Listeriosis

Today we discussed issues related to listeriosis. Some important points:

Listeria monocytogenes is an important cause of bacteremia and CNS infection in high risk groups. Listeria enters the body through the GI tract and then disseminates hematogenously; it is particularly "CNS-tropic"

Microbiology:
Aerobic gram positive bacillus that grows in cold temperatures, making it particularly suited to be a "refrigerator-proof" food-borne organism. Effectively cultured from normally sterile sites (e.g. blood, CSF), but not from stool samples.

Some of the implicated foods in outbreaks:
-Soft cheeses
-Coleslaw
-Deli meats
-Smoked fish
-Butter


Clinical syndromes
1) Self-limiting GI illness with foodborne ingestion in immunocompetent hosts
2) Bacteremia often without obvious focus. Non-specific presentation of fever, malaise, myalgias, back pain. This is the most common form to complicate pregnancy
3) Neonatal- early onset sepsis syndrome or late onset meningitis at 2 weeks
4) CNS infection (may follow bacteremia)- meningitis, encephalitis, brain abscess, brainstem involvement ("rhombencephalitis"; abrupt onset of asymmetric cranial nerve deficits, cerebellar signs, hemiparesis.
5) Others (rare): endocarditis, septic arthritis

Risk factors for listeriosis in adults
Deficits in cell-mediated immunity:
1) Pregnant women in 2nd or 3rd trimester- 30% of cases
2) HIV with low CD4 count (although Septra prophylaxis covers listeria)
3) Hematologic malignancy
4) Transplant
5) Steroids
6) Kidney or liver disease
7) Age over 60

Treatment:

Ampicillin is the drug of choice; this is why it is included in empiric meningitis treatment regimens in patients with risk factors.

Duration: Minimum 2 weeks IV for invasive infections (i.e. more than then self-limited GI illness); at least 3 weeks for CNS involvement

Link:

Click here for a recent CMAJ review of listeriosis