Bacteraemia with meningitis caused by Listeria innocua of unknown source in an elderly patient with type 2 diabetes mellitus: a case report and literature review

<i>Listeria innocua</i>, although considered non-pathogenic in healthy individuals, can cause severe bacteraemia and meningitis in elderly patients with poorly controlled diabetes mellitus.Third-generation cephalosporins are not effective against all Listeria species; empiric treatment in patients >65 years with diabetes mellitus and meningitis must include ampicillin.Recent molecular studies have identified some atypical <i>L. innocua</i> strains carrying virulence genes, challenging the traditional view of the harmlessness of this species.