Author: Dr Katherine Allnutt, Resident, Monash Health, Melbourne, Australia. DermNet NZ Editor-in-Chief: A/Prof Amanda Oakley, Dermatologist, Hamilton, New Zealand. February 2018.
Listeriosis is a bacterial infection caused by the bacteria Listeria monocytogenes. It is typically a food-borne illness and usually affects those with impaired immunity. Its presentation may range from febrile gastroenteritis to potentially fatal invasive disease, including sepsis, central nervous system infection and perinatal infection .
Listeriosis may also uncommonly present with cutaneous eruptions.
Most cases of reported listeriosis are sporadic but a number of outbreaks have occurred .
Clinical listeriosis mostly occurs in high-risk groups including :
Listeria monocytogenes is an anaerobic gram-positive bacillus found in vegetation, soil and animals. Consumption of contaminated food is thought to be the main route of transmission. The bacterium can survive acidic, salty and cold food processing techniques and can continue multiplying even with proper refrigeration . The incubation period is variable and outbreaks have occurred 3–70 days following exposure to implicated food products . The median incubation period is approximately 3 weeks.
The following are considered high-risk products :
Listeria monocytogenes may also be transmitted from mother to baby, via the placenta or from ascending vaginal infection .
Rarely, Listeria monocytogenes may be transmitted from animals to humans .
Most cases of cutaneous listeriosis in adults result from direct inoculation of the skin . This is most commonly seen in veterinarians or farmers who come in contact with animal products of conception or soil carrying the bacteria. Cutaneous listeriosis may also appear from invasive disease through haematogenous spread in individuals with impaired immunity .
In immune-competent individuals, non-invasive listeriosis typically manifests as febrile gastroenteritis with self-limiting nausea, vomiting and diarrhoea .
Maternal T-cell immunity is most affected during the third trimester and this is when listeriosis in pregnancy typically occurs .
Cutaneous listeriosis typically presents as purpuric, papulopustular or vesicopustular eruptions that are painless and non-pruritic .
Listeriosis is diagnosed by isolating Listeria monocytogenes from a site that is normally sterile, such as blood, cerebrospinal fluid, gastric washings, amniotic fluid, meconium, placenta or fetal tissue specimens . The bacterium may also be isolated from a skin biopsy.
Histopathology may demonstrate:
An elevated white cell count on full blood examination is usually found.
Imaging may demonstrate abscesses on internal organs such as the liver and brain.
Listeriosis presents like many other infectious diseases that cause fever and constitutional symptoms. The differential diagnosis for cutaneous listeriosis is wide and may include:
Listeriosis is treated with antibiotics.
Penicillin alone, or with gentamicin, is considered the drug of choice for treatment of listeriosis. Vancomycin, meropenem and linezolid have also been used successfully in case reports [1,11,12,13]. In patients who are allergic to pencillin, trimethoprim-sulphamethoxazole or erythromycin may be used . Listeria monocytogenes is resistant to cephalosporins.
The duration of treatment varies depending on age, location and severity of illness.
There is limited evidence on the role of antibiotics in primary cutaneous listeriosis but it has been proposed that a 5–7 day course of oral amoxicillin or trimethoprim-sulphamethoxazole may be warranted .
Listeriosis should be notified to the relevant local authorities . If contaminated products are implicated these may need to be recalled.
Immunisation for listeriosis is not currently available.
Listeriosis is usually a self-limiting disease in immunocompetent individuals, however, mortality rates in invasive disease may be as high as 20% . One third of cases of listeriosis in pregnancy result in miscarriage or stillbirth .
Primary cutaneous listeriosis usually resolves without long-term consequence .
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