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Classification   |    Detailed evidence-based information

Substances Included Synonyms

Therapeutic Toxic Class

    A) Listeria monocytogenes is a pathogenic (disease-causing) bacterium that is foodborne and causes an illness called listeriosis.

Specific Substances

    1) Listeria (synonym)
    2) L. monocytogenes (synonym)
    3) Listeriosis (synonym)
    4) Listeria monocytogenes (synonym)
    5) Listeriosis monocytogenes (synonym)
    6) Listeria food poisoning (synonym)
    7) Food poisoning Listeria (synonym)

Available Forms Sources

    A) SOURCES
    1) DIFFICULT TO DETERMINE VECTOR: In most cases there has been no obvious vector. It is very difficult to isolate the organism and the length of incubation often results in the suspected food having been thrown out (Wilkinson & Keate, 1984; Kerr & Dealler, 1989).
    2) FOOD SOURCES
    a) Most sources for human listeriosis remain unknown but evidence continues to implicate consumption of contaminated foodstuffs as the primary means of transmission (Schlech et al, 1983; Campbell, 1989; Kerr & Dealler, 1989).
    1) Since 1986, the epidemiologic data suggesting food as a vehicle for transmission of Listeria seem strong and consistent with the understanding of how cattle and sheep can acquire the infection from eating contaminated silage (Schlech, 1986; Gray, 1960).
    b) CANTALOUPE: Fresh produce is an uncommon cause of listeriosis outbreak. However, in 2011, cantaloupe consumption was significantly linked to an outbreak of 147 cases of Listeria monocytogenes illness across 28 states, resulting in 33 (22%) deaths. Ninety-six of the 147 (65%) cases occurred in 5 adjoining states including Colorado (40 illnesses), Texas (18), New Mexico (15), Oklahoma (12), and Kansas (11). Based on available records, 143 out of 145 (99%) patients with listeriosis required hospitalization. Most patients, 127 out of 147 (86%), were 60 years of age or older, 7 pregnancy-associated infections were reported resulting in one miscarriage. The median age of those who died was 81 years. Environmental investigation confirmed that the outbreak was associated with whole cantaloupes from a single farm in Colorado (McCollum et al, 2013).
    c) MILK AND MILK PRODUCTS: Camembert cheese, soft Mexican-style cheese, soft cheese, mayonnaise-based deli-salads, coleslaw, and unpasteurized milk. Polar Bar ice cream bars were voluntarily recalled by Kraft when 3 of 75 samples were found to contain Listeria monocytogenes on routine sampling in 1986 (Choi et al, 2014; Uyttendaele et al, 2009; MacDonald et al, 2005; Gilot et al, 1997; Farber et al, 1990; Breer & Schopfer, 1989; Azadian et al, 1989; Bula et al, 1988; Linnan et al, 1988; Matyunas, 1987; Anon, 1985; Fleming et al, 1985; Pollock et al, 1984; Schlech et al, 1983). Between 2009 and 2011 in the United States, cheese was implicated in 6 out of 12 outbreaks reported and involved 51 (23%) cases of illness. Specifically, soft cheeses made from pasteurized milk were linked to 5 outbreaks. The 6th outbreak was linked to an aged blue-vein cheese made from unpasteurized milk (Centers for Disease Control and Prevention, 2013).
    d) BUTTER: Vehicle for listeriosis (L. monocytogenes serotype 3a) (Lyytikainen et al, 2000)
    e) MEAT AND MEAT PRODUCTS: Raw, cooked, cured and fermented meat (eg, pork, poultry, beef, pate); contaminated beef from a meals-on-wheels delivery, meat frankfurters, turkey deli meat (Smith et al, 2010; Uyttendaele et al, 2009; Mataragas et al, 2008; Thevenot et al, 2006; Gottlieb et al, 2006; Mead et al, 2006; Breer & Schopfer, 1989; Morris & Ribeiro, 1989; Gilbert & Pini, 1988).
    f) SEAFOOD: Crab, lobster, fish, molluscan shellfish, shrimp, smoked cod roe, smoked mussels, imitation seafood (Uyttendaele et al, 2009; Elliot & Kvenberg, 2000; Gilbert & Pini, 1988).
    g) READY-TO-EAT FOODS: Hospital and community outbreaks; ready-to-eat scalded sausages; prepackaged ready-to-eat foods containing beef, seafood, and/or milk products (Little et al, 2010; Miya et al, 2010; Winter et al, 2009; Farber, 2000; Norrung et al, 1999).
    h) RAW SALAD VEGETABLES: Lettuce; diced celery; ready-to-eat meals containing vegetables (Gaul et al, 2013; Breer & Schopfer, 1989; Bendig & Strangeways, 1989; Gilbert & Pini, 1988).
    3) ANIMAL TRANSMISSION
    a) Rural households with on-site livestock are a potential source (Kersting et al, 2010).
    b) Indirect transmission from animals had been assumed but never proven, although transmission to veterinarians delivering infected calves is known to occur.
    1) An animal reservoir was confirmed in an outbreak of listeriosis in Nova Scotia. The food implicated was a locally produced coleslaw and the contaminated product was traced back to the place where it was grown.
    2) Cases of ovine listeriosis had occurred in the flocks of the farmer who had fertilized the cabbage patch with raw sheep manure (Schlech et al, 1983).
    3) It is reported that listeriosis is a possible occupational disease of slaughterhouse workers (Schlech et al, 1983).
    4) HUMAN SOURCES
    a) Humans may be asymptomatic carriers of Listeria. Between 1% to 5% of the human population excrete fecal Listeria (Bojsen-Moller, 1972; Schlech et al, 1983).
    b) Listeria is commonly found in the female genital tract without causing harm (Hearmon & Ghosh, 1989).
    c) Carrier state is more likely if the environment permits. About 29% in poultry industry workers excrete fecal Listeria (Anon, 1985). In households in rural areas that have on-site livestock, Listeria is isolated from household items, including shoes and kitchen sinks (Kersting et al, 2010).
    d) Human carriers and food processing plant (ie, cheese pasteurizing plants) contamination have been addressed (Jasper, 1989; Mascola et al, 1989).
    5) OTHER SOURCES
    a) Listeria monocytogenes has been found in soil, dusts, sewage, water, animal feed, silage, and decaying vegetation (Gellin & Broome, 1989).

