Listeriosis of the placenta: clinicopathologic study of seven cases.

Abstract

The purpose of our study was to evaluate the usefulness of placental examination in the diagnosis of prenatal listeriosis. Over a 7-year period, 4597 placentas with clinical indications for examination were retrospectively studied for morphologic evidence of listeriosis. The microbiology laboratory file records of positive Listeria monocytogenes cultures were used to confirm the diagnosis. The clinical records were studied for manifestations of the infection both in the neonates and in the mothers. Seven placentas were identified as having listeriosis. The presence of macroabscesses, as opposed to microabscesses, was the most characteristic finding in this study, and the silver impregnation method was more reliable in identification of the bacilli in the tissue sections than the tissue Gram stains. Listeriosis could be diagnosed by placental examination alone, and this examination frequently strengthened the clinical diagnosis. When the infection was not suspected clinically, the examination helped us reach the correct diagnosis.