Notes from the Field: Misidentification of a Specimen as Neisseria meningitidis During a University Classroom Laboratory Exercise — Utah, 2025

Investigation and Outcomes

Potential Exposures

The first potential exposure occurred on September 22 (Figure). On that date, microbiology stockroom employees began preparing bacterial isolates for a multiday laboratory experiment in a university microbiology classroom. The experiment involved students using morphologic characterization and biochemical tests to identify the provided unknown bacterium, which was intended to be Plesiomonas shigelloides. Employees handled the isolates on multiple instances during September 22–30. Employees wore gloves and laboratory coats but did not use respiratory protection, eye protection, or a Biological Safety Cabinet.

On September 29, laboratory students began working with the isolates in the classroom laboratory wearing gloves and laboratory coats. On October 1, all the students identified the stockroom-provided unknown bacterium as N. meningitidis, rather than the expected P. shigelloides. The bacterium was a gram-negative, oxidase- and catalase-positive diplococcus with carbohydrate fermentation patterns consistent with N. meningitidis.

Initiation of Public Health Response

The stockroom freezer was found to contain a vial labeled N. meningitidis, although the university did not test the contents before disposing of it. Public health officials quickly evaluated risk among potentially exposed persons, tested samples, provided public health recommendations, and assisted with the investigation. This evaluation was deemed to be an authorized public health response activity by the Utah DHHS. This activity was reviewed by CDC, deemed not research, and conducted consistent with applicable federal law and CDC policy.*

Identification of Potentially Exposed Persons and Recommendations for Postexposure Prophylaxis

University officials determined that 33 professors, students, and stockroom employees had manipulated the unknown bacterium during isolate preparation or the classroom project. Fifteen (45%) persons had documentation of previous receipt of ≥1 doses of MenACWY or MenB vaccine. Health officials recommended ciprofloxacin or ceftriaxone postexposure prophylaxis (PEP) and monitoring of clinical status of all potentially exposed persons for 10 days (3). Thirty-two (97%) persons received PEP within 14 days; one person declined. Two persons with headache (one exposed student and one household contact of an exposed employee) sought emergency care and received medical evaluations including lumbar puncture. Neither received a diagnosis of N. meningitidis infection. No other persons experienced symptoms.

Public Health Laboratory Identification of Bacterium and Retesting of Sample Provided to Students

On October 6, the Utah Public Health Laboratory (UPHL) received two of the suspected N. meningitidis isolates for testing. On October 7 and 8, mass spectrometry and whole-genome sequencing (WGS), respectively, identified the isolates as Neisseria sicca, a bacterium that is commonly found in the upper respiratory tract and is nonpathogenic in immunocompetent persons.

UPHL repeated the carbohydrate fermentation tests conducted by the students and obtained results suggesting N. meningitidis. However, in combination with mass spectrometry and WGS results, the N. sicca strain was determined to be an atypical carbohydrate fermenter, which had resulted in the misidentification of N. sicca as N. meningitidis. Because N. sicca is nonpathogenic, no further intervention was indicated.

Review of Stockroom Procedures and Inventory Controls

With assistance from Utah DHHS, the university investigated the stockroom and reviewed its procedures. The investigation found inadequate inventory controls for identifying, labeling, storing, and segregating biological materials according to handling practices and containment conditions. Additional practice gaps included limited stockroom employee supervision, inadequate availability and use of personal protective equipment, and insufficient documentation of sample inventory, disposition, and chain of custody.

Preliminary Conclusions and Actions

N. meningitidis infections (including deaths) acquired through laboratory exposure have been reported (4). Although no person was exposed to N. meningitidis in this event, persons for whom potential exposure was considered did experience unnecessary interventions, including invasive procedures and antibiotic PEP. After-action review underscored the importance of laboratory and stockroom safety procedures, including inventory controls, to ensure that cultures and stocks are accurately labeled and appropriately stored. These measures could help prevent cross-contamination or misuse of stocks and support appropriate occupational health measures (5). This event prompted an overhaul of stockroom documentation, supervision, and training protocols, as well as a careful inventory of existing stocks, with recommendations to separate stocks used for research from those used in a classroom. Instructional laboratories and stockrooms should establish clear guidelines outlining appropriate inventory controls and documentation, the use of safety equipment, and required training in the safe handling of microorganisms to prevent exposure.