Overview

Life Support

    A) This overview assumes that basic life support measures have been instituted.

Clinical Effects

    0.2.1) SUMMARY OF EXPOSURE
    A) CAUSATIVE ORGANISM
    1) Listeria monocytogenes is a gram-positive non-acid fast, non-sporulating rod facultative anaerobe. At least seven species of Listeria have been identified; however, L. monocytogenes is the primary pathogen in animals and man. There are at least 16 serotypes of L. monocytogenes but only three serotypes are generally responsible for more than 90% of human illness. These serotypes are 4b, 1/2b, 1/2a.
    B) EPIDEMIOLOGY
    1) The true incidence of infection with Listeria is difficult to obtain. It produces a minor flu-like illness in most cases and would not prompt medical attention. In addition, there are many asymptomatic carriers. According to data compiled by the CDC, in the United States, approximately 2500 persons become seriously ill with listeriosis each year; of these, 500 die. Between 2009 and 2011, the average annual incidence of listeriosis in the United States was 0.29 cases/100,000 population.
    C) TARGET POPULATION
    1) Pregnant women, newborns, elderly, immunosuppressed patients, those with cancer, diabetes, kidney disease, or AIDS, and patients who take glucocorticosteroid medications are at increased risk of serious infection.
    D) MECHANISM
    1) The bacteria is spread through the body generally through incorporation into lymphocytes and monocytes, and can cross the blood-brain barrier to produce meningitis.
    E) WITH POISONING/EXPOSURE
    1) ACUTE SYMPTOMS
    a) MILD TO MODERATE EFFECTS: LISTERIOSIS: In most cases, patients with listeriosis present with a mild, flu-like complaints with fever and chills, muscle aches, and sometimes gastrointestinal symptoms such as nausea, vomiting or diarrhea. PREGNANT WOMEN: In pregnant women, especially during the third trimester, listeriosis causes a mild illness with malaise, chills, fever, and back pain. Healthy children rarely develop a severe illness from Listeria.
    b) SEVERE EFFECTS: Septicemia, meningitis (or meningoencephalitis), and encephalitis may occur. Endocarditis and pericarditis may also rarely occur. Diaphoresis, headache, photophobia, nuchal rigidity, and coma may develop in adults with infection of the central nervous system with Listeria. However, such severe illness from Listeria is rare. In the fetus, severe uterine infection, abortion, premature delivery, or stillbirth may occur.
    2) ROUTE OF EXPOSURE
    a) Most sources for human listeriosis remain unknown but evidence continues to implicate consumption of contaminated foodstuffs (eg, milk and milk products, meat products, seafood, raw salad vegetables) as the primary means of transmission. Rural households with on-site livestock are a potential source. Humans may be asymptomatic carriers of Listeria. Between 1% to 5% of the human population excrete Listeria in feces. L. monocytogenes has also been found in soil, dusts, sewage, water, animal feed, silage, and decaying vegetation.
    3) TIME TO ONSET
    a) Gastrointestinal symptoms onset: from a few hours to up to 3 days; serious forms of listeriosis onset: generally unknown but may be a few days to 3 weeks.
    0.2.20) REPRODUCTIVE
    A) In pregnant women, especially during the third trimester, listeriosis causes a mild illness with malaise, chills, fever, and back pain.
    B) The fetus may suffer severe uterine infection, abortion, premature delivery, or stillbirth.

