Immunohistochemical identification of Listeria monocytogenes in formalin-fixed and paraffin-embedded placentas - Revista Brasileira de Ginecologia e Obstetrícia

PURPOSE: to identify Listeria monocytogenes (Lm) in human placentas by immunohistochemistry (IHC) and relate its presence to the histological alterations found on conventional examination, to the pregnancy trimester, age of pregnant women, cases of abortion and premature delivery, and to the occurrence of habitual abortion. METHODS: a retrospective study was carried out at the pathology service of a teaching hospital in the city of Porto Alegre in 2000. The paraffin blocks of 254 placentas, obtained from abortion, premature delivery and full-term birth, were analyzed by conventional histology using hematoxylin and eosin (HE) staining. The IHC assay consisted of a rabbit anti-listeria polyclonal antibody B65420R (Biodesign®) diluted 1:1000, in addition to the avidin-biotin-streptavidin complex; 148 placentas revealed inflammatory disorders, hemorrhage, necrosis and thrombosis. The c² test was used for statistical analysis. RESULTS: Listeria monocytogenes was detected in 33.78% of the placentas analyzed by IHC. Chorioamnionitis and villitis showed significant statistical difference in the positive placentas. Lm occurred in the 1st, 2nd and 3rd trimester of pregnancy. The age of pregnant women, the cases of abortion and/or premature births were not statistically different as to the presence or absence of Lm in the placentas. Habitual abortions occurred in patients with or without Lm in the placental tissue. CONCLUSION: Immunohistochemistry may be used to confirm the histopathological diagnosis of listeriosis in all trimesters of pregnancy.