Listeria Infection

Updated: Dec 01, 2022
Author: Terence Zach, MD; Chief Editor: Russell W Steele, MD 


Practice Essentials

Listeriosis is an infection caused by the gram-positive motile bacterium Listeria monocytogenes.[1, 2, 3]  Listeriosis is relatively rare and occurs primarily in newborn infants, elderly patients, and patients who are immunocompromised.[4, 5]  See the image below.

Electron micrograph of an artificially-colored Lis Electron micrograph of an artificially-colored Listeria bacterium in tissue.


L monocytogenes is acquired via the ingestion of contaminated food products. Newborns acquire Listeria transplacentally, by ascending infection via ruptured amniotic membranes or upon exposure during vaginal delivery.[5]


L monocytogenes is a gram-positive, motile, rod-shaped bacterium that is ubiquitous in the environment. L monocytogenes can be isolated in soil, wood, and decaying matter in the natural environment; however, the principal route of acquisition of Listeria is through the ingestion of contaminated food products. Listeria has been isolated from prepared meat (eg, hot dogs, deli meat), dairy products, unwashed raw vegetables, and seafood. Soft cheeses and unpasteurized milk have been the most frequently incriminated dairy products.[6, 7, 8, 9, 10, 11, 12]

Ingestion of Listeria by pregnant women can result in nausea, vomiting, diarrhea, fever, malaise, back pain, and headache.[13] Many pregnant women can carry Listeria asymptomatically in their GI tract or vagina. Maternal infection with Listeria can result in chorioamnionitis, premature labor, spontaneous abortion, or stillbirth. Fetal infection can occur via transplacental transmission. Vertical transmission can also occur from mother to infant via passage through an infected birth canal or ascending infection through ruptured amniotic membranes.[14, 15] Nosocomial outbreaks from one infected infant to others in the same nursery are rare but have been reported.

Two clinical presentations of neonatal infections occur: early onset (< 5 d) and late onset (>5 d). Early onset neonatal listeriosis is usually associated with sepsis or meningitis. Late-onset neonatal listeriosis frequently presents with purulent meningitis.[16]  Listeriosis often involves many organs with microabscesses or granulomas. A disseminated rash with small, pale, granulomatous nodules is histologically characteristic of granulomatosis infantisepticum. Beyond the neonatal period, most children with Listeria infections have an underlying immunodeficiency or are immunocompromised. Older children with Listeria infections frequently develop meningitis.[17, 18, 19]


United States statistics

The estimated annual incidence of listeriosis is approximately 2-3 cases per million population. In the United States, an estimated 1600 people contract listeriosis every year.[20]  Pregnant women account for 27% of all cases, and most occur during the third trimester.[5]

In a study of reported listeria cases from 2009-2011, the CDC reported a case fatality rate of 21%. Almost all cases occurred in high-risk groups, including older adults, pregnant women, and people who were immunocompromised.[21]

International statistics

The estimated annual incidence of listeriosis is approximately 4 cases per million population in Canada. Surveillance of listeria infections in Europe reported an incidence varying between 0.3 (Greece) and 7.5 (Sweden) cases per year.[22] After years of decreasing incidence, recent trends throughout Europe, in particular France and Scandinavia, show an increasing incidence.[23, 24, 25, 26, 27, 28, 29, 30, 31, 32] This trend is accounted for by increased cases in the population older than 60 years. Neonatal and maternal incidence remains stable.[33, 34]

Age-related demographics

Listeria infections occur most often in newborns and elderly patients. Neonatal infections can be subdivided into early onset and late-onset disease.

  • Early onset neonatal infections (< 5 d) begin at a mean age of 1.5 days.

  • Late-onset neonatal infections (>5 d) begin at a mean age of 14 days.

  • Postnatal infections usually occur in immunocompromised children and are less common than neonatal infections.


Prognosis is guarded and depends on whether meningitis or shock is present.[35]

Hydrocephalus, mental retardation, and other CNS sequelae have been reported following meningitis.


Early onset neonatal listeriosis has a 20-40% mortality rate.[33]  Late-onset neonatal listeriosis has a 0-20% mortality rate. The mortality rate in older children is less than 10%. Hydrocephalus, mental retardation, and other CNS sequelae have been reported in survivors of Listeria meningitis.