Laboratory Monitoring

    A) Monitor CBC, serum electrolytes and renal function in patients with moderate to severe illness
    B) Blood cultures may confirm the diagnosis. Cerebrospinal fluid and stool cultures may also be obtained.
    C) Perform a lumbar puncture in any patient with altered mental status or meningismus.
    D) Listeria monocytogenes is a small gram-positive rod-shaped anaerobic bacteria. CSF gram stain and CIE will frequently be negative. Bacterial growth is improved on all media when incubated with reduced oxygen and 5% to 10% carbon dioxide.

Treatment Overview

    0.4.2) ORAL/PARENTERAL EXPOSURE
    A) MANAGEMENT OF TOXICITY
    1) Treatment is primarily symptomatic and supportive. Initial assessment must reflect the magnitude and type of dehydration. Rapid correction of deficits and careful monitoring of intake and output are essential. Patients with mild fluid deficits can often be managed with oral fluid therapy consisting of clear liquids or specially formulated electrolyte solutions. Patients with moderate to severe dehydration are generally treated with IV fluids. Treat fever with antipyretics (acetaminophen or ibuprofen).
    2) ANTIBIOTIC THERAPY: Ampicillin is the recognized drug of choice. It may be given in combination with gentamicin for the treatment of bacteremia in immunocompromised patients and in all patients with meningitis or endocarditis. Trimethoprim-sulfamethoxazole has been used in patients allergic to penicillins. Erythromycin and doxycycline have been approved for the treatment of infections due to Listeria monocytogenes.
    B) DECONTAMINATION
    1) Not indicated.
    C) ANTIDOTE
    1) None.
    D) PATIENT DISPOSITION
    1) HOME CRITERIA: Patients with mild diarrhea may be treated on an outpatient basis if compliance will be adequate; close follow-up care is essential.
    2) ADMISSION CRITERIA: All patients with significant toxicity, severe dehydration, clinical instability, abnormal electrolyte concentrations, or baseline immunocompromised state should be admitted for intravenous rehydration and antibiotic therapy.
    3) OBSERVATION CRITERIA: Patients with severe symptoms should be sent to a healthcare facility for evaluation and treatment.
    4) CONSULT CRITERIA: Consult a poison center or medical toxicologist for assistance in managing patients with severe toxicity or in whom the diagnosis is not clear.
    E) PITFALLS
    1) Because early symptoms and signs are nonspecific, they may be attributed to other conditions.
    F) DIFFERENTIAL DIAGNOSIS
    1) The differential diagnosis includes other bacterial (eg, E. coli) or nonbacterial (eg, viruses, plants or mushrooms ingestion) causes of acute gastroenteritis; exposure to chemicals (eg, insecticides, pesticides).

Range Of Toxicity

    A) TOXICITY: INFECTIVE DOSE: Unknown; fewer than 1000 total organism; may vary with the strain and susceptibility of the patient. The FAO/WHO estimated a human LD50 of 1.9 x 10(6) monocytogenes colony forming units (cfu) based on outbreak data from a pregnant woman consuming contaminated soft cheese.

Clinical Effects

Gastrointestinal

    3.8.2) CLINICAL EFFECTS
    A) PERITONITIS
    1) WITH POISONING/EXPOSURE
    a) A 76-year-old woman with hemochromatosis and advanced liver disease developed listeria-induced bacterial peritonitis 2 days after consuming contaminated cheese. She presented to the emergency department with acute abdominal pain, nausea and vomiting, and increasing somnolence. Examination showed ascites and infrequent bowel sounds; however, abdominal CT show no signs of bowel ischemia, ileus, or intraabdominal foci. Laboratory analysis showed an elevated CRP of 186 mg/L (normal range; less than 5 mg/mL). Ascitic fluid analysis revealed elevated leukocytes with normal protein. She was started empirically on IV ceftriaxone and metronidazole for suspected spontaneous bacterial peritonitis. Forty-eight hours later, microbiology results showed a positive culture for Listeria monocytogenes in the ascitic fluid. IV ampicillin was added to her treatment. She was discharged 2 weeks after admission and recovered completely (Galan et al, 2011).
    B) NAUSEA AND VOMITING
    1) WITH POISONING/EXPOSURE
    a) Nausea, vomiting, and abdominal pain may occur.
    b) CASE SERIES: In a large outbreak (1566 individuals reported symptoms) of Listeria monocytogenes food poisoning in 2 schools, vomiting and fever were reported significantly more frequently in children than in adults (Aureli et al, 2000a).
    C) DIARRHEA
    1) WITH POISONING/EXPOSURE
    a) Diarrhea can occur following exposure (Aureli et al, 2000a).
    b) CASE SERIES: In a large outbreak in two schools (1566 individuals reported symptoms), diarrhea was more commonly reported among adults rather than children (Aureli et al, 2000a). Of children that developed symptoms and were hospitalized, diarrhea lasted a median of three days (range one to seven days).

