Listeria has also been recovered from many foods including unpasteurized dairy products, raw vegetables, meats, poultry, and fish. If left untreated during pregnancy, it can lead to premature delivery and fetal death. On exam of CSF, Gram stain is negative and glucose in normal in over half of cases and there is a predominance of mononuclear cells in about one third of cases. Listeria infection should thus be considered in the differential of high-risk patients presenting with compatible clinical findings. A history of eating any high-risk food items is helpful.
Diagnosis is established by positive blood cultures, or lumbar puncture and CSF cultures.
Gentamicin is generally contraindicated during pregnancy. In response to the outbreak linked to hot dogs and deli meats distributed by Sara Lee, there has been an increased number of foods tested for and found to contain Listeria . Because serotyping testing is not readily available and the infectious inoculum for Listeria is not established, the significance of these findings is not entirely clear but many food manufacturers have recalled their products. Some of the more widely distributed and well known products that have been recalled since January 1999 include Oscar Meyer variety lunchmeats and Thorn Apple Valley hot dogs and lunch meats. Except for the Sara Lee and Mragowski cheese outbreaks described above, NO human illnesses have been identified in association with these products.