Pregnant women, persons with immunodeficiency and elderly persons with multiple diseases must avoid foods that are rich with listeria and are eaten without heating.
Listeria monocytogenes is a bacterium found in soil, quite commonly in foods in small quantities and in the normal flora of the intestinal tract of animals and humans (ca. 5%).
The infection may be acquired through ingestion of unheated food rich with listeria. Both single cases and foodborne epidemics have been reported. The incubation time usually varies between weeks and several months.
The foetus can be infected through the mother. Other forms of person-to-person transmission do not occur.
Pregnant women, newborn infants, persons with immunodeficiency and elderly persons with multiple diseases are more susceptible to the infection.
Symptoms
Sepsis and meningitis are the most important clinical presentations, with a possible 15-25% mortality rate depending on the primary disease and the accuracy of antimicrobial therapy.
Listeriosis during pregnancy may be a mild flu-like disease. It may result in abortion or early sepsis of the newborn. The newborn child may develop meningitis days or weeks after delivery (late-onset listeriosis of the newborn).
Listeriosis in individuals with no underlying risk factors may present as a mild cold-like illness or gastroenteritis.
Diagnosis
Diagnosis is based on culture of normally sterile tissue, e.g. blood orcerebrospinal fluid (staining shows gram-positive rod-shaped bacteria), where listeria is grown with standard methods.
Special request is needed for listeria culture from other samples (e.g. faeces, cervical mucus). The interpretation of a faeces result may be difficult as asymptomatic carriage also occurs.
Treatment
Intravenous ampicillin with the dose of 2 g 6 times daily is the first-line drug in an adult. Synergism with aminoglycosides may prove clinically useful.
A gastroenteritis with mild symptoms in an immunocompetent, non-pregnant person does not require treatment. If treatment is needed, amoxicillin or trimethoprim-sulphamethoxazole may be used.
There is no scientific data on the duration of treatment. Relapses have been described in short treatments, so usually in bacteraemia at least 2 weeks' and in meningitis 3 weeks' treatment is recommended, and even longer treatment is recommended for persons with immunodeficiency.
Prevention
Specific regulations regarding listeriosis as a notifiable disease apply in many countries. Find out about local regulations and reporting methods.
Risk groups should be given additional recommendations on foodstuffs to be avoided (e.g. non-pasteurized dairy products, blue cheese / mould-ripened soft cheese and fromage frais / fresh cheese, uncooked fish products) and the preparation of food.
References
Janakiraman V. Listeriosis in pregnancy: diagnosis, treatment, and prevention. Rev Obstet Gynecol 2008 Fall;1(4):179-85. [PubMed]
van de Beek D, Cabellos C, Dzupova O, et al. ESCMID guideline: diagnosis and treatment of acute bacterial meningitis. Clin Microbiol Infect 2016;22 Suppl 3:S37-62. [PubMed]
Thønnings S, Knudsen JD, Schønheyder HC, et al. Antibiotic treatment and mortality in patients with Listeria monocytogenes meningitis or bacteraemia. Clin Microbiol Infect 2016;22(8):725-30. [PubMed]
Goulet V. What can we do to prevent listeriosis in 2006? Clin Infect Dis 2007 Feb 15;44(4):529-30. [PubMed]