A study yesterday in Morbidity and Mortality Weekly Report describes an outbreak earlier this year of Neisseria meningitidisconjunctivitis of an unknown source among young military trainees living in dormitories on a Texas Air Force base.
Officials at Joint Base San Antonio-Lackland led the investigation of 41 N meningitidis conjunctivitis cases, which are uncommon in adults with healthy immune systems, on the 11,800-trainee base from February to May. Eighty percent of patients reported a recent upper respiratory infection. The investigation also revealed 32 cases of Haemophilus conjunctivitis.
All trainees had received the quadrivalent (four-strain) meningococcal vaccine soon after arrival for basic training. N meningitidis is an unusual bacterial cause of conjunctivitis (pink eye), the authors noted.
“Bacterial conjunctivitis in adults involves direct inoculation into conjunctival membranes without entering the bloodstream or central nervous system,” they wrote. “The estimated N. meningitis nasopharyngeal carriage rate (including encapsulated and unencapsulated strains) is as high as 5%-10% in some U.S. populations, with a peak prevalence of 23.7% in adults aged 19 years.”
“Because the average age of a military trainee includes this age, colonization with N. meningitidis is expected to be high,” they added.
Topical antibiotics sufficient for all but 1 patient
Most patients’ infections (85%) were in one eye. One patient was hospitalized and treated for periorbital cellulitis with intravenous antibiotics, while all other patients recovered after they were given topical antibiotics. Whole-genome sequencing of isolates from the first two patients suggested that the bacterium was unencapsulated, and the cases were related.
Findings from this investigation suggest that nongroupable N. meningitidis conjunctivitis in otherwise healthy persons might be successfully treated with topical antimicrobials.
An investigation of trainee hygiene and cleaning practices determined that no protocols were broken, and no outbreak source was identified.
“When outbreaks of mucopurulent conjunctivitis occur in congregate living settings, culturing exudate can identify outbreak etiology, and whole genome sequencing can help guide treatment and response,” the researchers wrote.
“Previous studies indicated that systemic antimicrobial therapy might be needed to prevent invasive infections of N. meningitidis cases; findings from this investigation suggest that nongroupable N. meningitidis conjunctivitis in otherwise healthy persons might be successfully treated with topical antimicrobials,” they added.