Characterization of human invasive isolates of Listeria monocytogenes in Sweden 1986-2007.

Since 1986, 68% of the Listeria monocytogenes isolates from human cases of invasive listeriosis in Sweden are available for retrospective studies. The aim of the present study was to characterize 601 human invasive isolates of L. monocytogenes in Sweden from 1986 to 2007 by using serotyping and pulsed-field gel electrophoresis. Since 1996, serovar 4b was permanently reduced to the second or third most common serovar in human cases in Sweden. During the latter period, 2000-2007, only 13% belonged to serovar 4b and 71% to 1/2a. The dendrogram, based on pulsovars, reveals two clusters with different serovars. Cluster 1 exhibits serovars 4b and 1/2b, whereas cluster 2 consists of serovar 1/2a. Serovar 1/2a seems to be more heterogeneous than serovar 4b.

The impact of active intervention on the spread of penicillin-resistant Streptococcus pneumoniae in Swedish day-care centres.

Policies for handling cases of penicillin-non-susceptible Streptococcus pneumoniae (PNSP) in day-care groups vary between different counties in Sweden. The aim of this study was to evaluate the epidemiological effect of excluding PNSP-carriers from children's day-care centres (DCC). We followed the incidence in 14 DCC groups with ongoing PNSP-spread, by repeated group screens until no further cases could be identified. All identified carriers were excluded from DCC attendance in study area A (Skåne region) while they remained in the group in study area B (Göteborg and örebro), according to local policies. The intervention effect was evaluated by comparing the number of additional cases after the baseline screen (start of the intervention period) between the 2 study areas. All PNSP-isolates were characterized by resistance pattern, serotype and pulse-field gel electrophoresis. The relative risk for children in DCCs without active intervention was 6.4 (95% CI: 2.0-20.7). Each prevented case in area A can be estimated to have demanded the exclusion of 2 other children from day care for approximately 4 weeks each. The total cost-benefit outcome of this action has to be seen in the light of the local situation with regard to the population prevalence and the distribution of other risk factors.