Musculoskeletal

    3.15.2) CLINICAL EFFECTS
    A) PAIN
    1) WITH POISONING/EXPOSURE
    a) Joint and muscle pain were reported in adults following exposure to L. monocytogenes during a large outbreak in two schools in Italy (Aureli et al, 2000a).

Reproductive

    3.20.1) SUMMARY
    A) In pregnant women, especially during the third trimester, listeriosis causes a mild illness with malaise, chills, fever, and back pain.
    B) The fetus may suffer severe uterine infection, abortion, premature delivery, or stillbirth.
    3.20.3) EFFECTS IN PREGNANCY
    A) INFECTION
    1) CASE SERIES: Matyunas (1987) reported that in a series of 42 pregnant women who had ingested ice cream (from one bite of ice cream to 30 ice cream bars) contaminated with Listeria monocytogenes developed the following (Matyunas, 1987):
    a) Ten patients were in their first trimester of pregnancy, 15 in their second, and 17 in their third. Sixteen of these 42 women reported symptoms consistent with listeriosis. All patients were recommended to have antibiotic therapy and cultures of blood and stool.
    b) Cultures were negative in the 7 patients in which they were performed. Twenty patients received antibiotic therapy. Follow-up was available on 31 of these 42 patients, and no significant symptomatology was found.
    B) INFLUENZA-LIKE SYMPTOMS
    1) In pregnant women, especially during the third trimester, listeriosis causes a mild illness with malaise, chills, fever, and back pain. However, the fetus may suffer severe uterine infection, abortion, premature delivery, or stillbirth (Jackson et al, 2010; Cheung & Sirkin, 2009; Delgado, 2008; Hamilton, 1987; Mascola et al, 1989a).

Summary Of Exposure

    A) CAUSATIVE ORGANISM
    1) Listeria monocytogenes is a gram-positive non-acid fast, non-sporulating rod facultative anaerobe. At least seven species of Listeria have been identified; however, L. monocytogenes is the primary pathogen in animals and man. There are at least 16 serotypes of L. monocytogenes but only three serotypes are generally responsible for more than 90% of human illness. These serotypes are 4b, 1/2b, 1/2a.
    B) EPIDEMIOLOGY
    1) The true incidence of infection with Listeria is difficult to obtain. It produces a minor flu-like illness in most cases and would not prompt medical attention. In addition, there are many asymptomatic carriers. According to data compiled by the CDC, in the United States, approximately 2500 persons become seriously ill with listeriosis each year; of these, 500 die. Between 2009 and 2011, the average annual incidence of listeriosis in the United States was 0.29 cases/100,000 population.
    C) TARGET POPULATION
    1) Pregnant women, newborns, elderly, immunosuppressed patients, those with cancer, diabetes, kidney disease, or AIDS, and patients who take glucocorticosteroid medications are at increased risk of serious infection.
    D) MECHANISM
    1) The bacteria is spread through the body generally through incorporation into lymphocytes and monocytes, and can cross the blood-brain barrier to produce meningitis.
    E) WITH POISONING/EXPOSURE
    1) ACUTE SYMPTOMS
    a) MILD TO MODERATE EFFECTS: LISTERIOSIS: In most cases, patients with listeriosis present with a mild, flu-like complaints with fever and chills, muscle aches, and sometimes gastrointestinal symptoms such as nausea, vomiting or diarrhea. PREGNANT WOMEN: In pregnant women, especially during the third trimester, listeriosis causes a mild illness with malaise, chills, fever, and back pain. Healthy children rarely develop a severe illness from Listeria.
    b) SEVERE EFFECTS: Septicemia, meningitis (or meningoencephalitis), and encephalitis may occur. Endocarditis and pericarditis may also rarely occur. Diaphoresis, headache, photophobia, nuchal rigidity, and coma may develop in adults with infection of the central nervous system with Listeria. However, such severe illness from Listeria is rare. In the fetus, severe uterine infection, abortion, premature delivery, or stillbirth may occur.
    2) ROUTE OF EXPOSURE
    a) Most sources for human listeriosis remain unknown but evidence continues to implicate consumption of contaminated foodstuffs (eg, milk and milk products, meat products, seafood, raw salad vegetables) as the primary means of transmission. Rural households with on-site livestock are a potential source. Humans may be asymptomatic carriers of Listeria. Between 1% to 5% of the human population excrete Listeria in feces. L. monocytogenes has also been found in soil, dusts, sewage, water, animal feed, silage, and decaying vegetation.
    3) TIME TO ONSET
    a) Gastrointestinal symptoms onset: from a few hours to up to 3 days; serious forms of listeriosis onset: generally unknown but may be a few days to 3 weeks.

