Listeriosis

Today we discussed the interesting case of Listeriosis.

L. monocytogenes is a facultatively anaerobic, nonsporulating, gram-positive rod that grows over a broad temperature range, including refrigeration temperatures. (making small lapses in sanitation at food processing centres an even more dangerous event).

Here is a brief overview of some of the clinical manifestations.

Gastroenteritis
Usually develops within 48 hours of ingestion of a large inoculum of bacteria in contaminated foods (milk, deli meats, soft cheeses and salads). Manifestations include fever, diarrhea, headache, and constitutional symptoms. Unless in a high risk group (see below) no treatment is usually required.

Meningitis/Encephalitis
L. monocytogenes causes ~5–10% of all cases of community-acquired bacterial meningitis in adults in the United States. Case-fatality rates are reported to be 15–26%. This is usually a more sub-acute presentation with a predominance in chronically ill patients or at the extremes of age.
L. monocytogenes can directly invade the brain parenchyma, producing either cerebritis or focal abscess.

Infection in Pregnancy (Nothing makes an internist more uncomfortable than a pregnant patient - except maybe kids).
The usual presentation in pregnancy is a nonspecific acute or subacute febrile illness with myalgias, arthralgias, backache, and headache. Preterm delivery is a common complication. Prepartum treatment of bacteremic women enhances the chances of delivery of a healthy infant. Women usually do well after delivery: maternal deaths are very rare, even when the diagnosis is made late in pregnancy or postpartum. Overall mortality rates for fetuses infected in utero approach 50% in some series; among live-born neonates treated with antibiotics, mortality rates are much lower (~20%). Granulomatosis infantiseptica is an overwhelming listerial fetal infection a feared complication.

Treatment
High dose Ampicillin (2g q4h) or Pen G (4MU q4h) is the recommended therapy for serious Listeria infections. In penacillin allergic patients, desensitization is always an option, although good results have been demonstrated with Septra.

For more information, check out this review.