Abstract
In 2015, a suspected cluster of two invasive meningococcal disease (IMD) cases of serogroup W Neisseria meningitidis (MenW) occurred in elderly care home residents in England over 7 months; case investigations followed United Kingdom guidance. An incident control team reviewed epidemiological information. Phenotyping of case specimens informed public health action, including vaccination and throat swabs to assess carriage. Whole genome sequencing (WGS) was conducted on case and carrier isolates. Conventional phenotyping did not exclude a microbiological link between cases (case 1 W:2a:P1.5,2 and case 2 W:2a:NT). After the second case, 33/40 residents and 13/32 staff were vaccinated and 19/40 residents and 13/32 staff submitted throat swabs. Two MenW carriers and two MenC carriers were detected. WGS showed that MenW case and carrier isolates were closely related and possibly constituted a locally circulating strain. Meningococcal carriage, transmission dynamics and influence of care settings on IMD in older adults are poorly understood. WGS analyses performed following public health action helped to confirm the close relatedness of the case and circulating isolates despite phenotypic differences and supported actions taken. WGS was not sufficiently timely to guide public health practice.
Highlights
Neisseria meningitidis (Nm) is a major cause of meningitis and septicaemia globally and is associated with significant mortality and long-term morbidity among survivors
We describe two cases of meningococcal groups W (MenW) invasive meningococcal disease (IMD) in elderly residents of a care home who presented with bacteraemic pneumonia due to a relatively rare but expanding hypervirulent clone
In the United Kingdom (UK) IMD is infrequently diagnosed in care home residents and two cases from the same home was unusual
Summary
Neisseria meningitidis (Nm) is a major cause of meningitis and septicaemia globally and is associated with significant mortality and long-term morbidity among survivors. Meningococcal groups W (MenW) and Y (MenY) have historically been relatively uncommon causes of IMD, occurring more frequently in adults aged over 65 years who usually have underlying comorbidities. These capsular serogroups often have different clinical presentations from MenB, including pneumonia, septic arthritis, endocarditis and epiglottitis/supraglottitis [3]. In such cases, IMD may not be considered in the differential diagnosis and is only confirmed when N. meningitidis is unexpectedly isolated from blood culture or from culture of other sterile sites
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