Vital Signs

    3.3.3) TEMPERATURE
    A) WITH POISONING/EXPOSURE
    1) FEVER: Most patients with listeriosis present with fever. It produces a minor flu-like syndrome (Kessler & Dajani, 1990; Aureli et al, 2000a).
    2) CASE SERIES: In a large outbreak of food poisoning secondary to contamination with Listeria monocytogenes in two schools, fever and gastrointestinal symptoms were commonly reported. Of 2189 school-aged children and staff, 1566 reported symptoms with fever reported in 86% of children and 68% of adults. No cases of sepsis or death were reported among those requiring hospitalization (Aureli et al, 2000a).

Heent

    3.4.3) EYES
    A) WITH POISONING/EXPOSURE
    1) INTRAOCULAR LISTERIOSIS: An 88-year-old woman with a history of controlled open-angle glaucoma was diagnosed with intraocular listeriosis after consuming cantaloupe contaminated with Listeria monocytogenes. She underwent emergency vitrectomy after developing severe right eye pain, blurred and worsening vision, and increasing intraocular pressure (IOP). Just prior to surgery, her IOP was 47 mm Hg in the right eye and 13 mm Hg in the left eye (normal range 9 to 21 mm Hg). At initial presentation symptoms included absence of light perception, erythema, and fixed/nonreactive pupil in the right eye. She also reported nausea and anorexia. Days prior to surgery, she was treated unsuccessfully with cycloplegics, IOP-lowering agents, ocular steroids, and ocular antibiotics. During vitrectomy, vitreous and aqueous samples were obtained for culture and sensitivity; Listeria monocytogenes was isolated. She was treated with IV ampicillin and ocular vancomycin. About 2 weeks after surgery, she continued to have no light perception in her right eye, but eye pain was no longer present. Investigation revealed that the cantaloupe she consumed 2 to 4 times weekly for about one moth prior to the onset of illness was linked to the farm implicated in a Listeria outbreak (Ibraheem et al, 2013).
    2) CORNEAL ULCERATION: Listeriosis was found to be the cause of a corneal ulcer in a 65-year-old man. The patient had previously undergone an intracapsular cataract extraction in the right eye 5 years previously (Holland et al, 1987).
    3) OCULOGLANDULAR INFLAMMATION may also be seen (Hearmon & Ghosh, 1989).

Cardiovascular

    3.5.2) CLINICAL EFFECTS
    A) ENDOCARDITIS
    1) WITH POISONING/EXPOSURE
    a) Endocarditis is rare, but there are at least 20 cases in the world cardiovascular literature (Sheinman et al, 1985).
    b) Patients with prosthetic valves are at greater risk (Pocar et al, 2009; Lindholm, 2008; Karavidas et al, 2007).
    c) Complications reported to be associated with endocarditis from Listeria include cerebral septic emboli (Lindholm, 2008), spontaneous splenic rupture (Llanwarne et al, 2007), and acute thoracoabdominal aortic dissection (Kida et al, 2007).
    B) PERICARDITIS
    1) WITH POISONING/EXPOSURE
    a) There are at least 3 cases of pericarditis associated with L. monocytogenes bacteremia (Holoshitz et al, 1984).

Respiratory

    3.6.2) CLINICAL EFFECTS
    A) ACUTE LUNG INJURY
    1) WITH POISONING/EXPOSURE
    a) Adult respiratory distress syndrome is a rare complication (Lamont et al, 1988).

Neurologic

    3.7.2) CLINICAL EFFECTS
    A) CENTRAL NERVOUS SYSTEM FINDING
    1) WITH POISONING/EXPOSURE
    a) Diaphoresis, headache, photophobia, nuchal rigidity, and coma may develop in adults with infection of the central nervous system with Listeria. However, such severe illness from Listeria is rare. Pregnant women, newborns, and immunocompromised patients are at greater risk (Wilkinson & Keate, 1984; Hearmon & Ghosh, 1989; Pollock et al, 1984).
    b) CASE SERIES: In a large outbreak of Listeria monocytogenes food poisoning in two schools in Italy, headache was the most frequently reported symptom with 88% of adults and 86% of children complaining of symptoms (Aureli et al, 2000a).
    c) Cerebral septic emboli may occur secondary to Listeria endocarditis (Lindholm, 2008).
    B) MENINGITIS
    1) WITH POISONING/EXPOSURE
    a) Meningitis secondary to infection with Listeria is rare. When it does occur it develops slowly and may not cause the usual meningeal signs. The usual signs of a positive Kernig's sign and meningismus seen with meningitis are not generally present in adults.
    1) Mental status changes may be gradually worsening over a period of a week before the infection becomes apparent. Since listeriosis may develop slowly, listeriosis meningitis should be considered in any febrile patient with neurologic symptoms.
    2) Seizures or focal neurological aberrations may be seen as a late finding (Wilkinson & Keate, 1984).
    3) Meningitis is more commonly seen in immunocompromised patients, but may also occur in healthy individuals (Hearmon & Ghosh, 1989).
    a) One study found that patients with malignancies, as well as immunocompromised (transplant recipients) patients were more likely to develop meningitis following exposure to L. monocytogenes (serotype 3a). Of the 25 patients with confirmed cases, 16% (n=4) developed meningitis (Lyytikainen et al, 2000).
    C) ENCEPHALITIS
    1) WITH POISONING/EXPOSURE
    a) Encephalitis may occur (Center for Food Safety and Applied Nutrition (CFSAN), 2012).
    D) ABSCESS
    1) WITH POISONING/EXPOSURE
    a) Brain and spinal cord abscesses may occur (Moragas et al, 2010; Ricard et al, 2008; Soares-Fernandes et al, 2008; Manfredi et al, 2006; Treebupachatsakul et al, 2006; Lorber, 2005; Leiti et al, 2005; Cone et al, 2003; Addas & Jan, 2002; Rossi et al, 2001).

