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A Closer Look at Listeriosis

Matthew Powell, Pharm. D. Intern & Jennifer Seltzer, PharmD

April 4th, 2012

On March 21st, the U.S. Department of Agriculture's Food Safety and Inspection Service (FSIS) announced that Southside Market & BBQ, located in Elgin, Texas, was recalling over 2,300 pounds of ready-to-eat beef sausage.1  Routine FSIS testing discovered possible contamination with Listeria monocytogenes, an intracellular parasite and gram-positive rod that can cause the rare foodborne illness, listeriosis.2  While no illnesses have been linked to the Southside Market & BBQ sausage, listeriosis is a potentially fatal infection with a mortality rate in the United States of 16 percent (in reported cases).3  In July through October 2011, a Listeria outbreak linked to cantaloupe from Colorado infected 146 persons in 28 states.  Thirty deaths were reported, including two in Texas.4
            Listeria is naturally found in soil and decaying vegetable matter, and over 95% of cases of listeriosis in the United States are caused by the ingestion of contaminated foods, including fruits, vegetables, meat, milk, and cheese.2,3  Nosocomial acquisition is rare in the United States but accounts for approximately 16 percent of the reported cases worldwide.5  Symptoms of listeriosis include watery diarrhea, fever, nausea, vomiting, headache, and muscle and joint pain6; full recovery typically takes two days or less.7  Progression to an invasive infection, such as bacteremia or meningitis, is rare, with neonatal, elderly, pregnant, and immunocompromised patients at the greatest risk.7  The incubation period in a healthy adult ranges from six to ten hours but can be as long as six weeks in at-risk populations.7,9
            Infection during pregnancy is most common during the third trimester and can present as a flu-like illness with fever, chills, and back pain.2, 10 Prematurity, infected newborns, and fetal death can result from listerial infection during pregnancy.  Listerial meningoencephalitis is most common in neonates after three days of age and in elderly patients who are immunocompromised.  This form of listeriosis has varied presentations, ranging from fever with mental status changes to a fulminant illness with coma.8
                  Definitively differentiating listeriosis from other infectious diseases with similar symptoms is only possible through culturing the organism from blood or cerebrospinal fluid (CSF).  Listeria gram-stains can give misleading results, however, as the organism can be gram-variable and confused with Haemophilus species, or it may resemble diplococci or diptheroids such as Corynebacterium.11 Stool cultures using selective media may be useful in suspected Listeria gastroenteritis, but they are not indicated in suspected systemic listeriosis due to gastrointestinal colonization of L. monocytogenes in five to ten percent of the general population.8, 12 
            Intravenous ampicillin is the drug of choice for invasive Listeria infections.  The recommended dose for adults is 2 g every 4 hours, while infants and children should receive weight-based dosing.  High dose intravenous penicillin G, from 20 to 24 million units per day in adults, is an alternative.  Patients with a reported penicillin allergy should be skin tested and desensitized if necessary or treated with the second-line agent, trimethoprim-sulfamethoxazole.13, 14 Due to synergistic effects with beta-lactams, weight-based and renally-adjusted gentamicin is commonly added in patients with central nervous system (CNS) infections.13-15
            Preventing Listeria infections involves the safe storage and preparation of food.  Specific safety measures, along with recommendations for persons at higher risk, can be found at  For further information on the Southside Market & BBQ sausage recall, visit


  1. United States Department of Agriculture Food Safety and Inspection Service. Texas firm recalls beef sausage products due to possible Listeria contamination. Mar 21, 2012. Available at: Accessed April 2, 2012.

  2.   Gelfand MS. Epidemiology and pathogenesis of Listeria monocytogenes infection. In: UpToDate, Basow, DS (Ed), UpToDate, Waltham, MA, 2012.

  3.   Scallan E, Hoekstra RM, Angulo FJ, et al. Foodborne illness acquired in the United States--major pathogens. Emerg Infect Dis. 2011; 17:7-15.

  4. Centers for Disease Control and Prevention. Multistate outbreak of Listeriosis linked to whole cantaloupes from Jensen Farms, Colorado. Dec 8, 2011. Available at: Accessed April 2, 2012.

  5.  Siegman-Igra Y, Levin R, Weinberger M, et al. Listeria monocytogenes infection in Israel and review of cases worldwide. Emerg Infect Dis. 2002; 8:305-10.

  6.  Centers for Disease Control and Prevention. Listeriosis (Listeria infection). Available at: Accessed April 2, 2012.

  7.  Ooi ST, Lorber B. Gastroenteritis due to Listeria monocytogenes. Clin Infect Dis. 2005; 40:1327.

  8.  Gelfand MS. Clinical manifestations and diagnosis of Listeria monocytogenes infection. In: UpToDate, Basow, DS (Ed), UpToDate, Waltham, MA, 2012.

  9. Aureli P, Fiorucci GC, Caroli D, et al. An outbreak of febrile gastroenteritis associated with corn contaminated by Listeria monocytogenes. N Engl J Med. 2000; 342:1236-41.

  10. Mylonakis E, Paliou M, Hohmann EL, et al. Listeriosis during pregnancy: a case series and review of 222 cases. Medicine (Baltimore). 2002; 81:260-9.

  11. Lorber B. Listeria monocytogenes. In: Mandell GL, Bennett JE, Dolin R (Eds). Principles and Practice of Infectious Diseases, 7th ed. Philadelphia, Pennsylvania: Churchill Livingstone; 2010. MD Consult Web site. Available at: Accessed April 2, 2012.

  12. Acheson DWK. Differential diagnosis of microbial foodborne disease. In: UpToDate, Basow, DS (Ed), UpToDate, Waltham, MA, 2012.

  13. Gelfand MS. Treatment, prognosis, and prevention of Listeria monocytogenes infection. In: UpToDate, Basow, DS (Ed), UpToDate, Waltham, MA, 2012.

  14. Gilbert DN, Moellering RC Jr, Eliopoulos GM, et al. The Sanford guide to antimicrobial therapy 2011, 41st edition. Sperryville, VA: Antimicrobial Therapy, Inc.; 2011. p. 64.

  15. Mylonakis E, Hohmann EL, Calderwood SB. Central nervous system infection with Listeria monocytogenes: 33 years' experience at a general hospital and review of 776 episodes from the literature. Medicine (Baltimore). 1998;77:313-36.

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Last Reviewed: April 16, 2012

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