Chronic meningococcemia is an uncommon manifestation of meningococcal disease. Our objective was to asses whether a bacterial factor, a mutation in the lpxL1 gene resulting in underacylated lipopolysaccharide, might be important in chronic meningococcemia.

We identified 15 patients with chronic meningococcemia over a 50-year period. Chronic meningococcemia episodes were defined by a febrile episode of at least one week and presence of meningococci in blood and/or cerebrospinal fluid (CSF). Meningococcal isolates from these patients were characterised by serogrouping, multi-locus sequence typing, and in vitro interleukin 6 inducing capacity. lpxL1 gene mutations were determined by direct sequencing.

The median age was 21 years (range, 2–62) and median duration of symptoms before diagnosis was four weeks (range, 1–12). Of the 15 isolates, seven (47%) strains had a reduced interleukin 6 inducing capacity and were found to have a mutation in lpxL1 resulting in penta-acylated lipid A. This frequency is higher than previously reported among adult patients with meningococcal meningitis (7%; p < 0.0001) and invasive meningococcal disease (9%; p = 0.001).

We conclude that chronic meningococcemia patients are often infected with meningococci with a mutation in lpxL1 resulting in underacylated lipid A. The lpxL1 mutations may well explain the protracted and benign clinical course in these patients.