Laboratory Monitoring

Monitoring Parameters Levels

    4.1.1) SUMMARY
    A) Monitor CBC, serum electrolytes and renal function in patients with moderate to severe illness
    B) Blood cultures may confirm the diagnosis. Cerebrospinal fluid and stool cultures may also be obtained.
    C) Perform a lumbar puncture in any patient with altered mental status or meningismus.
    D) Listeria monocytogenes is a small gram-positive rod-shaped anaerobic bacteria. CSF gram stain and CIE will frequently be negative. Bacterial growth is improved on all media when incubated with reduced oxygen and 5% to 10% carbon dioxide.

Methods

    A) MULTIPLE ANALYTICAL METHODS
    1) LISTERIA MONOCYTOGENES is a small gram-positive anaerobe and non-sporulating bacillus (Pezeshkian et al, 1984). The rod-shaped bacteria can be mistaken as a contaminant due to its resemblance to diphtheroids (Katz & Weinstein, 1982).
    2) A cerebrospinal fluid (CSF) gram stain frequently will fail to demonstrate a causative organism and CIE will be negative (Wilkinson & Keate, 1984).
    a) In one group of 4 meningitis patients, 3 failed to demonstrate the organism microscopically from CSF, but CSF did grow positive cultures. These cases might have been diagnosed as "viral" meningitis (Hearmon & Ghosh, 1989).
    3) The organism may be decolorized by alcohol and be mistaken for gram-negative enteric bacteria or Hemophilus influenzae (Wilkinson & Keate, 1984).
    4) Growth is improved when incubated with reduced oxygen and 5% to 10% carbon dioxide.
    5) A DNA-probe method used for typing Legionella pneumophila has been successfully used for L. monocytogenes. Initial results demonstrated 8 distinct patterns from 24 epidemiologically unrelated strains (McLaughlin et al, 1988).
    6) One study used listeriolysin O (LLO) to detect antibodies against Listeria in patients. Ninety-six percent of patients with Lysteria were positive. Controls with other infections had a 12% positive reaction and healthy controls were 15.6% positive (Berche et al, 1990).

Treatment

Life Support

    A) Support respiratory and cardiovascular function.

Patient Disposition

    6.3.1) DISPOSITION/ORAL EXPOSURE
    6.3.1.1) ADMISSION CRITERIA/ORAL
    A) All patients with significant toxicity, severe dehydration, clinical instability, abnormal electrolyte concentrations, or baseline immunocompromised state should be admitted for intravenous rehydration and antibiotic therapy.
    6.3.1.2) HOME CRITERIA/ORAL
    A) Patients with mild diarrhea may be treated on an outpatient basis if compliance will be adequate; close follow-up care is essential.
    6.3.1.3) CONSULT CRITERIA/ORAL
    A) Consult a poison center or medical toxicologist for assistance in managing patients with severe toxicity or in whom the diagnosis is not clear.
    6.3.1.5) OBSERVATION CRITERIA/ORAL
    A) Patients with severe symptoms should be sent to a healthcare facility for evaluation and treatment.

Monitoring

    A) Monitor CBC, serum electrolytes and renal function in patients with moderate to severe illness
    B) Blood cultures may confirm the diagnosis. Cerebrospinal fluid and stool cultures may also be obtained.
    C) Perform a lumbar puncture in any patient with altered mental status or meningismus.
    D) Listeria monocytogenes is a small gram-positive rod-shaped anaerobic bacteria. CSF gram stain and CIE will frequently be negative. Bacterial growth is improved on all media when incubated with reduced oxygen and 5% to 10% carbon dioxide.

