P-574. Characterization of N. meningitidis in Military Trainees and Implications for Vaccination Strategies

Abstract Background N. meningitidis is a gram-negative pathogen that is part of normal oropharyngeal flora, but can also cause meningitis outbreaks in susceptible populations, especially when encapsulated. The United States military vaccinates all entering trainees with a quadrivalent vaccine against serogroups A, C, W, and Y, but does not currently vaccinate against serogroup B. This study identified the predominant meningococcal serogroups (A, B, C, W, X, Y) in trainees upon arrival to BMT. Methods Between June-August 2024, a convenience sample of 909 trainees received oropharyngeal swabs before meningococcal vaccination or penicillin prophylaxis. Swabs were cultured and subsequently serogrouped by polymerase chain reaction (PCR) as well as whole genome sequencing. For those that were PCR positive for serogroup B, the Meningococcal Antigen Typing System was used to determine coverage by the MenB-4C vaccines. Results Of the 909 samples collected, 35 (3.9%) trainees were found to have oropharyngeal carriage of N. meningitidis and 4 (0.4%) were found to have oral infection with N. gonorrhoeae. Of the N. meningitidis isolated, 11 (31%) were able to be classified by serogroup by PCR with serogroup B accounting for the majority (72.7%) of groupable isolates. By whole genome sequencing, all N. meningitidis strains were found to be non-groupable, except for one isolate in serogroup C. The FDA approved serogroup B vaccine targets sub-capsular proteins, and not the capsule itself. Sequencing predicts that six (75%) of the serogroup B PCR positive samples would be targeted by the MenB-4C vaccine, with one being unpredictable, and one not covered. Conclusion The vast majority of oropharyngeal isolates of N. meningitidis in a convenience sample of military trainees were non-groupable by whole genome sequencing despite having components of the capsule genes that are detectable by PCR. This data supports current practices of not vaccinating military trainees for serogroup B meningococcus. Disclosures All Authors: No reported disclosures