meningitidis is critically important to monitor changes and to inform appropriate prophylaxis and treatment recommendations.

  1. Potts CC, et al. Antimicrobial Susceptibility Survey of Invasive Neisseria meningitidis, United States 2012-2016. J Infect Dis. 2022. 225(11):1871-1875.
  2. McNamara LA, et al. Detection of Ciprofloxacin-Resistant, β-Lactamase-Producing Neisseria meningitidis Serogroup Y Isolates - United States, 2019-2020. MMWR. 2020. 69(24):735-739.
  3. Howie RL, et al. Serogroup Switching in Neisseria meningitidis with Dual Antibiotic Resistance. N Engl J Med 2026. 394:199-201.