Listeria monocytogenes is a gram-positive, non–spore-forming aerobic rod
-Oral, transplacental and birth canal transmission can occur
-Most common food sources include dairy, processed meats, hot dogs, soft cheeses and fruits
-infections are common in pregnant women (esp in the third trimester), neonates, immunocompromised patients, and elderly patients
-Fetal infection can result in either stillbirth or early death
Symptoms & Signs
Normal hosts: self-limited illness with fever, gastroenteritis
Pregnant women: relatively mild, fever, chills, and aches
Newborn infection: fever, diarrhea, respiratory distress, papular rash, hepatosplenomegaly, pneumonia, sepsis, meningitis
In utero infection: sepsis, widespread abscesses and granulomas in multiple internal organs
Diagnosis
Labs: elevated WBC with a predominance of polymorphonuclear neutrophils and monocytes
Diagnosis of listeriosis is by culture of blood, cerebrospinal fluid (CSF), or focal lesions
Cultures show gram positive rods that exhibit characteristic tumbling motility
Chief pathologic feature in neonatal sepsis: miliary granulomatosis with microabscesses in liver, spleen, CNS, lung, and bowel
Treatment
Antibiotics: ampicillin (drug of choice), gentamicin, trimethoprim-sulfamethoxazole
Listeria are uniformly resistant to all cephalosporins
Prevention
At-risk patients (eg, pregnant women) should avoid unpasteurized milk products