Oral Exposure

    6.5.1) PREVENTION OF ABSORPTION/PREHOSPITAL
    A) Decontamination is not indicated.
    6.5.2) PREVENTION OF ABSORPTION
    A) Decontamination is not indicated.
    6.5.3) TREATMENT
    A) MONITORING OF PATIENT
    1) Monitor CBC, serum electrolytes and renal function in patients with moderate to severe symptoms.
    2) Blood cultures may confirm the diagnosis. Cerebrospinal fluid and stool cultures may also be obtained.
    3) Perform a lumbar puncture in any patient with altered mental status or meningismus.
    4) Listeria monocytogenes is a small gram-positive rod-shaped anaerobic bacteria. CSF gram stain and CIE will frequently be negative. Bacterial growth is improved on all media when incubated with reduced oxygen and 5% to 10% carbon dioxide.
    B) FLUID/ELECTROLYTE BALANCE REGULATION
    1) INTRAVENOUS REHYDRATION: In the moderately to severely dehydrated patient with normal renal function, initial rehydration should take place over 30 to 45 minutes with normal saline (children: 20 mL/kg; adults: 1 to 2 L). This should be followed by maintenance fluids or a repeat bolus if there is evidence of ongoing hypovolemia.
    2) ORAL REHYDRATION: Although oral rehydration requires careful management and must be administered slowly, this approach is appropriate for patients with mild diarrhea who have normal vital signs and minimal evidence of dehydration, and are willing to take fluids orally. Oral rehydration is not appropriate in children with severe circulatory collapse or intractable vomiting (Finberg, 1982).
    C) ANTIBIOTIC
    1) PENICILLINS
    a) Ampicillin is the recognized drug of choice against listerial bacteremia (Wilkinson & Keate, 1984; Rapp et al, 1984; Gilbert et al, 1999).
    1) AMPICILLIN DOSE: ADULTS and CHILDREN: 200 mg/kg/day every 6 hours intravenously for a minimum of 14 days (Hoepich, 1991; Lorber, 1997).
    2) Delayed bactericidal activity in vitro has been reported (Winslow & Steele, 1984).
    3) Ampicillin has also been used in pregnant women just prior to birth (Kalstone, 1991).
    2) GENTAMICIN
    a) Gentamicin can be added to the ampicillin regimen for the treatment of patients with bacteremia or those severely immunocompromised, or the diagnosis of meningitis, brain abscess, or endocarditis (Tunkel et al, 2004; Lorber, 1997; Gilbert et al, 1999).
    3) PENICILLIN-ALLERGIC PATIENTS
    a) TRIMETHOPRIM-SULFAMETHOXAZOLE
    1) Trimethoprim-sulfamethoxazole has been used with in patients allergic to penicillins (Wilkinson & Keate, 1984; Winslow & Steele, 1984; Spitzer et al, 1986; Lorber, 1997; Gilbert et al, 1999).
    2) DOSE: ADULTS and CHILDREN: 20 mg trimethoprim and 100 mg sulfamethoxazole/kg/day intravenously in 3 to 4 divided doses for up to 14 days (Gilbert et al, 1999).
    3) Desensitization can be successfully done for patients with allergy to penicillin using increasing doses of penicillin V followed by full-dose parenteral therapy with penicillin G or ampicillin. Antibiotic therapy may not prevent abortion of the fetus (Wendel et al, 1985).
    b) ERYTHROMYCIN
    1) Erythromycin is approved for the treatment of infections due to Listeria monocytogenes (Prod Info ERY-TAB(R) delayed-release oral tablets, 2004; Prod Info PCE(R) oral tablets, 2002).
    2) Erythromycin has been used successfully in Listeria bacteremia (Holoshitz et al, 1984).
    3) ADULT DOSE: 250 mg orally every 6 hr or 500 mg orally every 12 hr or 250 mg orally every 6 hr or 333 mg orally every 8 hr or 500 mg orally every 12 hr; MAX 4 g/day, depending on type and severity of infection (Prod Info ERY-TAB(R) delayed-release oral tablets, 2004; Prod Info PCE(R) oral tablets, 2002)
    4) CHILDREN DOSE: 30 to 50 mg/kg/day orally divided every 6 to 8 hr; MAX 4 g/day as base, depending on type and severity of infection (Prod Info ERY-TAB(R) delayed-release oral tablets, 2004; Prod Info PCE(R) oral tablets, 2002)
    c) DOXYCYCLINE
    1) Doxycycline (calcium, hyclate, or monohydrate) is approved for treating Listeriosis caused by L. monocytogenes when penicillin is contraindicated (Prod Info DORYX(R) delayed-release tablets, 2005; Prod Info Vibramycin(R), 2003).
    2) DOXYCYCLINE HYCLATE DOSING
    a) ADULTS (IV) 200 mg IV on day 1 (given as 1 or 2 infusions, give infusions over 1 to 4 hours), followed by 100 to 200 mg/day for at least 24 to 48 hours after symptoms and fever have subsided (Prod Info doxycycline IV injection, 2004)
    b) ADULTS (ORAL) 100 mg orally every 12 hr on day 1 then 100 mg/day orally in 1 to 2 divided doses; severe infections, 100 mg ORALLY every 12 hours (Prod Info VIBRAMYCIN(R) oral capsules, oral suspension, oral syrup, 2003)
    c) CHILDREN (IV): (over 8 years, under 45 kg) 4.4 mg/kg IV on day 1 (given as 1 or 2 infusions, give infusions over 1 to 4 hours), then 2.2 to 4.4 mg/kg/day for at least 24 to 48 hours after symptoms and fever have subsided (Prod Info doxycycline IV injection, 2004)
    d) CHILDREN (ORAL) (over 8 years, under 45 kg) 4.4 mg/kg orally in 1 to 2 divided doses on day 1, then 2.2 to 4.4 mg/kg/day orally in 1 to 2 divided doses; (over 8 years, over 45 kg) use adult dose (Prod Info VIBRAMYCIN(R) oral capsules, oral suspension, oral syrup, 2003)
    d) CEFAZOLIN
    1) Cefazolin sodium has been used successfully in Listeria bacteremia (Holoshitz et al, 1984), but failure has also been reported (Kawler & Hof, 1984).
    e) CHLORAMPHENICOL
    1) Chloramphenicol has been successfully used in some meningitis patients who did not respond to ampicillin, even though the cultures were sensitive to ampicillin (Hearmon & Ghosh, 1989).
    2) Adverse reactions to chloramphenicol are common and it should not be considered a first-line agent (Richards et al, 1988; Stamm, 1982; Cherubin et al, 1981).

