Brain abscesses after Serratia marcescens infection on a neonatal intensive care unit: differences on serial imaging

Serratia are known to be a possible cause of severe cerebral infections in neonates. We describe imaging of three premature infants infected with Serratia marcescens. Born in the 31( st), 25( th) and 28( th) weeks of gestation, they presented with signs of septicaemia on postnatal days 9, 24 and 32. Initial sonography showed cysts in the first child, two areas with anechoic centre and echogenic rim in the second, and several echogenic areas in the third. Lesions were seen on CT, of low density in two cases and minimally increased density in the third. MRI in the first patient showed cysts with incomplete contrast enhancement of the lesions, while patient 2 showed five ring-enhancing fluid-containing lesions with thick walls. In the third patient two abscesses with contrast enhancement and several high-signal spots were seen. We discuss the pathophysiology of the lesions and the impact of the various imaging methods.