Two episodes of listeriosis in pregnancy and newborns: investigation, problems and considerations

In January 2013, 3 strains of Listeria monocytogenes isolated from one mother and her newborn and a second infant arrived at the Institute for Experimental Veterinary Medicine of Latium and Tuscany. At the same time the Local Health Unit Rome B sampled at retail a smoked salmon that was suspected to be involved in the transmission of the disease. The sample was tested for the presence of L. monocytogenes (UNI EN ISO 11290: 2005 part 1 and 2). Laboratory investigations have shown that all 3 strains isolated from patients belonged to serotype 4b of two different clusters (cluster B for the isolates from mother and child and cluster A to that obtained from another baby), so no epidemiological link was demonstrated in the human cases. The tests conducted on smoked salmon have shown the presence of L. monocytogenes serotype 1/2a. Therefore, no correlation has been demonstrated between the reported cases of listeriosis and the food analyzed.