[Investigation of Listeria monocytogenes serotype O antibodies in maternal and cord sera and the evaluation of risk factors for listeriosis in pregnant women]

Abstract

Listeria monocytogenes may lead to intrauterine infections which can be treated if diagnosed promptly. However, there is not a rapid routine screening test with high specificity and sensitivity for the diagnosis of listeriosis during pregnancy. We investigated the presence of different L. monocytogenes O antibodies for diagnosis of listeriosis in 275 paired maternal-cord sera using the agglutination test, and aimed to evaluate the correlation between poor pregnancy outcomes, level of L. monocytogenes serotype O antibodies and risk factors for listeriosis. Maternal-cord bloods were collected from a total of 275 pregnant women (age range 16-38 years) between April-August 2002 from a State Hospital in Ankara. A total of 550 sera were tested against antigens with the O formulation of serotypes 1/2c, 3b, 4ab, 4c, 4d by tube agglutination method and titers > or = 1/320 were considered as positive. Sixtynine patients with the history of poor pregnancy outcomes were in group I, while 206 patients with no obstetric pathology in previous pregnancies were in group II. L. monocytogenes antibodies to one or more serotypes were detected in 21.5% (59/275) of the patients, the rate being 20.3% in group I and 21.8% in group II. No statistically significant difference was detected between the two study groups (p > 0.05), indicating that this test was not an appropriate marker for the diagnosis of listeriosis during pregnancy. The total rate of positive results in cord sera was 0.7% (2/275) and the positive two sera were from samples in group II. The follow-up of the newborns, including the two cord blood positive ones, revealed no fetomaternal infection. The most frequently detected serotypes were 4ab (40%) and 1/2c (37%). Risk factors such as non-specific febrile illness during pregnancy (p < 0.001), consumption of ready-made food (p = 0.008), consumption of raw milk and milk products (p < 0.001) were found to be related to the presence of > or = 1/320 titers of L. monocytogenes antibodies. The major limiting factor in this study was the inability to obtain second serum samples from the mothers and newborns following delivery, to confirm the diagnosis by seroconversion. These results emphasize the need for the development of rapid, simple and reliable tests, alternative to culture methods, for the early and proper diagnosis of Listeria infections during pregnancy.