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Excerpt
Two probable cases of fatal laboratory-acquired meningococcal disease in microbiologists from Alabama and Michigan are described. A request for information on additional cases by the CDC was posted on selected listservs to members of several professional organizations. A probable case of laboratory-acquired meningococcal disease was defined as confirmed or probable meningococcal disease in a laboratory scientist who had occupational exposure to a Neisseria meningitidis isolate during the 14 days before onset of illness and who had illness with a serogroup that matched the source isolate. In addition to the two reported cases, CDC received an additional 14 reports of probable laboratory-acquired meningococcal disease worldwide from the previous 15 years. Six cases occurred in the United States from 1996 to 2001; prospective surveillance for laboratory-acquired meningococcal disease is ongoing.
Nine (56%) of 16 cases were caused by N. meningitidis serogroup B and 7 (44%) were caused by serogroup C. Eight (50%) cases were fatal. A median of 4 days (range, 2 to 10 days) passed between handling the source isolate and symptom onset. Procedures performed on the 16 source isolates included reading plates (50%), making subcultures on agar plates (50%) and performing serogroup identification at the bench (38%). The laboratory reportedly did not perform procedures within a biosafety cabinet in 15 of 16 cases.
Comment: N. meningitidis is classified as a biosafety level 2 organism. Guidelines recommend the use of a biosafety cabinet for mechanical manipulations of samples that have a substantial risk for droplet formation or aerosolization such as centrifuging, grinding and blending procedures. A recent study (R Boutet and J Stuart. N. meningitidis Meeting, Galveston, TX, 2000) indicated that manipulating suspensions of N. meningitidis outside a biosafety cabinet is associated with a high risk for contracting disease.
Research and laboratory scientists who are routinely exposed to N. meningitidis in solutions that might be aerosolized should consider vaccination with the quadrivalent (A,C,Y and W-135) meningococcal polysaccharide vaccine [CDC. MMWR 2000;49(RR-7)]. Penicillin therapy is indicated for laboratory scientists with percutaneous exposure to an invasive N. meningitidis isolate from a sterile site. Antimicrobial prophylaxis with rifampin, ciprofloxacin or ceftriaxone is appropriate for those with known mucosal exposure and should be considered for microbiologists who manipulate invasive N. meningitidis isolates in a manner that could induce aerosolization or droplet formation on an open bench top without effective protection.
