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Interesting Case Rounds. Shawn Dowling. Case. 35M. Engineer. Presents to emerg (MT area) Concerned that he has Listeriosis and that he’ll die Are you going t work this individual up? Counsel him?. In case anyone lives in a cave…. July; routine surveillance noted an  Listeriosis

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Interesting case rounds

Interesting Case Rounds

Shawn Dowling

Interesting case rounds


  • 35M. Engineer. Presents to emerg (MT area)

  • Concerned that he has Listeriosis and that he’ll die

  • Are you going t work this individual up? Counsel him?

In case anyone lives in a cave

In case anyone lives in a cave…

  • July; routine surveillance noted an Listeriosis

    • Outbreak traced to Maple Lead factory in ON

    • 29 confirmed cases, 31 Suspected cases

    • 5 deaths confirmed to be from outbreak, 10 under investigation

    • AB - Cases for 2008

      • Listeriosis cases as of August 26

      • 9Cases/7 under investigation for link to outbreak

        • Results pending = 5 (including 2 deaths)

        • Results confirmed = 2 not linked outbreak

      • Cases linked to national outbreak = 0



  • Discuss Listeria monocytogenes in terms of

    • Microbiology

    • Pathophysiology

    • At risk populations

    • Clinical Presentations

    • Investigations

    • Management

    • Prevention

Microbiology of listeria monocytogenes

Microbiology of Listeria monocytogenes

  • Only Listeria species that infects humans

  • Gram +ve rod, aerobic/facultative anaerobic

  • May resemble pneumococcus, diphtheria or haemophilus on gram stain



  • Facultative intracellular parasite

  • Usu in soil and decaying vegetable matter

  • Infection usu from oral ingestion-> mucosal penetration->systemic infection

  • Immunity to Listeria primarily occurs via T-cell activation of macrophages

  • Listeria has a predilection for CNS and placental tissue



  • Baseline incidence 1.55/100,000 (likely under-estimated) Canada wide, in AB 1/100,000

  • Sporadic illness

  • Outbreaks

  • <1% of FB illnesses but second highest mortality rate amongst foodborne illnesses (1st is Vibrio vulnificus), accts for 28% of all f.b. deaths

What is an outbreak

What is an outbreak?

  • Increase in incidence beyond the expected in a defined geographic area, within a defined period of time

  • A statistically significant increase in the rate of adverse events above that noted in the past

Steps to outbreak investigation

Steps to Outbreak Investigation

  • Verify diagnosis

  • Confirm outbreak

  • Identify and count cases

  • Develop epidemic curve

  • Take immediate control measures

  • Formulate and test hypotheses

  • Communicate findings

  • Implement interventions

Listeria outbreaks

Listeria Outbreaks

  • Have been associated with a number of foods: MC are deli meats, soft cheeses(unpasteurized), smoked seafood, meat spreads and paté’s

  • Attack rate ranges from 50-100%

  • Incubation period

    • Mean = 3 wks, (range 3 to 90 days)

  • Reportable disease - call the MOH

Predisposing conditions

Predisposing Conditions

  • Most systemic listerial infections occur in individuals with one or more predisposing conditions

    • Pregnancy (esp 3rd trimester)

    • Immunocompromised state (i.e. steroid Tx, malignancy - esp lymphoma, ESRD, HIV, etc.)

    • Age: neonates and Elderly (>65 yoa)

      • (1995) Listeria was causative agent for bacterial meningitis - 22% in elderly, 23% in neonates, 4% in those b/w 2-60

Case definition

Case Definition

  • Confirmed Case

  • Symptomatic individuals[1] with laboratory confirmation of infection:

    • Isolation of Listeria monocytogenes from a normally sterile site (e.g., blood or cerebrospinal fluid [CSF] or, less commonly, joint, pleural, or pericardial fluid)


    • In the setting of miscarriage or stillbirth, isolation of L. monocytogenes from placental or fetal tissue (including amniotic fluid and meconium)

Clinical manifestations

Febrile gastroenteritis

Focal Infections

Infection in pregnancy


CNS infections






Clinical Manifestations

Pt assessment

Pt Assessment

  • Detailed food Hx

    • List of detailed recalled products


    • Recommend food cultures - ? necessary in times of an outbreak - speak to MOH

Febrile gastroenteritis

Febrile Gastroenteritis

  • Usu occurs after ingestion of large inoculum, can occur in normal hosts

  • Sx: fever, watery diarrhea, N,V, HA, myalgias/arthralgias

  • Sx typically last 2 days

  • Usu self-limited, can progress to one of the other presentations if at-risk populations

  • Do not do stool cultures

  • Tx if: 1) persistent Sx, 2)high risk patients, 3)ingested food implicated in outbreak

Infection in pregnancy

Usu in 3rd trimester

Sx: fever, chills, back pain - nonspecific

LOW Threshold to get b.c. in febrile preg patient w/o source(esp when an outbreak of listeria)


Study of 11 pregnant pts; 2 fetal demises, 6 of 9 neonates had listerial infection, 3 not infected

Granulomatosis infantiseptica:

Disseminated abscess/granulomas

Infection in Pregnancy

Tx in pregnant

Tx in Pregnant

  • Supportive Tx

  • Any pregnant patient with documented listeria infection should be treated:

    • Ampicillin IV 2 g Q4H

    • If allergic

      • TMP/SMX IV (do not use during 1st trimester or last month of pregnancy) - 5mg/kg of TMP

      • Alt: vancomycin if PCN allergic and CNS infection

Cns infection

CNS Infection

  • Range of clinical presentation - fever + AMS to fulminant course + coma

  • Can present like classic meningitis or with focal CNS signs, ataxia, tremor, seizures

Interesting case rounds

  • Can also present like a cerebritis

    • Fever, HA, hemiplegia (resembling a stroke)

  • Can present like a rhomboencephalitis

    • Biphasic course of HA, fever, N/V followed by CN palsies, ataxia, tremor, decreased LOC, sz and hemiparesis

Cns investigations

CNS Investigations

  • CT if focal neuro signs, papilledema or AMS

  • LP

    • One of the nonTB causes of high lymphocyte counts (>25%)

    • Protein up

    • Glucose down (39%)

    • Gram stain - low sensitivity, low specificity

  • May need MRI - better than CT for cerebellar or brainstem lesions

Tx with cns infection

Tx with CNS infection

  • Ampicillin is drug of choice

    • Will likely be covering for other agents

    • Ceftriaxone does not cover Listeria

    • May consider adding synergistic gent dosing (1mg/kg Q8H) in CNS infection & sepsis

Prevention measures

Thoroughly cook/heat raw food from animal sources

Beef, pork & poultry

Additional recommendations for persons at high risk :

avoiding unpasteurized cheeses. There is no need to avoid pasteurized cheeses, cream cheese, cottage cheese or yogurt),

reheating leftovers of ready-to-eat foods such as hot dogs should be steaming hot before eating, and

avoiding foods or thoroughly reheat cold cuts before eating from delicatessen counters especially pregnant women and immuno-suppressed persons although the risk is relatively low

Prevention Measures

Recommendations for patients with known exposure

Recommendations for patients with known exposure

  • ASx patients - reassure, discuss Sx

  • Sx patients + exposure

    • Febrile gastro + high risk; early blood cultures

    • Pregnant patient; Tx if Listeria +ve

    • CNS infection/sepsis - Tx as normal, consider adding Ampicillin (Vanco of PCN allergic) coverage +/- gent (synergistic dosing) in HIGH RISK patients

More sites

More Sites

  • Health Canada


  • AB Health and Wellness


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