Meningitis due to Listeria monocytogenes in adults

INTRODUCTION: Listeria monocytogenes is the third most common cause of community-acquired bacterial meningitis in adults. AIMS: To describe the characteristics of meningitis caused by Listeria (LM) in adults and to compare them with those of meningitis due to other causations (nLM). PATIENTS AND METHODS: A retrospective analysis of a series of hospital cases was conducted, including patients aged between ≥ 14 years diagnosed with LM in a referral hospital between 1982 and 2011. RESULTS: The study involves 16 cases of LM, 12.1% of the cases of community-acquired meningitis with an identified aetiology. Predisposing factors were age (mean of 65 versus 52 years; p = 0.019) and immunosuppression/comorbidity (62.5% versus 3.4%; p < 0.001), treatment with corticoids (37.5%) and chronic liver disease (25%) being the most frequent. The classical triads of acute bacterial meningitis, clinical features and analysis of the cerebrospinal fluid (CSF) were observed in 50 and 75% of the cases, respectively. Patients with LM presented lower leukocyte counts in CSF, a lower percentage of neutrophils, a greater frequency of lymphocytic pleocytosis and a lower frequency of Gram stain positive than those with nLM. The mortality rate was 12.5%, similar to that of patients with nLM. CONCLUSIONS: LM mainly affects patients who are immunosuppressed or with comorbidity, as well as elderly patients, although it may occur in the absence of risk factors. Clinically it does not differ from other causes of meningitis, but the initial CSF study may suggest it. Its mortality rate is similar to that of meningitis due to other aetiologies.