Of all pregnancy-related cases, 22% resulted in fetal loss or neonatal death, but the mothers usually survived.[5]

A French nationwide prospective study by Charlier et al that included 818 listeriosis cases reported that the strongest mortality predictors in both bacteremia and neurolisteriosis were ongoing cancer, multi-organ failure, aggravation of any preexisting organ dysfunction, and monocytopenia. Blood-culture positive patients and those receiving adjunctive dexamethasone had higher neurolisteriosis mortality.[36]


Rhombencephalitis (brainstem encephalitis) is a well-recognized complication of CNS listeriosis.[37]  Cranial nerve involvement has been reported in an immunocompetent toddler with novel H1N1 influenza.[38]




Consider listeriosis in cases of neonatal sepsis or meningitis and in cases of sepsis or meningitis in children who are immunocompromised.

  • Listeria is acquired by ingestion of contaminated food products.

  • Mothers who acquire Listeria may experience influenzalike illnesses, with headache, malaise, fever, backache, nausea, vomiting, diarrhea, and chills. Mothers with Listeria infections may also undergo premature labor.[13]

  • Listeria in newborns can be classified as early onset or late-onset infection.

  • Meconium-stained amniotic fluid is common in newborns with early onset Listeria.

  • Respiratory difficulty is common, including a history of cyanotic episodes, rapid breathing, and grunting.

  • Parents and health care providers may report poor feeding and fever.

Physical Examination

Listeriosis presents in the same manner as other more common neonatal pathogens, such as group B streptococci and Escherichia coli.

  • Respiratory distress - Tachypnea, grunting, apnea, and retractions

  • Temperature instability

  • Poor feeding

  • Lethargy/irritability

  • Seizures

  • Granulomatosis infantisepticum

    • Erythematous rash

    • Small, pale nodules or granulomas





Laboratory Studies

Laboratory studies that may be included in the workup are as follows:

  • Blood culture

  • Cerebrospinal fluid culture

  • Respiratory tract culture

  • Histopathology and culture of rash

  • Culture of other infected tissues

    • Joint

    • Pericardial fluid

    • Pleural fluid

    • Amniotic fluid

    • Placenta

    • Gastric aspirate

Imaging Studies

CT scanning or MRI may be useful in detecting abscesses in the brain or liver.



Medical Care

Care of a newborn with Listeria infection includes antibiotics as well as careful monitoring of the patient's temperature, respiratory system, fluid and electrolyte balance, nutrition, and cardiovascular support. Critically ill newborns are best treated in a neonatal ICU.

Consultations with neonatologists or pediatric infectious diseases specialists may be useful when caring for newborns.


Advice for all persons to avoid Listeria infection is as follows:

  • Wash hands, knives, and cutting boards after handling uncooked food.

  • Thoroughly cook all meat.

  • Thoroughly wash all vegetables.

  • Keep raw meats separate from other foods during preparation to avoid cross-contamination.

Advice for pregnant patients or patients with immunocompromise is as follows:

  • Avoid soft cheeses such as Feta, Brie, blue cheese, Mexican-style cheese, and Camembert.

  • Thoroughly reheat leftovers.

  • Avoid deli foods unless thoroughly heated.




Class Summary

These agents are used for suspected bacterial infections. Ampicillin in combination with an aminoglycoside such as gentamicin is the therapy of choice. Listeria is not susceptible to cephalosporins of any generation. Therefore, cephalosporins should not be used to treat Listeria infections.

Ampicillin (Marcillin, Omnipen, Polycillin, Principen)

DOC. Interferes with synthesis of cell wall mucopeptide during active multiplication, resulting in bactericidal activity.

Usual neonatal dosage for treatment of septicemia or meningitis depends on gestational and postnatal age. Higher doses are used with severe infections or meningitis.

Gentamicin (Garamycin, Gentacidin)

Useful in combination with ampicillin against listeria.

Sulfamethoxazole and Trimethoprim (Bactrim, Cotrim, Septra)

Second-line DOC for non-neonatal penicillin-allergic patients. Inhibits bacterial growth by inhibiting synthesis of dihydrofolic acid.

Penicillin G (Pfizerpen)

Can be used as an alternative to ampicillin. Interferes with synthesis of cell wall mucopeptide during active multiplication, resulting in bactericidal activity.


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