New Guidelines Respond to Current Public Health Need Following Listeria Warnings

Listeriosis is an infection caused by the bacteria Listeria monocytogenes Listeria  is commonly  found in water, soil, raw , and processed foods. The ability of the Listeria bacteria to grow at temperatures as low as 4°C ( 39 °F ) allows Listeria to multiply in refrigerated foods

Most infections are caused by eating foods contaminated with theListeria bacteria  such as uncooked meats , vegetables (including raw sprouts) , cantaloupes, or soft cheeses  and ice cream made with unpasteurized milk.  Listeriosis may also occur through mother to child to child transmission or cross infection. The incubation period has been reported to be as short as is from 24 hours .However,  periods ranging from 11 to 70 days, with a mean of 31 days Once the bacteria has entered the body it grows and hides within the infected person’s cellsListeria has a predilection for the placenta and central nervous system.

What are the Symptoms of Listeria?

Infected pregnant women may experience no symptoms or flu-like symptoms such as fever, muscle or back pain. Diarrhea and abdominal pain are common. Some women may also experience  intense headache, nausea, vomiting , stiff neck and other signs of meningitis.

Diagnosis of listeria infection is made by culturing the organism from a sterile site such as blood, amniotic fluid, or spinal fluid. Stool culture is not useful. The laboratory should be informed of the suspicion of listeriosis.

Effects on Pregnancy

About one-third of listeriosis cases happen during pregnancy. Listeria infections during pregnancy can lead to miscarriage or stillbirth, premature delivery, or infection of the newborn. The affected fetus may show decreased movement with dilated echogenic bowels (intestines) and ascites on ultrasound examination.

Treatment of Listeria During Pregnancy

The American Congress of Obstetricians and Gynecologists (ACOG) recommends exposed pregnant women “…with a fever higher than 38.1  o C (100.6  o F) and signs and symptoms consistent with listeriosis for whom no other cause of illness is known should be simultaneously tested and treated for presumptive listeriosis.” The treatment of choice is high dose IV ampicillin for at least 14 days. Trimethoprim with sulfamethoxazole (Bactrim , Septra) has been recommended in women who are allergic to penicillin.

ACOG recommends no testing or treatment for asymptomatic pregnant women with no symptoms who report consumption of a product that was recalled for suspected listeria contamination or a product that was implicated in an outbreak of listeria .

The ACOG Committee Opinion “Management of Pregnant Women With Presumptive Exposure to Listeria monocytogenes” is available at :


Women can decrease their chances of getting listeriosis by eating pasteurized foods (such as cheeses and milk) , washing raw fruits and vegetables thoroughly under running tapwater , and avoiding hot dogs, luncheon meats, or deli meats unless they have been properly reheated to steaming ( 160 degrees F.)


  1. Goulet V, et. al., What is the incubation period for listeriosis? BMC Infect Dis. 2013 Jan 10;13:11. doi: 10.1186/1471-2334-13-11. PMID: 233051742.
  2. Hasbún J, et. al., Chorioamnionitis caused by Listeria monocytogenes: a case report of ultrasound features of fetal infection. Fetal Diagn Ther. 2013;33(4):268-71. doi: 10.1159/000345091. PMID: 23429225
  3. Janakiraman V.Listeriosis in pregnancy: diagnosis, treatment, and prevention. Rev Obstet Gynecol. 2008 Fall;1(4):179-85. PMID: 1917302
  4. Lamont RF, et. al., Listeriosis in human pregnancy: a systematic review. J Perinat Med. 2011 May;39(3):227-36. PMID: 21517700

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