Range Of Toxicity

Summary

    A) TOXICITY: INFECTIVE DOSE: Unknown; fewer than 1000 total organism; may vary with the strain and susceptibility of the patient. The FAO/WHO estimated a human LD50 of 1.9 x 10(6) monocytogenes colony forming units (cfu) based on outbreak data from a pregnant woman consuming contaminated soft cheese.

Minimum Lethal Exposure

    A) The FAO/WHO estimated a human LD50 of 1.9 x 10(6) monocytogenes colony forming units (cfu) based on outbreak data from a pregnant woman consuming contaminated soft cheese (Food Quality and Standards Service, Food and Agriculture Organization of the United Nations and Food Safety Department, World Health Organization, 2004).
    B) The FDA/USDA/CDC developed a dose-response curve based on mouse data adjusted to reflect human epidemiological data. Based on their dose-response graph, the estimated human LD50 is approximately 10(13) L monocytogenes colony forming units (cfu) (US Food and Drug Administration, 2003). However, according to a recent study with guinea pigs, this may be underestimated (Williams et al, 2009).
    C) ANIMAL DATA
    1) The number of ingested L. monocytogenes cells which will cause human disease in normal or highly susceptible hosts is not currently known. Ingestion of 10(9) L. monocytogenes cells by monkeys resulted in significant illness and shedding of the organism in the feces. At smaller doses, lymphopenia, neutrophilia and fecal shedding occurred, but no obvious symptoms of illness (Farber et al, 1991).
    2) Animal studies using on-human primates and guinea pigs have both estimated LD50 of approximately 10(7) Listeria monocytogenes colony forming units (cfu) (Smith et al, 2003; Williams et al, 2007; Smith et al, 2008).

Maximum Tolerated Exposure

    A) INFECTIVE DOSE: Unknown; fewer than 1000 total organism; may vary with the strain and susceptibility of the patient (Center for Food Safety and Applied Nutrition (CFSAN), 2012).
    B) The true incidence of infection with Listeria is difficult to obtain. It produces a minor flu-like syndrome in most cases, that would not be severe enough to prompt medical attention. In addition, there are many asymptomatic carriers. According to data compiled by the CDC since 1997, in the United States, an estimated 2500 persons become seriously ill with listeriosis each year. Of these, 500 die (Centers for Disease Control and Prevention, 2009).

Pharmacology Toxicology

Toxicologic Mechanism

    A) TYPICAL HOSTS
    1) Listeriosis is usually a disease of the extremes of age or compromised hosts (people suffering from malignancy, alcoholism, diabetes mellitus, those receiving steroids or other immunosuppressive agents, and those with other immune deficiency states) (Hearmon & Ghosh, 1989; Lyytikainen et al, 2000). The fetus and newborns are also particularly susceptible (Benenson, 1985).
    B) PREGNANCY: Sepsis due to listeriosis in pregnancy commonly presents as a primary bacteremia and in the absence of appropriate antibiotic therapy may result in spontaneous abortion (Nieman & Lorber, 1980).
    C) EPIDEMIOLOGY
    1) RESERVOIRS: Listeriosis monocytogenes is widespread in the environment. Key sources include infected animals, humans (asymptomatic carriers or symptomatic cases), water, mud, soil, silage, and foods (Benenson, 1985; Armstrong, 1985).
    2) INCUBATION/COMMUNICABILITY: The incubation period is probably a few days to 3 weeks. Person-to-person transmission can occur through direct contact, or contact with body fluids. The period of communicability is uncertain (Benenson, 1985).

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