Surveillance of listeriosis in Navarre, Spain, 1995-2005 – epidemiological patterns and characterisation of clinical and food isolates

We monitored the incidence of human listeriosis in Navarre, a region in north of Spain between 1995 and 2005, and carried out the characterisation of Listeria monocytogenes isolates obtained from clinical samples and ready-to-eat products (sliced cooked meat, smoked salmon and liver pate). The active surveillance requesting hospitals to notify all listeriosis cases (n=40) yielded higher incidence rates (average annual rate 0.65/100,000 inhabitants, range 0.18-1.18/100,000 inhabitants) than expected. Pregnant women were the largest group affected (n=13, 32.5% of the cases), with a peak in incidence during the last three years of the study period. From the 40 human cases we obtained 33 Listeria isolates. Serological and molecular characterisation by PFGE identified 20 different pulsotypes, which on three occasions enabled us to link sporadic cases into clusters. Although we could not identify the incriminated food product we found two clinical pulsotypes among smoked salmon and cooked meat isolates. Surveillance of listeriosis in Spain should be improved and coordinated with other European Union Member States in order to better estimate the burden of disease and to prevent foodborne outbreaks.